Title of Invention

PROCESS AND APPARATUS FOR PRODUCING AROMATIC COMPOUNDS, INCLUDING CATALYST REDUCTION

Abstract

ABSTRACT IN/PCT/2002/00801/CHE "Process and apparatus for producing aromatic compounds, including catalyst reduction" The invention concerns a method for producing aromatic compounds from a hydrocarbon cut using a catalyst which preferably circulates in mobile red, said method comprising at least the following successive steps carried out at least in a zone; treating the cut in the presence of hydrogen and performing at least a dehydrogenation reaction of naphthenes; separating the gas effluent containing hydrogen, from the liquid product and from the catalyst, regenerating the catalyst, reducing the catalyst and re-introducing the catalyst in the treating step; recycling in the treating step part at least of the gas effluent containing hydrogen called recycling gas; method wherein the reduction step is carried out in the presence of the recycling gas introduced in an amount such that the amount of input pure hydrogen ranges between 1-10 kg/kg of the catalyst, the effluent derived from the reduction being then separated from the catalyst bed. The invention also concerns the associated device.

Full Text

PROCESS AND APPARATUS FOR PRODUCING AROMATIC COMPOUNDS, INCLUDING CATALYST REDUCTION The invention relates to processes (preferably moving bed processes) for producing aromatic compounds from hydrocarbons, in which a hydrocarbon feed supplemented by a hydrogen-rich gas is transformed. More specifically, it relates to continuous reforming or still more specifically to BTX (butane, toluene, xylems) production with continuous catalyst regeneration. More particularly, it relates to the catalyst reduction step, and optionally also the first reactor in which dehydrogenation of the apothems contained in the feed primarily occurs. The catalyst generally comprises a support (for example formed from at least one refractory oxide, the support also possibly including one or more elites), at least one noble metal (preferably platinum), and preferably at least one promoter metal (for example tin or rhenium), at least one halogen and optionally one or more additional elements (such as alkalis, alkaline-earths, lanthanides, silicon, group IVB elements, non noble metals, group IIIA elements, etc.). As an example, such catalysts contain platinum and at least one other metal deposited on a chlorinated alumina support. In general, such catalysts are used to convert naphthenic or paraffin hydrocarbons which can be transformed by dehydrocyclisation and/or dehydrogenation, in reforming or for the production of aromatic hydrocarbons (for example production of benzene, toluene, or ortho-, meta- or para-xylene). Such hydrocarbons originate from fractionating crude oil by distillation, or from other transformation processes such as catalytic cracking or steam cracking. Such catalysts have been widely described in the literature. Many chemical reactions occur during the reforming process. They are well known; reactions which are beneficial for the formation of aromatic compounds and improving the octane index which can be cited are naphthene dehydrogenation, cyclopentane ring isomerisation, paraffin isomerisation, paraffin dehydrocyclisation; the deleterious reactions include paraffin and naphthene hydrogenolysis and hydrocracking. The reaction rates of such a variety of reactions are very different and are highly endothermic for dehydrogenation reactions and exothermic for the other reactions. For this reason, the reforming process is carried out in a plurality of reactors which are subjected to varying temperature drops. Experience has shown that naphthene dehydrogenation reactions occur in the first reactor or reactors. Thirty years ago, reforming processes or aromatic production processes were carried out at 40 bars, while twenty years ago, it was 15 bars, and today's reforming reactors operate at pressures below 10 bars, in particular in the range 3 to 8 bars. However, such a reduction in the hydrogen pressure is accompanied by more rapid catalyst deactivation by coking. Coke, a compound with a high molecular weight and primarily based on carbon and hydrogen, is deposited on the active sites of the catalyst. The H/C mole ratio of the coke formed is in the range about 0.3 to 1.0. The carbon and hydrogen atoms form condensed polyaromatic structures with a variable degree of crystalloid depending on the nature of the catalyst and the operating conditions employed in the reactors. While the transformation selectivity of hydrocarbons to coke is very low, the amount of coke that accumulates on the catalyst can be large. Typically, for fixed bed units, such amounts are in the range 2.0 to 20.0 or 25.5% by weight. For slurry reactor units,, these amounts are in the range 3.0 to 10.0% by weight at the outlet from the last reactor. The coke is mainly