Title of Invention	A PROCESS FOR CATALYTIC REFORMING OF FEED HYDROCARBONS TO FORM AROMATICS HYDROCARBONS
Abstract	The present invention relates to a process for catalytic reforming of feed hydrocarbons to form aromatics comprising contacting the feed, under catalytic reforming conditions, with catalyst disposed in the tubes of a furnace, wherein the catalyst is a monofuctional non-acidic catalyst and comprises a Group VIII metal and zeolite L, and wherein the furnace tubes are from 2 to 8 inches in inside diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes.

Title of Invention

A PROCESS FOR CATALYTIC REFORMING OF FEED HYDROCARBONS TO FORM AROMATICS HYDROCARBONS

Abstract

The present invention relates to a process for catalytic reforming of feed hydrocarbons to form aromatics comprising contacting the feed, under catalytic reforming conditions, with catalyst disposed in the tubes of a furnace, wherein the catalyst is a monofuctional non-acidic catalyst and comprises a Group VIII metal and zeolite L, and wherein the furnace tubes are from 2 to 8 inches in inside diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes.

Full Text	dcaclivation or foiiling rale luul liigh aromalics yield. More particularly, the prcscnl invention pertains lo use of such catalyst in a gas or oil fired furnace. BACKGROUND OF THE INVENTION 15 Reforming embraces several reactions, such as dehydrogenation, isoraerization, dehydroisomerization, cycUzation and dehydrocyclization. In tlie process of the present invention, aromatics are formed from the feed hydrocarbons to the reforming reaction zone, and dehydrocyclization is the most important reaction. U.S. Patent No. 4,104,320 to Bernard and Nuiy discloses that it is possible to 20 dehydrocyclize paraffins to produce aromatics with high selectivity using a monofunctional non-acidic type-zeolite L catalyst. The zeolite L based catalyst in "320 has exchangeable cations of which at least 90% are sodium, lithium, potassium, rubidium or cesium, and contains at least one Group VIII noble metal (or tin or germanium). In particular, catalysts having platinum on potassium form L-zeolite 25 exchanged with a rubidium or cesium salt were claimed by Bernard and Nury to achieve exceptionnlly high selectivity for n-hexane conversion to benzene. As cii"^clnscd in tlie Bernard and Nury patent, the zeolite L is tjpically synthesized in llic p(i\|;issium form, A \|>orlion, tisiinlly not more than 80%, of Ihc potassium ci.tions can he cNcliangcd sn llinl olhor cafinns replace the exchangeable potassium. Ti i.i"rrr";[HiiKiing ;ilk:)li I-XL-II;III\|IC(I l,-/C(ililc cnlalysts disclosed in U.S. Patent No. 1.104.,120. "Ihcsc high Sflcclivity cnlnlysts of ncrnard and Nury, and of Buss and IlLighc;. nri," ;i)l "non-acidic" nnd are rflcrred to as "nionofunctional catalysts". These catalysis iivc liii.:hly selective for foriiiinjt nromatics via dehydrocyclization of paraffins. 10 Having discovered a highly selective catalyst, commercialization seemed promising. Unfortunately, (bat was not the case, because the high selectivity, I.-zcolite catalysts did not aciiieve long enough run length to make them feasible for use in catalytic reforming, U.S. Patent No. 4,456,527 discloses the surprising finding that if the sulfur content of the feed was reduced to ultra low levels, below levels used 15 in the past for catalysts especially sensitive to sulfur, that then long run lengths could be achieved with the L-zeolite non-acidic catalyst. Specifically, it was found that the concciilration of sulfur in the hydrocarbon feed to the L-zeolite catalyst should beat ultra low levels, preferably less than 100 parts per billion (ppb), more preferably less than 50 ppb, to achieve improved stability/activity for the catalyst used. 20 It was also found that zeolite L reforming catalysts are surprisingly sensitive to the presence of water, particularly while under reaction conditions. Water has been found to greatly accelerate the rate of deactivation of these catalysts. U.S. Patent No. 4,830,732, which is herein incorporated by reference discloses the surprising scrisilivity of zeolite 1. catalysis to water and ways to mitigate the problem. ?5 \ I.S. Patent Ni.. 5,3 I"l ;il..which arc herein incorporated by reference, discloSe a zeolite L based refortninii (■:H;iI\".\| wherein the enlaly.";! is Irealed at high temperature and low water content Id lb" tib\" improve llie shibilily nflhe cataly.sl, that is, to lower the deactivation rale ol tit!- i-.il."iK-st unticr reiiuiiiinj; roii"litions, .""() During c(>ninuT(i;ili.-;ilinn df/cdlile I- reforming catalysis, it was foniHl lb:il llii- tiHi.i lew ,";iiiriir lr\i-K e:iii";i"J Itie iincxpeeled problem ol"coking, carbiiii/nlini) luui clal dusting of llic reactor system metallurgy. This problem has necessitated the use special sleds and/or steels having protective layers to prevent coking, carburizatioii id metal dusting. When used, protective layers are provided on the steel surfaces at are to be contacted with hydrocarbons at process temperatures, e.g., at mperalures bcfwcen about 800- [ I SO°F. For example, a tin protective layer has been L"d in the reactors and furnace tubes of a catalytic reformer operated at ultra low Ifiir levels. This has effectively reduced the rate of coke formation exterior to the talyst particles in the reactors. Without this protection, coke buildup would have suhed in massive coke-plugging and in reactor system shutdowns. These problems z described in detail in Heyse ei al., US 5,674,376. Heyse et al, disclose the use of ccial steels and protective coatings, including tin coatings, to prevent carburizatlon d mcial dusting. In a preferred embodiment, Heyse et al., teach applying a tin paint a steel portion of a reactor system and heating in hydrogen to produce a rburization-resistant intermetalUc layer containing iron and nickel stannides. The forming system of Heyse et al., is a high temperature, low sulfur and low water stem that uses a conventional reformer designs, i.e., furnaces for heating the feed d catalysts located in conventiona] reactors. Recently, several patents and patent applications of RAULO (Research isociation for Utilization of Light Oil) and Idemitsu Kosan Co. have been published lating to use of halogen in zeolite L based monofiinctional reforming catalysts, ich halogen containing monofunctional catalysts have been reported to have iprovcd stability (catalyst life) when used in catalytic reforming, particularly in forming feedstocks boiling above C7 hydrocarbons in addition to C6 and C7 dmcarbons. In ih"is regard, sec HP 201 ,S56A; EP 498,182A; U.S. Patent 1, "1.681,865; ami U.S. Patent No. 5,091,351. EP 403,976 In Yoncda cl al., and assigned to RAULO, discloses the use of 11)1 ine treated zeolite L based catalysts in small diameter tubes of about one-inch iidc diameter (22-2 mm to 28 mm in the examples). Heating medium proposed for .■ ■^itKill tubes were inollen metal or molten salt so as to maintain precise control of .■ \|i-ni\|icralurc of the lubes. Accordingly, EP 403,976 docs not teach the use of a ii\ cnUniial type Inrnacc or convcnlional type furnace tubes. Conventiona! Iiiniaces I"[- cjilalylic rcfon. have tubes nriisually lliree or more increasxe in inside clianu-U-i-il(^ mm or more), wlu-icas VV AO"\}>l(i leaches that using tubes having an inside tharneler greater lb;m 50 mm is undesirable. Also, conventional furnaces arc hcjled usinj; gas or oil Hrcd hurncrs. 5 Typical catalylic reforming processes employ a series ofconvenlional furnafcs io ht-at (he naplidia fcctfsfock hernre each reforming reactor stage, as the reforming reaction is endoihcmiic. Thus, in a three-stage reforming process, the overall rt"lorming unit would comprise a first furnace followed by a first-stage reactor vessel containing the reforming catalyst (over which catalyst the endothermic reforming 3 reaction occurs); a second furnace followed by a second-stage reactor containing refonning catalyst over which the reforming reaction is further progressed; and a third fiimace followed by a third-stage reactor with catalyst to fiirther progress the reforming reaction conversion levels. For example, U.S. Patent No. 4,155,835 to Autal ilJustrates a three-stage > reforming process, with three furnaces (30,44, 52) and three reforming reactors (40, 48, 56) shown in the drawing in Antal. Example reforming reactors used according to the prior art are shown, for instance, in U.S. Patent No. 5,211,837 to Russet al., particularly the radial flow reactor shown in Figure 2 of Russ et al. hi some catalytic reforming units, as many as five or six stages of furnaces I followed by reactors are used in series for the catalytic reforming unit. In particular, reforming of hydrocarbons over a Pt L zeolite catalyst is a highly endothermic reaction and can require as many as 5 or 6 stages or more of ftimaces followed by reactors. The present invention allows such a multistage process to be greatly simplified to two, or more preferably one, furnace reactor. I SUMMARY OF THE INVENTION According to a preferred embodiment of the present invention, a process for catalytic reforming of feed hydrocarbons is provided. The process comprises passing hydrocarbons over a catalyst comprising a Group VIII metal and a large pore /cotitc clisposcii \silhin a funiacc, wlicrein said furnace comprises a first chamber and a second adjuinini! chamber separated by a heat exchange surface, wherein said catalyst is localci) \vil])i;i .s;iii) first chamber and one or more burners are located wilhiti said secoiul clinmbcr. Preferably, the catalyst is no more than 4 inches rroni the heal excliaiige surface and at least a portion of the catalyst is more than one inch from Ihc heat exchange surface. A preferred enihodimcni of the process comprises contacting the feed, under catalytic rcforitiine conditions, with catalyst disposed in the tubes of a furnace, wherein the catalyst is a monofiinctional, non-acidic catalyst and comprises a Group VlII melal and zeolite L, and wherein the furnace tubes are from 2 to 8 inches in inside diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes. In a preferred embodiment of the present invention, the furnace can be basically a conventional type furnace, except that catalyst is disposed in the tubes of the furnace and the reactor metallurgy is constructed to avoid carburization and metal dusting problems caused by the low sulfur environment. The furnace is heated by conventional means for naphtha reforming units, such as by gas burners or oil burners. Also, in the present invention, the size of the tubes is conventional, in the range 2 to 8 inches, preferably 3 to 6 inches, more preferably 3 to 4 inches, in inside diameter. Mono functional zeolite L based catalyst is contained inside the tubes of the conventional furnace in accordance with a particularly preferred embodiment of the present invention. In a particularly preferred embodiment, the furnace tubes are made of a material having a resistance to carburization and metal dusting under low sulfiir reforming conditions at least as great as that of type 347 stainless steel. The furnace tubes can be: (a) made of type 347 stainless steel or a steel having a resistance to carburization and metal dusting at least as great as type 347 stainless steel; or (b) treated liy a method comprising plating, cladding, painting or coating (fit- furnace tube surfaces for contacling the feed to provide improved resistance to earhnii/ation and niclal dusting; or (c) ctiiislniclcd of, or liricd with, a ceramic material. Among Dlhci- factors, (lie present iiivenlion is based on my conccplioii nm] unexpeted lliuiirii; lh:U. iisitif; llic cnlalysls defined herein, particularly non-acitlie. monorunclional Inrf.e pnrc /eolile based reforming catalyst, the conventional anangcmcnl of fiiniaccs and multi-stage reforming reactors can be coalesced into one or iiuire stages of conventional furnaces, eliminating the refonner reactor vessels downstream of the furnace. In one embodiment of the present invention, the defined monofunctional reforming catalyst is disposed in the tubes of a conventional furnace. A jircferred embodiment of the present invention is also based on my finding that a conventional multi-stage furnaces/reactors reforming arrangement (consisting of, for example, three to six, or as many as nine stages of ilimaces and reactors) can be replaced by as few as one basically conventional furnace containing monofiinctional zeolite L reforming catalyst in the tubes of the furnace. The present invention is also based on my discovery that zeolite catalysts of improved stability (i.e. having a deactivation rate of less than 0.04 degrees F per hour at reforming conditions) can be effectively and economically used in a furnace reactor for caalytic reforming. The improved stability of these catalysts further allows them to be used at operating conditions that enable long run lengths without frequent or continuous catalyst I I regeneration. My invention allows for simplified processing schemes and significantly less capital equipment than conventional catalytic reforming systems. In an alternative embodiment of the present invention the furnace may be constructed such that the burners arc located within tubes located in the fiirnace and the catalyst located in the area surrounding the lubes. The catalyst containing area may be a single chamber or a multitude of chambers. In such an arrangement it has been found that no portion of the catalyst should be more than 4 inches from the lube surface for heat flux reasons. Catalyst that is more than 4 inches from the heated surface may not he effective at dehydrocyclization of the hydrocarbons due "»"> llic hil"hiy cndothermic nature of the dehydrocyclization reactions and the heat flux dc[iL"ndcnce on the distance frcMu the burner tube or heat exchange surface. More ptffcrably the catalyst should he [lo more than 3 inches from a burner tube surface. Slii! more preferably the catalyst should be no more than 2 inches from a burner tiihe Mirfaic. it has also been foiiiid thai (licre is preferably one or more inches of catalyst - / - packed around llic Imrncr tubed and more preferably 1.5 or more inches catalyst pafkcd around llic hiiiricr Inhc siirracc. Tliis reduces the amount of heat cxchantie sill faff in tJte f\irnai:c rejiclor and helps to minimize the number offumacc reactors rctiuired for rcforniin[;. 5 In still another embiniimenl of (lie present invention the furnace reactor conipiises two or more chaniiiers. One or more chambers contain burners. One or more adjoinine chambers coiilain the catalyst. The burner chamber(s) and (he adjoining catalyst chambcr(s) are separated by a surface effective to provide heat exchange. This surface between the burner chamber(s) and tlie catalyst chambers is 10 herein referred to as the heat exchange surface. The chambers may have a variety of shapes. It is important however that catalyst should preferably be no more than 4 inches from a heat exchange surface for heat flux reasons. Catalyst that is more than the preferred distance &om the heated surface may not be effective at i dehydrocyclization of the hydrocarbons due to the highly endothermic nature of the 15 dehydrocyclization reactions and the heat flux dependence on the distance from the heat exchange surface. Thus catalyst that is more than 4 inches from the heat exchange surface may be effectively wasted. When I state that the catalyst is no more than an effective distance &om the heat exchange surface to avoid wasting the catalyst it is meant that at least 80 % of the catalyst be within that distance from the heat 20 exchange surface, preferably at least 85 % of the catalyst, more preferably at least 90 %, still more preferably at least 95 %, and most preferably essentially all of the catalyst is whithin the stated distance from the heal exchange surface. As stated above 1 have found that for the catalyst of the present invention, the catalyst should preferably be no more than 4 inches from the heat exchange surface. More preferably 25 the catalyst should be no more than 3 inches from the heat exchange surface. Still more preferably the catalyst should be no more than 2 inches from the heat exchanj;c surface. It has also been found lliat there is preferably more than one, and more preferably 1.5 or more, inches ofcalalyst packed around the heat exchange surface. Tills reduces the amount of lie;il exchange surface in the furnace reactor and helps to 30 (nininiize (fic miiuhcr of rimvAce reactors required for refornjing. AsKtalcc! in the background. U.S. Patent No. 4,155,8:^5 illustrates the ii,si.Mira lliR-c-Atagc rcforniin)! unit ccrnprisiTii; llirec conventional furnaces, and three relinming reactor vessels fonlnining catalyst, with one reactor being located downs (ream of each of the three furnaces. In contrast, the present invention coalesces 5 01- collapses the furnaces and separate leactors into one or more furnace lubes reactor sjstLMii. without the separalc renelor vessels. According to the present invention, t preferably, the system is only one furnace tube reactor, that is, coalescence to one furnace. I have found that the present invention is particularly advantageously carried 10 out at relatively low hydrogen to hydrocarbon feed mole ratios of 0.5 to 3.0, preferably 0.5 to 2.0, more preferably 1.0 to 2.0, most preferably 1.0 to 1.5, on a molar basis, I have also found that in the process of the present invention high space velocities can be used. Preferred space velocities are from 1.0 to 7.0 volimies of feed per hour per volume of catalyst, more preferably 1.5 to 6 hour"", and still more 15 preferably 3 to 5 hour"". The relatively low hydrogen to hydrocarbon feed mole ratio and the high space velocities when using the present invention make it feasible to use less total catalyst and at a lower overall gas flow rate. These benefits in turn allow the use of a furnace reactor with a reasonable number of tubes. j 20 Preferably, the Group VIII metals used in the catalyst disposed in the furnace i lubes comprises platinum, palladium, iridium, and other Group VHI metals. Platinum is most preferred as the Group VIII metal in the catalyst used in the present invention. Also, preferred catalysts for use in the present invention are non-acidic zcolilc L catalysts, wherein exchangeable ions from the zeolite L, such as sodium 25 and/or potassium, luivc been exchanged with alkali or alkaline earth metals. A p;ir(icularly preferred catalyst is I"t Ba L zeolite, wherein the zeolite L has been cxi-lianged using a baiium containing solution. These catalysts are described in more tlctail in the Buss and Hughes references cited above in the Background section, which references arc incorporated herein by reference, particularly as to description of 30 I"t l./cniitccalalysl. Accordifty to .-(ftoliKT pa-lcncd cnihodiment of the present invcniion, the /I"lilik-1, Ixiscii c;il;ily":l is [inKiiiceit hy Ircatincnl in a gaseous environment in a Icitiperadire range hclvvccn 1025""I" and nVS^F while maintaining the water level in lift" diluent gas hc}aw i(H/O ppni. /"rcfcrably, (lie high temperature treatment is 5 earriod oul at a water level in (lie cflUient gas below 200 ppm. Preferred high tern\|ieratnrc treated catalysts arc described in the Mulaskey ct al. patents cited above in llic Background section, w]iich references are incorporated by reference herein, particularly as to description ofhigh temperature treated Pt L zeolite catalysts. According to another preferred embodiment of the present invention, the 10 zeolite L based catalyst contains at least one halogen in an amoimt between O.J and I 2.0 wt. % based on zeolite L. Preferably, the halogens are fliiorine and chlorine and are present on the catalyst in an amount between 0.1 and 1.0 wt. % fluorine and 0.1 and 1.0 wt. % chlorine at the Start of Run. Preferred halogen containing catalysts are i described in the RAULO and IKC patents cited above in the Background section, 15 wliich references are incorporated by reference herein, particularly as to description of halogen containing Pt L zeolite catalysts. The above mentioned halogens may be added to the catalyst ex situ for example when the catalyst is made or may be added in situ, for instance at the start of the run. The preferred halogen contents of the catalyst mentioned above should preferably be present on the catalyst at the start of the rtm, 20 when feed is introduced to the catalyst under reforming conditions. Preferred feeds for the process of the present invention are naphtha boiling range hydrocarbons, that is, hydrocarbons boiling within the range of C^ to Cio paraffins and naphthenes, more preferably in the range of Cj to Cs paraffins and naphthenes, and most preferably of Ce to C7 paraffins and naphthenes. The feedstock 25 can onitain minor amounts of hydrocarbons boiling outside the specified range, sucli as 5 to 20%, preferably only 2 to 7% by weight. There are several different paraffins at each of the various carbon miinbers. Accordingly, it will be understood that the bniling point has .s 30 In a preferred cmbodiuieTit oT ilic present invention, the feed contacting the cal;ilvsl preferably coiilains less (ban 50 ppb sulfur, more preferably less than 10 ji]ib sutliir. In Ihe prcscnl invention, low catalyst rates are important. Ultra low sulfur in Ilk" (ccd contributes fo Ihc success of tlie present invention. Two patents that tench about the need to avoid sulfur poisoning of Pt L zeolite catalysts and teach how to achieve ultra low sulfur conditions are U. S. Patents 4,456,527 and 5,322,615, which 5 are herein incorporated by reference. In one embodiment of the present invention, the furnace tubes are filled with catalyst, and a conventional furnace with its associated tubes are used as a combination heating means and catalytic reaction means. In a particularly preferred embodiment of the present invention the catalyst is 10 selected to have a particularly low deactivation rate under reforming conditions. Preferably, the catalyst selected for use and reaction conditions selected are such that the catalyst deactivation rate is controlled to less than 0.04T per hour, more preferably less than 0.03°F, still more preferably less than 0.02F, and most preferably less than O.OrF per hour, at an aromatics yield of 50 wt % lising a C6-C7 UDEX i 15 raffinate feed at a liquidhourly space velocity of 4 hour" aiid a hydrogen to hydrocarbon mole ratio of 2. Utilizing a catalyst and conditions having the particularly preferred low deactivation rate allows for less catalyst to be used in the furnace reactor and allows the use of larger diameter tubes. In another embodiment of the invention that does not use tubes, the catalyst can be further away from a heat 20 exchange surface than when using a catalyst that has a high deactivation rate. This in tum allows the total length of tubes or in the alternative embodiment the heat exchange surface area to be minimized and makes it economical to replace the multitude of fumace/ reactor loops (usually 3-6 or more reactors in a conventional Pt I. zeolite catalyst refonner) with a single fumace reactor. 