Title of Invention	"A NOVEL CATALYST COMPOSITE MATERIAL USEFUL FOR DESULFURIZATION OF HYDROCARBON FEEDSTOCK AND PROCESS FOR THE PREPARATION THEREOF"
Abstract	The present invention discloses a new method of preparation of catalyst composite materials comprising of mixed sulfides of metallic elements belonging to Group VI and Group VIII supported on a siliceous mesoporous material whose pore-surface has been coated with oxides such as alumina or titania, that are sufficiently active to desulfurize petroleum oils such as diesel fractions to low levels of sulfur. The method of preparation involves the use of two organic additives and a heteropoly acid as the source of the Group VI metal. The large surface area of the support and the preparation process allow for the loading of a large amount of the metals in a single impregnation step.

Title of Invention

"A NOVEL CATALYST COMPOSITE MATERIAL USEFUL FOR DESULFURIZATION OF HYDROCARBON FEEDSTOCK AND PROCESS FOR THE PREPARATION THEREOF"

Abstract

The present invention discloses a new method of preparation of catalyst composite materials comprising of mixed sulfides of metallic elements belonging to Group VI and Group VIII supported on a siliceous mesoporous material whose pore-surface has been coated with oxides such as alumina or titania, that are sufficiently active to desulfurize petroleum oils such as diesel fractions to low levels of sulfur. The method of preparation involves the use of two organic additives and a heteropoly acid as the source of the Group VI metal. The large surface area of the support and the preparation process allow for the loading of a large amount of the metals in a single impregnation step.