deposited in the last or in the last two reactors. Coke deposition, which is faster at low pressure, necessitates more rapid catalyst regeneration. Currently, regeneration cycles are as short as 2-3 days. Many patents concern processes for reforming or producing aromatic compounds with continuous or sequential catalyst regeneration. The processes employ at least two reactors in which a moving bed of catalyst circulates from top to bottom traversed by a feed composed of hydrocarbons and hydrogen, with the feed being re¬heated between each reactor. It should be noted that this moving bed utilization is highly advantageous linked to the use of a reduced H2/HC ratio in the first reactor, but any other higher values of the H2/HC ratio are possible in this reactor, in particular those of the prior art. Our co-pending application No. IN/PCT/2002/00790/CHE relates to a process for producing aromatic compounds from a hydrocarbon cut using a catalyst circulating in a moving bed, the process comprising at least the following successive steps: a first step for treating the cut employing a naphthene dehydrogenation reaction carried out in the presence of hydrogen in a ratio (H2)i/HC where (H2)i represents the molar quantity of pure hydrogen introduced into said first step and HC represents the molar quantity of feed introduced into said first step; followed by at least one subsequent treatment step carried out in the presence of hydrogen in a mole ratio (H2)2/(HC)2, where (H2)2 represents the molar quantity of pure hydrogen introduced into said subsequent step and (HC)2 represents the molar quantity of feed entering said subsequent step; separating the gaseous hydrogen-containing effluent from the liquid product and the catalyst, recycling at least a portion of the gaseous hydrogen-containing effluent, termed the recycle gas, to said first treatment step; regenerating and reducing the catalyst then re-introducing the catalyst into said first treatment step, reduction taking place in the presence of hydrogen in a mole ratio (H2)red/HC where (H2)red represents the quantity of pure hydrogen introduced into the reduction step; which at least a portion of the gaseous effluent from the reduction step is introduced into said first step and/or into at least one subsequent step following dehydrogenation; characterized in that the sum of the mole ratios (H2)i/HC + (H2)red/HC is less than or equal to the mole ratio (H2)2/(HC)2, or the sum of said mole ratios is greater than the mole ratio (H2)2/(HC)2 but where (H2)iHC is lower than (H2)2/(HC)2. The invention also provides a reactor for the said process. Experience has shown that the first reactor is the seat of rapid reactions producing large amounts of hydrogen. The Applicant's French patent FR-A-2 657 087 describes such a reforming process. Figure 1 reproduced in this document (corresponding to Figure 2 of FR-A-2 657 087) employs 4 reactors. An initial feed composed of hydrocarbons and hydrogen is circulated through at least two reaction zones disposed in series, side by side, each of these reaction zones being of the moving bed type, the feed circulating successively in each reaction zone, and the catalyst also circulating in each reaction zone and flowing continuously in the form of a moving bed from top to bottom in each zone, the catalyst being withdrawn from the bottom of each reaction zone and being transported in a stream of hydrogen to the top of the next reaction zone, the catalyst that is continuously withdrawn from the bottom of the last reaction zone traversed by the feed then being sent to a regeneration zone. Referring to Figure 1, the feed composed of hydrocarbons and hydrogen in a set H2/HC ratio traverses reactor 1 (29) and is re-heated, traverses reactor 2 (42), is re-heated, traverses reactor 3 (55a), is re-heated, traverses reactor 4 (55), and is sent to a separation section. The catalyst drops into reactor 1 (29), is traversed by the feed and is withdrawn from (29) via lines (31) and (32). It is recovered in a hopper (34a), lifted to the upper surge drum (39) of reactor 2 via a lifting means (34) and (36); it flows from the surge drum (39) via lines (40) and (41) towards reactor 2 (42); it is withdrawn from (42) via lines (44) and (45), is recovered in a hopper (47a), lifted to upper surge drum (52a) of reactor 3 via a lifting means (47) and (49a); it flows from the surge drum (52a) via lines (53a) and (54a) towards reactor 3 (55a); it is withdrawn from (55a) via lines (62a), is recovered in a hopper (47b), lifted to upper surge drum (52) of reactor 4 via a lifting means (47c) and (49); it flows from the surge drum (52) via lines (53) and (54) towards reactor 4 (55); it is withdrawn from (55) via lines (62), is recovered in a hopper, lifted to upper surge drum (7a) of regenerator (10) via a lifting means (60a), (6a) and (6b); it flows from this surge drum (7a) via line (9) towards