25 The present invention may again be contrasted to U.S. Patent No. 4,1 55,835 to Antal. The Antal reference uses reformer reactor vessels separate from the foiu"cnlional furnaces, v."hcrcas the present invention does not. Further, althougli the Antal process reduces the sulfur to very low sulfur levels ill the feed, as low a.s 0.2 pjini sulfur, the present invention is preferably carried out ai 30 sulfur lL"\els more than an ouler of magnitude lower, such as below 10 ppb sulfur, in the I"vcd [o llic luonoUinctiona] n-i\litc L based catalyst conliiincd in the furnnco R-acinr system ofliic present iiiveniion. Preferred reru f! eondilicms for the furnace reactor of the present invention nsiiin (lie preferred catalyst eoniprising a monofunctional zeolite L include a !.l [S V 5 lielween 1.5 and 6: a liydrogen to hydrocarbon ratio between 0.5 and 3.0; and a heal o\eh;uiye surface temperature for the rcactants (interior temperature) between fiOOT and 960°F at the inlet and between S60""F and 960°F at the outlet at Start of Run (SOR). and between 600°F and 1025^ at the inlet and between 920°F and 1025°r at the outlet at End of Run (EOR). EOR is the time at which the run is ended usually 10 due to deactivation of the catalyst. The catalyst of the present invention is considered at EOR at a point when the outlet temperature is no higher than 1025"?. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow diagram for a furnace tube reactor system. 15 Figure 2 is an overhead cross section view of a furnace tube reactor system showing the burners (X) and the reactor tubes (o). Figure 3 is a simplified scheme showing a vertical cross-section with gas-fired heaters (shaded) adjacent to a parallel series of furnace tubes that contain catalyst. I I Figure 4 shows 4 cross section views of alternative embodiment furnace 1 20 reactor systems showing the burners (X) and the catalyst chamber or chambers as cross-hatched areas. DETAILED DESCRIPTION OF THE DRAWINGS The drawing shown herein are for descriptive purposes only of possible 25 cnibii(iimenls ofllie invention and arc not intended in any way to limit the invention. Figure I is a schematic How diagram for a furnace tube reactor system. Hydrocarbon is fed to the unit through line (!). Thesulfur content of the hydrocarbon is a-fiticcd to the Llcsircd low k\"c]s in the sulfur control unit (2). The liydrotarbon ihen [.iocs via line (.1) to an optional licat exchanger orprchcatcr (4). The optionally 30 luMlcd effluent (iocs via line (5) lo the furnace reactor (6) where it is siniuliancou.sly luMlcd and contaiifd with llie catalyst. The reactor effluent then goes via line (7) to a slnhUizcr hght gas is rcitinvcd from tlic stabilizer by line (8) and liquid prodiicl lca\ cs (he stiihilizcr by line (% wliicli goes to product distillation (not shown). I-igure 2 is an overhead cross section view of a furnace tube reactor system Khinving the burners (X) and the reactor tubes (o). The furnace tubes are filled willi 5 liic calalysl. This is only one possible furnace tube arrangement. Figure 3 is a simplified scheme showing a vertical cross-section with gas-fired heaters (shaded) adjacent to a parallel series of furnace tubes that contain catalyst. Figure 4 shows 4 cross section views of alternative embodiment furnace reactor systems showing the burners (X) and the catalyst chamber or chambers as 10 cross-hatched areas. There are numerous other possible furnace reactor configurations. The four arrangements in Figure 4 are only meant as illustrations of I possible embodiments of the chamber coniigurations useful in the present invention furnace reactor. I 15 DETAILED DESCRIPTION OF THE INVENTION The catalyst used in the process of the present invention comprises a Group VIII metal and zeolite L. The catalyst of the present iiivention is a non-acidic, monofunctional catalyst. j The Group VIII metal of the catalyst of the present invention preferably is a 20 noble metal, such as platinum or palladium. Platinum is particularly preferred. Preferred amounts ofplatinum are 0.1 to 5 wt. %, more preferably 0.1 to3 wi. %, and most preferably 0.3 to 1.5 wt. %, based on zeolite L. In the present application the terms "L zeolite" and "zeolite L" are used synonymously to refer to LTL type zeolite. The zeolite L component of the catalyst is 25 described in published literature, such as U.S. Patent No. 3,216,789. The chemical fomuila for zeolite 1, may be represented as follows: (0.9-1.3) M2/„0 : AI2O3 (5.2-6.9) SiO;: y\hO wherein M designates a cation, n represents the valence of M, and y may be any value from 0 to about 9. Zeolite L, its X-ray diffraction pattern, its properties, and method 30 for its preparation arc described in detail in U.S. Patent No. 3,216,789. Zeolite I, has been charaelerized in "/eolile Molecular Sieves" by Donald W. Dreck, John Wiley and Sons, 1974, (reprinted 1984) as having a framework com^jrising 18 tetrahedra unit J cancrinite-type cages linked by double six rings in columns arid cross-linked by single oxygen bridges to form planar 12-membered rings. The hydnjicarbon sorption pores for zeolite L are reportedly approximately 7A in diameter. The Breck reference and I 5 U.S. Patent No. 3,216,789 are incorporated herein by reference, particularly with respect to their disclosure of zeolite L. \| t The various zeolites are generally defmed in terms of their X-ray diffraction patterns. Several factors have an effect on the X-ray diffraction pattern of a zeolite. Such factors include temperature, pressure, crystal size, impurities and type of cations 10 present. For instance, as the crystal size of the type-L zeolite becomes smaller, the X-ray diffraction pattern becomes somewhat broader and less precise. Thus, the term "zeolite L" includes any of the various zeolites made of cancrinite cages having an X-ray diffraction pattern substantially the same as the X-ray diffraction patterns shown in U.S. Patent No. 3,216,789. Type-L zeolites are conventionally synthesized 15 in the potassium form, that is, in the theoretical formula previously given; most of the M cations are potassium. M cations are exchangeable so that a given ^pe-L zeolite, for example, a type-L zeolite in the potassium form, can be used to obtain type-L zeolites containing other cations by subjecting the type-L zeolite to ion-exchange treatment in an aqueous solution of an appropriate salt or salts. However, it is 20 difficult to exchange all tlie original cations, for example, potassium, since some cations in the zeolite are in sites that are difficult for the reagents to reach. Preferred L zeolites for use in the present invention are those synthesized in the potassium form. Preferably, the potassium form L zeolite is ioii exchanged to replace a portion of the potassium, most preferably with an alkaline earth metal, barium being an especially 25 preferred alkaline earth metal for this purpose as previously stated. The catalysis used in llie process of the present invention are monofunetional catiilysis, meaning that they do not have the acidic function of conventional reforming catalysts. Traditional or conventional reforming catalysts are bifunctional, in that they have an acidic function and a melaHic function. Examples of bifunctional catalysis 30 i[iclii No. 3,415,737 to Kluksdahi; platinum-tin on acidic alumina: and platinum-iridiura with bismuth on an acidic carrier as disclosed in U.S. Patent No. 3,878,089 to Wilhelm (see also the other acidic catalysts containing bism ith, cited above in the Background section). 5 Examples of monofunctional catalysts include platinum on zeolite L, wherein the zeolite L has been ejtchanged with an alkali metal, as disclosed in U.S. Patent No. 4,104,320 to Bernard et al.; platinum on zeolite L, wherein the zeolite L has been exchanged with an alkaline earth melal, as disclosed in U.S. Patent No. 4,6^4,518 to Buss and Hughes; platinum on zeolite L as disclosed in U.S. Patent No. 4,456,527 to 10 Buss, Field and Robinson; and platinum on hatogenated zeolite L as disclosed in the RAULO and IKC patents cited above. According to another embodiment of the present invention, the catalyst is a high temperature reduced or activated (HTR) catalyst. Preferably, the pretreatment process used on the catalyst occurs in the presence 15 of a reducing gas such as hydrogen, as described in U.S. Patent No. 5,382,353 issued January 17,1995,and U.S. Patent application 08/475,821, which are hereby expressly incorporated by reference in their entirety. Generally, the contacting occurs at a pressure of from 0 to 300 psig and a temperature of from 1025"F to i275T for from 1 hour to 120 hours, more preferably for at least 2 hours, and most preferably for at 20 least 4-48 hours. More preferably, the temperature is from 1050"? to 1250°?. In general, the length of time for the pretreatment vnll be somewhat dependent upon the fmat treatment temperature, with the higher the fmal temperature the shorter the treatment time that is needed. For a commercial size plant, it is necessary to limit the moisture content of the 25 environment during the high tcmpemture treatment in order to prevent significant calalyst deactivation. In the temperature range of from 1025°F to 1275""F, the presence of moisture is believed to have a severely detrimental effect on the catalyst activity. It has therefore been found necessary to limit the moisture content of llic environment to as little water as possible during said treatment period, to at least less 30 than 200 ppmv, preferably less than 100 ppmv water. jn one emDoaiinem, in order to limit exposure ot the catalyst to water vapor at high temperatures, it is preferred that the catalyst be reduced initially at a temperature between 300»F and 700"?. After most of the water generated during catalyst reduction has evolved from the catalyst, the temperature is raised slowly in ramping or 5 stepwise fashion to a maximum temperature between 1025T and 1250°?. The temperatuie program and gas flow rates should be selected to limit water vapor levels in the reactor effluent to less than 200 ppmv and, preferably, less than 100 ppmv when the catalyst bed temperature exceeds 1025"?. The rate of temperature increase to the final activation temperature will typically average between 5 and 50"? 10 per hour. Generally, tlie catalyst will be heated at a rate between 10 and 25°F per I hour. It is preferred that the gas flow through the catalyst bed during this process exceed 500 volumes per volume of catalyst per hour, where the gas flow volume is measured at standard conditions of one atmosphere and 60"?. In other words, the gas flow volume is greater than 500 gas hourly space volume (GHSV). GHSVs in excess 15 of 5000 per hour will normally exceed the compressor capacity. GHSVs between 600 and 2000 per hour are most preferred. The pretreatment process occurs prior to contacting the reforming catalyst with a hydrocarbon feed. The large-pore zeolitic catalyst is generally treated in a reducing atmosphere in the temperature range of from 1025"? to 1275°F. Although other 20 reducing gasses can be used, dry hydrogen is preferred as a reducing gas. The hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally ranging from 1% to 99% by volume. More typically, however, the amount of hydrogen in the mixture ranges from about 10 to 50% by volume. 25 In another embodiment, the catalyst can be pretreated using an inert gaseous environment in the lempcraliirc range of from 1025-1275°F, as described in U.S. patent application number 08/450,697, filed May 25, 1995, which is hereby expressly incorporated liy reference in its entirety. The preferred inert gas is nitrogen, for reasons of availability and cost. Oilier 30 inert gases, however, can he used such as helium, argon, and krypton or mi.xlures tlieteof According to on especially preferred embodiment of the present invention, the ni)ti-;icidic. nionofunctional e;itnlyst used in Ihc process of the present invention conliiins a halogen. This may be confusing at first, in that halogens are often nscd lo contribute to Ihc acidity of alumina supports for acidic, bifunctional refomiing 5 catalysts. However, the use of halogens with catalysts based on zeolite L can be made while retaining the non-acidic, monofunctional characteristic of the catalyst. Mctiiods for making non-acidic halogen containing zeolite L based catalysts are disclosed in (he RAULO and IKC references cited above in the Background section. The term "non-acidic" is understood by those skilled in this area of art, 10 particularly by the contrast between nionofunctional (non-acidic) reforming catalysts and bifunctional (acidic) reforming catalysts. One method of achieving non-acidity is by the presence of alkali and/or alkaline earth metals in the zeolite L, and preferably is achieved, along with other enhancement of the catalyst, by exchanging cations such as sodium and/or potassium from the synthesized L zeolite using alkali or alkaline earth 15 metals. Preferred alkali or alkaline earth metals for such exchanging include potassium and barium. The term "non-acidic" also coimotes high selectivity of the catalyst for conversion of aliphatics, especially paraffins, to aromatics, especially benzene, toluene and/or xylenes. High selectivity includes at least 30% selectivity for aromatics 10 formation, preferably 40%, more preferably 50%. Selectivity is the percent of the conversion that goes to aromatics, especially to BTX (Benzene, Toluene, Xylene) aromatics when feeding a Cs to Cg aliphatic feed. Preferred feeds to the process of the present invention are Ce to C9 naphthas. The catalyst of the present invention has an advantage with paraffmic feeds, which 5 nitrmally give poor aromatics yields with conventional bifunctional refonning ciilalysls. However, naphthenic feeds are also readily converted to aromatics over the catalyst of the present invention. More preferably, feeds lo the process of the present invention are C(, to C7 naphthas. The furnace reactor system of Ihc present invention is particularly 0 advantageously applicti to convciling C^ and C^ naphthas to aromatics. I"arlicularly prcfcnod cntafylic rcComiing conditions for the present invcnlinn inclittle, as described iibovc IHICILT Sunimaty of the Invention, an LHSV between 1,5 and C).()"", a hydrogen to hydrocarbon ratio between 0.5 and 2.0, a reactants tcniperaliire between 600°F and 1025°F, and an outlet pres.sure between 35 and 5 75 p.sig. Preferably, the catalyst used in the process of the present invention is bound. Binding the catalyst improves its crush strength, compared to a non-bound catalyst comprising platinum on zeolite L powder. Preferred binders for the catalyst of the present invention are alumina or silica. Silica is especially preferred for the catalyst 10 used in the present invention. Preferred araoimts of binder are from 5 to 90 wt. % of the finished catalyst, more preferably from 10 to 50 wt. %, and still more preferably from 10to30wt. %. As the catalyst may be bound or unbound, the weight percentages given herein are based on the zeolite L component of the catalyst, unless Otherwise indicated. I 15 The term "catalyst" is used herein in a broad sense to include the final catalyst as well as precursors of the final catalyst. Precursors of the final catalyst include, for example, the unbound form of the catalyst and also the catalyst prior to final activation by reduction. The term "catalyst" is thus used to refer to the activated catalyst in some contexts herein, and in other contexts to refer to precursor forms of 20 the catalyst, as will be understood by skilled persons from the context. Also with regard to use of the halogenated fonn of the monofiinctional catalyst in the present invention, the percent halogen in the catalyst is that at Start of Run (SOR). During the course of the run or use of the catalyst, some of the halogen usually is lost from the catalyst, 25 A preferred ciiibodimci^t fvirnace tube reactor system of the present invention refers to a reforniiny system in which non-acidic, highly selective zeolite L based catalyst is contained within a plurality of conventional furnace tubes which are Ihcniselves contained within a furnace. See Figure 1 which shows a schematic tli:i!^rarn of a furnace reactor reforming process. 30 The furnace lubes arc preferably parallel to each other and are preferably \c!lir[i[ly arraniied. Typically, rows of furnace tubes altcrnale with rows of burners. Figure 2 and 3 slow a suitable arrangement for the burners and furnace tubes. I-"if!urc 2 sliinvs a liori/onlal cross sct-tion of the preferred embodiment furnace reactor where the Xs designate burners and the Os designate tubes. Figure 3 shows a longitiidriiai view of the preferred embodiment furnace tube reactor where the burners arc shown impiriging down piirallcl to Ihc tubes. The lubes are preferably 2 to 8 inches in diameter, more preferably 3 to 6 inches in diameter, and most preferably 3 (o 4 inches in diameter, and can be up (o 45 feet long. The furnace tubes are preferably less than or equal to 30 feet long and preferably are at least 10 feet long. The arrangement of the furnace tubes and the burners can vary. Thus the furnace tubes can be positioned vertically, or horizononlally, or m an arbor coil arrangement or in a helical coil arrangement. The burners can likewise be oriented in a number of different ways, for instance at the bottom of the furnace pointing up or at the side of the furnace pointing horizontally. i Preferably the furnace tubes are positioned vertically with the burners pointed down i parallel to the tubes. Furnace reactors can be linked in series or in parallel, but preferably the system is designed so that a single fiimace reactor is used. Replacement of the 3 to 6 I or more conventional refonning reactors and furnace loops in a Pt L zeolite reformer with a single furnace reactor is preferable and is feasible with a Pt L zeolite catalyst having a high activity and a low deactivation rate. We have found that replacement of a multitude of conventional reactors and furnace loops results in greatly reduced investment costs for a Pt L zeolite reformer. In a preferred embodiment, utilizing vertical tubes filled with catalyst, the feed comes in at the top of the tubes. The burners are mounted in the roof of the furnace and fire down into the firebox. The maximum heat flux would then be at the point where feed is coming into the furnace tubes, which is desirable. Alternatively, a inulli-zone furnace can be used. Here the heat flux can be varied more controllalily. I IK- heat flux siippMcd to the reactor inlets is preferably greater than that applied near the reactor outlet. it is desirable Ibat the furnace lube surfaces or the heat exchange surfaces thai i-oul;icl llie hydrocai lions and resulting aroniatics are made of a material having a a-sislance to carlnirization and melal dusting at least as great as that of type 347 stainless steel iiiulcr low sulfur rcfomiing conditions. The resistance to carbiiri/alion and nielai dusting ean he readily detennined using the procedure outlined below in I-xjiniple 4. In a preferred cinbodinicnt of tlie invention, the furnace tube reactors are made of (a) 347 stainless steel or a sleel having a resistance to carbunzation and metal dusting at least as great as 347 stainless steel; or (b) the furnace tubes are treated by a method comprising plating, cladding, painting or coating the surfaces for contacting the feed to provide improved resistance to carbunzation and metal dusting; or (c) the furnace tubes are constructed of or lined with a ceramic material. More preferably the furnace tubes are constructed of a type 300 series steel provided with an intermetallic coating on the surfaces that contact hydrocarbons. In one embodiment of the invention, the fiimace tubes have a metal-containing coating, cladding, plating, or paint applied to at least a portion (preferably at least 50%, more preferably at least 75% and most preferably to all) of the surface area that is to be contacted with hydrocarbons at conversion temperature. After coating, the metal-coated reactor system is preferably heated to produce intermetallic and/or metal carbide layers. A preferred metal-coated reactor system preferably comprises a base construction material (such as a carbon steel, a chromium steel, or a stainless steel) having one or more adherent metallic layers attached thereto. Examples of metallic layers include elemental chromium and iron-tin intemietallic compounds such as FeSnj. As used herein, the term "metal-containing coating" or "coating" is intended to include claddings, platings, paints and other coatings that contain either elemental mclals. metal oxides, organometallic compounds, metal alloys, mixtures of these components and the like. Hie mctal(s) or metal compounds are preferably a key cntiiponent(s) of the coating, Mowable paints that can be sprayed or brushed arc a preferred type of coating. In a preferred embodiment, the coated steel is heat treated to prniluce intermeliillic compounds, thus reacting the coating metal with the steel. F.spccially preferred are mclals that interact with, and preferably react with, tlio liasi- material of the reactor syslcm to produce a continuous and adherent metallic pmtL"ctivc layer al icmpcraliitcs hcloworal the intended hydrocarbon conversion condilions, Metals Ihal nieh hcl()\vor at reforming process conditions are espceially preferred as they can more readily provide complete coverage of the substrate inalcrial. These metals incUidc those selected from among tin, antimony, gcniiaiiiiitn, 5 arsenic, bisnnilli, ahitninnm. gallium, indium, copper, lead, and mixtures, intcrmclallic compounds and alloys thereof. Preferred metal-containing coatings comprise metals selected from the group consisting of tin, antimony, germanium, arsenic, bismuth, akiminum, and mixtures, intermetalUc compounds and alloys of these metals. I-.spccially preferred coatings include tin-, antimony-and germanium-containing 10 coatings. These metals will form continuous and adherent protective layers. Tin coatings are especially preferred ~ they are easy to apply to steel, are inexpeiisive and arc environmentally benign. , I It is preferred that the coatings be sufficiently thick that they completely cover the base metallurgy and that the resulting protective layers remain intact over years of I 15 operation. For example, tin paints may be applied to a (wet) thickness of between I to 6 mils, preferably between about 2 to 4 mils. In general, the thickness after curing is preferably between about 0.1 to 50 mils, more preferably between about 0.5 to 10 mils. Metal-containing coatings can be applied in a variety of ways, which are well I 20 known in the art, such as electroplating, chemical vapor deposition, and sputtering, to name just a few. Preferred methods of applying coatings include paintmg and plating. Where practical, it is preferred that the coating be applied in a paint-like formulation (hereinafter "paint"). Such a paint can be sprayed, brushed, pigged, etc. on reactor .system surfaces. 