Full Text	FIELD OF THE INVENTION The present invention relates to novel catalyst composite materials. More specifically, it relates to a novel catalyst composite material useful for desulfurization of hydrocarbon feedstock and process for the preparation thereof. BACKGROUND OF THE INVENTION The sulfur content of hydrocarbon fuels typically from petroleum is being lowered all over the world in stages. In the case of diesel fuel, it is expected that it will be limited to 50 ppm or below by the year 2005 in most parts of the world. Many types of sulfur compounds are present in straight run and cracked distillates. The ease of hydrodesulfurization (HDS) of these molecules over conventional Co-Mo (or Ni-Mo) catalysts depends on their molecular structure. Among these S-compounds, 4,6-disubstituted dibenzothiophenes are the most difficult to desulfurize. For example, the relative rate of desulfurization of (unsubstituted) dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) over a Co-Mo-HDS catalyst has been reported to be 6:1 (F. Bataille, J. Mijoin, J.L. Lemberton, G. Perot, G. Berhault, M. Lacroix, F. Mauge, S. Kasztelan and M. Breyesse, Stud. Surf. Sci. Catal., 130 (2000) 2831). Another study has reported the pseudo first order rate constants for HDS of DBT, 4-MDBT (4-methyldibenzothiophene) and 4,6-DMDBT on a Co-Mo catalyst to be 0.058, 0.018 and 0.006 min-1, respectively (X. Ma, K. Sakanishi and I. Mochida, Ind. Eng. Chem. Res., 33 (1994) 218). Therefore, due to the presence of these refractory 4,6-dialkyldibenzothiophene compounds, the desulfurization of diesel to less than 50 ppm is difficult. Work is in progress throughout the world on the development of new processes for deep desulfurization of diesel. Some new catalyst technologies have been reported recently for deep HDS of diesel. Besides, research on biodesulfurization methods for S reduction in diesel is also in progress. The technological innovations for deep desulfurization include the introduction of multiple hydrogen injection and removal of H2S and NH3 from intermediate sections of the reactor. These improvements are rather expensive to implement in existing reactors and totally new reactor systems need to be constructed. In this context, it will be much more economical to design an active catalyst that can desulfurize diesel to the desired low sulfur specification. Such a catalyst can be loaded in existing HDS reactors without any additional expense. Co-(Ni)-Mo catalysts are widely used in desulfurizing petroleum fractions. These catalysts are active in the sulfided state converting the sulfur in sulfur compounds into H2S in the presence of H2. Various types of species such as M0S2, Co-(Ni)-Mo-S and Co (Ni) sulfides have been reported to be present on the surface of sulfided Co-Mo-alumina catalyst. Of these, only the Co-Mo-S phase has been found to be mainly responsible for HDS activity (H. Topsoe, B.S. Clausen and F.E. Massoth, "Hydrotreating Catalysts", SpringerVerlag, Berlin, 1996). The structure of the Co-Mo-S phase is now clearly established. This phase consists of microcrystallites of M0S2, the edge sites of which are substituted by Co (P. Ratnasamy and S. Sivasanker, Catal. Rev.-Sci. Eng., 22 (1980) 401). In the presence of H2 some S atoms are lost as H2S creating anion vacancies. These vacancies (coordinately unsaturated site, CUS) can arise on the basal plane and at the edges and corners of crystallites. The smaller the crystallite, the larger is the proportion of edge and corner anion vacancies to vacancies at the basal plane. The S-containing molecules adsorb at these vacancies on the CUS and undergo desulfurization. The CUS at the basal surface, though may be sufficiently active to desulfurize non-beta substituted dibenzothiophene compounds, cannot easily desulfurise the di-beta substituted compounds due to steric hindrance. These compounds can, however, undergo HDS at the edge (or preferably the corner) CUS. Hence, the number and location of these sites determine the overall activity of the catalyst. A large number of innovations in hydrodesulfurization catalysts has been published or patented over the years. A few relevant ones are described below. US 5468709 describes a catalyst made from an alumina carrier substance, atleast one active metal element selected from Gr.VI metals in the periodic table, one active metal element chosen from Gr.VIII metals in the periodic table, phosphoric acid and an additive agent such as ethers of alcohols or alcohols (ethylene glycol, sugers as additives). US 6239066 gives the process for forming high activity catalysts, consisting of wetting the catalyst composition by contact with a chelating agent such as EDTA, MEA etc in a carrier liquid, aging the so wetted substrate and drying and calcining. EP 1041133 describes a catalyst with organic additives selected from a group of compounds comprising at least two hydroxyl groups and 2-10 carbon atoms and the polyethers of these compounds along with M0O3, NiO and P2O5. EP 1043069 A discloses the preparation of a sulfided hydrotreating catalyst as 50% alumina, one hydrogenation metal component and an organic compound comprising at least one covalently bonded nitrogen atom and atleast one carbonyl moiety. Thus a catalyst containing 26% M0O3,4.7% NiO, 6.7% P2O5 on gamma-alumina as carrier was impregnated with diammonium salt of EDTA solution, aged for three days and dried at 130°C. Some patents refer particularly to support improvements. US Patent 5,897,768 discloses the incorporation of zeolitic and acidic components in HDS catalysts to isomerize or disproportionate the dialkyldibenzothiophene compounds leading to ease of their desufurization. However, due to the presence of acidic components, one would expect unwanted cracking of other components causing lower product yields, besides rapid deactivation due to fast coke deposition. US Patent 6,239,066 Bl reports the preparation of the catalysts containing nanocrystalline alumina of crystallite size upto 25 A at the surface and also possessing mesopores. Mesoporous silicas such as MCM-41 (C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli and J.S. Beck, Nature 359 (1992) 710) has been reported to be a good support for HDS catalysts. Another ordered mesoporous material, with thicker walls than MCM-41, invented by Stucky and others form the University of California at Santa Barbara, California, USA (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548) called Santa Barbara -15 (abbreviated as SBA-15) has also been reported to be good supports for HDS catalysts. The supports possess a large surface area of about 1000 m per gram and can effectively support and disperse a larger amount of the active sulfide species. Besides, these possess uniform pores in the mesopore region (20 - 200 A) permitting the easy diffusion of the sulfur containing molecule. C. Song and K.M. Reddy have found that they could load more than double the amount of Co and Mo oxides on MCM-41 than present in typical Co-Mo-alumina catalysts and reported that the activity of the catalyst was more than double that of the alumina based catalyst for converting the model compound, dibenzothiophene (Applied Catalysis A: General, 176 (1999) 1). Similarly Vradman and others showed that the deposition of Ni and W sulfides on SBA-15 produced highly active catalysts in desulfurizing model compounds (L. Vradman, M.V. Landau, M. Herskowitz, V. Ezersky, M. Talianker, S. Nikitenko, Y. Koltypin and A. Gedanken, Journal of Catalysis, 213 (2003) 163). However, it is known that Co (Ni) and Mo (W) specie do not bind strongly on silica surfaces and silica supported catalysts generally deactivate faster due to sintering of the active sulfide phase. Again, the alumina surface possesses slight acidity which acts synergistically in the HDS reaction. The inclusion of Al ions in MCM-41, no doubt, will increase the binding of the active species. However, as other elements like Al can be incorporated only in small amounts (Si/Al ratio >25) sufficient Al ions may not be available on the surface to interact with the Co-Mo-species in Al-containing MCM-41. Further, MCM-41 itself is not very stable and its structure tends to collapse during the impregnation and catalyst preparation and sulfidation steps. As a result MCM-41 supported catalysts are not suited to processing real feeds where other components such as N is also present (P.J. Kooyman, P. Waller, A.D. van Langeveld, K.M. reddy and J.A.R. van Veen, Catalysis Letters, 90(2003)131). SBA-15 (Santa Barbara - 15), another mesoporous silica, is sturdier than MCM-41 due to its thicker silica walls and its structure is expected to be more resilient to destruction. Even so, it still possesses the disadvantages of a silica support. In the case of SBA-15, it is much more difficult to incorporate Al on its surface than on MCM-41 (Si/Al 100 A) compared to MCM-41 (typically, 30 - 40 A). The small size of the pores in MCM-41 should, in principle, restrict the diffusion of the molecules inside its pores when sulfide crystallites are present inside them. In the case of SBA-15, the diffusion of the molecules will be easier (due its large pores) even when the sulfide crystallites are present inside them. The disadvantages of a siliceous surface can be counteracted and the benefits of the large area SBA-15 can be exploited as a support if its surface is modified by covering with a suitable oxide, alumina or titania. OBJECTIVES OF THE INVENTION The main objective of the present invention is to provide a novel catalyst useful for desulfurization of hydrocarbon feedstock Another object of the present invention is to provide a process for the preparation of novel catalyst useful for desulfurization of hydrocarbon feedstock SUMMARY OF THE INVENTION The present invention provides for novel catalyst composite materials suitable for the desulfurization of petroleum oils. The invention also provides a process for the preparation of said catalyst composite materials. The catalyst composite materials of the present invention consist of a porous support, prepared from an ordered siliceous mesoporous material such as SBA-15 with a surface area in the range of 800 - 1000 m2/g and a pore-volume of about 1.0 - 1.2 ml/g by coating its pore-surface with a layer of alumina or titania, the coating being done by deposition / anchoring of Al or Ti-alkoxides on the surface and calcining the resultant material, and Group VI (Mo or W) and Group VIII (Co or Ni) metals loaded on to it as two different miscible interacting complexes or organometallic derivatives. The catalyst composite material consisting of the support and the complexes are dried at low enough temperatures in the range of 80 - 120°C to prevent the decomposition of the organometallics. It is then sulfided externally prior to loading in the reactor or insitu after loading in the reactor. The catalyst so prepared and sulfided contain more number of active sites for desulfurization and are also more suited for the desulfurization of refractory S-compounds such as 4.6-dibenzothiophene. The preparation process also enables the incorporation of the promoter phosphorous into the catalyst without an additional impregnation step. The hydrocarbon feedstock, typically belonging to the diesel fraction, is contacted with the catalyst composite materials in the presence of hydrogen at typical hydrotreating conditions of temperature and pressure to bring down its sulfur content to below 50 ppm. The use of this type of catalyst is 1 expected to improve liquid yields due to minimal cracking and due to higher activity of the catalyst, be able to operate at lower temperatures than prior-art catalysts. Accordingly the present invention provides a novel catalyst composite materials useful for desulfurization of hydrocarbon feedstocks, the said catalyst comprising composite material impregnated thin metal oxide layer coated mesoporous siliceous support material having the general formula (MO3)x (M'O)y (SiO2)z (M1'O)a (P205)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2is silicon oxide, M1 is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles. In an embodiment of the present invention the composite material used for impregnating siliceous material in a composite mixture is consisting of at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group. In another embodiment of the present invention the siliceous material used is SBA-15. In yet another embodiment of the siliceous material used contains ordered mesopores of size ranging from 30-200 A . In yet another embodiment of the present invention the meatal oxide layer used for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide. In yet another embodiment the amount of alumina or titania used for coating the mesopores of siliceous material is in the range of 5-20Wt% of the siliceous material support. In yet another embodiment the active metal used from group VI metals is selected from Mo and W. In yet another embodiment the active metal used from group VIII is selected from Co and Ni. In yet another embodiment the amount of active metal selected from group VI used is in the range of 10-40 Wt% as oxides. In yet another embodiment the amount of active metal selected from group VIII used is in the range of 2-10 Wt% as oxides. In yet another embodiment the phosphoric acid salt used is a hetero polyacid or poly oxometallate of group VI metal. In yet another embodiment the hetro polyacid of group VI metal used is phosphomolybdic acid. In yet another embodiment the organic additive having at least one aldehyde group used is glyoxylic acid. In still another embodiment the organic additive having at least one carboxylic group used is ethylene diaammine teteracetic acid (EDTA). The present invention further provides a process for the preparation of a novel catalyst composite material having the general formula (MO3)x (M'O)y (SiO2)z (M1'O)a (P2O5)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles, the said process comprises coating the surface of siliceous support material with an uniform layer of metal oxide, impregnating the above said metal oxide layer coated siliceous support material with an aqueous solution composite components mixture containing at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group, at a temperature in the range of 25-50°C, drying the above said impregnated siliceous material at a temperature of 20-25 °C, for a period of 15-20 hrs followed by further heating at a temperature in the range of 100-120°C, for a period of 6-8 hrs to obtain the desired catalyst composite material. In yet another embodiment the siliceous material used is SBA-15. In yet another embodiment the siliceous material used contains ordered mesopores of size ranging from 30-200 A0 . In yet another embodiment the metal oxide layer used for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide. In yet another embodiment the amount of alumina or titania used for coating the mesopores of siliceous material is in the range of 5-20Wt% of the siliceous material support. In yet another embodiment the active metal used from group VI metals is selected from Mo and W. In yet another embodiment the active metal used from group VIII is selected from Co and Ni. In yet another embodiment the amount of active metal selected from group VI used is in the range of 10-40 Wt% as oxides. In yet another embodiment the amount of active metal selected from group VIII used is in the range of 2-10 Wt% as oxides. In yet another embodiment the phosphoric acid salt used is a hetero polyacid or poly oxometallate of group VI metal. In yet another embodiment the hetro polyacid of group VI metal used is phosphomolybdic acid. In yet another embodiment the organic additive having at least one aldehyde group used is glyoxylic acid. In yet another embodiment the organic additive having at least one carboxylic group used is ethylene diaammine teteracetic acid (EDTA). In still another embodiment water is removed from the impregnated composite material under vacuum to prevent the decomposition of the organic additives or metal complexes. DETAILED DESCRIPTION OF THE INVENTION There are two main components in HDS catalysts, the support and the active component, the metal sulfide crystallites. Any improvement in catalytic activity is generally associated with improvements in both the support and the active catalytic species. Useful support improvements are: 1) thermal stability, 2) ease of diffusion of reactants and products through its pores, 3) ability to disperse the active component and maintain the dispersion and 4) synergistic effects (with the active species) enhancing the overall activity of the catalyst. Support improvements can be done out by increasing its surface area, optimizing pore characteristics to minimize diffusion effects, increasing thermal stability and enhancing interaction between support and metal sulfide particles to reduce sintering and increase synergism. The typical support used in the preparation of HDS catalysts of the Co-Mo or Ni-Mo (W) type is alumina, especially of the gamma form prepared from microcrystalline boehmite (pseudo-boehmite). These aluminas typically have surface areas in the range of 200 - 300 m and pore volumes of 0.5 - 0.8 ml per gram, respectively. The pore size distribution of these materials can vary from microporous (below 20A diameter) to mesoporous (20 - 500 A diameter) and macroporous (>500 A diameter). The micropores and the macropores are not advantageous as the former restrict the diffusion of the reactants, while the latter lead to low surface areas and poor mechanical strength of the materials. The most desired are the mesopores, preferably in the range between 40 - 150 A, with an average pore size of about 70 - 100 A. Thus, the literature is full of efforts to prepare aluminas possessing the right mesopores. In early 1990s, a new class of siliceous materials called M41S containing ordered mesopores with uniform diameter were reported by the Mobil Oil Co. (C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli and J.S. Beck, Nature 359 (1992) 710). At least three types of materials were reported, MCM-41, in which the mesopores were arranged in a hexagonal pattern, MCM-48, in which the pores were arranged in a cubic symmetry and MCM-50 made up of lamellar sheets of pores. The most common and more stable preparations had pores in the diameter of 20 - 50 A. These materials were synthesized using micellar surfactants as the templates. Though the M41S materials were typically most stable and formed easily in the siliceous form, other hetero-ions such as Al, Ti, Sn etc. could be introduced in small amounts. These materials had very large surface areas of 1000 - 1200 m2 and pore volumes of 1.2 to 1.4 ml per gram, respectively. These were however found to be rather unstable under hydrothermal conditions and lost crystallinity and ordering of the mesopore structure even when simple impregnations were attempted on them. A more stable mesoporous material called, SBA-15 containing much thicker walls was later on reported by Zhao and others (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548). These were prepared from poly-block copolymers of ethylene and propylene glycols. The typical pore dimensions of most of the reported SBA-15 preparations are in the range of 100 - 140 A. These are much more thermally and hydro-thermally stable than the M-41S materials. Thus, both the thermal stability and right pore dimensions make SBA-15 an ideal support for HDS catalysts. Both MCM-41 (or MCM-48) and SBA-15 are siliceous materials and do not stabilize the supported Co and Mo species, unlike alumina the preferred support for HDS catalysts. This weak interaction of the metal species with silica causes rapid deactivation through crystal growth. One trick for improving the metal-support interaction is to incorporate Al-ions in the framework. Though, a reasonable amount of Al (upto a few mole % of Al) can be incorporated into MCM-41 during the synthesis, these have not been found to be good supports for HDS catalysts (Catalysis Letters 90 (2003) 131). Further, the incorporation of other ions decreases the crystallinity, ordering of the pore system and stability of MCM-41. On the other hand in the case of the more stable SBA-15, the incorporation of ions like Al or Ti in the framework is difficult and very little incorporation takes place (less than one mole %) during direct synthesis. At this low level of incorporation, hardly any benefits due to Al can be seen. The present invention provides for the preparation of an ordered mesoprous siliceous support such as SBA-15 with a uniform coating of an oxide material such as alumina or titania on the surface of the pores and its use a s a support for HDS catalysts. The preparation involves the anchoring of the metal (Al or Ti) alkoxides on to the surface of SBA-15 by refluxing it with the alkoxides in toluene as the solvent. The alkoxides react with the surface silanol groups and get attached to the silanol surface as a monodispersed layer. The material is dried and the alkoxides converted into an oxide layer by careful calcination in air or oxygen rich nitrogen. The loading of the metal can be as high as 10 - 30 mole % sufficient to cover much of the surface of the pores. The deposited oxides now act as anchors for the active mixed-metal sulfide crystallites. The large surface area (800 - 900 m per gram) and the large pore volume (~ lml per gram) allow for the loading of substantial amounts of the active metals in a single loading step. The pores of SB A-15 are also of the right size (~ 100A) for use in HDS catalysts. The loading of the metal oxides on SBA-15 can also be carried out by chemical vapour deposition or other known methods using other salts of aluminum or titanium. The other component is the active species. The conventional method of making