regenerator (10); it is withdrawn from (10) via lines (16) and is recovered in a hopper (17a), lifted to upper surge drum (63) of reactor 1 via a lifting means (17) and (19); it flows from this surge drum (63) via line (66) to a reduction drum (20) where the catalyst at least partially regains it metallic form; finally, it flow via lines (27) and (28) towards reactor 1 (29). The feed in the reactor(s) for reforming or producing aromatic compounds is generally treated at pressures of 0.1 to 4 MPa, preferably 0.3-0.8 MPa, at 400-700°C, preferably 480-600°C, at space velocities of 0.1 to 10 h', preferably 1-4 h', and with recycled hydrogen/hydrocarbon (mole) ratios of 0.1 to 10, preferably 3-10, more particularly 3-4 for regenerative reforming and 4-6 for the aromatic compound production process. Traditionally, after the last reactor, a first separation is carried out between the hydrocarbons and a recycled hydrogen which is re-injected into fresh feed. The non-recycled effluent undergoes a separation process to produce hydrogen known as exported hydrogen, which may contain up to 10% by volume or preferably 4% by volume of light hydrocarbons such as ethane and propane. By comparison, recycle hydrogen can contain more than 10%, generally more than 12% or 15% by volume of Ci"^, C2H4 to Cio aromatic compounds. The coked catalysts are regenerated. The catalyst is generally regenerated in three principal steps: (a) a combustion step wherein the coke is eliminated by burning with an oxygen-containing gas; (b) a halogenation’s step wherein the catalyst is flushed with a halogenated gas to re¬introduce halogen into the catalyst and re-disperse the metallic phase; (c) a drying or claiming step, which eliminates the water produced by coke combustion from the catalyst. It is completed by a reduction step wherein the catalyst is reduced prior to introducing the feed, which is generally carried out between the regenerator (where steps a, b, c are carried out) and the first reactor where the reaction takes place. Reduction consists of chemical transformation of the metallic phase contained in the catalyst. After preparing the catalyst or after the claiming step undergone by the catalyst undergoing regeneration, the metal or metals are present on the catalyst surface in the form of the oxide or the ox chloride, which are practically inactive from a catalytic viewpoint. Before injecting the hydrocarbon feed to be treated, it is thus vital for the catalyst to be reduced. In practice, such reduction is carried out at high temperature (between 300-800°C, more generally 450°C to 550°C) in the presence of exported or purified hydrogen, and for periods generally m the range from a few minutes to a few hours. The purified hydrogen originates from an exported hydrogen purification unit. It generally contains less than 1% by volume of C2"*". Then a purified or exported hydrogen gas is supplied for reduction and which is then withdrawn and lost once the reduction operation is complete, and a (non purified) recycle hydrogen is supplied for the reaction in a H2/HC ratio which is unique to the reforming unit. The present invention proposes the use of recycle hydrogen for reduction, and when the process is operated with a moving bed of catalyst, it optionally combines the reduction zone and the first reactor. This disposition can increase the available quantity of exported hydrogen - a product with a high added value. If necessary, the invention can also do away with purifying the hydrogen from the reforming process. More precisely, the invention concerns a process for producing aromatic compounds from a hydrocarbon cut using a catalyst (preferably circulating in a moving bed), the process comprising at least the following successive steps carried out in at least one zone: treating the cut in the presence of hydrogen and using at least one naphthene dehydrogenation reaction, separating a gaseous hydrogen-containing effluent, a liquid product and the catalyst, regenerating the catalyst, reducing the catalyst and re-introducing the catalyst to the treatment step, and optionally and preferably recycling at least a portion of the gaseous hydrogen-containing effluent, termed the recycle gas, to the treatment step, in which process the reduction step is carried out in the presence of a recycle gas introduced in a quantity such that the quantity of pure hydrogen supplied is in the range 1-10 kg/kg of catalyst, the effluent from the reduction step then being separated from the catalyst bed. The invention also proposes a supplemental step to the process, consisting of recycling at least a portion of the gaseous hydrogen-containing effluent (recycle gas) separated from the liquid and the catalyst to the reduction step. Advantageously, in the treatment zone where the naphthene dehydrogenation reaction takes place, the quantity of recycle gas is such that the H2/HC mole ratio is at most 10, H2 representing the quantity, expressed in moles of pure hydrogen, supplied to the zone of the treatment step in which the dehydrogenation reaction principally occurs, and HC representing the quantity, expressed in moles, of hydrocarbons in the cut entering said zone. The reduction step is generally carried out at 300-800°C, preferably 400-600°C, with the catalyst residence time being 15 min to 2 hours, preferably 30 min to 1 hour 30 minutes. The aromatic compound production process (and more particularly the zone in which the naphthene dehydrogenation reaction is principally accomplished) is carried out at 400-700°C, at 0.1-0.4 MPa, with space velocities of 0.1-10 h', with H2/HC mole ratios of 0.1 to 10. Advantageously, reforming is carried out at 0.3-0.8 MPa, at 480-600°C, with space velocities of 1-4 h' and with preferred H2/HC ratios of at most 4 or even at most 2 in the step involving dehydrogenation. BTX aromatic compounds are advantageously produced at 0.3-0.8 MPa, at 480-600°C, with space velocities of 1-4 h' and with preferred H2/HC ratios of at most 6 or even at most 3 in the step involving dehydrogenation. The treatment step can be conducted in one or more zones; thus for the reforming shown in Figure 1, four treatment zones are used. The invention thus pertains to the reduction step carried out on the catalyst and optionally to the first zone (or first reactor) of the treatment step. The invention will be better explained with reference to Figure 2. The catalyst circulates from regenerator (106) to the upper surge drum (101) of the first reactor (103), via a transfer means (107) which, for example, is a lift (107); it falls under gravity via lines (108) towards the reduction zone (102). This reduction zone can be axial or radial and can comprise one or more sections. The catalyst leaving the reduction zone passes via line(s) (109) into the first reactor (103) from which it is withdrawn via lines (110); it is then sent to the upper surge drum (104) of the second reactor (105) via a transfer means (111), advantageously a lift. The hydrogen-containing gas used for the reduction step is supplied via line (112). Advantageously, it is supplied at the temperature of the reduction step, via at least one heating means (113). The resulting stream (114) reduces the catalyst in chamber (102). A stream (115) leaves. A hydrogen-containing gas supplied via at least one line (117) is added to the feed supplied via at least one line (116) and the resulting stream enters the first reactor via line (119), in which reactor the naphthene dehydrogenation reactions principally take place. Define (Hi); as the quantity in moles of hydrogen (expressed as pure hydrogen) supplied to the first reactor (103) (excluding any hydrogen which may originate from reduction) via line (119); (H2)red as the quantity in moles of hydrogen (expressed as pure hydrogen) provided to reactor (102) via line (114); (H2)2 as the quantity in moles of hydrogen (expressed as pure hydrogen) supplied to reactor (105) in which the subsequent step occurs (not principally including naphthene dehydrogenation reactions); (HC) as the quantity in moles of feed entering the first reactor; (HC)2 as the quantity in moles of feed entering the reactor for the subsequent step (105). In Figure 2 (HC)2 is equal to HC since all of the effluent from the first reactor is treated in the second reactor. It is possible to envisage the case where only a portion of the effluent from the first step is treated in the subsequent step, and the case where feed is added to the effluent from the first step prior to the reactor for the subsequent step. In accordance with the invention, the quantity (H2)i is such that: (H2)l (H2)red (H2)2 + HC HC (HC)2 In general, (H2)i/HC is at most 10, preferably 0.1 to 10. All quantities are expressed in moles. The quantity of hydrogen supplied to the reduction step (calculated as pure hydrogen) is selected such that the HSV with respect to the catalyst is in the range 1 to 10 kg of hj'drogen/kg of catalyst/h, preferably in the range 2 to 6 kg of hydrogen/kg of catalyst/h. The flow rate of the gas is sufficient to eliminate the heat supplied by any C2^ hydrocarbon cracking reactions contained in the reduction gas. The quality of the hydrogen is less critical than in the prior art. Thus advantageously, a gas can be used for reduction which may contain large quantities of impurities, for example 15% by volume of C2"^. Highly advantageously, recycle hydrogen is used in the first reactor (principally naphthene dehydrogenation reactions), but purified hydrogen and exported hydrogen could be used, although this solution is not as important economically. It should be noted that the ratio H2/HC defined above is the ratio conventionally used in the treatment process, more particularly in the first zone. Thus preferably, it is 2-4 for reforming and 3-6 for aromatic compound production. This means that the ratio (H2)i/HC, in the treatment zone where the naphthene dehydrogenation reaction occurs, is lower than the ratio H2/HC of the prior art when (Figure 2) the hydrogen supplied for reduction is withdrawn from the reduction step and does not pass into said zone (except for the small amount that passes along with the moving catalyst bed). Thus when implementing the invention, the ratio (H2)i/HC in said zone has been able to be reduced and as a result, the naphthene dehydrogenation reaction is favored. Advantageously, stream (118) is supplied at the reaction temperature of the first reactor (103) by at least one heating means (120). The resulting stream (119) reacts in reactor (103) and produces an effluent (121). Preferably, the gas streams (115) and (121) are mixed in a line (122) and constitute the feed for the next reactor (105), which is advantageously supplied at the reaction temperature by means of at least one heating means (123). In this preferred disposition, mixing the reduction hydrogen effluent with the effluent from the first reactor can produce a ratio (H2)2/(HC)2 at the inlet to the second reactor that may be higher than in the prior art, thus encouraging hydrocarbon transformation after dehydrogenation. Thus the gaseous effluents from reduction and the step implementing dehydrogenation are introduced into at least one step following dehydrogenation. It is even possible to add recycle gas to said step following dehydrogenation. More generally, at least a portion of the gaseous effluent from the reduction step can be introduced into the step implementing dehydrogenation and/or at least one step following dehydrogenation. The effluent leaving reactor (105) via line (124) is then treated in a conventional treatment process; for example, it is sent to a third treatment zone, or it may be withdrawn, etc... The same is true for the catalyst. The invention thus consists of diminishing the supply of hydrogen via line (119) in the first zone of the treatment step, compared with the prior art, and increasing the quantity of hydrogen in the reduction step. In all cases, the quantity of hydrogen used for reduction is controlled. This quantity of hydrogen used for reduction can be adjusted to the operator's requirements. It may correspond to maintaining the global H2/HC ratio (reduction + 1^' reactor). It may reach a globally higher H2/HC ratio while maintaining a hydrogen deficit in the first reactor. This results in maintaining the H2/HC ratio (with respect to the prior art) in the second reactor (after major dehydrogenation of the naphthenes), or in an increase in this ratio, favoring other reactions. Supplemental hydrogen can also be injected. This provides major advantages: (a) a high hydrogen flow rate with respect to the quantity of catalyst in the reduction zone, which limits deleterious thermal effects of hydrogenolysis and hydrocracking of C2* hydrocarbons which may be present in the hydrogen used for reduction, such that the process of the invention can function with recycle hydrogen and in the absence of purification. (b) The first reactor is the primary seat of naphthene dehydrogenation reactions (for the reforming emits or for the production of aromatic compounds) which are strong hydrogen producers; a reduction in the quantity of hydrogen introduced into the feed for this first reactor favors these dehydrogenation reactions which are more rapid. Despite these reactions that are more favourable to coking, it has been shown that coking has no time to develop in a manner which is substantial with respect to the prior art situation. From the operator's viewpoint, the advantages of the invention result from: (a) the possibility of using a less pure hydrogen for reduction and limiting the residence time in the reduction zone; (b) limiting dechlorination and metallic sintering in the reduction zone, and thus increasing the service life of the catalyst; (c) optimizing the H2/HC ratio in the first reactor which reduces the quantity of catalyst necessary in this first reactor for naphthene dehydrogenation. The invention also concerns an apparatus for producing aromatic compounds carrying out he process of the invention. Said apparatus for producing aromatic compounds from a hydrocarbon cut using a catalyst circulating in a moving bed comprises: • at least one zone for treating the cut involving a naphthene dehydrogenation reaction, said zone being provided with at least one line for introducing the cut, at least one line for withdrawing a treated cut, at least one line for introducing catalyst into the top of said zone and at least one line for withdrawing catalyst located at the bottom of said zone, said zone also comprising at least one line for introducing a hydrogen-containing gas, and also comprising at least one gaseous stream withdrawal line; • at least one zone for separating catalyst, liquid product and gaseous hydrogen-contemning effluent; • at least one catalyst regenerating zone; • at least one zone for reducing regenerated catalyst corrected to said zone carrying out naphthene dehydrogenation such that the reduced catalyst enters said dehydrogenation zone via said line for introducing catalyst, said reduction zone being provided with: • at least one line for introducing hydrogen-containing gas; • and at least one line for withdrawing a gas stream; • at least one line for recycling at least a portion of the gaseous hydrogen-containing effluent from said separation zone to said zone carrying out the dehydrogenation reaction; • said apparatus also comprising at least one line for recycling at least a portion of the gaseous hydrogen-containing effluent to the line for introducing gas into said reduction zone. Advantageously, the apparatus comprises at least one reaction zone located after said zone carrying out the dehydrogenation reaction, said reaction zone comprising at least one catalyst inlet line and a catalyst withdrawal line, at least one line for introducing a hydrogen -containing gas and at least one line for withdrawing a gaseous effluent, and at least one line for entry of a reaction effluent from the preceding zone and a line for the reaction effluent from the present zone, in which apparatus the line for introducing a hydrogen-containing gas is connected to lines for withdrawing gaseous streams from the dehydrogenation zone and the reduction zone. Advantageously, the line for introducing a hydrogen-containing gas is also connected to a line supplying recycled gaseous effluent. The following example illustrates the invention without limiting its scope. A catalyst circulated at 800 kg/h and 90839 kg/h of feed were treated. Reduction was carried out with 18294 kg/h of an 83.7% by volume pure hydrogen-rich gas with a molar mass of 9.6 kg/kmole, with an Hi HSV of 4 h'\ and with a catalyst residence time of 1 hour. In the first treatment zone (first reactor), 9976 kg/h of a 83.7% by volume pure hydrogen-rich gas with a molar mass of 9.6 kg/kmole was injected into a 90839 kg/h feed. Thus the (Hi)i/HC ratio was 1.13. In the prior art, for the same feed and catalyst flow rate, a recycle gas with a molar mass of 9.6 kg/kmole containing 83.7% by volume of hydrogen was injected into the first reactor at a flow rate of 28270 kg/h. All of the effluent passed into the second reactor. The resultant mole ratio (H2)2/HC was 3.2. Reduction was carried out with a 92.1% by volume hydrogen-rich gas, with a molar mass of 4.4 kg/kmole at a flow rate of 600 kg/h, with a residence time of 2 hours for the catalyst. It can be seen that using the process of the present invention, a non-purified hydrogen containing more than 10% by volume of impurities, and generally more than 15% by volume, can be used both in the present reforming reactor and in the reducing reactor; and the flow rate of the hydrogen-rich gas injected into the feed for the first reactor is less than the quantity added for reduction. These conditions can be adjusted. When a H2/HC ratio of less than 1.1 is desired, the reaming hydrogen-rich gas (which has not been injected into the feed that enters the first reactor) has to be injected into the effluent from the first reactor before it enters the second reactor. If a higher (H2)i/HC is desired in the first reactor, it is possible to reduce the flow rate of the reduction hydrogen H2. Thus with an H2 HSV in the reduction zone of 2 h', for example, it is possible to operate under the conditions of the example with a (H2)i/HC ratio of 1.4 in the first reactor. It is possible to have a residence time and a reduction H2 HSV and a (H2)i/HC ratio in the first reactor such that the case of the example is not applicable. It is possible for the quantities of reduction hydrogen and hydrogen injected into the feed not to be sufficient to have a suitable H2/HC ratio at the inlet to the second reactor. In this case, it is possible to provide for supplemental injection of a hydrogen-rich gas into effluents leaving the first reactor, or at least into the feed for the second reactor. We have described the use of a reaction gas for reduction for a moving bed process. However, it is also applicable to a fixed bed process. It should be noted that this moving bed utilization is highly advantageous linked to the use of a reduced H2/HC ratio in the first reactor, but any other higher values of the H2/HC ratio are possible in this reactor, in particular those of the prior art. WE CLAIM: 1. A process for producing aromatic compounds from a hydrocarbon cut using a catalyst, the process comprising at least the following successive steps carried out in at least one zone: treating the cut in the presence of hydrogen using at least one naphthene dehydrogenation reaction; separating out a gaseous hydrogen-containing effluent to form a gas, termed the recycle gas, a liquid product and the catalyst; regenerating the catalyst; reducing the catalyst and re-introducing the catalyst into the treatment step; wherein the reduction step is carried out in the presence of a recycle gas introduced in a quantity such that the quantity of pure hydrogen supplied is in the range 1-10 kg/kg of catalyst, the effluent from the reduction step then being separated from the catalyst bed. 2. The process as claimed in claim 1, wherein the catalyst circulates as a moving bed. 3. The process as claimed in any one of the preceding claims, comprising recycling at least a portion of the gaseous hydrogen-containing effluent, termed the recycle gas, to the treatment step implementing dehydrogenation. 4. The process as claimed in any one of the preceding claims, wherein the reduction step is carried out between 300-800°C, the catalyst residence time being 15 min-2 h. 5. The process as claimed in any one of the preceding claims, wherein the reduction step is carried out between 400-600°C. 6. The process as claimed in any one of the preceding claims, wherein the process is carried out at 400-700°C, at 0.1-4 MPa, with space velocities of 0.1-10 h '^ and (H2)i/HC mole ratios of at most 10. 7. The process as claimed in any one of the preceding claims, wherein it concerns reforming carried out at 0.3-0.8 MPa, at 480-600°C, with space velocities of 1-4 h"' and with (H2)i/HC ratios of at most 4 in the step implementing dehydrogenation. 8. The process as claimed in any one of claims 1 to 6, wherein it concerns aromatic compound production carried out at 0.3-0.8 MPa, at 480-600°C, with space velocities of 1-4 h"' and (H2)i/HC ratios of at most 6 in the step implementing dehydrogenation. 9. The process as claimed in any one of the preceding claims, wherein the recycle gas contains more than 10% by volume of C2+ impurities. 10. The process as claimed in any one of the preceding claims, wherein at least a portion of the gaseous effluent from the reduction step is introduced into the step implementing dehydrogenation and/or is introduced into at least one step following dehydrogenation. 11. The process as claimed in any one of the preceding claims, wherein recycle gas is added to said step following dehydrogenation. 12. An apparatus for producing aromatic compounds from a hydrocarbon cut using a catalyst circulating in a moving bed, comprising: at least one zone for treating the cut involving a naphthene dehydrogenation reaction, said zone being provided with at least one line for introducing the cut, at least one line for withdrawing a treated cut, at least one line for introducing catalyst into the top of said zone and at least one line for withdrawing catalyst located at the bottom of said zone, said zone also comprising at least one line for introducing a hydrogen-containing gas, and also comprising at least one gaseous stream withdrawal line; at least one zone for separating catalyst, liquid product and gaseous hydrogen containing effluent; at least one catalyst regenerating zone; at least one zone for reducing regenerated catalyst connected to said zone carrying out naphthene dehydrogenation such that the reduced catalyst enters said dehydrogenation zone via said line for introducing catalyst, said reduction zone being provided with at least one line for introducing hydrogen-containing gas; and at least one line for withdrawing a gas stream; at least one line for recycling at least a portion of the gaseous hydrogen-containing effluent from said separation zone to said zone carrying out the dehydrogenation reaction; said apparatus being wherein it also comprises at least one line for recycling at least a portion of the gaseous hydrogen-containing effluent to the line for introducing gas into said reduction zone. 13. An apparatus according to claim 12, wherein it comprises at least one reaction zone located after said zone carrying out the dehydrogenation reaction, said reaction zone comprising at least one catalyst inlet line and a catalyst withdrawal line, at least one line for introducing a hydrogen containing gas and at least one line for withdrawing a gaseous is effluent, and at least one line for entry of a reaction effluent from the preceding zone and a line for the reaction effluent from the present zone, in which apparatus the line for introducing a hydrogen-containing gas is connected to lines for withdrawing gaseous streams from the dehydrogenation zone and the reduction zone. 14. An apparatus according to claim 13, wherein the line for introducing a hydrogen-containing gas is also connected to a line supplying recycled gaseous effluent.

Documents:

in-pct-2002-0801-che abstract-duplicate.pdf

in-pct-2002-0801-che abstract.pdf

in-pct-2002-0801-che claims-duplicate.pdf

in-pct-2002-0801-che claims.pdf

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in-pct-2002-0801-che petition.pdf