25 One preferred protective layer is prepared from a metal-containing paint. Pieferably, the paint comprises or produces a reactive metal that interacts witli the slecl. Tin is a preferred inelal and is exemplified herein; disclosures herein about tin arc jienerally applicable to oilier metals such as germanium. Preferred paints comprise a metal component selected from the group consisting of: a hydrogen decomposable 30 niel;i! compound sucli as an nrjianometallic compound, finely divided metal and a riu-l;il oxide, prefeiably a metal oxide that can be reduced at process or furnace tube temperature in a preferred embodiment the cure stop produces a metalic protetive layer bonded to the steel through an intemedizate bonding layer, for example a carbide -ricli bonding layer, as described in U.S. Patent No. 5,674,376, which is incorporated herein by reference in its entirety. This patent also describes useful 5 coatings and paint formulations. Tin protective layers are especially preferred. For example, a tin paint may be used. A preferred paint contains at least four components or their functional equivalents; (i) a hydrogen decomposable tin compound, (ii) a solvent system, (iii) finely divided tin metal and (iv) tin oxide. As the hydrogen decomposable tin 10 compound, organometalHc compounds such as tin octanoate or neodecanoate are particularly useful. Component (iv), the tin oxide is a porous tin-containing compound that can sponge-up the organometallic tin compound, and can be reduced to metallic tin. The paints preferably contain finely divided solids to minimize settling. Finely divided tin metal, component (iii) above, is also added to insure that 15 metallic tin is available to react with the surface to be coated at as low a temperature I as possible. The particle size of the tin is preferably small, for example one to five microns. Tin fomis metallic stannides {e.g., iron stannldes and nickel/iron staimides) when heated under reducing conditions, e.g. in the presence of hydrogen. In one embodiment, there can be used a tin paint containing stannic oxide, tin 20 metal powder, isopropyl alcohol and 20% Tin Ten-Cem (manufactured by Mooney Chemical Inc., Cleveland, Ohio). Twenty percent Tin Ten-Cem contains 20% tin as stannous octanoate in octanoic acid or staimous neodecanoate in neodecanoic acid. When tin paints are applied at appropriate thicknesses, heating under reducing conditions will result in tin migrating to cover small regions (e.g., welds) that were 25 not painted. This will completely coat the base metal. Additional information on the composhion of tin protective layers is disclosed in I I.S. Patent No. 5.406,014 to Ilcyse el al., which is incorporated herein by relVrence. Here it is taught that a double layer is formed when tin is coated on a clironiium-rich, nickel-containing steel. Both an inner chromium-rich layer and an 30 outer slannidc layer arc produced. The outer layer contains nickel stannides. When a tin paint was applied In a "SM type stainless steel and heated at about 1200 °V, there resulted a chromium-rich steel layer containing about 17% chromium and substantially no nickel, comparable to 430 grade stainless steel. Tin/iron paints are also useliil in the present invention. A preferred tin/iron paint will contain various tin compounds to which iron has been added in amounts up 5 to one third Fe/Sn by weight. The addition of iron can, for example, be in the form of Fe2O3. The addition of iron to a tin containing paint should afford noteworthy advantages; in particular: (i) it should facilitate the reaction; of the paint to fonn iron ■ - " " I stannides thereby acting as a flux; (ii) it should dilute the nickel concentration in the stannide layer thereby providing a coating having better protection against coking; and 10 (iii) it should result in a paint that affbrds the anti-coking protection of iron stannides J I even if the underlying surface does not react well. I Some of the coatings, such as the tin paint described above, are preferably cured, for example, by heat treatment. Cure conditions depend on the particular metal coating and curing conditions that are selected so as to produce an adherent protective 15 layer. Gas flow rates and contacting time depend on the cure; temperature used, the coating metal and the specific components of the coating composition. The coated materials are preferably cured in the absence of oxygen. If they are not already in the metallic state, they are preferably cured inja reducing aUnosphere, preferably a hydrogen-containing atmosphere, at elevated temperatures. Cure 20 conditions depend on the coating metal and are selected so they produce a continuous and uninterrupted protective layer that adheres to the steel substrate. The resulting protective layer is able to withstand repeated temperature cycling, and does not degrade in the reaction environment. Preferred protective layers are also useful in reactor systems that are subjected to oxidizing environments, such as those associated 25 with coke bum-off. In general, the contacting of the reactor system having a metal-conlairiing coaling, plating, cladding, paint or other coating applied to a portion thereof with hydrogen is done for a time and at a temperature sufficient to produce a metallic protective layer. These conditions may be readily determined. For example, coaled 30 compons may be heated in the prescnce of hydrogen in a simple test apparains; the formation of thc proleclive later may he determined using petrographic analysis. It is preferred thai cure conditions result in a protective layer that is firmly j hoiidcil to the slecl. This may be accomplished, for exampl^, by curing the applied coating at elevated temperatures. Metal or metal compounds contained in the paint, I plating, cladding or other coating are preferably cured under conditions effective to 5 produce molten metals and/or compounds. Thus, germanium and antimony paints are preferably cured between 1 OOO^F and 1400°F. Tin paints are preferably cured t between 900""F and 11OOT. Curing is preferably done over a period of hours, often with temperatures increasing over time. The presence of hydrogen is especially advantageous when the paint contains reducible oxides and/or oxygen-containing 10 organometallic compounds. As an example of a suitable paint cure for a tin paint, the system including painted portions can be pressurized with flowing nitrogen, followed by the addition of a hydrogen-containing stream. The reactor inlet temperature can be raised to 800°F at a rate of SO-lOO^F/hr. Thereafter the temperature can be raised to a level of 950- 15 975F at a rate of 50°F/lir, and held within that range for about 48 hours. Tlie Furnace Tube Construction Material There are a wide variety of base construction materials that can be used in the furnace tubes or the heat exchange surfaces. If the tubes/surfaces are to be protected 20 with a metallic coating, then a wide range of steels nuiy be used. In general, steels are chosen so that they meet the strength and flexibility requirements for the catalytic reforming process. These requirements are well known in the art and depend on process conditions, such as operating temperatures and pressures. Useful steels include carbon steel; low alloy steels such as 1.25, 2.5, 5, 7, and 25 "^ climine steel; 300 scries stainless steels including 304, 316 and 346; heat rcsistnni siLTls including nK-40 and nP-50, as well as treated steels such as aluminizcd or cliroinized steels, i"rcfcrrcd slccls include the 300 series stainless steels and licat rcsi.slanl slccls. 30 [H"t"l or flake. For cxiiinplc, nii."l;illic tin, germanium and antimony (whether applied ciircclly as a plating or cladtiinji or produced in-situ) readily react with steel at cicviiled lernperatures lo form a bomlint; layer as is described in U.S. Patent No. 5,406.014 or \V() ")4/15896, both Ir) llcysc ct al, The "014 patent is incorporated herein by 5 rcli"ienec in its entirely. If Ihe lubes/surfaces are not to be protected with a metallic coating, they can be protected against carburi?:ali()n and metal dusting with a ceramic coating. These types of coalings are wcU known in the art. See US Pat. 4,161,510, The furnace tube reactors may also be constructed of uncoated steels, so long 10 as the steels have a resistance to carburization and metal dusting at least as great as 347 stainless steel under low sulfur reforming conditions. See Example 4 below. Useful steels include the 300 series stainless steels including type 304, 316 and 347 stainless steels; heal resistant steels including HK-40 and HP-50, as well as treated steels such as aluminized or cliromized steels. 15 As stated earlier, I have also found that in the process of the present invention high space velocities are advantageously used. Relatively high space velocities allow lower total tube volume to be used. Lower space rates conversely require more tube volume to contain the appropriate (desired) amount of catalyst and thus may be less desirable, particularly if the total fumace size must be significantly larger to 20 accommodate the increased volume of tubes. The diameter and length of the fumace tubes can be varied so that a desired pressure drop and heat flux across the tubes is attained. The length and diameter of the fumace tubes, and the location and number of burners, allow for regulation of the skin temperature of the fumace tubes as well as the radial and axial temperature 25 pruilleofthe furnace tubes. Tlicse parameters can be designed to allow for appropriate conversion of particular feeds. However, the concept of the present invention requires that the furnace be basically conventional. Accordingly, the size of llic fnmace tubes will be at least two inches in inside diameter, more preferably at Irasi ihrcc inches in inside diatnclcr. Also, the fumace will be heated by convcnlioiial 30 Micajis. such as by gas or oil llicd Inimcrs. The pressure drop across tlie length of the furnace tubes preferably is less llinn or ec[iial to 70 psi, more preferably less than 60 psi, most preferably less than 50 psi. The outlet pressure is preferably between 25 and 100 psig, more preferably between 35 and 75 psig, and most preferably between 40 and 50 psig. The outlet pressure is 5 the reaction mixture pressure at the outlet of the iumace tubes, that is, as the tulies and eonlained reaction mixture cnmc out of the furnace. To obtain a more complete understanding of the present invention, the following examples illustrating certain aspects of the invention are set forth. It should be understood, however, that the invention is not intended to be limited in any way to 10 the specific details of the examples. EXAMPLES Example 1 This example compares a conventional adiabatic multi-stage reactor system to 15 the externally heated fiimace tube reactor of the present invention. The catalyst used in this comparison is platinum on halogenated zeolite L as disclosed in the RAULO and IKC patents cited earlier. The total volume of catalyst in the two systems is the same. The same light naphtha is used as feed to both reactor systems. The light naphtha feed contained 2 percent Cj"s, 90 percent Ce"s (primarily paraffins but also 20 minor amounts of naphthenes), and 8 percent by volume Cy"s. The conditions and parameters in the example have been adjusted to give the same total run length for the two systems in the comparison This example shows that, in accordance with the concept of the present invention, a single externally heated conventional furnace can effectively replace a 5 six-reactor multi-stage reactor system with catalyst disposed in the tubes of the furnace. The present invention also provides a substantially increased aromatics yield. The increase in yield results in more aromatics produced during the run. Alternatively the furnace tube reactor can be operated at lower severity allowing a much lower licnctivation rale for a given yield thus allowing a run length of substantially longer 10 (h;iii a year. Wc have al.sn found Ihe this result can be accomplished in the furnace liibi? reactor sysloin of the present invention at a lower peak catalyst temperature viTsiis the use of niuhi-.stage adiaKitic reactors with conventional furnaces preccclinj", each ofthe reaclur stages. This example i-(inip:iR"s n coiivcniional adiabalic mulli-slage reactor system in lliL- liirnacc luhc reactor system ofllie present invention. The catalyst used in this eoiiiparison is plaliniim on lialogenatcd zeolite L, as disclosed in the RAULO and IKC 5 jviliTils cited earlier. The diameter oftiihes in lliis example in the furnace tube reactor is latger (ban iu ibe first example and tUc total volume of catalyst is twice as much as t in tbc first example. The total volume of catalyst in the two compared systems is the same (1170 cubic feet). The same light naphtha is used as feed to both reactor systems. The conditions and parameters in the example have been adjusted to give (lie 10 same total nin length foi the two systems in the comparison. The feed rate of the two systems is also the same. I I I bis example shows that fur a lower activity catalyst, at a lower space velocity than ITi llie previous example, in acenrdaiice with the concept oflhe present invention, a sini"le furnace reaclcir with catalv.st disposed in the tubes oflhc furnace can cni-cli\cl> replace a six-rcacl(ir tmilti-sliigc rcaclnr system. This example also shows thnl IIICR- is a siihslantially heller arniiirilics yield using the Furnace reactor. The increase in yield results in more aromatics proLiuccd during the run. Alternatively the furnace luhc rcaclnr can be operated al lower severity allowing a much lower deactivation rate for a 5 given yield tlius allowing a rnn Icnglli of substantially longer than a year. Example 3 In the following example, a high temperature reduced catalyst is used in an externally heated furnace tube reactor and compared to use of the same HTR catalyst 10 in an adiabatic multi-stage reactor system. This example illustrates that a six-reactor multi-stage reactor system can be cflVvlively replaced by a system in accord with the present invention wlicrein catalyst 15 is disposed in the lubes of a conventional single externally heated furnace. Tiic ciil;ilyst used in this example is a high temperature reduced catalyst comprising Pi on I. /colile. riiis o.xarnplc also illiislrates thai the system of the present invention proxides an increa.sed arotnalics yield. This result is accomplished at a lower peak / -29- CMliilyst tcmpemliirc in Ilic cxk-ni;)I)y Jicatcd furnace tube rt-aclor syslcjii [bm in ihc s\"sk"Tn comprisiiij! scvcnil ruriiaccs iuid separate reactors in series. Bxample 4 5 "I"ll (Iclcnninc liic resislance of various substrates to coking, carburizatioii and inclnl dusting under ultra low sulfur rcfoniiing conditions, the following test can he nin. The test makes it especially easy to do side by side comparisons, for example comparisons with type 347 stainless steel. Tlie test uses a Lindbcrg quartz tube furnace with temperatures controlled lo 10 within one degree with a thermocouple placed on the exterior of the tube in the heated zone. The furnace tube had an Internal diameter of 5/8 inches. Several preliminary lest runs are conducted at an applied temperature of nOO^F using a thermocouple suspended within the hot zone of the tube. The internal thermocouple constantly measured up to 10°F lower than the external thermocouple. 15 Samples of steels and other construction materials are then tested at 1100°F, 11 SOT and 1200""F for 24 hr, and at HOOT for 90 br, under conditions that simulate the exposure of the materials under conditions of low-sulfur reforming. The samples of various materials should be clean and free of scale, grease or tarnish. Compared samples should be equally smooth. The samples are placed in an open quartz boat 20 within the hot zone of the flimace tube. The boats are 1 by !4 inch and fit well within the two-inch hot zone of the tube. The boats are attached to silica glass rods for easy placement and removal. No internal thermocouple is used when the boats are placed inside the tube. Prior to start-up, the test materials are cut to a size and shape suitable for 25 ready-visual identification. After any pretreatment, such as roasting, the samples are weighed. Most samples weigh less than 300 mg. Typically, each run is conducted with three to five samples in a boat. A sample of 347 stainless steel is pref;cnl in e;ich iiiii as an internal .standard. After the samples arc placed, the lube is flushed with sulfur-frcc nitrogen for a 30 \"c\\ tniniitcs. A (."nhuri/.ing [las ofa commercially bottled mixture of 7% proparie in livdnigen is bubbled llirnufli a liter flask of high purity toluene at room teInpor."lIll^^• in onk"r entrain iilioiil !"% (nliiciK" in Ihc feed gas mix. This carbiirizing gas conUiin"; less lli;in 10 ppl) sulfur, (i;is flows of 25 to 30 cc/niin., and atmospheric pressure, are Tuiiinlaincd in Ihe apparatus. Tlio samples are brought to operating temperatures ri(;! nilL-ofaboul 100"l7niin. • After exposing the materials to the carburizing gas for the desired time and tcniperatiire, Ihe apparatus is quenched with an air stream applied to the exterior of the t tube. When the apparatus is sufficiently cool, the hydrocarbon gas is swept out willi niirogen and the boat is removed for inspection and analysis. After completion of each run, the condition of the boat and cacii material is carefully noted. Typically the boat is photographed. Then, each material and its associated coke and dust is weighed to determine changes. Care is taken to keep any coke deposits with the appropriate substrate material. The samples are then mounted in an epoxy resin, ground and polished in preparation for petrographic and scanning electron microscopy analysis. The degree of surface corrosion is determined; this indicates the metal dusting and carbunzation response of each material. In general, a qualitative visual analysis of metal reactivities is readily made. The residence time of the carburizing gas used in these tests is considerably higher than in typical commercial operation. Thus, it is believed that the test conditions may be more severe than commercial conditions. Nevertheless, the test provides a reliable indication of the relative resistance of the materials to carbunzation and metal dusting. Example 5 -- Preparing Tin-Coated Steel Pieces of 321 SS were coated with a tin-containing paint. The paint consisted of-.i mixture of 2 parts powdered tin oxide, 2 parts finely powdered tin (I-5 microns), 1 part stannous iicodccanoalc in ncodecanoic acid (20% Tin Tem-Cem manufactured by Mooney Chemical Inc., Cleveland, Ohio which contained 20% tin as stannous nendccanoatc) mixed with isopropanol, as described in US 5.674,376. Ihe coating was applied lo !hc steel surf;iee by painting and letting the paint dry in air. After dryitig, the painted steel was eontaclcd with flowing hydrogen gas at 1 lOOT fur 24 hours. Example 6 -- Analysis of Steel Samples of coated and preferably heat cured steels were mounted in a clear epoxy resin and then ground and polished in preparation for analysts with the petrographic and scanning electron microscopes (SEM). Coupons were analyzed i before and after refonning conditions. EDX analysis can be used to determine the chemical composition of the layers. For example, tin intermetallic layers may be analyzed for iron, nickel and tin. Example 7 Determination of the Deactivation Rate of a Catalyst Deactivation rate of a catalyst sample as used in the present invention can be ktemiined in an isothermal pilot plant or similar unit under the following standard :()tiditions using a standard feed. The feed to the unit slioiild be a C6-C7 UDEX raffinate from a convcntion.il efnnner. Tlie UDEX raf(in:i{c feed should have the following composition as neasured by G:is ("hr()m:il 11 \vt%, and a (otnl CR content oflcss than 6 wl %. The feed should contain less linn 10 ppbof snll"tir;itid less than 3 ppm of wnlcr. The pilot plant sbtnild ;ilso he Vii-i- of any other possible source of sufur contamination. care must be taken to avoid sulfare contamination of the sytem and to avoid using a previously sulfar onliiminnled sysk-rn. Two pa(t*nts that (each how to clean-up a sulfur conlaminated system arc II. S. Palcnts 5.0."t5.7Q2 and 4,940,532 both of which are herein iiicorporalcd by reference. Tho MI.SV of the unit should be set at 4 (1/lir) with a sy."Jlem pressure of 85 psig . IIic hydrogeii/liydrocarbon mole ratio of the system should be 2. The pilot plant unit should be operated at a temperature sufTicient to maintain the aromntics in the reactor effluent at 50 wt %. The temperature is increased lo maintain the 50 wt % aromatics and the results plotted over a 8 week period (1344 hours) of continuous stable operation under said conditions. The fouling rate can be determined for the period of stable operation by dividing the change in temperature over the period by the number of hours. I WE CLAIM: 1. A process for catalytic reforming of feed hydrocarbons to form aromatic hydrocarbons comprising: passing feed hydrocarbons over a non-acidic catalyst comprising a Group VIII metal and zeolite L disposed within a furnace under catalytic reforming conditions; wherein said furnace comprises one or more first chambers and one or more second adjoining chambers separated by a heat exchange surface; wherein said catalyst is located within said first chamber and one or more gas or oil burners are located within said second chamber; and wherein catalytic reforming conditions comprise a temperature of between 600°F and 1025°F, a pressure of between 35 and 75 psig, and a hydrogen to hydrocarbon mole ratio of between 0.5 and 3.0. 2. The process as claimed in claim 1, wherein the first chamber comprises the tubes of a furnace; wherein the heat exchange surface comprises the wall of the tubes; and wherein the furnace tubes are from 2 to 8 inches in inside diameter. 3. The process as claimed in claim 1, wherein the catalyst is no more than 4 inches from the heat exchange surface and at least a portion of said catalyst is more than one inch from said heat exchange surface. 4. The process as claimed in claim 1, wherein the catalyst under said reforming conditions has a deactivation rate of less than 0.04°F per hour. 35 5. The process as claimed in claim 2, wherein the furnace tubes are 3 to 6 inches in diameter. 6. The process as claimed in claim 1, wherein the catalyst is no more than 3 inches from the heat exchange surface and at least a portion of said catalyst is more than 1.5 inches from said heat exchange surface. 7. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV of 1.0 to 7. 8. The process as claimed in claim 1, wherein the Group VIII metal is platinum. 9. The process as claimed in claim 1, wherein the catalyst is produced by steps comprising treatment in a gaseous environment in a temperature range between 1025°F and 1275°F while maintaining the water level in the effluent gas below 1000 ppm. 10. The process as claimed in claim 9, wherein the water level is below 200 ppm. 11. The process as claimed in claim 1, wherein the catalyst contains at least one halogen in an amount between 0.1 and 2.0 wt. % based on zeolite L. 12. The process as claimed in claim 11, wherein the halogens are fluorine and chlorine and are present on the catalyst in an amount between 0.1 and 1.0 wt. % fluorine and 0.1 and 1.0 wt. % chlorine at the start of run. 13. The process as claimed in claim 1, wherein the feed hydrocarbon contains less than 50 ppb sulfur. 14. The process as claimed in claim 1, wherein the feed hydrocarbon contains less than 10 ppb sulfur. 15. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV between 3 and 5, a hydrogen to hydrocarbon ratio between 1 and 1.5, a furnace tube interior temperature between 600""F and 960°F at the inlet and between 860°F and 1025°F at the outlet at SOR and between 600°F and 1025°F at the inlet and between 920""F and lOas^F at the outlet at FOR, and an outlet pressure of between 35 and 75 psig. 16. The process as claimed in claim 2, wherein said furnace tubes are made of a material having a resistance to carburization and metal dusting under low sulfur reforming conditions at least as great as that of type 347 stainless steel. 17. The process as claimed in claim 2, wherein said furnace tubes are made of type 347 stainless steel. 18. The process as claimed in claim 2, wherein said furnace tubes have been treated by a method comprising plating, cladding, painting or coating the furnace 37 tube surfaces for contacting the feed hydrocarbon to provide improved resistance to carburization and metal dusting. 19. The process as claimed in claim 2, wherein said furnace tubes are constructed of or lined with a ceramic material. 20. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV between 3 and 5, and a hydrogen to hydrocarbon ratio between 1.0 and 1.5. 21. The process as claimed in claim 1, wherein the catalyst under said reforming conditions has a deactivation rate of less than 0.03°F per hour. 22. The process as claimed in claim 1, wherein the deactivation rate is less than 0.02°F per hour. 23. The process as claimed in claim 1, wherein the deactivation rate is less than O.OPF per hour.