HDS catalysts say of the Co (Ni)-Mo-alumina type, involves the deposition of salts of Mo and Co from aqueous solutions by impregnation, drying and calcination to give a deposit of oxides of Co (Ni) and Mo. The catalyst is then sulfided at high temperatures, say 300 - 340°C, to convert the oxides into the sulfides. This method possesses limitations. For example, due to the high calcination temperature (about 500°C) used in the preparation, the metals, especially Co (Ni), interact with the support (alumina) and a fraction of the impregnated metals is lost as a useful desulfurizing catalyst. Again, as the metal components are deposited separately as oxides, after sulfidation, a substantial amount of these active components end up as inactive individual sulfide phases. Further, due to the high temperatures of calcination, the oxides (especially Mo) agglomerate into large clusters, thereby leading to large sulfide particles after sulfidation; these sulfide particles expose more the basal planes and are less active for desulfurizing the sterically hindered S-compounds. One more limitation of the prior-art method of preparing catalysts is that the oxides of Co and Mo deposited on the surface of the support undergo sulfidation at different temperatures. The temperature required for sulfidation increases in the order, Ni > Mo > Co. As a result when a typical catalyst containing mixed oxides of Co (Ni) and Mo is sulfided, discrete phases of the individual phases are formed at different temperatures and the formation of the active mixed metal sulfide phase is less. Further, a yet another limitation of the process of the prior-art is that due to the limited solubility of the Mo salts in water and the low pick up of the salts by alumina, the loading of Mo is small and multiple impregnation steps with intermediate calcinations are required for loading substantial quantities of the metals. The multiple calcinations causes loss of the active centres by reaction with the support, besides causing growth of the metal oxide phase on the surface. Further due to the need to impregnate the Mo and Co (Ni) salts from solutions with different pH values, the impregnation of the two metals is carried out separately, generally, Mo being loaded first in multiple steps, depending on the loading required, and calcined before loading the next metal Co (Ni). This method not only increases the number of preparation steps, it also prevents the intimate mixing of the two metallic components. The present invention provides for a catalyst composite material that does not possess the above limitations. Accordingly, the metal components Co (Ni) and Mo are incorporated on the surface of the support as miscible organometallic derivatives. The organometallic derivatives or complexes of the individual metals are prepared by adding the organic complexing agents or organic additives to the metal salts, namely a heteropoly acid or a polyoxometallate in the case of the group VI metal and as a hydrated carbonate species in the case of the group VIII metal. The two solutions containing the metals and the complexing agents or additives are mixed. The mixture of complexes and additives containing the active metals is loaded on the support by a single impregnation step at a low temperature, say below 50°C and pre-dried at a similar low temperature. The water component present in the composite material made up of the complexes and the support is removed at a low enough temperature, say below 150°C, to prevent the decomposition of the complexes / additives. The catalyst composite comprising of the mixture of complexes / additives and the support is sulfided directly without any calcination and conversion of the metals into oxides as practiced in the prior-art. The sulfidation may be carried out insitu in the reactor or externally before loading in the reactor. Another embodiment of the invention provides for the inclusion of the promoter phosphorus into the catalyst during the preparation of the complex besides loading of phosphorous in any other form as practiced in the prior-art. The invention also provides for the exclusion of phosphorous from the catalyst, if necessary, by the use of a non-phosphorous containing group VI metal precursor. The catalyst of the present invention is prepared from a heteropoly acid (HP A) containing phosphorous as the source of Mo (or W), hydrated Co (or Ni)-carbonate as the source of Co (or Ni), an aqueous solution of a complexing agent, such as glyoxylic acid to dissolve the HP A, hydrogen form of EDTA to solubilize the Co-carbonate and sufficient water to make a mixture of the desired composition to load the required amount of the metals. An important embodiment of the present invention is that the group VI and group VIII metals are incorporated along with different organic additives that are interchangeable with one another so that when the solution of the two organometallic compounds are mixed, a solution containing both the metals in a similar environment results. As described above, the catalysts according to the present invention are basically composed of the following: a carrier substance, at least one organic derivative of a heteropoly anion formed by an organic compound having at least two oxygen atoms, one of which being part of an aldehyde (-CHO) group, and one EDTA complex of the active metal selected from the Gr. VIII metals in the periodic table. The carrier is impregnated by a single step process with a homogeneous solution containing organic derivatives of group VI and VIII metal elements. The amount of the selected active metal element is 10-40 % and 2 - 10 % of the catalyst weight once converted to oxide weight, respectively for the group VI and group VIII metals. The phosphorous content in the catalyst can be increased by adding additional phosphorous as a phosphate salt or phosphoric acid to the mixture of the complexes of the metals. In one embodiment of the process, the catalyst contains one or more elements selected from the group VI, and one or more elements chosen from the group VIII. The typical group VI elements are Mo and W while the typical group VIII elements are Ni and Co. It is necessary that the carrier substance possesses a large surface area, and a large pore-volume. The support is preferably SBA-15 with its surface uniformly coated by deposition of a film of alumina or titania, the preparation of which has already been described. The glyoxylic acid complex of the HPA and EDTA complex of cobalt/nickel carbonates are prepared separately and mixed together with the required amount of water and the mixed organometallic species formed is used as the impregnating solution. The wet impregnated material is dried at a temperature between 80 - 120°C. The catalyst may be loaded in the reactor and presulfided as per the procedures in current practice and well known in the art. Experiments reveal that the complexing agents / additives break down easily during sulfidation and do not leave any carbonaceous residue that may be detrimental to the catalyst activity. In a less preferred embodiment of the present invention, the deposition of the active metals of the group VI and VIII is carried out over the surface modified SBA-15 by simple impregnation methods known in the art using compounds of Mo such as ammonium molybdates or cobalt nitrate. In this case, phosphorous may be added to the support prior to impregnation with the salts or it is added to one of the impregnating solutions. The present invention is illustrated with following examples, which are only illustrative in character. EXAMPLE 1 This example isllustrates the synthesis of siliceous SBA-15 used in the following examples. It was prepared according to a published procedure (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548) using the amphilic copolymer, poly (ethylene-glycol)-block;-poly (propylene-glycol)-block-poly (ethylene-glycol) (average molecular weight 5800, supplied by Aldrich chemical Co., USA). 16.33 g of the above polymer was dissolved in 120 ml of water and 240 g of 2 M HC1 with stirring. This solution was heated at 40° C for 2 h followed by dropwise addition of 34.7 g of tetraethylorthosilicate (Aldrich Chemical Co., USA) with vigorous stirring. This gel was stirred for 24 h at 40° C and then crystallized in a Teflon-lined autoclave at 100° C for 2 days. After crystallization, the solid product was filtered, washed with deionized water and dried in air at room temperature for 12 h. The material was calcined at 550° C for 6 h to obtain a white light powder. The XRD of the sample was typical of that reported for SBA-15 in the literature. It had a surface area of 853 m /g and a pore size of about 90 A. EXAMPLE 2 This example illustrates the preparation of an alumina coated SBA-15 support from the siliceous SBA-15, whose preparation is described in Example 1. Freshly activated SBA-15 (9 g) was refluxed with stirring for 4 h in tolurene (500 ml, dried by distillation over sodium metal) for azeotropic removal of water from the mesoporous material. To the refluxing solution, 2 g of aluminum isopropoxide (equivalent to 1 g alumina) dissolved in 100 ml of freshly distilled toluene was added. Stirring and refluxing was continued for another 4 h. The solid was filterd, washed with toluene once and dried in an oven at 110° C (for 4 h) and calcined carefully at 300° C for 6 h in air. The calcined powder was pelleted and broken into small pieces (1-2 mm size). The product is named as SBA-15 (alumina). XRD analysis showed that the SBA-15 structure was intact. EXAMPLE 3 This example illustrates the preparation of a titania coated SBA-15 support from the siliceous SBA-15, whose preparation is described in Example 1. Freshly activated SBA-15 (9 g) was refluxed with stirring for 4 h in tolurene (500 ml, dried by distillation over sodium metal) for azeotropic removal of water from the mesoporous material. To the refluxing solution, 4 g of titanium tert-butoxide (equivalent to 1 g titania) dissolved in 100 ml of freshly distilled toluene was added. Stirring and refluxing was continued for another 4 h. The solid was filterd, washed with toluene once and dried in an oven at 110° C (for 4 h) and calcined carefully at 300° C for 6 h in air. The calcined powder was pelleted and broken into small pieces (1-2 mm size). The product is named as SBA-15 (titania). XRD analysis showed that the SBA-15 structure was intact. EXAMPLE 4 This example illustrates the procedure for preparing a HDS catalyst by conventional impregnation method. 6.3 g of freshly activated SBA-15 (alumina) powder (prepared according to Example 2) was weighed in an evaporating dish. 0.72 g of orthophosphoric acid (85 %) was dissolved in 15 ml of water and added to it. The mixture was stirred well with a glass rod and kept at room temperature for 3h. Then, it was kept over a water bath and evaporated to dryness with gentle mixing. It was further dried in an oven at 110° C for 3 hours and calcined at 300° C for 3h in N2 and 3 h in air. A solution of 5.45 g of ammonium molybdate tetrahydrate in 22 ml of water was added to the above phosphorous impregnated SBA-15 (alumina) powder kept in the evaporating dish. The mixture was stirred well with a glass rod and kept for 2 h with periodic stirring. It was slowly allowed to evaporate to dryness over a water bath over a period of about 1 h. The dried mixture was further dried in an oven at 110° C for 6 h and then calcined carefully at 400° C for 3h in N2 and 3 h in air. A solution of 3.77 g of Co (No3)2.6H2o in 15 ml water was added to the above freshly calcined material kept in a evaporating dish. The mixture was stirred for 2 h gently at room temperature. It was then slowly allowed to evaporate to dryness over a water bath over a period of about 1 h. The dried mixture was further dried in an oven at 110° C for 6 h and then calcined carefully at 500° C for 3h in N2 and 3 h in air. The catalyst contained 28.26 % Mo, 5.95% Co and 2.8 % P as oxides. The powder was pelletted and broken into small pieces (1-2 mm size) and stored as catalyst "A". EXAMPLE 5 This example illustrates the preparation of Co-Mo-SBA-15 catalyst according to the improved preparation method of this patent making use of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below. Solution A: 12.76 g phosphomolybdic acid (equivalent to 12.06 g M0O3) was taken in a 100 ml beaker. 3 g of water was added to it followed by 3 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution. Solution B: In another beaker, 19.82 g of wet, freshly made C0CO3 (equivalent to 3.07 g CoO) was weighed. 3 g of water and 5.57 g of H-EDTA were added to it and the mixture was stirred to get a pink coloured Co-EDTA complex. The solutions A and B were mixed to get a clear blue homogeneous solution. This was impregnated on 20 g of freshly calcined pelletted and sized (1-2 mm) particles of siliceous SBA-15 support prepared according to Example 1. Thus a single step impregnation of cobalt-molybdenum with a high concentration of active species was achieved. The mixture was gently mixed for 2 h and the excess solution (if any) was drained. The impregnated powder was dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a blue coloured catalyst. This was stored in air-tight container under N2 immediately. The catalyst contained 33.24% of Mo and 8.67 % of Co as oxides (MoO3 and CoO) and 3 % of P as P2O5. The material is called "Catalyst B". EXAMPLE 6 This example illustrates the preparation of Co-Mo-SBA-15 (alumina) catalyst in the presence of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below. Solution A: 11.12 g phosphomolybdic acid (equivalent to 10.51 g M0O3) was taken in a 100 ml beaker. 2.7 g of water was added to it followed by 2.7 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution. Solution B: Freshly made wet C0CO3 (18.2 g) equivalent to 2.82 g CoO was weighed in the beaker, 5g water and 5.12 g H-EDTA were added to it. The mixture was stirred to get a clear pink solution. Solutions A and B were mixed and impregnated on 20 g freshly calcined and dry SBA-15 (alumina) support particles (prepared according to Example 2). The mixture was kept for 2 h with gentle mixing and the excess solution (if any) was drained. The impregnated particles was dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a light green catalyst. This was stored in an air-tight container under N2 immediately. The catalyst contained 28.96 % of Mo and 7.97 % of Co as oxides (M0O3 and CoO) and 2.5 % of P as P2O5. The material is called "Catalyst C" EXAMPLE 7 This example illustrates the preparation of Co-Mo-SBA-15 (titania) catalyst in the presence of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below. Solution A: 10.82 g phosphomolybdic acid (equivalent to 10.23 g M0O3) was taken in a 100 ml beaker. 3 g of water was added to it followed by 2.6 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution. Solution B: Freshly made wet C0CO3 (12.54 g) equivalent to 1.94 g CoO was weighed in the beaker, 6 g water and 3.52 g H-EDTA were added to it. The mixture was stirred to get a clear pink solution. Solutions A and B were mixed and impregnated on 20 g freshly calcined and dry SBA-15 (titania) particles (prepared according to Example 3). The mixture was kept for 2 h with gentle mixing and the excess solution (if any) was drained. The impregnated particles were dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a light green catalyst. This was stored in an air-tight container under N2 immediately. The catalyst contained 28.19 % of Mo and 5.49 % of Co as oxides (M0O3 and CoO) and 2..7 % of P as P2O5. The material is called "Catalyst D" EXAMPLE 8 In this example, the presulfiding of the catalyst composite material of this invention and the testing of the activity using a diesel oil feed is described. About fifteen grams the catalyst (1-2 mm size) prepared as illustrated in Examples 4 to 7 was loaded in a high pressure down-flow reactor (100 ml volume). The compositions of the catalysts used in the sulfidation and activity tests are presented in Table 1. The catalyst was diluted with its volume of ceramic beads of similar size before loading. The drying of the catalyst was done at 100°C for two hours in a slow flow of nitrogen (6 litres per hour). The reactor was then pressurized to 40 bars with hydrogen and the sulfiding feed (a commercial diesel oil from a hydrocracker containing 45 ppm S (wt.) spiked with dimethyl disulfide to give a total S content of 1 wt %) was injected at a weight hourly space velocity (WHSV) of 1 h"' calculated on the basis of the dry oxide weight of the catalysts. A hydrogen flow of 300 volumes to oil volume (was maintained. The temperature was slowly raised to 270°C in 6 hours and the sulfidation continued for 16 hours. The temperature was then raised to 320 and 340°C in steps holding for 4 hours at each temperature. The sulfidation feed was changed to one with 0.5% S and the sulfidation continued for 4 hours. The diesel required to be desulfurized (containing 2500 ppm S by wt.) was then injected to find out the activity of the catalyst after adjusting the temperature of the reactor to the desired value. PFPD (gas chromatograph, GC) analysis of the feed revealed that it contained essentially dibenzothiophene and its alkyl derivatives as S-compounds. The S content was analyzed by X-ray Flourescence analysis (XRF). The desulfurization activity test was carried out at a pressure of 40 atmospheres (bars), a temperature of 330°C, a weight hourly space velocity (WHSV) of 2 h-1 and H2/oil ratio of 300. The results of the experiments are also presented in Table 1. The tests reveal the following: 1) The catalysts prepared by coating the SBA-15 with alumina or titania are more active than the siliceous SBA-15 supported catalyst Catalysts A, C and D are more active than B), 2) the catalysts prepared using organic additives are more active than those prepared by impregnation (Catalysts C and D are more active than A) and 3) Titania coating of the SBA-15 support gives a more active catalyst than alumina coating. Table 1. The composition of the catalysts used and their HDS activity (Table Removed) The advantages of the present invention are are: Since, the catalysts are not calcined, loss of the active metal through reaction with the support does not occur and bulk oxide phases are not formed on the surface. Besides, as the active metals are present as intimately mixed complexes, the possibility of forming a mixed Co(Ni)-Mo-S phase is greatly enhanced. The mixed sulfide phases are also expected to be smaller in size than those prepared from the oxide precursors due to the low temperature of drying and the absence of large bulk metal oxide phases. Small crystallites of the mixed metal phase will be more effective in the desulfurization of the refractory hindered dialkyl- dibenzothiophene compounds. The use of the complexes for impregnating the metals also enables the loading of substantially large quantities of the metals in a single step than hitherto possible. We claim: 1. A novel catalyst composite materials useful for desulfurization of hydrocarbon feed stocks, the said catalyst comprising composite components material impregnated thin metal oxide layer coated mesoporous siliceous support material having the general formula (Formula Removed) where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles. 2. A catalyst as claimed in claim 1, wherein the siliceous material contains ordered mesopores of size ranging from 30-200 A0 . 3. A catalyst as claimed in claims 1-2, wherein the meatal oxide layer for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide. 4. A catalyst as claimed in claims 1-3, wherein the amount of alumina or titania for coating the mesopores of siliceous material is in the range of 5-20 Wt% of the siliceous material support. 5. A catalyst as claimed in claims 1-4, wherein the active metal from group VI metals is selected from Mo and W. 6. A catalyst as claimed in claims 1-5, wherein the active metal used from group VIII is selected from Co and Ni. 7. A catalyst as claimed in claims 1-6, wherein the amount of active metal selected from group VI is in the range of 10-40 Wt% as oxides. 8. A catalyst as claimed in claims 1-7, wherein the amount of active metal selected from group VIII is in the range of 2-10 Wt% as oxides. 9. A catalyst as claimed in claims 1-8, wherein the phosphoric acid salt is a hetero polyacid or poly oxometallate of group VI metal. 10. A catalyst as claimed in claims 1-9, wherein the hetro polyacid of group VI metal is phosphomolybdic acid. 11. A process for the preparation of a novel catalyst composite material as claimed in claim 1,having the general formula (MO3)x (M'O)y (SiO2)z (Mi'O)a (P2O5)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles, the said process comprises; coating the surface of siliceous support material with an uniform layer of metal oxide, impregnating the above said metal oxide layer coated siliceous support material with an aqueous solution composite components mixture containing at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group, at a temperature in the range of 25-50°C, drying the above said impregnated siliceous material at a temperature of 20-25 °C, for a period of 15-20 hrs followed by further heating at a temperature in the range of 100-120°C, for a period of 6-8 hrs to obtain the desired catalyst composite material. 12. A process as claimed in claim 11, wherein the organic additive having at least one aldehyde group is glyoxylic acid. 13. A process as claimed in claim 11, wherein the organic additive having at least one carboxylic group is ethylene dia a mine teteracetic acid (EDTA). 14. A process as claimed in claim 11, wherein water is removed from the impregnated composite material under vacuum to prevent the decomposition of the organic additives or metal complexes.