Full Text

dcaclivation or foiiling rale luul liigh aromalics yield. More particularly, the prcscnl invention pertains lo use of such catalyst in a gas or oil fired furnace.
BACKGROUND OF THE INVENTION
15 Reforming embraces several reactions, such as dehydrogenation,
isoraerization, dehydroisomerization, cycUzation and dehydrocyclization. In tlie process of the present invention, aromatics are formed from the feed hydrocarbons to the reforming reaction zone, and dehydrocyclization is the most important reaction. U.S. Patent No. 4,104,320 to Bernard and Nuiy discloses that it is possible to 20 dehydrocyclize paraffins to produce aromatics with high selectivity using a
monofunctional non-acidic type-zeolite L catalyst. The zeolite L based catalyst in "320 has exchangeable cations of which at least 90% are sodium, lithium, potassium, rubidium or cesium, and contains at least one Group VIII noble metal (or tin or germanium). In particular, catalysts having platinum on potassium form L-zeolite 25 exchanged with a rubidium or cesium salt were claimed by Bernard and Nury to achieve exceptionnlly high selectivity for n-hexane conversion to benzene. As cii"^clnscd in tlie Bernard and Nury patent, the zeolite L is tjpically synthesized in llic p(i|;issium form, A |>orlion, tisiinlly not more than 80%, of Ihc potassium ci.tions can he cNcliangcd sn llinl olhor cafinns replace the exchangeable potassium.

Ti i.i"rrr";[HiiKiing ;ilk:)li I-XL-II;III|IC(I l,-/C(ililc cnlalysts disclosed in U.S. Patent No. 1.104.,120.
"Ihcsc high Sflcclivity cnlnlysts of ncrnard and Nury, and of Buss and IlLighc;.
nri," ;i)l "non-acidic" nnd are rflcrred to as "nionofunctional catalysts". These catalysis
iivc liii.:hly selective for foriiiinjt nromatics via dehydrocyclization of paraffins.
10 Having discovered a highly selective catalyst, commercialization seemed
promising. Unfortunately, (bat was not the case, because the high selectivity,
I.-zcolite catalysts did not aciiieve long enough run length to make them feasible for
use in catalytic reforming, U.S. Patent No. 4,456,527 discloses the surprising finding
that if the sulfur content of the feed was reduced to ultra low levels, below levels used
15 in the past for catalysts especially sensitive to sulfur, that then long run lengths could
be achieved with the L-zeolite non-acidic catalyst. Specifically, it was found that the
concciilration of sulfur in the hydrocarbon feed to the L-zeolite catalyst should beat
ultra low levels, preferably less than 100 parts per billion (ppb), more preferably less
than 50 ppb, to achieve improved stability/activity for the catalyst used.
20 It was also found that zeolite L reforming catalysts are surprisingly sensitive to
the presence of water, particularly while under reaction conditions. Water has been
found to greatly accelerate the rate of deactivation of these catalysts. U.S. Patent No.
4,830,732, which is herein incorporated by reference discloses the surprising
scrisilivity of zeolite 1. catalysis to water and ways to mitigate the problem.
?5 \ I.S. Patent Ni.. 5,3 I"l ;il..which arc herein incorporated by reference, discloSe a zeolite L based refortninii
(■:H;iI\".| wherein the enlaly.";! is Irealed at high temperature and low water content Id
lb" tib\" improve llie shibilily nflhe cataly.sl, that is, to lower the deactivation rale ol
tit!- i-.il."iK-st unticr reiiuiiiinj; roii"litions,
.""() During c(>ninuT(i;ili.-;ilinn df/cdlile I- reforming catalysis, it was foniHl lb:il
llii- tiHi.i lew ,";iiiriir lr\i-K e:iii";i"J Itie iincxpeeled problem ol"coking, carbiiii/nlini) luui

clal dusting of llic reactor system metallurgy. This problem has necessitated the use special sleds and/or steels having protective layers to prevent coking, carburizatioii id metal dusting. When used, protective layers are provided on the steel surfaces at are to be contacted with hydrocarbons at process temperatures, e.g., at mperalures bcfwcen about 800- [ I SO°F. For example, a tin protective layer has been L"d in the reactors and furnace tubes of a catalytic reformer operated at ultra low Ifiir levels. This has effectively reduced the rate of coke formation exterior to the talyst particles in the reactors. Without this protection, coke buildup would have suhed in massive coke-plugging and in reactor system shutdowns. These problems z described in detail in Heyse ei al., US 5,674,376. Heyse et al, disclose the use of ccial steels and protective coatings, including tin coatings, to prevent carburizatlon d mcial dusting. In a preferred embodiment, Heyse et al., teach applying a tin paint a steel portion of a reactor system and heating in hydrogen to produce a rburization-resistant intermetalUc layer containing iron and nickel stannides. The forming system of Heyse et al., is a high temperature, low sulfur and low water stem that uses a conventional reformer designs, i.e., furnaces for heating the feed d catalysts located in conventiona] reactors.
Recently, several patents and patent applications of RAULO (Research isociation for Utilization of Light Oil) and Idemitsu Kosan Co. have been published lating to use of halogen in zeolite L based monofiinctional reforming catalysts, ich halogen containing monofunctional catalysts have been reported to have iprovcd stability (catalyst life) when used in catalytic reforming, particularly in forming feedstocks boiling above C7 hydrocarbons in addition to C6 and C7 dmcarbons. In ih"is regard, sec HP 201 ,S56A; EP 498,182A; U.S. Patent 1, "1.681,865; ami U.S. Patent No. 5,091,351.
EP 403,976 In Yoncda cl al., and assigned to RAULO, discloses the use of 11)1 ine treated zeolite L based catalysts in small diameter tubes of about one-inch iidc diameter (22-2 mm to 28 mm in the examples). Heating medium proposed for .■ ■^itKill tubes were inollen metal or molten salt so as to maintain precise control of .■ |i-ni|icralurc of the lubes. Accordingly, EP 403,976 docs not teach the use of a ii\ cnUniial type Inrnacc or convcnlional type furnace tubes. Conventiona! Iiiniaces

I"[- cjilalylic rcfon. have tubes nriisually lliree or more increasxe in inside clianu-U-i-il(^ mm or more), wlu-icas VV AO"\}>l(i leaches that using tubes having an inside tharneler greater lb;m 50 mm is undesirable. Also, conventional furnaces arc hcjled usinj; gas or oil Hrcd hurncrs.
5 Typical catalylic reforming processes employ a series ofconvenlional furnafcs
io ht-at (he naplidia fcctfsfock hernre each reforming reactor stage, as the reforming reaction is endoihcmiic. Thus, in a three-stage reforming process, the overall rt"lorming unit would comprise a first furnace followed by a first-stage reactor vessel containing the reforming catalyst (over which catalyst the endothermic reforming 3 reaction occurs); a second furnace followed by a second-stage reactor containing
refonning catalyst over which the reforming reaction is further progressed; and a third fiimace followed by a third-stage reactor with catalyst to fiirther progress the reforming reaction conversion levels.
For example, U.S. Patent No. 4,155,835 to Autal ilJustrates a three-stage > reforming process, with three furnaces (30,44, 52) and three reforming reactors (40, 48, 56) shown in the drawing in Antal. Example reforming reactors used according to the prior art are shown, for instance, in U.S. Patent No. 5,211,837 to Russet al., particularly the radial flow reactor shown in Figure 2 of Russ et al.
hi some catalytic reforming units, as many as five or six stages of furnaces I followed by reactors are used in series for the catalytic reforming unit. In particular, reforming of hydrocarbons over a Pt L zeolite catalyst is a highly endothermic reaction and can require as many as 5 or 6 stages or more of ftimaces followed by reactors. The present invention allows such a multistage process to be greatly simplified to two, or more preferably one, furnace reactor.
I
SUMMARY OF THE INVENTION
According to a preferred embodiment of the present invention, a process for catalytic reforming of feed hydrocarbons is provided. The process comprises passing hydrocarbons over a catalyst comprising a Group VIII metal and a large pore /cotitc clisposcii \silhin a funiacc, wlicrein said furnace comprises a first chamber and a second adjuinini! chamber separated by a heat exchange surface, wherein said

catalyst is localci) \vil])i;i .s;iii) first chamber and one or more burners are located wilhiti said secoiul clinmbcr. Preferably, the catalyst is no more than 4 inches rroni the heal excliaiige surface and at least a portion of the catalyst is more than one inch from Ihc heat exchange surface.
A preferred enihodimcni of the process comprises contacting the feed, under catalytic rcforitiine conditions, with catalyst disposed in the tubes of a furnace, wherein the catalyst is a monofiinctional, non-acidic catalyst and comprises a Group VlII melal and zeolite L, and wherein the furnace tubes are from 2 to 8 inches in inside diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes.
In a preferred embodiment of the present invention, the furnace can be basically a conventional type furnace, except that catalyst is disposed in the tubes of the furnace and the reactor metallurgy is constructed to avoid carburization and metal dusting problems caused by the low sulfur environment. The furnace is heated by conventional means for naphtha reforming units, such as by gas burners or oil burners. Also, in the present invention, the size of the tubes is conventional, in the range 2 to 8 inches, preferably 3 to 6 inches, more preferably 3 to 4 inches, in inside diameter. Mono functional zeolite L based catalyst is contained inside the tubes of the conventional furnace in accordance with a particularly preferred embodiment of the present invention.
In a particularly preferred embodiment, the furnace tubes are made of a material having a resistance to carburization and metal dusting under low sulfiir reforming conditions at least as great as that of type 347 stainless steel. The furnace tubes can be:
(a) made of type 347 stainless steel or a steel having a resistance to carburization and metal dusting at least as great as type 347 stainless steel; or
(b) treated liy a method comprising plating, cladding, painting or coating (fit- furnace tube surfaces for contacling the feed to provide improved resistance to earhnii/ation and niclal dusting; or
(c) ctiiislniclcd of, or liricd with, a ceramic material.

Among Dlhci- factors, (lie present iiivenlion is based on my conccplioii nm] unexpeted lliuiirii; lh:U. iisitif; llic cnlalysls defined herein, particularly non-acitlie. monorunclional Inrf.e pnrc /eolile based reforming catalyst, the conventional anangcmcnl of fiiniaccs and multi-stage reforming reactors can be coalesced into one or iiuire stages of conventional furnaces, eliminating the refonner reactor vessels downstream of the furnace. In one embodiment of the present invention, the defined monofunctional reforming catalyst is disposed in the tubes of a conventional furnace. A jircferred embodiment of the present invention is also based on my finding that a conventional multi-stage furnaces/reactors reforming arrangement (consisting of, for example, three to six, or as many as nine stages of ilimaces and reactors) can be replaced by as few as one basically conventional furnace containing monofiinctional zeolite L reforming catalyst in the tubes of the furnace. The present invention is also based on my discovery that zeolite catalysts of improved stability (i.e. having a deactivation rate of less than 0.04 degrees F per hour at reforming conditions) can be effectively and economically used in a furnace reactor for caalytic reforming. The improved stability of these catalysts further allows them to be used at operating
conditions that enable long run lengths without frequent or continuous catalyst
I I
regeneration. My invention allows for simplified processing schemes and significantly less capital equipment than conventional catalytic reforming systems.
In an alternative embodiment of the present invention the furnace may be constructed such that the burners arc located within tubes located in the fiirnace and the catalyst located in the area surrounding the lubes. The catalyst containing area may be a single chamber or a multitude of chambers. In such an arrangement it has been found that no portion of the catalyst should be more than 4 inches from the lube surface for heat flux reasons. Catalyst that is more than 4 inches from the heated surface may not he effective at dehydrocyclization of the hydrocarbons due "»"> llic hil"hiy cndothermic nature of the dehydrocyclization reactions and the heat flux dc[iL"ndcnce on the distance frcMu the burner tube or heat exchange surface. More ptffcrably the catalyst should he [lo more than 3 inches from a burner tube surface. Slii! more preferably the catalyst should be no more than 2 inches from a burner tiihe Mirfaic. it has also been foiiiid thai (licre is preferably one or more inches of catalyst

- / -
packed around llic Imrncr tubed and more preferably 1.5 or more inches catalyst
pafkcd around llic hiiiricr Inhc siirracc. Tliis reduces the amount of heat cxchantie
sill faff in tJte f\irnai:c rejiclor and helps to minimize the number offumacc reactors
rctiuired for rcforniin[;.
5 In still another embiniimenl of (lie present invention the furnace reactor
conipiises two or more chaniiiers. One or more chambers contain burners. One or more adjoinine chambers coiilain the catalyst. The burner chamber(s) and (he adjoining catalyst chambcr(s) are separated by a surface effective to provide heat exchange. This surface between the burner chamber(s) and tlie catalyst chambers is 10 herein referred to as the heat exchange surface. The chambers may have a variety of shapes. It is important however that catalyst should preferably be no more than 4 inches from a heat exchange surface for heat flux reasons. Catalyst that is more than
the preferred distance &om the heated surface may not be effective at
i
dehydrocyclization of the hydrocarbons due to the highly endothermic nature of the
15 dehydrocyclization reactions and the heat flux dependence on the distance from the heat exchange surface. Thus catalyst that is more than 4 inches from the heat exchange surface may be effectively wasted. When I state that the catalyst is no more than an effective distance &om the heat exchange surface to avoid wasting the catalyst it is meant that at least 80 % of the catalyst be within that distance from the heat
20 exchange surface, preferably at least 85 % of the catalyst, more preferably at least 90 %, still more preferably at least 95 %, and most preferably essentially all of the catalyst is whithin the stated distance from the heal exchange surface. As stated above 1 have found that for the catalyst of the present invention, the catalyst should preferably be no more than 4 inches from the heat exchange surface. More preferably
25 the catalyst should be no more than 3 inches from the heat exchange surface. Still more preferably the catalyst should be no more than 2 inches from the heat exchanj;c surface. It has also been found lliat there is preferably more than one, and more preferably 1.5 or more, inches ofcalalyst packed around the heat exchange surface. Tills reduces the amount of lie;il exchange surface in the furnace reactor and helps to
30 (nininiize (fic miiuhcr of rimvAce reactors required for refornjing.

AsKtalcc! in the background. U.S. Patent No. 4,155,8:^5 illustrates the ii,si.Mira
lliR-c-Atagc rcforniin)! unit ccrnprisiTii; llirec conventional furnaces, and three
relinming reactor vessels fonlnining catalyst, with one reactor being located
downs (ream of each of the three furnaces. In contrast, the present invention coalesces
5 01- collapses the furnaces and separate leactors into one or more furnace lubes reactor
sjstLMii. without the separalc renelor vessels. According to the present invention,
t preferably, the system is only one furnace tube reactor, that is, coalescence to one
furnace.
I have found that the present invention is particularly advantageously carried
10 out at relatively low hydrogen to hydrocarbon feed mole ratios of 0.5 to 3.0, preferably
0.5 to 2.0, more preferably 1.0 to 2.0, most preferably 1.0 to 1.5, on a molar basis,
I have also found that in the process of the present invention high space
velocities can be used. Preferred space velocities are from 1.0 to 7.0 volimies of feed
per hour per volume of catalyst, more preferably 1.5 to 6 hour"", and still more
15 preferably 3 to 5 hour"".
The relatively low hydrogen to hydrocarbon feed mole ratio and the high space
velocities when using the present invention make it feasible to use less total catalyst
and at a lower overall gas flow rate. These benefits in turn allow the use of a furnace
reactor with a reasonable number of tubes. j
20 Preferably, the Group VIII metals used in the catalyst disposed in the furnace
i
lubes comprises platinum, palladium, iridium, and other Group VHI metals. Platinum is most preferred as the Group VIII metal in the catalyst used in the present invention.
Also, preferred catalysts for use in the present invention are non-acidic zcolilc L catalysts, wherein exchangeable ions from the zeolite L, such as sodium
25 and/or potassium, luivc been exchanged with alkali or alkaline earth metals. A p;ir(icularly preferred catalyst is I"t Ba L zeolite, wherein the zeolite L has been cxi-lianged using a baiium containing solution. These catalysts are described in more tlctail in the Buss and Hughes references cited above in the Background section, which references arc incorporated herein by reference, particularly as to description of
30 I"t l./cniitccalalysl.