Full Text

FIELD OF THE INVENTION
The present invention relates to novel catalyst composite materials. More specifically, it relates to a novel catalyst composite material useful for desulfurization of hydrocarbon feedstock and process for the preparation thereof.
BACKGROUND OF THE INVENTION
The sulfur content of hydrocarbon fuels typically from petroleum is being lowered all over the world in stages. In the case of diesel fuel, it is expected that it will be limited to 50 ppm or below by the year 2005 in most parts of the world. Many types of sulfur compounds are present in straight run and cracked distillates. The ease of hydrodesulfurization (HDS) of these molecules over conventional Co-Mo (or Ni-Mo) catalysts depends on their molecular structure. Among these S-compounds, 4,6-disubstituted dibenzothiophenes are the most difficult to desulfurize. For example, the relative rate of desulfurization of (unsubstituted) dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) over a Co-Mo-HDS catalyst has been reported to be 6:1 (F. Bataille, J. Mijoin, J.L. Lemberton, G. Perot, G. Berhault, M. Lacroix, F. Mauge, S. Kasztelan and M. Breyesse, Stud. Surf. Sci. Catal., 130 (2000) 2831). Another study has reported the pseudo first order rate constants for HDS of DBT, 4-MDBT (4-methyldibenzothiophene) and 4,6-DMDBT on a Co-Mo catalyst to be 0.058, 0.018 and 0.006 min-1, respectively (X. Ma, K. Sakanishi and I. Mochida, Ind. Eng. Chem. Res., 33 (1994) 218). Therefore, due to the presence of these refractory 4,6-dialkyldibenzothiophene compounds, the desulfurization of diesel to less than 50 ppm is difficult.
Work is in progress throughout the world on the development of new processes for deep desulfurization of diesel. Some new catalyst technologies have been reported recently for deep HDS of diesel. Besides,

research on biodesulfurization methods for S reduction in diesel is also in progress. The technological innovations for deep desulfurization include the introduction of multiple hydrogen injection and removal of H2S and NH3 from intermediate sections of the reactor. These improvements are rather expensive to implement in existing reactors and totally new reactor systems need to be constructed. In this context, it will be much more economical to design an active catalyst that can desulfurize diesel to the desired low sulfur specification. Such a catalyst can be loaded in existing HDS reactors without any additional expense.
Co-(Ni)-Mo catalysts are widely used in desulfurizing petroleum fractions. These catalysts are active in the sulfided state converting the sulfur in sulfur compounds into H2S in the presence of H2. Various types of species such as M0S2, Co-(Ni)-Mo-S and Co (Ni) sulfides have been reported to be present on the surface of sulfided Co-Mo-alumina catalyst. Of these, only the Co-Mo-S phase has been found to be mainly responsible for HDS activity (H. Topsoe, B.S. Clausen and F.E. Massoth, "Hydrotreating Catalysts", SpringerVerlag, Berlin, 1996). The structure of the Co-Mo-S phase is now clearly established. This phase consists of microcrystallites of M0S2, the edge sites of which are substituted by Co (P. Ratnasamy and S. Sivasanker, Catal. Rev.-Sci. Eng., 22 (1980) 401). In the presence of H2 some S atoms are lost as H2S creating anion vacancies. These vacancies (coordinately unsaturated site, CUS) can arise on the basal plane and at the edges and corners of crystallites. The smaller the crystallite, the larger is the proportion of edge and corner anion vacancies to vacancies at the basal plane. The S-containing molecules adsorb at these vacancies on the CUS and undergo desulfurization. The CUS at the basal surface, though may be sufficiently active to desulfurize non-beta substituted dibenzothiophene compounds, cannot easily desulfurise the di-beta substituted compounds due to steric hindrance. These compounds can,

however, undergo HDS at the edge (or preferably the corner) CUS. Hence, the number and location of these sites determine the overall activity of the catalyst.
A large number of innovations in hydrodesulfurization catalysts has been published or patented over the years. A few relevant ones are described below.
US 5468709 describes a catalyst made from an alumina carrier substance, atleast one active metal element selected from Gr.VI metals in the periodic table, one active metal element chosen from Gr.VIII metals in the periodic table, phosphoric acid and an additive agent such as ethers of alcohols or alcohols (ethylene glycol, sugers as additives). US 6239066 gives the process for forming high activity catalysts, consisting of wetting the catalyst composition by contact with a chelating agent such as EDTA, MEA etc in a carrier liquid, aging the so wetted substrate and drying and calcining. EP 1041133 describes a catalyst with organic additives selected from a group of compounds comprising at least two hydroxyl groups and 2-10 carbon atoms and the polyethers of these compounds along with M0O3, NiO and P2O5. EP 1043069 A discloses the preparation of a sulfided hydrotreating catalyst as 50% alumina, one hydrogenation metal component and an organic compound comprising at least one covalently bonded nitrogen atom and atleast one carbonyl moiety. Thus a catalyst containing 26% M0O3,4.7% NiO, 6.7% P2O5 on gamma-alumina as carrier was impregnated with diammonium salt of EDTA solution, aged for three days and dried at 130°C.
Some patents refer particularly to support improvements. US Patent 5,897,768 discloses the incorporation of zeolitic and acidic components in HDS catalysts to isomerize or disproportionate the dialkyldibenzothiophene compounds leading to ease of their desufurization. However, due to the presence of acidic components, one would expect unwanted cracking of

other components causing lower product yields, besides rapid deactivation due to fast coke deposition. US Patent 6,239,066 Bl reports the preparation of the catalysts containing nanocrystalline alumina of crystallite size upto 25 A at the surface and also possessing mesopores.
Mesoporous silicas such as MCM-41 (C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli and J.S. Beck, Nature 359 (1992) 710) has been reported to be a good support for HDS catalysts. Another ordered mesoporous material, with thicker walls than MCM-41, invented by Stucky and others form the University of California at Santa Barbara, California, USA (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548) called Santa Barbara -15 (abbreviated as SBA-15) has also been reported to be good supports for HDS catalysts. The supports possess a large surface area of about 1000 m per gram and can effectively support and disperse a larger amount of the active sulfide species. Besides, these possess uniform pores in the mesopore region (20 - 200 A) permitting the easy diffusion of the sulfur containing molecule. C. Song and K.M. Reddy have found that they could load more than double the amount of Co and Mo oxides on MCM-41 than present in typical Co-Mo-alumina catalysts and reported that the activity of the catalyst was more than double that of the alumina based catalyst for converting the model compound, dibenzothiophene (Applied Catalysis A: General, 176 (1999) 1). Similarly Vradman and others showed that the deposition of Ni and W sulfides on SBA-15 produced highly active catalysts in desulfurizing model compounds (L. Vradman, M.V. Landau, M. Herskowitz, V. Ezersky, M. Talianker, S. Nikitenko, Y. Koltypin and A. Gedanken, Journal of Catalysis, 213 (2003) 163). However, it is known that Co (Ni) and Mo (W) specie do not bind strongly on silica surfaces and silica supported catalysts generally deactivate faster due to sintering of the active sulfide phase. Again, the alumina surface possesses slight acidity

which acts synergistically in the HDS reaction. The inclusion of Al ions in MCM-41, no doubt, will increase the binding of the active species. However, as other elements like Al can be incorporated only in small amounts (Si/Al ratio >25) sufficient Al ions may not be available on the surface to interact with the Co-Mo-species in Al-containing MCM-41. Further, MCM-41 itself is not very stable and its structure tends to collapse during the impregnation and catalyst preparation and sulfidation steps. As a result MCM-41 supported catalysts are not suited to processing real feeds where other components such as N is also present (P.J. Kooyman, P. Waller, A.D. van Langeveld, K.M. reddy and J.A.R. van Veen, Catalysis Letters, 90(2003)131).
SBA-15 (Santa Barbara - 15), another mesoporous silica, is sturdier than MCM-41 due to its thicker silica walls and its structure is expected to be more resilient to destruction. Even so, it still possesses the disadvantages of a silica support. In the case of SBA-15, it is much more difficult to incorporate Al on its surface than on MCM-41 (Si/Al 100 A) compared to MCM-41 (typically, 30 - 40 A). The small size of the pores in MCM-41 should, in principle, restrict the diffusion of the molecules inside its pores when sulfide crystallites are present inside them. In the case of SBA-15, the diffusion of the molecules will be easier (due its large pores) even when the sulfide crystallites are present inside them.
The disadvantages of a siliceous surface can be counteracted and the benefits of the large area SBA-15 can be exploited as a support if its surface is modified by covering with a suitable oxide, alumina or titania.
OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide a novel catalyst useful for desulfurization of hydrocarbon feedstock

Another object of the present invention is to provide a process for the preparation of novel catalyst useful for desulfurization of hydrocarbon feedstock
SUMMARY OF THE INVENTION
The present invention provides for novel catalyst composite materials suitable for the desulfurization of petroleum oils. The invention also provides a process for the preparation of said catalyst composite materials.
The catalyst composite materials of the present invention consist of a porous support, prepared from an ordered siliceous mesoporous material such as SBA-15 with a surface area in the range of 800 - 1000 m2/g and a pore-volume of about 1.0 - 1.2 ml/g by coating its pore-surface with a layer of alumina or titania, the coating being done by deposition / anchoring of Al or Ti-alkoxides on the surface and calcining the resultant material, and Group VI (Mo or W) and Group VIII (Co or Ni) metals loaded on to it as two different miscible interacting complexes or organometallic derivatives. The catalyst composite material consisting of the support and the complexes are dried at low enough temperatures in the range of 80 - 120°C to prevent the decomposition of the organometallics. It is then sulfided externally prior to loading in the reactor or insitu after loading in the reactor. The catalyst so prepared and sulfided contain more number of active sites for desulfurization and are also more suited for the desulfurization of refractory S-compounds such as 4.6-dibenzothiophene. The preparation process also enables the incorporation of the promoter phosphorous into the catalyst without an additional impregnation step.
The hydrocarbon feedstock, typically belonging to the diesel fraction, is contacted with the catalyst composite materials in the presence of hydrogen at typical hydrotreating conditions of temperature and pressure to bring down its sulfur content to below 50 ppm. The use of this type of catalyst is
1

expected to improve liquid yields due to minimal cracking and due to higher activity of the catalyst, be able to operate at lower temperatures than prior-art catalysts.
Accordingly the present invention provides a novel catalyst composite materials useful for desulfurization of hydrocarbon feedstocks, the said catalyst comprising composite material impregnated thin metal oxide layer coated mesoporous siliceous support material having the general formula (MO3)x (M'O)y (SiO2)z (M1'O)a (P205)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2is silicon oxide, M1 is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles.
In an embodiment of the present invention the composite material used for impregnating siliceous material in a composite mixture is consisting of at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group.
In another embodiment of the present invention the siliceous material used is SBA-15.
In yet another embodiment of the siliceous material used contains ordered mesopores of size ranging from 30-200 A .
In yet another embodiment of the present invention the meatal oxide layer used for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide.