Accordifty to .-(ftoliKT pa-lcncd cnihodiment of the present invcniion, the
/I"lilik-1, Ixiscii c;il;ily":l is [inKiiiceit hy Ircatincnl in a gaseous environment in a
Icitiperadire range hclvvccn 1025""I" and nVS^F while maintaining the water level in
lift" diluent gas hc}aw i(H/O ppni. /"rcfcrably, (lie high temperature treatment is
5 earriod oul at a water level in (lie cflUient gas below 200 ppm. Preferred high
tern|ieratnrc treated catalysts arc described in the Mulaskey ct al. patents cited above
in llic Background section, w]iich references are incorporated by reference herein,
particularly as to description ofhigh temperature treated Pt L zeolite catalysts.
According to another preferred embodiment of the present invention, the
10 zeolite L based catalyst contains at least one halogen in an amoimt between O.J and
I 2.0 wt. % based on zeolite L. Preferably, the halogens are fliiorine and chlorine and
are present on the catalyst in an amount between 0.1 and 1.0 wt. % fluorine and 0.1
and 1.0 wt. % chlorine at the Start of Run. Preferred halogen containing catalysts are
i described in the RAULO and IKC patents cited above in the Background section,
15 wliich references are incorporated by reference herein, particularly as to description of halogen containing Pt L zeolite catalysts. The above mentioned halogens may be added to the catalyst ex situ for example when the catalyst is made or may be added in situ, for instance at the start of the run. The preferred halogen contents of the catalyst mentioned above should preferably be present on the catalyst at the start of the rtm,
20 when feed is introduced to the catalyst under reforming conditions.
Preferred feeds for the process of the present invention are naphtha boiling range hydrocarbons, that is, hydrocarbons boiling within the range of C^ to Cio paraffins and naphthenes, more preferably in the range of Cj to Cs paraffins and naphthenes, and most preferably of Ce to C7 paraffins and naphthenes. The feedstock
25 can onitain minor amounts of hydrocarbons boiling outside the specified range, sucli as 5 to 20%, preferably only 2 to 7% by weight. There are several different paraffins at each of the various carbon miinbers. Accordingly, it will be understood that the bniling point has .s 30 In a preferred cmbodiuieTit oT ilic present invention, the feed contacting the
cal;ilvsl preferably coiilains less (ban 50 ppb sulfur, more preferably less than 10 ji]ib

sutliir. In Ihe prcscnl invention, low catalyst rates are important. Ultra low sulfur in Ilk" (ccd contributes fo Ihc success of tlie present invention. Two patents that tench about the need to avoid sulfur poisoning of Pt L zeolite catalysts and teach how to achieve ultra low sulfur conditions are U. S. Patents 4,456,527 and 5,322,615, which 5 are herein incorporated by reference.
In one embodiment of the present invention, the furnace tubes are filled with catalyst, and a conventional furnace with its associated tubes are used as a combination heating means and catalytic reaction means.
In a particularly preferred embodiment of the present invention the catalyst is 10 selected to have a particularly low deactivation rate under reforming conditions.
Preferably, the catalyst selected for use and reaction conditions selected are such that the catalyst deactivation rate is controlled to less than 0.04T per hour, more preferably less than 0.03°F, still more preferably less than 0.02*F, and most preferably
less than O.OrF per hour, at an aromatics yield of 50 wt % lising a C6-C7 UDEX
i
15 raffinate feed at a liquidhourly space velocity of 4 hour" aiid a hydrogen to hydrocarbon mole ratio of 2. Utilizing a catalyst and conditions having the particularly preferred low deactivation rate allows for less catalyst to be used in the furnace reactor and allows the use of larger diameter tubes. In another embodiment of the invention that does not use tubes, the catalyst can be further away from a heat
20 exchange surface than when using a catalyst that has a high deactivation rate. This in tum allows the total length of tubes or in the alternative embodiment the heat exchange surface area to be minimized and makes it economical to replace the multitude of fumace/ reactor loops (usually 3-6 or more reactors in a conventional Pt I. zeolite catalyst refonner) with a single fumace reactor.
25 The present invention may again be contrasted to U.S. Patent No. 4,1 55,835 to
Antal. The Antal reference uses reformer reactor vessels separate from the foiu"cnlional furnaces, v."hcrcas the present invention does not.
Further, althougli the Antal process reduces the sulfur to very low sulfur levels ill the feed, as low a.s 0.2 pjini sulfur, the present invention is preferably carried out ai
30 sulfur lL"\els more than an ouler of magnitude lower, such as below 10 ppb sulfur, in

the I"vcd [o llic luonoUinctiona] n-i\litc L based catalyst conliiincd in the furnnco R-acinr system ofliic present iiiveniion.
Preferred reru f! eondilicms for the furnace reactor of the present invention nsiiin (lie preferred catalyst eoniprising a monofunctional zeolite L include a !.l [S V 5 lielween 1.5 and 6: a liydrogen to hydrocarbon ratio between 0.5 and 3.0; and a heal o\eh;uiye surface temperature for the rcactants (interior temperature) between fiOOT and 960°F at the inlet and between S60""F and 960°F at the outlet at Start of Run (SOR). and between 600°F and 1025^ at the inlet and between 920°F and 1025°r at the outlet at End of Run (EOR). EOR is the time at which the run is ended usually 10 due to deactivation of the catalyst. The catalyst of the present invention is considered at EOR at a point when the outlet temperature is no higher than 1025"?.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic flow diagram for a furnace tube reactor system.
15 Figure 2 is an overhead cross section view of a furnace tube reactor system
showing the burners (X) and the reactor tubes (o).
Figure 3 is a simplified scheme showing a vertical cross-section with gas-fired heaters (shaded) adjacent to a parallel series of furnace tubes that contain catalyst.
I I
Figure 4 shows 4 cross section views of alternative embodiment furnace
1
20 reactor systems showing the burners (X) and the catalyst chamber or chambers as cross-hatched areas.
DETAILED DESCRIPTION OF THE DRAWINGS The drawing shown herein are for descriptive purposes only of possible 25 cnibii(iimenls ofllie invention and arc not intended in any way to limit the invention. Figure I is a schematic How diagram for a furnace tube reactor system. Hydrocarbon is fed to the unit through line (!). Thesulfur content of the hydrocarbon is a-fiticcd to the Llcsircd low k\"c]s in the sulfur control unit (2). The liydrotarbon ihen [.iocs via line (.1) to an optional licat exchanger orprchcatcr (4). The optionally 30 luMlcd effluent (iocs via line (5) lo the furnace reactor (6) where it is siniuliancou.sly luMlcd and contaiifd with llie catalyst. The reactor effluent then goes via line (7) to a

slnhUizcr hght gas is rcitinvcd from tlic stabilizer by line (8) and liquid prodiicl lca\ cs (he stiihilizcr by line (% wliicli goes to product distillation (not shown).
I-igure 2 is an overhead cross section view of a furnace tube reactor system Khinving the burners (X) and the reactor tubes (o). The furnace tubes are filled willi 5 liic calalysl. This is only one possible furnace tube arrangement.
Figure 3 is a simplified scheme showing a vertical cross-section with gas-fired heaters (shaded) adjacent to a parallel series of furnace tubes that contain catalyst.
Figure 4 shows 4 cross section views of alternative embodiment furnace reactor systems showing the burners (X) and the catalyst chamber or chambers as 10 cross-hatched areas. There are numerous other possible furnace reactor
configurations. The four arrangements in Figure 4 are only meant as illustrations of
I
possible embodiments of the chamber coniigurations useful in the present invention furnace reactor.
I
15 DETAILED DESCRIPTION OF THE INVENTION
The catalyst used in the process of the present invention comprises a
Group VIII metal and zeolite L. The catalyst of the present iiivention is a non-acidic,
monofunctional catalyst. j
The Group VIII metal of the catalyst of the present invention preferably is a 20 noble metal, such as platinum or palladium. Platinum is particularly preferred.
Preferred amounts ofplatinum are 0.1 to 5 wt. %, more preferably 0.1 to3 wi. %, and most preferably 0.3 to 1.5 wt. %, based on zeolite L.
In the present application the terms "L zeolite" and "zeolite L" are used synonymously to refer to LTL type zeolite. The zeolite L component of the catalyst is 25 described in published literature, such as U.S. Patent No. 3,216,789. The chemical fomuila for zeolite 1, may be represented as follows:
(0.9-1.3) M2/„0 : AI2O3 (5.2-6.9) SiO;: y\hO wherein M designates a cation, n represents the valence of M, and y may be any value from 0 to about 9. Zeolite L, its X-ray diffraction pattern, its properties, and method 30 for its preparation arc described in detail in U.S. Patent No. 3,216,789. Zeolite I, has been charaelerized in "/eolile Molecular Sieves" by Donald W. Dreck, John Wiley

and Sons, 1974, (reprinted 1984) as having a framework com^jrising 18 tetrahedra unit
J cancrinite-type cages linked by double six rings in columns arid cross-linked by single
oxygen bridges to form planar 12-membered rings. The hydnjicarbon sorption pores for zeolite L are reportedly approximately 7A in diameter. The Breck reference and
I
5 U.S. Patent No. 3,216,789 are incorporated herein by reference, particularly with
respect to their disclosure of zeolite L. |
t
The various zeolites are generally defmed in terms of their X-ray diffraction
patterns. Several factors have an effect on the X-ray diffraction pattern of a zeolite.
Such factors include temperature, pressure, crystal size, impurities and type of cations
10 present. For instance, as the crystal size of the type-L zeolite becomes smaller, the X-ray diffraction pattern becomes somewhat broader and less precise. Thus, the term "zeolite L" includes any of the various zeolites made of cancrinite cages having an X-ray diffraction pattern substantially the same as the X-ray diffraction patterns shown in U.S. Patent No. 3,216,789. Type-L zeolites are conventionally synthesized
15 in the potassium form, that is, in the theoretical formula previously given; most of the M cations are potassium. M cations are exchangeable so that a given ^pe-L zeolite, for example, a type-L zeolite in the potassium form, can be used to obtain type-L zeolites containing other cations by subjecting the type-L zeolite to ion-exchange treatment in an aqueous solution of an appropriate salt or salts. However, it is
20 difficult to exchange all tlie original cations, for example, potassium, since some cations in the zeolite are in sites that are difficult for the reagents to reach. Preferred L zeolites for use in the present invention are those synthesized in the potassium form. Preferably, the potassium form L zeolite is ioii exchanged to replace a portion of the potassium, most preferably with an alkaline earth metal, barium being an especially
25 preferred alkaline earth metal for this purpose as previously stated.
The catalysis used in llie process of the present invention are monofunetional catiilysis, meaning that they do not have the acidic function of conventional reforming catalysts. Traditional or conventional reforming catalysts are bifunctional, in that they have an acidic function and a melaHic function. Examples of bifunctional catalysis
30 i[iclii
No. 3,415,737 to Kluksdahi; platinum-tin on acidic alumina: and platinum-iridiura
with bismuth on an acidic carrier as disclosed in U.S. Patent No. 3,878,089 to
Wilhelm (see also the other acidic catalysts containing bism ith, cited above in the
Background section).
5 Examples of monofunctional catalysts include platinum on zeolite L, wherein
the zeolite L has been ejtchanged with an alkali metal, as disclosed in U.S. Patent No. 4,104,320 to Bernard et al.; platinum on zeolite L, wherein the zeolite L has been exchanged with an alkaline earth melal, as disclosed in U.S. Patent No. 4,6^4,518 to Buss and Hughes; platinum on zeolite L as disclosed in U.S. Patent No. 4,456,527 to 10 Buss, Field and Robinson; and platinum on hatogenated zeolite L as disclosed in the RAULO and IKC patents cited above.
According to another embodiment of the present invention, the catalyst is a high temperature reduced or activated (HTR) catalyst.
Preferably, the pretreatment process used on the catalyst occurs in the presence 15 of a reducing gas such as hydrogen, as described in U.S. Patent No. 5,382,353 issued January 17,1995,and U.S. Patent application 08/475,821, which are hereby expressly incorporated by reference in their entirety. Generally, the contacting occurs at a pressure of from 0 to 300 psig and a temperature of from 1025*"F to i275T for from 1 hour to 120 hours, more preferably for at least 2 hours, and most preferably for at 20 least 4-48 hours. More preferably, the temperature is from 1050"? to 1250°?. In general, the length of time for the pretreatment vnll be somewhat dependent upon the fmat treatment temperature, with the higher the fmal temperature the shorter the treatment time that is needed.
For a commercial size plant, it is necessary to limit the moisture content of the 25 environment during the high tcmpemture treatment in order to prevent significant calalyst deactivation. In the temperature range of from 1025°F to 1275""F, the presence of moisture is believed to have a severely detrimental effect on the catalyst activity. It has therefore been found necessary to limit the moisture content of llic environment to as little water as possible during said treatment period, to at least less 30 than 200 ppmv, preferably less than 100 ppmv water.

jn one emDoaiinem, in order to limit exposure ot the catalyst to water vapor at high temperatures, it is preferred that the catalyst be reduced initially at a temperature between 300»F and 700"?. After most of the water generated during catalyst reduction has evolved from the catalyst, the temperature is raised slowly in ramping or 5 stepwise fashion to a maximum temperature between 1025T and 1250°?.
The temperatuie program and gas flow rates should be selected to limit water vapor levels in the reactor effluent to less than 200 ppmv and, preferably, less than 100 ppmv when the catalyst bed temperature exceeds 1025"?. The rate of temperature increase to the final activation temperature will typically average between 5 and 50"? 10 per hour. Generally, tlie catalyst will be heated at a rate between 10 and 25°F per
I
hour. It is preferred that the gas flow through the catalyst bed during this process exceed 500 volumes per volume of catalyst per hour, where the gas flow volume is measured at standard conditions of one atmosphere and 60"*?. In other words, the gas flow volume is greater than 500 gas hourly space volume (GHSV). GHSVs in excess
15 of 5000 per hour will normally exceed the compressor capacity. GHSVs between 600 and 2000 per hour are most preferred.
The pretreatment process occurs prior to contacting the reforming catalyst with a hydrocarbon feed. The large-pore zeolitic catalyst is generally treated in a reducing atmosphere in the temperature range of from 1025"? to 1275°F. Although other
20 reducing gasses can be used, dry hydrogen is preferred as a reducing gas. The
hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally ranging from 1% to 99% by volume. More typically, however, the amount of hydrogen in the mixture ranges from about 10 to 50% by volume.
25 In another embodiment, the catalyst can be pretreated using an inert gaseous
environment in the lempcraliirc range of from 1025-1275°F, as described in U.S. patent application number 08/450,697, filed May 25, 1995, which is hereby expressly incorporated liy reference in its entirety.
The preferred inert gas is nitrogen, for reasons of availability and cost. Oilier
30 inert gases, however, can he used such as helium, argon, and krypton or mi.xlures tlieteof

According to on especially preferred embodiment of the present invention, the ni)ti-;icidic. nionofunctional e;itnlyst used in Ihc process of the present invention conliiins a halogen. This may be confusing at first, in that halogens are often nscd lo contribute to Ihc acidity of alumina supports for acidic, bifunctional refomiing 5 catalysts. However, the use of halogens with catalysts based on zeolite L can be made while retaining the non-acidic, monofunctional characteristic of the catalyst. Mctiiods for making non-acidic halogen containing zeolite L based catalysts are disclosed in (he RAULO and IKC references cited above in the Background section.
The term "non-acidic" is understood by those skilled in this area of art, 10 particularly by the contrast between nionofunctional (non-acidic) reforming catalysts and bifunctional (acidic) reforming catalysts. One method of achieving non-acidity is by the presence of alkali and/or alkaline earth metals in the zeolite L, and preferably is achieved, along with other enhancement of the catalyst, by exchanging cations such as sodium and/or potassium from the synthesized L zeolite using alkali or alkaline earth 15 metals. Preferred alkali or alkaline earth metals for such exchanging include potassium and barium.
The term "non-acidic" also coimotes high selectivity of the catalyst for conversion of aliphatics, especially paraffins, to aromatics, especially benzene, toluene and/or xylenes. High selectivity includes at least 30% selectivity for aromatics 10 formation, preferably 40%, more preferably 50%. Selectivity is the percent of the conversion that goes to aromatics, especially to BTX (Benzene, Toluene, Xylene) aromatics when feeding a Cs to Cg aliphatic feed.
Preferred feeds to the process of the present invention are Ce to C9 naphthas. The catalyst of the present invention has an advantage with paraffmic feeds, which 5 nitrmally give poor aromatics yields with conventional bifunctional refonning
ciilalysls. However, naphthenic feeds are also readily converted to aromatics over the catalyst of the present invention.
More preferably, feeds lo the process of the present invention are C(, to C7 naphthas. The furnace reactor system of Ihc present invention is particularly 0 advantageously applicti to convciling C^ and C^ naphthas to aromatics.

I"arlicularly prcfcnod cntafylic rcComiing conditions for the present invcnlinn inclittle, as described iibovc IHICILT Sunimaty of the Invention, an LHSV between 1,5 and C).()"", a hydrogen to hydrocarbon ratio between 0.5 and 2.0, a reactants tcniperaliire between 600°F and 1025°F, and an outlet pres.sure between 35 and 5 75 p.sig.
Preferably, the catalyst used in the process of the present invention is bound. Binding the catalyst improves its crush strength, compared to a non-bound catalyst comprising platinum on zeolite L powder. Preferred binders for the catalyst of the present invention are alumina or silica. Silica is especially preferred for the catalyst 10 used in the present invention. Preferred araoimts of binder are from 5 to 90 wt. % of the finished catalyst, more preferably from 10 to 50 wt. %, and still more preferably from 10to30wt. %.
As the catalyst may be bound or unbound, the weight percentages given herein are based on the zeolite L component of the catalyst, unless Otherwise indicated.
I
15 The term "catalyst" is used herein in a broad sense to include the final catalyst
as well as precursors of the final catalyst. Precursors of the final catalyst include, for example, the unbound form of the catalyst and also the catalyst prior to final activation by reduction. The term "catalyst" is thus used to refer to the activated catalyst in some contexts herein, and in other contexts to refer to precursor forms of
20 the catalyst, as will be understood by skilled persons from the context.
Also with regard to use of the halogenated fonn of the monofiinctional catalyst in the present invention, the percent halogen in the catalyst is that at Start of Run (SOR). During the course of the run or use of the catalyst, some of the halogen usually is lost from the catalyst,
25 A preferred ciiibodimci^t fvirnace tube reactor system of the present invention
refers to a reforniiny system in which non-acidic, highly selective zeolite L based catalyst is contained within a plurality of conventional furnace tubes which are Ihcniselves contained within a furnace. See Figure 1 which shows a schematic tli:i!^rarn of a furnace reactor reforming process.
30 The furnace lubes arc preferably parallel to each other and are preferably
\c!lir[i[ly arraniied. Typically, rows of furnace tubes altcrnale with rows of burners.

Figure 2 and 3 slow a suitable arrangement for the burners and furnace tubes. I-"if!urc
2 sliinvs a liori/onlal cross sct-tion of the preferred embodiment furnace reactor where
the Xs designate burners and the Os designate tubes. Figure 3 shows a longitiidriiai
view of the preferred embodiment furnace tube reactor where the burners arc shown
impiriging down piirallcl to Ihc tubes.
The lubes are preferably 2 to 8 inches in diameter, more preferably 3 to
6 inches in diameter, and most preferably 3 (o 4 inches in diameter, and can be up (o
45 feet long. The furnace tubes are preferably less than or equal to 30 feet long and
preferably are at least 10 feet long. The arrangement of the furnace tubes and the
burners can vary. Thus the furnace tubes can be positioned vertically, or
horizononlally, or m an arbor coil arrangement or in a helical coil arrangement. The
burners can likewise be oriented in a number of different ways, for instance at the
bottom of the furnace pointing up or at the side of the furnace pointing horizontally.
i Preferably the furnace tubes are positioned vertically with the burners pointed down
i
parallel to the tubes.
Furnace reactors can be linked in series or in parallel, but preferably the system is designed so that a single fiimace reactor is used. Replacement of the 3 to 6
I
or more conventional refonning reactors and furnace loops in a Pt L zeolite reformer with a single furnace reactor is preferable and is feasible with a Pt L zeolite catalyst having a high activity and a low deactivation rate. We have found that replacement of a multitude of conventional reactors and furnace loops results in greatly reduced investment costs for a Pt L zeolite reformer.
In a preferred embodiment, utilizing vertical tubes filled with catalyst, the feed comes in at the top of the tubes. The burners are mounted in the roof of the furnace and fire down into the firebox. The maximum heat flux would then be at the point where feed is coming into the furnace tubes, which is desirable. Alternatively, a inulli-zone furnace can be used. Here the heat flux can be varied more controllalily. I IK- heat flux siippMcd to the reactor inlets is preferably greater than that applied near the reactor outlet.
it is desirable Ibat the furnace lube surfaces or the heat exchange surfaces thai i-oul;icl llie hydrocai lions and resulting aroniatics are made of a material having a

a-sislance to carlnirization and melal dusting at least as great as that of type 347 stainless steel iiiulcr low sulfur rcfomiing conditions. The resistance to carbiiri/alion and nielai dusting ean he readily detennined using the procedure outlined below in I-xjiniple 4.
In a preferred cinbodinicnt of tlie invention, the furnace tube reactors are made of (a) 347 stainless steel or a sleel having a resistance to carbunzation and metal dusting at least as great as 347 stainless steel; or (b) the furnace tubes are treated by a method comprising plating, cladding, painting or coating the surfaces for contacting the feed to provide improved resistance to carbunzation and metal dusting; or (c) the furnace tubes are constructed of or lined with a ceramic material. More preferably the furnace tubes are constructed of a type 300 series steel provided with an intermetallic coating on the surfaces that contact hydrocarbons.
In one embodiment of the invention, the fiimace tubes have a metal-containing coating, cladding, plating, or paint applied to at least a portion (preferably at least 50%, more preferably at least 75% and most preferably to all) of the surface area that is to be contacted with hydrocarbons at conversion temperature. After coating, the metal-coated reactor system is preferably heated to produce intermetallic and/or metal carbide layers. A preferred metal-coated reactor system preferably comprises a base construction material (such as a carbon steel, a chromium steel, or a stainless steel) having one or more adherent metallic layers attached thereto. Examples of metallic layers include elemental chromium and iron-tin intemietallic compounds such as FeSnj.
As used herein, the term "metal-containing coating" or "coating" is intended to include claddings, platings, paints and other coatings that contain either elemental mclals. metal oxides, organometallic compounds, metal alloys, mixtures of these components and the like. Hie mctal(s) or metal compounds are preferably a key cntiiponent(s) of the coating, Mowable paints that can be sprayed or brushed arc a preferred type of coating. In a preferred embodiment, the coated steel is heat treated to prniluce intermeliillic compounds, thus reacting the coating metal with the steel.
F.spccially preferred are mclals that interact with, and preferably react with, tlio liasi- material of the reactor syslcm to produce a continuous and adherent metallic

pmtL"ctivc layer al icmpcraliitcs hcloworal the intended hydrocarbon conversion condilions, Metals Ihal nieh hcl()\vor at reforming process conditions are espceially preferred as they can more readily provide complete coverage of the substrate inalcrial. These metals incUidc those selected from among tin, antimony, gcniiaiiiiitn, 5 arsenic, bisnnilli, ahitninnm. gallium, indium, copper, lead, and mixtures, intcrmclallic compounds and alloys thereof. Preferred metal-containing coatings comprise metals selected from the group consisting of tin, antimony, germanium, arsenic, bismuth, akiminum, and mixtures, intermetalUc compounds and alloys of these metals. I-.spccially preferred coatings include tin-, antimony-and germanium-containing 10 coatings. These metals will form continuous and adherent protective layers. Tin
coatings are especially preferred ~ they are easy to apply to steel, are inexpeiisive and
arc environmentally benign. ,
I
It is preferred that the coatings be sufficiently thick that they completely cover the base metallurgy and that the resulting protective layers remain intact over years of
I
15 operation. For example, tin paints may be applied to a (wet) thickness of between I to 6 mils, preferably between about 2 to 4 mils. In general, the thickness after curing is preferably between about 0.1 to 50 mils, more preferably between about 0.5 to 10 mils.
Metal-containing coatings can be applied in a variety of ways, which are well
I
20 known in the art, such as electroplating, chemical vapor deposition, and sputtering, to name just a few. Preferred methods of applying coatings include paintmg and plating. Where practical, it is preferred that the coating be applied in a paint-like formulation (hereinafter "paint"). Such a paint can be sprayed, brushed, pigged, etc. on reactor .system surfaces.
25 One preferred protective layer is prepared from a metal-containing paint.
Pieferably, the paint comprises or produces a reactive metal that interacts witli the slecl. Tin is a preferred inelal and is exemplified herein; disclosures herein about tin arc jienerally applicable to oilier metals such as germanium. Preferred paints comprise a metal component selected from the group consisting of: a hydrogen decomposable
30 niel;i! compound sucli as an nrjianometallic compound, finely divided metal and a riu-l;il oxide, prefeiably a metal oxide that can be reduced at process or furnace tube

temperature in a preferred embodiment the cure stop produces a metalic protetive layer bonded to the steel through an intemedizate bonding layer, for example a
carbide -ricli bonding layer, as described in U.S. Patent No. 5,674,376, which is incorporated herein by reference in its entirety. This patent also describes useful 5 coatings and paint formulations.
Tin protective layers are especially preferred. For example, a tin paint may be used. A preferred paint contains at least four components or their functional equivalents; (i) a hydrogen decomposable tin compound, (ii) a solvent system, (iii) finely divided tin metal and (iv) tin oxide. As the hydrogen decomposable tin 10 compound, organometalHc compounds such as tin octanoate or neodecanoate are particularly useful. Component (iv), the tin oxide is a porous tin-containing compound that can sponge-up the organometallic tin compound, and can be reduced to metallic tin. The paints preferably contain finely divided solids to minimize settling. Finely divided tin metal, component (iii) above, is also added to insure that 15 metallic tin is available to react with the surface to be coated at as low a temperature
I
as possible. The particle size of the tin is preferably small, for example one to five microns. Tin fomis metallic stannides {e.g., iron stannldes and nickel/iron staimides) when heated under reducing conditions, e.g. in the presence of hydrogen.
In one embodiment, there can be used a tin paint containing stannic oxide, tin
20 metal powder, isopropyl alcohol and 20% Tin Ten-Cem (manufactured by Mooney Chemical Inc., Cleveland, Ohio). Twenty percent Tin Ten-Cem contains 20% tin as stannous octanoate in octanoic acid or staimous neodecanoate in neodecanoic acid. When tin paints are applied at appropriate thicknesses, heating under reducing conditions will result in tin migrating to cover small regions (e.g., welds) that were
25 not painted. This will completely coat the base metal.
Additional information on the composhion of tin protective layers is disclosed in I I.S. Patent No. 5.406,014 to Ilcyse el al., which is incorporated herein by relVrence. Here it is taught that a double layer is formed when tin is coated on a clironiium-rich, nickel-containing steel. Both an inner chromium-rich layer and an
30 outer slannidc layer arc produced. The outer layer contains nickel stannides. When a tin paint was applied In a "SM type stainless steel and heated at about 1200 °V, there

resulted a chromium-rich steel layer containing about 17% chromium and substantially no nickel, comparable to 430 grade stainless steel.
Tin/iron paints are also useliil in the present invention. A preferred tin/iron paint will contain various tin compounds to which iron has been added in amounts up 5 to one third Fe/Sn by weight. The addition of iron can, for example, be in the form of Fe2O3. The addition of iron to a tin containing paint should afford noteworthy advantages; in particular: (i) it should facilitate the reaction; of the paint to fonn iron
■ - " " I
stannides thereby acting as a flux; (ii) it should dilute the nickel concentration in the stannide layer thereby providing a coating having better protection against coking; and
10 (iii) it should result in a paint that affbrds the anti-coking protection of iron stannides
J I
even if the underlying surface does not react well. I
Some of the coatings, such as the tin paint described above, are preferably cured, for example, by heat treatment. Cure conditions depend on the particular metal coating and curing conditions that are selected so as to produce an adherent protective
15 layer. Gas flow rates and contacting time depend on the cure; temperature used, the coating metal and the specific components of the coating composition.
The coated materials are preferably cured in the absence of oxygen. If they are not already in the metallic state, they are preferably cured inja reducing aUnosphere, preferably a hydrogen-containing atmosphere, at elevated temperatures. Cure
20 conditions depend on the coating metal and are selected so they produce a continuous and uninterrupted protective layer that adheres to the steel substrate. The resulting protective layer is able to withstand repeated temperature cycling, and does not degrade in the reaction environment. Preferred protective layers are also useful in reactor systems that are subjected to oxidizing environments, such as those associated
25 with coke bum-off.
In general, the contacting of the reactor system having a metal-conlairiing coaling, plating, cladding, paint or other coating applied to a portion thereof with hydrogen is done for a time and at a temperature sufficient to produce a metallic protective layer. These conditions may be readily determined. For example, coaled
30 compons may be heated in the prescnce of hydrogen in a simple test apparains; the formation of thc proleclive later may he determined using petrographic analysis.

It is preferred thai cure conditions result in a protective layer that is firmly
j
hoiidcil to the slecl. This may be accomplished, for exampl^, by curing the applied coating at elevated temperatures. Metal or metal compounds contained in the paint,
I
plating, cladding or other coating are preferably cured under conditions effective to
5 produce molten metals and/or compounds. Thus, germanium and antimony paints are
preferably cured between 1 OOO^F and 1400°F. Tin paints are preferably cured t
between 900""F and 11OOT. Curing is preferably done over a period of hours, often with temperatures increasing over time. The presence of hydrogen is especially advantageous when the paint contains reducible oxides and/or oxygen-containing
10 organometallic compounds.
As an example of a suitable paint cure for a tin paint, the system including painted portions can be pressurized with flowing nitrogen, followed by the addition of a hydrogen-containing stream. The reactor inlet temperature can be raised to 800°F at a rate of SO-lOO^F/hr. Thereafter the temperature can be raised to a level of 950-
15 975*F at a rate of 50°F/lir, and held within that range for about 48 hours.
Tlie Furnace Tube Construction Material
There are a wide variety of base construction materials that can be used in the furnace tubes or the heat exchange surfaces. If the tubes/surfaces are to be protected
20 with a metallic coating, then a wide range of steels nuiy be used. In general, steels are chosen so that they meet the strength and flexibility requirements for the catalytic reforming process. These requirements are well known in the art and depend on process conditions, such as operating temperatures and pressures.
Useful steels include carbon steel; low alloy steels such as 1.25, 2.5, 5, 7, and
25 "^ climine steel; 300 scries stainless steels including 304, 316 and 346; heat rcsistnni siLTls including nK-40 and nP-50, as well as treated steels such as aluminizcd or cliroinized steels, i"rcfcrrcd slccls include the 300 series stainless steels and licat rcsi.slanl slccls.
30

[H"t"l or flake. For cxiiinplc, nii."l;illic tin, germanium and antimony (whether applied ciircclly as a plating or cladtiinji or produced in-situ) readily react with steel at cicviiled lernperatures lo form a bomlint; layer as is described in U.S. Patent No. 5,406.014 or \V() ")4/15896, both Ir) llcysc ct al, The "014 patent is incorporated herein by 5 rcli"ienec in its entirely.
If Ihe lubes/surfaces are not to be protected with a metallic coating, they can be protected against carburi?:ali()n and metal dusting with a ceramic coating. These types of coalings are wcU known in the art. See US Pat. 4,161,510,
The furnace tube reactors may also be constructed of uncoated steels, so long
10 as the steels have a resistance to carburization and metal dusting at least as great as
347 stainless steel under low sulfur reforming conditions. See Example 4 below.
Useful steels include the 300 series stainless steels including type 304, 316 and 347
stainless steels; heal resistant steels including HK-40 and HP-50, as well as treated
steels such as aluminized or cliromized steels.
15 As stated earlier, I have also found that in the process of the present invention
high space velocities are advantageously used. Relatively high space velocities allow lower total tube volume to be used. Lower space rates conversely require more tube volume to contain the appropriate (desired) amount of catalyst and thus may be less desirable, particularly if the total fumace size must be significantly larger to 20 accommodate the increased volume of tubes.
The diameter and length of the fumace tubes can be varied so that a desired pressure drop and heat flux across the tubes is attained. The length and diameter of the fumace tubes, and the location and number of burners, allow for regulation of the skin temperature of the fumace tubes as well as the radial and axial temperature 25 pruilleofthe furnace tubes. Tlicse parameters can be designed to allow for
appropriate conversion of particular feeds. However, the concept of the present invention requires that the furnace be basically conventional. Accordingly, the size of llic fnmace tubes will be at least two inches in inside diameter, more preferably at Irasi ihrcc inches in inside diatnclcr. Also, the fumace will be heated by convcnlioiial 30 Micajis. such as by gas or oil llicd Inimcrs.

The pressure drop across tlie length of the furnace tubes preferably is less llinn or ec[iial to 70 psi, more preferably less than 60 psi, most preferably less than 50 psi. The outlet pressure is preferably between 25 and 100 psig, more preferably between 35 and 75 psig, and most preferably between 40 and 50 psig. The outlet pressure is 5 the reaction mixture pressure at the outlet of the iumace tubes, that is, as the tulies and eonlained reaction mixture cnmc out of the furnace.
To obtain a more complete understanding of the present invention, the following examples illustrating certain aspects of the invention are set forth. It should be understood, however, that the invention is not intended to be limited in any way to 10 the specific details of the examples.
EXAMPLES Example 1 This example compares a conventional adiabatic multi-stage reactor system to 15 the externally heated fiimace tube reactor of the present invention. The catalyst used in this comparison is platinum on halogenated zeolite L as disclosed in the RAULO and IKC patents cited earlier. The total volume of catalyst in the two systems is the same. The same light naphtha is used as feed to both reactor systems. The light naphtha feed contained 2 percent Cj"s, 90 percent Ce"s (primarily paraffins but also 20 minor amounts of naphthenes), and 8 percent by volume Cy"s. The conditions and parameters in the example have been adjusted to give the same total run length for the two systems in the comparison

This example shows that, in accordance with the concept of the present invention, a single externally heated conventional furnace can effectively replace a 5 six-reactor multi-stage reactor system with catalyst disposed in the tubes of the
furnace. The present invention also provides a substantially increased aromatics yield. The increase in yield results in more aromatics produced during the run. Alternatively the furnace tube reactor can be operated at lower severity allowing a much lower licnctivation rale for a given yield thus allowing a run length of substantially longer 10 (h;iii a year. Wc have al.sn found Ihe this result can be accomplished in the furnace liibi? reactor sysloin of the present invention at a lower peak catalyst temperature viTsiis the use of niuhi-.stage adiaKitic reactors with conventional furnaces preccclinj", each ofthe reaclur stages.

This example i-(inip:iR"s n coiivcniional adiabalic mulli-slage reactor system in
lliL- liirnacc luhc reactor system ofllie present invention. The catalyst used in this
eoiiiparison is plaliniim on lialogenatcd zeolite L, as disclosed in the RAULO and IKC
5 jviliTils cited earlier. The diameter oftiihes in lliis example in the furnace tube reactor
is latger (ban iu ibe first example and tUc total volume of catalyst is twice as much as
t in tbc first example. The total volume of catalyst in the two compared systems is the
same (1170 cubic feet). The same light naphtha is used as feed to both reactor
systems. The conditions and parameters in the example have been adjusted to give (lie
10 same total nin length foi the two systems in the comparison. The feed rate of the two
systems is also the same.
I I
I bis example shows that fur a lower activity catalyst, at a lower space velocity than ITi llie previous example, in acenrdaiice with the concept oflhe present invention, a
sini"le furnace reaclcir with catalv.st disposed in the tubes oflhc furnace can cni-cli\cl>

replace a six-rcacl(ir tmilti-sliigc rcaclnr system. This example also shows thnl IIICR- is a siihslantially heller arniiirilics yield using the Furnace reactor. The increase in yield results in more aromatics proLiuccd during the run. Alternatively the furnace luhc rcaclnr can be operated al lower severity allowing a much lower deactivation rate for a 5 given yield tlius allowing a rnn Icnglli of substantially longer than a year.
Example 3 In the following example, a high temperature reduced catalyst is used in an externally heated furnace tube reactor and compared to use of the same HTR catalyst 10 in an adiabatic multi-stage reactor system.

This example illustrates that a six-reactor multi-stage reactor system can be cflVvlively replaced by a system in accord with the present invention wlicrein catalyst 15 is disposed in the lubes of a conventional single externally heated furnace. Tiic
ciil;ilyst used in this example is a high temperature reduced catalyst comprising Pi on I. /colile. riiis o.xarnplc also illiislrates thai the system of the present invention proxides an increa.sed arotnalics yield. This result is accomplished at a lower peak

/ -29-
CMliilyst tcmpemliirc in Ilic cxk-ni;)I)y Jicatcd furnace tube rt-aclor syslcjii [bm in ihc s\"sk"Tn comprisiiij! scvcnil ruriiaccs iuid separate reactors in series.
Bxample 4 5 "I"ll (Iclcnninc liic resislance of various substrates to coking, carburizatioii and inclnl dusting under ultra low sulfur rcfoniiing conditions, the following test can he nin. The test makes it especially easy to do side by side comparisons, for example comparisons with type 347 stainless steel.
Tlie test uses a Lindbcrg quartz tube furnace with temperatures controlled lo 10 within one degree with a thermocouple placed on the exterior of the tube in the heated zone. The furnace tube had an Internal diameter of 5/8 inches. Several preliminary lest runs are conducted at an applied temperature of nOO^F using a thermocouple suspended within the hot zone of the tube. The internal thermocouple constantly measured up to 10°F lower than the external thermocouple.
15 Samples of steels and other construction materials are then tested at 1100°F,
11 SOT and 1200""F for 24 hr, and at HOOT for 90 br, under conditions that simulate the exposure of the materials under conditions of low-sulfur reforming. The samples of various materials should be clean and free of scale, grease or tarnish. Compared samples should be equally smooth. The samples are placed in an open quartz boat
20 within the hot zone of the flimace tube. The boats are 1 by !4 inch and fit well within the two-inch hot zone of the tube. The boats are attached to silica glass rods for easy placement and removal. No internal thermocouple is used when the boats are placed inside the tube.
Prior to start-up, the test materials are cut to a size and shape suitable for 25 ready-visual identification. After any pretreatment, such as roasting, the samples are weighed. Most samples weigh less than 300 mg. Typically, each run is conducted with three to five samples in a boat. A sample of 347 stainless steel is pref;cnl in e;ich iiiii as an internal .standard.
After the samples arc placed, the lube is flushed with sulfur-frcc nitrogen for a 30 \"c\\ tniniitcs. A (."nhuri/.ing [las ofa commercially bottled mixture of 7% proparie in livdnigen is bubbled llirnufli a liter flask of high purity toluene at room teInpor."lIll^^• in

onk"r entrain iilioiil !"% (nliiciK" in Ihc feed gas mix. This carbiirizing gas conUiin"; less lli;in 10 ppl) sulfur, (i;is flows of 25 to 30 cc/niin., and atmospheric pressure, are Tuiiinlaincd in Ihe apparatus. Tlio samples are brought to operating temperatures ri(;! nilL-ofaboul 100"l7niin.
• After exposing the materials to the carburizing gas for the desired time and
tcniperatiire, Ihe apparatus is quenched with an air stream applied to the exterior of the t
tube. When the apparatus is sufficiently cool, the hydrocarbon gas is swept out willi niirogen and the boat is removed for inspection and analysis.
After completion of each run, the condition of the boat and cacii material is carefully noted. Typically the boat is photographed. Then, each material and its associated coke and dust is weighed to determine changes. Care is taken to keep any coke deposits with the appropriate substrate material. The samples are then mounted in an epoxy resin, ground and polished in preparation for petrographic and scanning electron microscopy analysis. The degree of surface corrosion is determined; this indicates the metal dusting and carbunzation response of each material. In general, a qualitative visual analysis of metal reactivities is readily made.
The residence time of the carburizing gas used in these tests is considerably higher than in typical commercial operation. Thus, it is believed that the test conditions may be more severe than commercial conditions. Nevertheless, the test provides a reliable indication of the relative resistance of the materials to carbunzation and metal dusting.
Example 5 -- Preparing Tin-Coated Steel Pieces of 321 SS were coated with a tin-containing paint. The paint consisted of-.i mixture of 2 parts powdered tin oxide, 2 parts finely powdered tin (I-5 microns), 1 part stannous iicodccanoalc in ncodecanoic acid (20% Tin Tem-Cem manufactured by Mooney Chemical Inc., Cleveland, Ohio which contained 20% tin as stannous nendccanoatc) mixed with isopropanol, as described in US 5.674,376. Ihe coating was applied lo !hc steel surf;iee by painting and letting the paint dry in air. After dryitig, the painted steel was eontaclcd with flowing hydrogen gas at 1 lOOT fur 24 hours.

Example 6 -- Analysis of Steel Samples of coated and preferably heat cured steels were mounted in a clear epoxy resin and then ground and polished in preparation for analysts with the petrographic and scanning electron microscopes (SEM). Coupons were analyzed
i
before and after refonning conditions. EDX analysis can be used to determine the chemical composition of the layers. For example, tin intermetallic layers may be analyzed for iron, nickel and tin.
Example 7 Determination of the Deactivation Rate of a Catalyst
Deactivation rate of a catalyst sample as used in the present invention can be ktemiined in an isothermal pilot plant or similar unit under the following standard :()tiditions using a standard feed.
The feed to the unit slioiild be a C6-C7 UDEX raffinate from a convcntion.il efnnner. Tlie UDEX raf(in:i{c feed should have the following composition as neasured by G:is ("hr()m:il 11 \vt%, and a (otnl CR content oflcss than 6 wl %. The feed should contain less linn 10 ppbof snll"tir;itid less than 3 ppm of wnlcr. The pilot plant sbtnild ;ilso he Vii-i-

of any other possible source of sufur contamination. care must be taken to avoid
sulfare contamination of the sytem and to avoid using a previously sulfar
onliiminnled sysk-rn. Two pa(t*nts that (each how to clean-up a sulfur conlaminated system arc II. S. Palcnts 5.0."t5.7Q2 and 4,940,532 both of which are herein iiicorporalcd by reference. Tho MI.SV of the unit should be set at 4 (1/lir) with a sy."Jlem pressure of 85 psig . IIic hydrogeii/liydrocarbon mole ratio of the system should be 2. The pilot plant unit should be operated at a temperature sufTicient to maintain the aromntics in the reactor effluent at 50 wt %. The temperature is increased lo maintain the 50 wt % aromatics and the results plotted over a 8 week period (1344 hours) of continuous stable operation under said conditions. The fouling rate can be determined for the period of stable operation by dividing the change in temperature over the period by the number of hours.
I

WE CLAIM:
1. A process for catalytic reforming of feed hydrocarbons to form aromatic hydrocarbons comprising: passing feed hydrocarbons over a non-acidic catalyst comprising a Group VIII metal and zeolite L disposed within a furnace under catalytic reforming conditions; wherein said furnace comprises one or more first chambers and one or more second adjoining chambers separated by a heat exchange surface; wherein said catalyst is located within said first chamber and one or more gas or oil burners are located within said second chamber; and wherein catalytic reforming conditions comprise a temperature of between 600°F and 1025°F, a pressure of between 35 and 75 psig, and a hydrogen to hydrocarbon mole ratio of between 0.5 and 3.0.
2. The process as claimed in claim 1, wherein the first chamber comprises the tubes of a furnace; wherein the heat exchange surface comprises the wall of the tubes; and wherein the furnace tubes are from 2 to 8 inches in inside diameter.
3. The process as claimed in claim 1, wherein the catalyst is no more than 4 inches from the heat exchange surface and at least a portion of said catalyst is more than one inch from said heat exchange surface.
4. The process as claimed in claim 1, wherein the catalyst under said reforming conditions has a deactivation rate of less than 0.04°F per hour.
35

5. The process as claimed in claim 2, wherein the furnace tubes are 3 to 6 inches in diameter.
6. The process as claimed in claim 1, wherein the catalyst is no more than 3 inches from the heat exchange surface and at least a portion of said catalyst is more than 1.5 inches from said heat exchange surface.
7. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV of 1.0 to 7.
8. The process as claimed in claim 1, wherein the Group VIII metal is platinum.
9. The process as claimed in claim 1, wherein the catalyst is produced by steps comprising treatment in a gaseous environment in a temperature range between 1025°F and 1275°F while maintaining the water level in the effluent gas below 1000 ppm.

10. The process as claimed in claim 9, wherein the water level is below 200 ppm.
11. The process as claimed in claim 1, wherein the catalyst contains at least one halogen in an amount between 0.1 and 2.0 wt. % based on zeolite L.
12. The process as claimed in claim 11, wherein the halogens are fluorine and

chlorine and are present on the catalyst in an amount between 0.1 and 1.0 wt. % fluorine and 0.1 and 1.0 wt. % chlorine at the start of run.
13. The process as claimed in claim 1, wherein the feed hydrocarbon contains less than 50 ppb sulfur.
14. The process as claimed in claim 1, wherein the feed hydrocarbon contains less than 10 ppb sulfur.
15. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV between 3 and 5, a hydrogen to hydrocarbon ratio between 1 and 1.5, a furnace tube interior temperature between 600""F and 960°F at the inlet and between 860°F and 1025°F at the outlet at SOR and between 600°F and 1025°F at the inlet and between 920""F and lOas^F at the outlet at FOR, and an outlet pressure of between 35 and 75 psig.
16. The process as claimed in claim 2, wherein said furnace tubes are made of a material having a resistance to carburization and metal dusting under low sulfur reforming conditions at least as great as that of type 347 stainless steel.
17. The process as claimed in claim 2, wherein said furnace tubes are made of type 347 stainless steel.
18. The process as claimed in claim 2, wherein said furnace tubes have been treated by a method comprising plating, cladding, painting or coating the furnace
37

tube surfaces for contacting the feed hydrocarbon to provide improved resistance to carburization and metal dusting.
19. The process as claimed in claim 2, wherein said furnace tubes are constructed of or lined with a ceramic material.
20. The process as claimed in claim 1, wherein the catalytic reforming conditions include a LHSV between 3 and 5, and a hydrogen to hydrocarbon ratio between 1.0 and 1.5.
21. The process as claimed in claim 1, wherein the catalyst under said reforming conditions has a deactivation rate of less than 0.03°F per hour.
22. The process as claimed in claim 1, wherein the deactivation rate is less than 0.02°F per hour.
23. The process as claimed in claim 1, wherein the deactivation rate is less than O.OPF per hour.

Documents:

2837-mas-1998 abstract-duplicate.pdf

2837-mas-1998 abstract.pdf

2837-mas-1998 claims-duplicate.pdf

2837-mas-1998 claims.pdf

2837-mas-1998 correspondence-others.pdf

2837-mas-1998 correspondence-po.pdf

2837-mas-1998 description (complete)-duplicate.pdf

2837-mas-1998 description (complete).pdf

2837-mas-1998 drawings-duplicate.pdf

2837-mas-1998 drawings.pdf

2837-mas-1998 form-19.pdf

2837-mas-1998 form-2.pdf

2837-mas-1998 form-26.pdf

2837-mas-1998 form-3.pdf

2837-mas-1998 form-4.pdf

2837-mas-1998 form-6.pdf

2837-mas-1998 others.pdf

2837-mas-1998 petition.pdf

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Patent Number

216624

Indian Patent Application Number

2837/MAS/1998

PG Journal Number

17/2008

Publication Date

25-Apr-2008

Grant Date

17-Mar-2008

Date of Filing

22-Dec-1998

Name of Patentee

CHEVRON CHEMICAL COMPANY LLC

Applicant Address

555 MARKET STREET, P.O 7141, SAN FRANCISCO, CALIFORNIA 94120-7141,

Inventors:

#	Inventor's Name	Inventor's Address
1	NICHOLAS J HARITATOS	1354 CONTRA COSTA DRIVE E1 CERRITO, CALIFORNIA 94530,

PCT International Classification Number

C10G 035/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	08/995 587	1997-12-22	U.S.A.