In yet another embodiment the amount of alumina or titania used for coating the mesopores of siliceous material is in the range of 5-20Wt% of the siliceous material support.
In yet another embodiment the active metal used from group VI metals is selected from Mo and W.
In yet another embodiment the active metal used from group VIII is selected from Co and Ni.
In yet another embodiment the amount of active metal selected from group VI used is in the range of 10-40 Wt% as oxides.
In yet another embodiment the amount of active metal selected from group VIII used is in the range of 2-10 Wt% as oxides.
In yet another embodiment the phosphoric acid salt used is a hetero polyacid or poly oxometallate of group VI metal.
In yet another embodiment the hetro polyacid of group VI metal used is phosphomolybdic acid.
In yet another embodiment the organic additive having at least one aldehyde group used is glyoxylic acid.
In still another embodiment the organic additive having at least one carboxylic group used is ethylene diaammine teteracetic acid (EDTA).
The present invention further provides a process for the preparation of a novel catalyst composite material having the general formula (MO3)x (M'O)y (SiO2)z (M1'O)a (P2O5)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles, the said process comprises coating the surface of siliceous support material with an uniform layer of metal oxide, impregnating the above said metal oxide layer coated

siliceous support material with an aqueous solution composite components mixture containing at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group, at a temperature in the range of 25-50°C, drying the above said impregnated siliceous material at a temperature of 20-25 °C, for a period of 15-20 hrs followed by further heating at a temperature in the range of 100-120°C, for a period of 6-8 hrs to obtain the desired catalyst composite material.
In yet another embodiment the siliceous material used is SBA-15.
In yet another embodiment the siliceous material used contains ordered mesopores of size ranging from 30-200 A0 .
In yet another embodiment the metal oxide layer used for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide.
In yet another embodiment the amount of alumina or titania used for coating the mesopores of siliceous material is in the range of 5-20Wt% of the siliceous material support.
In yet another embodiment the active metal used from group VI metals is selected from Mo and W.
In yet another embodiment the active metal used from group VIII is selected from Co and Ni.
In yet another embodiment the amount of active metal selected from group VI used is in the range of 10-40 Wt% as oxides.
In yet another embodiment the amount of active metal selected from group VIII used is in the range of 2-10 Wt% as oxides.
In yet another embodiment the phosphoric acid salt used is a hetero polyacid or poly oxometallate of group VI metal.

In yet another embodiment the hetro polyacid of group VI metal used is phosphomolybdic acid.
In yet another embodiment the organic additive having at least one aldehyde group used is glyoxylic acid.
In yet another embodiment the organic additive having at least one carboxylic group used is ethylene diaammine teteracetic acid (EDTA).
In still another embodiment water is removed from the impregnated composite material under vacuum to prevent the decomposition of the organic additives or metal complexes.
DETAILED DESCRIPTION OF THE INVENTION
There are two main components in HDS catalysts, the support and the active component, the metal sulfide crystallites. Any improvement in catalytic activity is generally associated with improvements in both the support and the active catalytic species. Useful support improvements are: 1) thermal stability, 2) ease of diffusion of reactants and products through its pores, 3) ability to disperse the active component and maintain the dispersion and 4) synergistic effects (with the active species) enhancing the overall activity of the catalyst. Support improvements can be done out by increasing its surface area, optimizing pore characteristics to minimize diffusion effects, increasing thermal stability and enhancing interaction between support and metal sulfide particles to reduce sintering and increase synergism.
The typical support used in the preparation of HDS catalysts of the Co-Mo or Ni-Mo (W) type is alumina, especially of the gamma form prepared from microcrystalline boehmite (pseudo-boehmite). These aluminas typically have surface areas in the range of 200 - 300 m and pore volumes of 0.5 - 0.8 ml per gram, respectively. The pore size distribution of these

materials can vary from microporous (below 20A diameter) to mesoporous (20 - 500 A diameter) and macroporous (>500 A diameter). The micropores and the macropores are not advantageous as the former restrict the diffusion of the reactants, while the latter lead to low surface areas and poor mechanical strength of the materials. The most desired are the mesopores, preferably in the range between 40 - 150 A, with an average pore size of about 70 - 100 A. Thus, the literature is full of efforts to prepare aluminas possessing the right mesopores.
In early 1990s, a new class of siliceous materials called M41S containing ordered mesopores with uniform diameter were reported by the Mobil Oil Co. (C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli and J.S. Beck, Nature 359 (1992) 710). At least three types of materials were reported, MCM-41, in which the mesopores were arranged in a hexagonal pattern, MCM-48, in which the pores were arranged in a cubic symmetry and MCM-50 made up of lamellar sheets of pores. The most common and more stable preparations had pores in the diameter of 20 - 50 A. These materials were synthesized using micellar surfactants as the templates. Though the M41S materials were typically most stable and formed easily in the siliceous form, other hetero-ions such as Al, Ti, Sn etc. could be introduced in small amounts. These materials had very large surface areas of 1000 - 1200 m2 and pore volumes of 1.2 to 1.4 ml per gram, respectively. These were however found to be rather unstable under hydrothermal conditions and lost crystallinity and ordering of the mesopore structure even when simple impregnations were attempted on them.
A more stable mesoporous material called, SBA-15 containing much thicker walls was later on reported by Zhao and others (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548). These were prepared from poly-block copolymers of ethylene and propylene glycols. The typical pore dimensions

of most of the reported SBA-15 preparations are in the range of 100 - 140 A. These are much more thermally and hydro-thermally stable than the M-41S materials. Thus, both the thermal stability and right pore dimensions make SBA-15 an ideal support for HDS catalysts.
Both MCM-41 (or MCM-48) and SBA-15 are siliceous materials and do not stabilize the supported Co and Mo species, unlike alumina the preferred support for HDS catalysts. This weak interaction of the metal species with silica causes rapid deactivation through crystal growth. One trick for improving the metal-support interaction is to incorporate Al-ions in the framework. Though, a reasonable amount of Al (upto a few mole % of Al) can be incorporated into MCM-41 during the synthesis, these have not been found to be good supports for HDS catalysts (Catalysis Letters 90 (2003) 131). Further, the incorporation of other ions decreases the crystallinity, ordering of the pore system and stability of MCM-41. On the other hand in the case of the more stable SBA-15, the incorporation of ions like Al or Ti in the framework is difficult and very little incorporation takes place (less than one mole %) during direct synthesis. At this low level of incorporation, hardly any benefits due to Al can be seen.
The present invention provides for the preparation of an ordered mesoprous siliceous support such as SBA-15 with a uniform coating of an oxide material such as alumina or titania on the surface of the pores and its use a s a support for HDS catalysts. The preparation involves the anchoring of the metal (Al or Ti) alkoxides on to the surface of SBA-15 by refluxing it with the alkoxides in toluene as the solvent. The alkoxides react with the surface silanol groups and get attached to the silanol surface as a monodispersed layer. The material is dried and the alkoxides converted into an oxide layer by careful calcination in air or oxygen rich nitrogen. The loading of the metal can be as high as 10 - 30 mole % sufficient to cover much of the surface of the pores. The deposited oxides

now act as anchors for the active mixed-metal sulfide crystallites. The large surface area (800 - 900 m per gram) and the large pore volume (~ lml per gram) allow for the loading of substantial amounts of the active metals in a single loading step. The pores of SB A-15 are also of the right size (~ 100A) for use in HDS catalysts. The loading of the metal oxides on SBA-15 can also be carried out by chemical vapour deposition or other known methods using other salts of aluminum or titanium.
The other component is the active species. The conventional method of making HDS catalysts say of the Co (Ni)-Mo-alumina type, involves the deposition of salts of Mo and Co from aqueous solutions by impregnation, drying and calcination to give a deposit of oxides of Co (Ni) and Mo. The catalyst is then sulfided at high temperatures, say 300 - 340°C, to convert the oxides into the sulfides. This method possesses limitations. For example, due to the high calcination temperature (about 500°C) used in the preparation, the metals, especially Co (Ni), interact with the support (alumina) and a fraction of the impregnated metals is lost as a useful desulfurizing catalyst. Again, as the metal components are deposited separately as oxides, after sulfidation, a substantial amount of these active components end up as inactive individual sulfide phases. Further, due to the high temperatures of calcination, the oxides (especially Mo) agglomerate into large clusters, thereby leading to large sulfide particles after sulfidation; these sulfide particles expose more the basal planes and are less active for desulfurizing the sterically hindered S-compounds. One more limitation of the prior-art method of preparing catalysts is that the oxides of Co and Mo deposited on the surface of the support undergo sulfidation at different temperatures. The temperature required for sulfidation increases in the order, Ni > Mo > Co. As a result when a typical catalyst containing mixed oxides of Co (Ni) and Mo is sulfided, discrete phases of the

individual phases are formed at different temperatures and the formation of the active mixed metal sulfide phase is less.
Further, a yet another limitation of the process of the prior-art is that due to the limited solubility of the Mo salts in water and the low pick up of the salts by alumina, the loading of Mo is small and multiple impregnation steps with intermediate calcinations are required for loading substantial quantities of the metals. The multiple calcinations causes loss of the active centres by reaction with the support, besides causing growth of the metal oxide phase on the surface. Further due to the need to impregnate the Mo and Co (Ni) salts from solutions with different pH values, the impregnation of the two metals is carried out separately, generally, Mo being loaded first in multiple steps, depending on the loading required, and calcined before loading the next metal Co (Ni). This method not only increases the number of preparation steps, it also prevents the intimate mixing of the two metallic components.
The present invention provides for a catalyst composite material that does not possess the above limitations. Accordingly, the metal components Co (Ni) and Mo are incorporated on the surface of the support as miscible organometallic derivatives. The organometallic derivatives or complexes of the individual metals are prepared by adding the organic complexing agents or organic additives to the metal salts, namely a heteropoly acid or a polyoxometallate in the case of the group VI metal and as a hydrated carbonate species in the case of the group VIII metal. The two solutions containing the metals and the complexing agents or additives are mixed. The mixture of complexes and additives containing the active metals is loaded on the support by a single impregnation step at a low temperature, say below 50°C and pre-dried at a similar low temperature. The water component present in the composite material made up of the complexes and the support is removed at a low enough temperature, say below 150°C, to

prevent the decomposition of the complexes / additives. The catalyst composite comprising of the mixture of complexes / additives and the support is sulfided directly without any calcination and conversion of the metals into oxides as practiced in the prior-art. The sulfidation may be carried out insitu in the reactor or externally before loading in the reactor.
Another embodiment of the invention provides for the inclusion of the promoter phosphorus into the catalyst during the preparation of the complex besides loading of phosphorous in any other form as practiced in the prior-art. The invention also provides for the exclusion of phosphorous from the catalyst, if necessary, by the use of a non-phosphorous containing group VI metal precursor.
The catalyst of the present invention is prepared from a heteropoly acid (HP A) containing phosphorous as the source of Mo (or W), hydrated Co (or Ni)-carbonate as the source of Co (or Ni), an aqueous solution of a complexing agent, such as glyoxylic acid to dissolve the HP A, hydrogen form of EDTA to solubilize the Co-carbonate and sufficient water to make a mixture of the desired composition to load the required amount of the metals. An important embodiment of the present invention is that the group VI and group VIII metals are incorporated along with different organic additives that are interchangeable with one another so that when the solution of the two organometallic compounds are mixed, a solution containing both the metals in a similar environment results.
As described above, the catalysts according to the present invention are basically composed of the following: a carrier substance, at least one organic derivative of a heteropoly anion formed by an organic compound having at least two oxygen atoms, one of which being part of an aldehyde (-CHO) group, and one EDTA complex of the active metal selected from the Gr. VIII metals in the periodic table. The carrier is impregnated by a single step process with a homogeneous solution containing organic

derivatives of group VI and VIII metal elements. The amount of the selected active metal element is 10-40 % and 2 - 10 % of the catalyst weight once converted to oxide weight, respectively for the group VI and group VIII metals. The phosphorous content in the catalyst can be increased by adding additional phosphorous as a phosphate salt or phosphoric acid to the mixture of the complexes of the metals.
In one embodiment of the process, the catalyst contains one or more elements selected from the group VI, and one or more elements chosen from the group VIII. The typical group VI elements are Mo and W while the typical group VIII elements are Ni and Co.
It is necessary that the carrier substance possesses a large surface area, and a large pore-volume. The support is preferably SBA-15 with its surface uniformly coated by deposition of a film of alumina or titania, the preparation of which has already been described.
The glyoxylic acid complex of the HPA and EDTA complex of cobalt/nickel carbonates are prepared separately and mixed together with the required amount of water and the mixed organometallic species formed is used as the impregnating solution. The wet impregnated material is dried at a temperature between 80 - 120°C. The catalyst may be loaded in the reactor and presulfided as per the procedures in current practice and well known in the art. Experiments reveal that the complexing agents / additives break down easily during sulfidation and do not leave any carbonaceous residue that may be detrimental to the catalyst activity.
In a less preferred embodiment of the present invention, the deposition of the active metals of the group VI and VIII is carried out over the surface modified SBA-15 by simple impregnation methods known in the art using compounds of Mo such as ammonium molybdates or cobalt nitrate. In this case, phosphorous may be added to the support prior to impregnation with the salts or it is added to one of the impregnating solutions.

The present invention is illustrated with following examples, which are only illustrative in character.
EXAMPLE 1
This example isllustrates the synthesis of siliceous SBA-15 used in the following examples. It was prepared according to a published procedure (D. Zhao, J. Feng, Q. Ho, N. Melosh, G.H. Fredrickson, B.F. Chmelka and G.D. Stucky, Science 279 (1998) 548) using the amphilic copolymer, poly (ethylene-glycol)-block;-poly (propylene-glycol)-block-poly (ethylene-glycol) (average molecular weight 5800, supplied by Aldrich chemical Co., USA). 16.33 g of the above polymer was dissolved in 120 ml of water and 240 g of 2 M HC1 with stirring. This solution was heated at 40° C for 2 h followed by dropwise addition of 34.7 g of tetraethylorthosilicate (Aldrich Chemical Co., USA) with vigorous stirring. This gel was stirred for 24 h at 40° C and then crystallized in a Teflon-lined autoclave at 100° C for 2 days. After crystallization, the solid product was filtered, washed with deionized water and dried in air at room temperature for 12 h. The material was calcined at 550° C for 6 h to obtain a white light powder. The XRD of the sample was typical of that reported for SBA-15 in the literature. It had a surface area of 853 m /g and a pore size of about 90 A.
EXAMPLE 2
This example illustrates the preparation of an alumina coated SBA-15 support from the siliceous SBA-15, whose preparation is described in Example 1. Freshly activated SBA-15 (9 g) was refluxed with stirring for 4 h in tolurene (500 ml, dried by distillation over sodium metal) for azeotropic removal of water from the mesoporous material. To the refluxing solution, 2 g of aluminum isopropoxide (equivalent to 1 g

alumina) dissolved in 100 ml of freshly distilled toluene was added. Stirring and refluxing was continued for another 4 h. The solid was filterd, washed with toluene once and dried in an oven at 110° C (for 4 h) and calcined carefully at 300° C for 6 h in air. The calcined powder was pelleted and broken into small pieces (1-2 mm size). The product is named as SBA-15 (alumina). XRD analysis showed that the SBA-15 structure was intact.
EXAMPLE 3 This example illustrates the preparation of a titania coated SBA-15 support from the siliceous SBA-15, whose preparation is described in Example 1. Freshly activated SBA-15 (9 g) was refluxed with stirring for 4 h in tolurene (500 ml, dried by distillation over sodium metal) for azeotropic removal of water from the mesoporous material. To the refluxing solution, 4 g of titanium tert-butoxide (equivalent to 1 g titania) dissolved in 100 ml of freshly distilled toluene was added. Stirring and refluxing was continued for another 4 h. The solid was filterd, washed with toluene once and dried in an oven at 110° C (for 4 h) and calcined carefully at 300° C for 6 h in air. The calcined powder was pelleted and broken into small pieces (1-2 mm size). The product is named as SBA-15 (titania). XRD analysis showed that the SBA-15 structure was intact.
EXAMPLE 4
This example illustrates the procedure for preparing a HDS catalyst by conventional impregnation method. 6.3 g of freshly activated SBA-15 (alumina) powder (prepared according to Example 2) was weighed in an evaporating dish. 0.72 g of orthophosphoric acid (85 %) was dissolved in 15 ml of water and added to it. The mixture was stirred well with a glass rod and kept at room temperature for 3h. Then, it was kept over a water bath and evaporated to dryness with gentle mixing. It was further dried in

an oven at 110° C for 3 hours and calcined at 300° C for 3h in N2 and 3 h in air.
A solution of 5.45 g of ammonium molybdate tetrahydrate in 22 ml of water was added to the above phosphorous impregnated SBA-15 (alumina) powder kept in the evaporating dish. The mixture was stirred well with a glass rod and kept for 2 h with periodic stirring. It was slowly allowed to evaporate to dryness over a water bath over a period of about 1 h. The dried mixture was further dried in an oven at 110° C for 6 h and then calcined carefully at 400° C for 3h in N2 and 3 h in air.
A solution of 3.77 g of Co (No3)2.6H2o in 15 ml water was added to the above freshly calcined material kept in a evaporating dish. The mixture was stirred for 2 h gently at room temperature. It was then slowly allowed to evaporate to dryness over a water bath over a period of about 1 h. The dried mixture was further dried in an oven at 110° C for 6 h and then calcined carefully at 500° C for 3h in N2 and 3 h in air. The catalyst contained 28.26 % Mo, 5.95% Co and 2.8 % P as oxides. The powder was pelletted and broken into small pieces (1-2 mm size) and stored as catalyst "A".
EXAMPLE 5
This example illustrates the preparation of Co-Mo-SBA-15 catalyst according to the improved preparation method of this patent making use of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below.
Solution A: 12.76 g phosphomolybdic acid (equivalent to 12.06 g M0O3) was taken in a 100 ml beaker. 3 g of water was added to it followed by 3 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution.

Solution B: In another beaker, 19.82 g of wet, freshly made C0CO3 (equivalent to 3.07 g CoO) was weighed. 3 g of water and 5.57 g of H-EDTA were added to it and the mixture was stirred to get a pink coloured Co-EDTA complex.
The solutions A and B were mixed to get a clear blue homogeneous solution. This was impregnated on 20 g of freshly calcined pelletted and sized (1-2 mm) particles of siliceous SBA-15 support prepared according to Example 1. Thus a single step impregnation of cobalt-molybdenum with a high concentration of active species was achieved. The mixture was gently mixed for 2 h and the excess solution (if any) was drained. The impregnated powder was dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a blue coloured catalyst. This was stored in air-tight container under N2 immediately. The catalyst contained 33.24% of Mo and 8.67 % of Co as oxides (MoO3 and CoO) and 3 % of P as P2O5. The material is called "Catalyst B".
EXAMPLE 6
This example illustrates the preparation of Co-Mo-SBA-15 (alumina) catalyst in the presence of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below.
Solution A: 11.12 g phosphomolybdic acid (equivalent to 10.51 g M0O3) was taken in a 100 ml beaker. 2.7 g of water was added to it followed by 2.7 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution.
Solution B: Freshly made wet C0CO3 (18.2 g) equivalent to 2.82 g CoO was weighed in the beaker, 5g water and 5.12 g H-EDTA were added to it. The mixture was stirred to get a clear pink solution.

Solutions A and B were mixed and impregnated on 20 g freshly calcined and dry SBA-15 (alumina) support particles (prepared according to Example 2). The mixture was kept for 2 h with gentle mixing and the excess solution (if any) was drained. The impregnated particles was dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a light green catalyst. This was stored in an air-tight container under N2 immediately. The catalyst contained 28.96 % of Mo and 7.97 % of Co as oxides (M0O3 and CoO) and 2.5 % of P as P2O5. The material is called "Catalyst C"
EXAMPLE 7
This example illustrates the preparation of Co-Mo-SBA-15 (titania) catalyst in the presence of organic additives. An impregnating mixture of molybdenum and cobalt complexes was prepared as follows. Two solutions, Solution A and Solution B were prepared as described below.
Solution A: 10.82 g phosphomolybdic acid (equivalent to 10.23 g M0O3) was taken in a 100 ml beaker. 3 g of water was added to it followed by 2.6 g glyoxylic acid (50 %). The mixture was heated on a water bath to form a green coloured clear solution.
Solution B: Freshly made wet C0CO3 (12.54 g) equivalent to 1.94 g CoO was weighed in the beaker, 6 g water and 3.52 g H-EDTA were added to it. The mixture was stirred to get a clear pink solution.
Solutions A and B were mixed and impregnated on 20 g freshly calcined and dry SBA-15 (titania) particles (prepared according to Example 3). The mixture was kept for 2 h with gentle mixing and the excess solution (if any) was drained. The impregnated particles were dried at room temperature for 16 h and further dried at 110°C for 8 h to obtain a light green catalyst. This was stored in an air-tight container under N2 immediately. The catalyst

contained 28.19 % of Mo and 5.49 % of Co as oxides (M0O3 and CoO) and 2..7 % of P as P2O5. The material is called "Catalyst D"
EXAMPLE 8
In this example, the presulfiding of the catalyst composite material of this invention and the testing of the activity using a diesel oil feed is described.
About fifteen grams the catalyst (1-2 mm size) prepared as illustrated in Examples 4 to 7 was loaded in a high pressure down-flow reactor (100 ml volume). The compositions of the catalysts used in the sulfidation and activity tests are presented in Table 1. The catalyst was diluted with its volume of ceramic beads of similar size before loading. The drying of the catalyst was done at 100°C for two hours in a slow flow of nitrogen (6 litres per hour). The reactor was then pressurized to 40 bars with hydrogen and the sulfiding feed (a commercial diesel oil from a hydrocracker containing 45 ppm S (wt.) spiked with dimethyl disulfide to give a total S content of 1 wt %) was injected at a weight hourly space velocity (WHSV) of 1 h"' calculated on the basis of the dry oxide weight of the catalysts. A hydrogen flow of 300 volumes to oil volume (was maintained. The temperature was slowly raised to 270°C in 6 hours and the sulfidation continued for 16 hours. The temperature was then raised to 320 and 340°C in steps holding for 4 hours at each temperature. The sulfidation feed was changed to one with 0.5% S and the sulfidation continued for 4 hours. The diesel required to be desulfurized (containing 2500 ppm S by wt.) was then injected to find out the activity of the catalyst after adjusting the temperature of the reactor to the desired value. PFPD (gas chromatograph, GC) analysis of the feed revealed that it contained essentially dibenzothiophene and its alkyl derivatives as S-compounds. The S content was analyzed by X-ray Flourescence analysis (XRF).

The desulfurization activity test was carried out at a pressure of 40 atmospheres (bars), a temperature of 330°C, a weight hourly space velocity (WHSV) of 2 h-1 and H2/oil ratio of 300. The results of the experiments are also presented in Table 1.
The tests reveal the following: 1) The catalysts prepared by coating the SBA-15 with alumina or titania are more active than the siliceous SBA-15 supported catalyst Catalysts A, C and D are more active than B), 2) the catalysts prepared using organic additives are more active than those prepared by impregnation (Catalysts C and D are more active than A) and 3) Titania coating of the SBA-15 support gives a more active catalyst than alumina coating.
Table 1. The composition of the catalysts used and their HDS activity
(Table Removed)
The advantages of the present invention are are:
Since, the catalysts are not calcined, loss of the active metal through reaction with the support does not occur and bulk oxide phases are not formed on the surface. Besides, as the active metals are present as intimately mixed complexes, the possibility of forming a mixed Co(Ni)-Mo-S phase is greatly enhanced. The mixed sulfide phases are also expected to be smaller in size than those prepared from the oxide precursors due to the low temperature of drying and the absence of large bulk metal oxide phases.
Small crystallites of the mixed metal phase will be more effective in the desulfurization of the refractory hindered dialkyl- dibenzothiophene compounds.
The use of the complexes for impregnating the metals also enables the loading of substantially large quantities of the metals in a single step than hitherto possible.

We claim:
1. A novel catalyst composite materials useful for desulfurization of
hydrocarbon feed stocks, the said catalyst comprising composite
components material impregnated thin metal oxide layer coated
mesoporous siliceous support material having the general formula
(Formula Removed)
where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles.
2. A catalyst as claimed in claim 1, wherein the siliceous material contains ordered mesopores of size ranging from 30-200 A0 .
3. A catalyst as claimed in claims 1-2, wherein the meatal oxide layer for coating the mesopores of siliceous material is selected from titanium oxide and aluminum oxide.
4. A catalyst as claimed in claims 1-3, wherein the amount of alumina or titania for coating the mesopores of siliceous material is in the range of 5-20 Wt% of the siliceous material support.
5. A catalyst as claimed in claims 1-4, wherein the active metal from group VI metals is selected from Mo and W.
6. A catalyst as claimed in claims 1-5, wherein the active metal used from group VIII is selected from Co and Ni.
7. A catalyst as claimed in claims 1-6, wherein the amount of active metal selected from group VI is in the range of 10-40 Wt% as oxides.
8. A catalyst as claimed in claims 1-7, wherein the amount of active metal selected from group VIII is in the range of 2-10 Wt% as oxides.
9. A catalyst as claimed in claims 1-8, wherein the phosphoric acid salt is a
hetero polyacid or poly oxometallate of group VI metal.
10. A catalyst as claimed in claims 1-9, wherein the hetro polyacid of group VI metal is phosphomolybdic acid.
11. A process for the preparation of a novel catalyst composite material as claimed in claim 1,having the general formula (MO3)x (M'O)y (SiO2)z (Mi'O)a (P2O5)b where M is selected from group VI metals, M' is selected from group VIII metals, SiO2 is silicon oxide, M1' is selected from titanium and aluminium, P2O5 is phosphorous oxide and x has a value ranging between 4.0-28.0, y is ranging between 3.0 -13.0 and z is ranging between 31.0- 87.5, a is ranging between 5.0-25.0, b is ranging between 0.5-3.0, such that x + y + z + a + b adds to 100 moles, the said process comprises; coating the surface of siliceous support material with an uniform layer of metal oxide, impregnating the above said metal oxide layer coated siliceous support material with an aqueous solution composite components mixture containing at least one active metal selected from group VI metals, at least one active metal selected from group VIII metals, phosphoric acid salt, two organic additives of which one is having at least one aldehyde group and another is having at least one carboxylic acid group, at a temperature in the range of 25-50°C, drying the above said impregnated siliceous material at a temperature of 20-25 °C, for a period of 15-20 hrs followed by further heating at a temperature in the range of 100-120°C, for a period of 6-8 hrs to obtain the desired catalyst composite material.
12. A process as claimed in claim 11, wherein the organic additive having at least one aldehyde group is glyoxylic acid.
13. A process as claimed in claim 11, wherein the organic additive having at least one carboxylic group is ethylene dia a mine teteracetic acid (EDTA).
14. A process as claimed in claim 11, wherein water is removed from the impregnated composite material under vacuum to prevent the decomposition of the organic additives or metal complexes.

Documents:

792-DEL-2005-Abstract-(03-02-2012).pdf

792-DEL-2005-Claims-(03-02-2012).pdf

792-DEL-2005-Claims-(16-03-2012).pdf

792-DEL-2005-Correspondence Others-(03-02-2012).pdf

792-DEL-2005-Correspondence Others-(09-03-2012).pdf

792-DEL-2005-Correspondence Others-(16-03-2012).pdf

792-DEL-2005-Form-3-(03-02-2012).pdf

792-delnp-2005-abstract.pdf

792-delnp-2005-claims.pdf

792-delnp-2005-correspondence-others.pdf

792-delnp-2005-description (complete).pdf

792-delnp-2005-form-1.pdf

792-delnp-2005-form-18.pdf

792-delnp-2005-form-2.pdf

792-delnp-2005-form-3.pdf

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Patent Number

252412

Indian Patent Application Number

792/DEL/2005

PG Journal Number

20/2012

Publication Date

18-May-2012

Grant Date

14-May-2012

Date of Filing

31-Mar-2005

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DESHPANDE SHILPA SHIRISH	NATIONAL CHEMICAL LABORATORY DR. HOMI BHABHA ROAD PUNE-411008 MAHARASHTRA, INDIA.
2	PARDHY SANJEEVANI AMRIT	NATIONAL CHEMICAL LABORATORY DR. HOMI BHABHA ROAD PUNE-411008 MAHARASHTRA, INDIA.
3	SIVASANKER SUBRAMANIAN	NATIONAL CHEMICAL LABORATORY DR. HOMI BHABHA ROAD PUNE-411008 MAHARASHTRA, INDIA.

PCT International Classification Number

B01J 21/12

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA