| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 01.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 18.01.00 |
| PATENT TITLE |
High activity catalysts having a bimodal mesopore structure |
| PATENT ABSTRACT | Provided are high activity catalysts based upon gamma alumina containing substrates impregnated with one or more catalytically active metals, which catalysts in addition contain a nanocrystalline phase of alumina of a crystallite size at the surface of less than 25 .ANG.. Also provided are processes for preparing such high activity catalysts and various uses thereof |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 25.09.95 |
| PATENT CT FILE DATE | May 13, 1994 |
| PATENT CT NUMBER | This data is not available for free |
| PATENT CT PUB NUMBER | This data is not available for free |
| PATENT CT PUB DATE | 23.11.95 |
| PATENT REFERENCES CITED |
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Bin Othman et al., "A Thermometric Titration Study of the Interaction of AL.sup.3+,Cd.sup.2+ Pb.sup.2+ and Zn.sup.2+ with Ethylenediaminetetraacetic Acid," Thermochimica Acta, 157, 1990 pp. 335-345. Henrik Topsoe and Bjerne S. Clausen, "Importance of Co-Mo-S Type Structures in Hydrodesulfurization," Catal. Rev.-Sci. Eng., 26, Nos. 3 & 4, 1984, pp. 395-420. Gabor Kisfaludi et al., "An ExAFS Study of the Spreading of MoO.sub.3 on the Surface of .gamma.-AL.sub.2 O.sub.3," Journal of Catalysis, 130, 1991, pp. 192-201. B. Mahipal Reddy et al., "Dispersion and Activity of Molybdena-Alumina Catalysts Prepared by Impregnation and Solid/Solid Wetting Methods," Journal of Catalysis, 136, 1992, pp. 50-58. J. M. J. G. Lipsch and G. C. A. Schuit, "The CoO-MoO.sub.3 -AL.sub.2 O.sub.3 Catalyst," Journal of Catalysis, 15, 1969, pp. 174-178. J. Sonnemans and P. Mars, "The Mechanism of Pyridine Hydrogenolysis on Molybdenum-Containing Catalyst I. The Monolayer MoO.sub.3 -AL.sub.2 O.sub.3 Catalyst: Preparation and Catalytic Properties," Journal of Catalysis, 31, 1973, pp. 209-219. P. Arnoldy et al., "Temperature-Programmed Sulfiding of MoO.sub.3 /AL.sub.2 O.sub.3 Catalysts", Journal of Catalysis, 92, 1985, pp. 35-55. N. Giordano et al., "Structure and Catalytic Activity of MoO.sub.3. AL.sub.2 O.sub.3 Systems I. Solid-State Properties of Oxidized Catalysts," Journal of Catalysis, 36, 1975, pp. 81-92. G. L. Schrader and C. P. Cheng, "In Situ Laser Raman Spectroscopy of the Sulfiding of Mo/.gamma.-AL.sub.2 O.sub.3 Catalysts," Journal of Catalysis, 80, 1983, pp. 369-385. Seo IL Kim and Seong Ihl Woo, "Effect of Sulfiding Temperatures on the Formation of Sulfides of MO/AL.sub.2 O.sub.3 and CoMo/AL.sub.2 O.sub.3," Applied Catalysis, 74, 1991, pp. 109-123. Terry F. Hayden and J. A. Dumesic, "Studies of the Structure of Molybdenum Oxide and Sulfide Supported on Thin Films of Alumina," Journal of Catalysis, 103, 1987, pp. 366-384. 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Stanislaus et al., "Effect of Phosphorus on the Acidity of .gamma.-Alumina and on the Thermal Stability of .gamma.-alumina Supported Nickel-Molybdenum Hydrotreating Catalysts," Applied Catalysis, 39, 1988, pp. 239-253, (Elsevier Science Publishers B.V., Amsterdam--Printed in The Netherlands). J. B. Peri and R. B. Hannan, "Surface Hydroxyl Groups on.gamma.-Alumina," J. Physical Chem.istry, Oct. 1960, pp. 1526-1530. J. B. Peri, "Infrared and Gravimetric Study of the Surface Hydration of .gamma.-Alumina," Journal of Physical Chemistry, vol. 69, No. 1, Jan. 1965, pp. 211-219. J. B. Peri, "A Model for the Surface of.gamma.-Alumina," Journal of Physical Chemistry, vol. 69, No. 1, Jan. 1965, pp. 220-230. H. Knozinger and P. Ratnasamy, "Catalytic Aluminas: Surface Models and Characterization of Surface Sites," Catal. Rev.-Sci. Eng., 17 (1), 1978, pp. 31-70. J. A. Robert van Veen, "A Method for the Quantitative Determination of the Basic Hydroxyl Groups on an Alumina Surface," J. of Colloid and Interface Sci., vol. 121, No. 1, Jan. 1988, pp. 214-219. J. A. R. van Veen et al., "Chemistry of Phosphomolybdate Adsorption on Alumina Surfaces. 1. The Molybdate/Alumina System," J. Phys. Chem., 94, 1990, pp. 5275-5282. J. A. R. van Veen et al., "Chemistry of Phosphomolybdate Adsorption on Alumina Surfaces. 2. The Molybdate/Phosphated Alumina and Phosphomolybdate/Alumina Systems," J. Phys. Chem., 94, 1990, pp. 5282-5285. Jenny M. Lewis and Ronald A. Kydd, "Adsorption Mechanism of Phosphoric Acid on.gamma.-Alumina," Journal of Catalysis, 132, 1991, pp. 465-471. P. J. Mangnus et al., "Influence of Phosphate on the Structure of Sulfided Alumina Supported Cobalt-Molybdenum Catalysts," Applied Catalysis, 68, 1991, pp. 161-177. S. Eijsbouts et al., "The Effect of Phosphate on the Hydrodenitrogenation Activity and Selectivity of Alumina-Supported Sulfided Mo, Ni and Ni-Mo Catalysts," J. of Catalysis, 131, 1991, pp. 412-. Teh C. Ho, "Hydrodenitrogenation Catalysis," Catal. Rev.-Sci. Eng., 30 (1), 1988, pp. 117. X. S. Li et al., "Reversible Hydrogen Adsorption on MoS.sub.2 Studied by Temperature-Programmed Desorption and Temperature-Programmed Reduction," J. of Catalysis, 137, 1992, pp. 385-393. Josef Polz et al., "Hydrogen Uptake by MoS.sub.2 and Sulfided Alumina-Supported Mo Catalysts," Journal of Catalysis120 1989, pp. 22-28. S. Kasztelan, "On the Existence of Heterolytic Reaction Mechanisms in Hydrotreating Catalysis," American Chemical Society, vol. 38, No. 3, 1993, 642-645. G. Perot et al., "Mechanism of Hydrodenitrogenation of Aromatic Compounds--Structural and Competition Effects," American Chemical Society, vol. 38, No. 3, 1993, pp. 712-715. A. Violante and P. Violante, "Influence of pH, Concentration, and Chelating Power of Organic Anions on the Synthesis of Aluminum Hydroxides and Oxyhydroxides," Clays and Clay Minerals, vol. 28, No. 6, 1980, pp. 425-434. Y. Yoshimura et al., "Molybdate Catalysts Prepared By A Novel Impregnation Method" "Effect of Citric Acid As A Ligand on the Catalytic Activities," Appl Catalysis A:Gen, 79, 1991, 145-159. Menno Wouter Jacob Craje, "On the Identificaiton of `Co-Sulfide` Species in Sulfided Co and CoMo Catalysts," Delft: Interfacultair Reactor Instituut, Delft University of Technology--ILL., 1992, Thesis Technische Universiteit Delft, pp. 125-127. M. Daage and H. H. Murray, "Coordination of DBT on MoS.sub.2 : A Molecular Mechanics Study," American Chemical Society, vol. 38, No. 3, 1993, pp. 660-664. J. Van Doorn et al., "High-Resolution Electron Microscopy of Spent Ni-Mo/AL.sub.2 O.sub.3 Hydriotreating Catalysts," Applied Catalysis, 63, 1990, pp. 77-90, Elsevier Sci Pub B.V., Amsterdam. S. Eijsbouts et al., "MoS Structures in High-Activity Hydrotreating Catalysts. I. Semi-Quantitative Method for Evaluation of Transmission Electron Microscopy Results. Correlations Between Hydrodesulfurization and Hydrodenitrogenation Activities and MoS.sub.2 Dispersion," Appl Catalysis A: General, 105, 1993, pp. 53-68, Elsevier Science Publishers B.V., Amsterdam. S. Eijsbouts et al., "MoS.sub.2 Structures in High Activity Hydrotreating Catalysts. II. Evolution of the Active Phase During the Catalyst Life Cycle. Deactivaiton Model," Appl Catalysis A: General 105, 1993, pp. 69-82, Elsevier Science Publishers B.V. Amsterdam. C. W. Fitz, Jr., and H. F. Rase, "Effects of Phosphorus on Nickel-Molybdenum Hydrodesulfurization/Hydrogenitrogenation Catalysts of Varying Metals Content," Prod. Res. Dev., 22, 1983, pp. 40-44. J. M. Lewis and R. K. Kydd, "The moO.sub.3 -Al.sub.2 O.sub.3 Interaction: Influence of Phospohrus on MoO.sub.3 Impregnation and Reactivity in Thiophene HDS," J. of Catal., 136, 1992, pp. 478-486. J. Ryczkowski, "Modification of Preparation Technique for Highly Dispersed Ni/.gamma.-AL.sub.2 O.sub.3 Catalysts," React. Kinet. Catal. Lett., vol. 40, No. 2, 1989, pp. 189-194. J. Donald Carruthers and David J. DiCamillo, "Pilot Plant Testing of Hydrotreating Catalysts Influence of Catalyst Condition, Bed Loading and Dilution," Appl Catal, 43, 1988, pp. 253-276. D. Nazimek, "The Hydrogenolysis of n-Butane Over Ni/AL.sub.2 O.sub.3 Catalysts of High Nickel Dispersion," Applied Catalysis, 12, 1984, pp. 227-236. Arthur E. Martell and Melvin Calvin, "Chemistry of the Metal Chelate Compounds," New York, Prentice-Hall, Inc., 1952, pp. 516-558. Primary Examiner: Griffin; Walter D. Attorney, Agent or Firm: Lerman; Bart E., Kelly; Michael J. -------------------------------------------------------------------------------- |
| PATENT CLAIMS |
1. A catalyst composition comprising a particulate porous support containing gamma alumina, having a surface area of at least 100 square meters per gram, as measured by nitrogen adsorption, and a pore volume of at least 0.25 cubic centimeters per gram, as measured by mercury porosimetry, and impregnated with one or more catalytically active metals, characterized in that the catalyst contains a nanocrystalline phase of alumina of a crystallite size at the surface of from 8 .ANG. to 25 .ANG. in combination with the gamma alumina which has a crystallite size at the surface of the catalyst of greater than 30 .ANG.; and that the catalyst possesses an at least bimodal mesopore structure. 79. A process for the catalytic hydrocracking of a hydrocarbon-containing feed comprising the step of contacting the feed under hydrocracking conditions with a catalyst composition comprising a particulate porous support containing gamma alumina, having a surface area of at least 100 square meters per gram, as measured by nitrogen adsorption, and a pore volume of at least 0.25 cubic centimeters per gram, as measured by mercury porosimetry, and impregnated with one or more catalytically active metals for hydrocracking, characterized in that the catalyst contains a nanocrystalline phase of alumina of a crystallite size at the surface of from 8 .ANG. to 25 .ANG. in combination with the gamma alumina which has a crystallite size at the surface of the catalyst of greater than 30 .ANG.; and that the catalyst possesses an at least bimodal mesopore structure. |
| PATENT DESCRIPTION |
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to high activity catalysts based upon gamma alumina containing substrates impregnated with one or more catalytically active metals, processes for preparing the same and uses thereof. More specifically, the present invention relates to process for improving the activity of such catalysts, the improved activity catalysts produced thereby, and various specific catalysts and uses thereof. 2. Description of Related Art The art relating to particulate porous gamma alumina containing supports, impregnating such supports with various catalytically active metals, metal compounds and/or promoters, and various uses of such impregnated supports as catalysts, is extensive and relatively well developed. As a few of the many exemplary disclosures relating to these fields may be mentioned the following United States patents, all of which are incorporated herein by reference for all purposes as if fully set forth U.S. Pat. Nos. 2,935,463, 3,032,514, 3,124,418, 3,152,865, 3,232,887, 3,287,280, 3,297,588, 3,493,493, 3,749,664, 3,778,365, 3,897,365, 3,909,453, 3,983,197, 4,090,874, 4,090,982, 4,154,812, 4,179,408, 4,255,282, 4,328,130, 4,357,263, 4,402,865, 4,444,905, 4,447,556, 4,460,707, 4,530,911, 4,588,706, 4,591,429, 4,595,672, 4,652,545, 4,673,664, 4,677,085, 4,732,886, 4,797,196, 4,861,746, 5,002,919, 5,186,818, 5,232,888, 5,246,569 and 5,248,412. While the prior art shows a continuous modification and refinement of such catalysts to improve their catalytic activity, and while in some cases highly desirable activities have actually been achieved, there is a continuing need in the industry for even higher activity catalysts, which are provided by the present invention. As an example of this need may be mentioned the need for a higher activity first stage hydrocracking catalyst. In a typical hydrocracking process, higher molecular weight hydrocarbons are converted to lower molecular weight fractions in the presence of a hydrocracking catalyst which is normally a noble metal impregnated silica-alumina/zeolite. State-of-the-art hydrocracking catalysts possess a very high activity and are capable of cracking high volume throughputs. Such catalysts, however, are highly sensitive to contaminants such as sulfur, metals and nitrogen compounds, which consequently must be removed from the hydrocarbon stream prior to the cracking. This is accomplished in first stage hydrocracking processes such as hydrodenitrogenation, hydrodesulfurization and hydrodemetallation. Hydrotreating catalysts utilized in these processes are typically a combination Group VIB and Group VIII metal impregnated alumina substrate. State-of-the-art hydrotreating catalysts, however, are not sufficiently active to allow processing of the same high volume throughputs as can be processed by the hydrocracking catalysts. As such, the first stage hydrocracking processes form a bottleneck in the overall hydrocracking process, which must be compensated, for example, in the size of the hydrotreating unit relative to the hydrocracking unit. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a high activity catalyst composition comprising, in one aspect, a particulate porous support containing gamma alumina, having a surface area of at least 100 square meters (as measured by nitrogen adsorption) and a pore volume of at least 0.25 cubic centimeters per gram (as measured by mercury porosimetry), and impregnated with one or more catalytically active metals, whereby the catalyst further contains in part a nanocrystalline phase of alumina of a crystallite size at the surface of up to 25 .ANG.. In another aspect, the present invention provides a high activity catalyst comprising a particulate porous support containing gamma alumina, having a surface area of at least 100 square meters (as measured by nitrogen adsorption) and a pore volume of at least 0.25 cubic centimeters per gram (as measured by mercury porosimetry), and impregnated with one or more catalytically active metals, and which catalyst displays a relative volume activity (RVA) of at least 115, preferably at least 120, and especially at least 125, in a first stage hydrocracking process as measured by the procedure described in the article by Carruthers and DiCarnillo, "Pilot Plant Testing of Hydrotreating Catalysts," Applied Catalysts 43 (1988) 253-276, utilizing as the standard a catalyst commercially available under the trade designation HC-H (as of May 1994) from Unocal Corporation, Brea, Calif. In addition to the above catalyst, the present invention also provides a process for improving the activity of a catalyst composition comprising a particulate porous support comprising gamma alumina and amorphous alumina, having a surface area of at least 100 square meters (as measured by nitrogen adsorption) and a pore volume of at least 0.25 cubic centimeters per gram (as measured by mercury porosimetry), and impregnated with one or more catalytically active metals, by the steps of: (1) wetting the catalyst composition by contact with a chelating agent in a carrier liquid; (2) aging the so-wetted substrate while wet; (3) drying the so-aged substrate at a temperature and under conditions to substantially volatilize the carrier liquid; and (4) calcining the so-dried substrate. This process can readily be applied to existing catalysts comprising a particulate porous support containing gamma alumina and amorphous alumina, or can be utilized in a catalyst manufacture process prior to, concurrently with and/or subsequent to the impregnation of the support containing gamma alumina and amorphous alumina, with one or more catalytically active metals and/or compounds thereof. In addition, the process can be utilized to improve the activity of spent catalysts during regeneration, which spent catalysts comprise a particulate porous support containing gamma alumina and amorphous alumina, wherein the spent catalyst is wetted as in step (1) above subsequent to the removal of carbonaceous deposits therefrom, followed by steps (2), (3) and (4). By performing these steps in the indicated order, It is believed (without wishing to be bound by any particular theory) that an interaction takes place between at least the amorphous gamma alumina, chelating agent and catalytically active components, resulting in the appearance of a nanocrystalline phase of alumina of a crystallite size at the surface of the catalyst of up to 25 .ANG., and preferably between 8 .ANG. and 25 .ANG., in combination with the gamma alumina which has a crystallite size at the surface of the catalyst of greater than 30 .ANG., and typically in the range of 30 .ANG. to 70 .ANG.. Crystallite size at the catalyst surface can be measured via well-known techniques involving transmission electron microscopy. Concurrent with the appearance of this nanocrystalline phase, an increase in the surface area of the catalyst is also achieved. In addition, in preferred embodiments, an at least bimodal mesopore structure is generated with a porosity peaking in a first region of pore size 40 .ANG. or less, and more preferably in the range of 20 .ANG. to 40 .ANG., and in a second region of pore size 50 .ANG. or greater, and more preferably in the range of 50 .ANG. to 150 .ANG., as measured by nitrogen porosimetry using the desorption isotherm. The resulting high activity catalysts find use in a wide variety of fields as detailed in the many previously incorporated references. A particularly preferred use is as a first stage hydrocracking catalyst In hydrodenitrogenation, hydrodesulfurization and hydrodemetallation. These and other features and advantages of the present invention will be more readily understood by those of ordinary skill in the art from a reading of the following detailed description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Substrates As indicated above, substrates suitable for use preparing the catalysts of the present invention are particulate porous substrates which comprise at least in part gamma alumina and amorphous alumina, and preferably at least 5 wt % amorphous alumina based on the weight of the substrate. As specific examples may be mentioned substantially alumina substrates, as well as composite substrates in which the alumina acts at least in part as a carrier for other substrates such as silica-aluminas and zeolites. Such substrates and their methods of manufacture are in general well-known to those of ordinary skill in the art, as exemplified by the many previously incorporated references, and reference may be had thereto for further details. Catalytically Active Metals The present invention is applicable to catalysts impregnated with one or more of a wide variety of catalytically active metals well-known to those of ordinary skill in the art as exemplified, for example, by the numerous Incorporated references. In the context of the present invention, "catalytically active metals" includes both the metals themselves as well as metal compounds. In addition to the catalytically active metals, the catalysts may also be impregnated with one or more well-known promoters such as phosphorous, tin, silica and titanium (including compounds thereof). Typically, the catalytically active metals are transition metals selected from the group consisting of Group VIB metals, Group VIII metals and combinations thereof. The specific choice of metal(s), promoter(s) and loadings, of course, depends upon the desired end use of the catalyst, and these variables can readily be adjusted by those of ordinary skill in the art based upon the end use. As specific examples thereof may be mentioned the following (wt % is based on the total catalyst weight): __________________________________________________________________________ Hydrotreating Operations Hydrodenitrogenation Ni and/or Co, and preferably Ni, in an amount up to 7 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 35 wt % calculated as MoO .sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 10 wt % calculated as P.sub.2 O.sub.5 Hydrodesulfurization Ni and/or Co, and preferably Co, in an amount up to 9 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 35 wt % calculated as MoO.sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 10 wt % calculated as P.sub.2 O.sub.5 Hydrodemetallation optionally Ni and/or Co, and preferably including Ni and/or Co, in an amount up to 5 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 20 wt % calculated as MoO.sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 10 wt % calculated as P.sub.2 O.sub.5 Hydroconversion Ni and/or Co, and preferably Ni, in an amount up to 5 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 20 wt % calculated as MoO.sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 6 wt % calculated as P.sub.2 O.sub.5 Hydrocracking Ni and/or Co, and preferably Ni, in an amount up to 5 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 20 wt % calculated as MoO.sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 10 wt % calculated as P.sub.2 O.sub.5 Hydrogenation/ a noble metal, and preferably Pt or Pt in combination with Dehydrogenation Rh, in an amount up to 2 wt % calculated on an elemental basis Reforming a noble metal, and preferably Pt or Pt in combination with another noble metal such Re and/or Ir, and/or Sn, in an amount up to 2 wt % calculated on an elemental basis Non-Hydrotreating Operations Isomerization a noble metal, and preferably Pt or Pt in combination with another noble metal, in an amount up to 2 wt % calculated on an elemental basis Claus Process Ni and/or Co, and preferably Ni, in an amount up to 5 wt % calculated as NiO and/or CoO Mo and/or W, preferably Mo, in an amount up to 20 wt % calculated as MoO.sub.3 and/or WO.sub.3 optionally P, and preferably including P, in an amount up to 6 wt % calculated as P.sub.2 O.sub.5. __________________________________________________________________________ Such catalysts are prepared by impregnating the substrates with the appropriate components, followed by various drying, sulfiding and/or calcining steps as required for the appropriate end use. Such catalyst preparation is generally well-known to those of ordinary skill in the relevant art, as exemplified by the numerous previously incorporated references, and further details may be had by reference thereto or numerous other general reference works available on the subject. The Inventive Process As indicated above, the activity of catalytically active metal impregnated carriers comprising gamma alumina and amorphous alumina is improved in accordance with the present invention by the steps of: (1) wetting the catalyst composition by contact with a chelafing agent in a carrier liquid; (2) aging the so-wetted substrate while wet; (3) drying the so-aged substrate at a temperature and under conditions to substantially volatilize the carrier liquid; and (4) calcining the so-dried substrate. Chelating agents suitable for use in this process include those known to form more stable complexes with transition metals and aluminum and, consequently, possess high stability constants with respect thereto. Particularly preferred for use in the present invention is ethylenediaminetetraacetic acid (EDTA) and derivatives thereof including, for example, N-hydroxy ethylenediaminetetraacetic acid and diammonium ethylenediaminetetraacetic acid. Also suitable are tris(2-aminoethyl)amine and triethylenetetraamine. Other candidates include diethylenetriaminepentaacetic acid, cyclohexanediaminetetraacetic acid, ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid, tetraethylenepentaamine and the like. The suitability of other chelating agents can be readily determined by those of ordinary skill in the art by treating a catalyst sample in accordance with the present invention then determining with the aid of transmission electron microscopy whether or not the nanocrystalline alumina structure of appropriate crystallite size has formed. The amount of chelating agent utilized is not critical to obtaining the effect, but does have an influence on the degree of effect. Widely varying amounts of chelating agent can be utilized depending on a number of factors such as solubility in the carrier liquid, type of catalyst support and metals impregnated or to be impregnated thereon. Generally, the catalyst composition should be wetted by a carrier liquid containing the chelating agent in amounts ranging from 0.01-1.0 grams of chelating agent per gram of catalyst composition. The catalyst composition may be wetted by any normal method such as dipping or spraying. To ensure adequate infiltration of the chelating agent, dipping is preferred followed by a soaking period. The preferred carrier liquid is water or a water/ammonia solution. Aging of the substrate is a function of the temperature during aging. At room temperature, it is preferred to age the wetted substrate for at least 10 days, more preferably at least 14 days. As temperature increases, the required aging time decreases. At 60.degree. C., it is preferred to age the wetted substrate for at least one day, more preferably at least three days. The aging can be further accelerated to as little as one hour by heating the wetted sample in a microwave oven. Preferably aging is accomplished at a temperature in the range of 20.degree. C. to 90.degree. C. Subsequently, the aged catalyst is dried to substantially remove the carrier liquid. It is preferred that the drying take place rapidly at elevated temperatures in the range of 100.degree. C. to 250.degree. C. Preferably, a forced air heater is utilized to speed drying to a preferred time of less than one hour. The so-dried catalyst is then calcined under conditions well-known to those of ordinary skill in the art. Preferably, however, the calcination takes place in two stages--a first lower temperature stage in which the temperature is sufficiently high to drive off or decompose any remaining chelating agent, but which is not so high that the chelating agents combusts to form carbonaceous deposits. This first stage temperature will vary depending on the particularly chelating agent, but typically a temperature within the range of 250.degree. C. to 350.degree. C. will be sufficient. Once any remaining chelating agent is substantially removed, the catalyst may then be calcined under the normal higher temperature conditions commonly utilized. As indicated above, the process In accordance with the present invention is not only applicable to pre-formed catalysts, but also can be applied to regenerated catalysts in a like manner. Specifically, subsequent to the removal of carbonaceous material from a spent catalyst via well-known procedures, such catalysts are then be treated by steps (1) through (4) in an identical manner as described above. This procedure can also be adapted during the production of new catalyst. Specifically, the substrate can be wetted with the chelating agent/carrier liquid either prior to, concurrently with and/or subsequent to the impregnation of the support with the appropriate catalytically active metals, followed by steps (2) through (4) as described above. It is only important to ensure that the aging step takes place while the impregnated support is wet from the carrier liquid for the chelating agent and/or impregnation metals. The present invention as described above will be further exemplified by the following specific examples which are provided by way of illustration and not limitation thereof. The abbreviations in these examples have the following meanings: EDTA ethylenediaminetetraacetic acid MEA monoethanolamine SA(N.sub.2) surface area measured by nitrogen adsorption SA/gAl.sub.2 O.sub.3 surface area per gram alumina RVA relative volume activity in a 1st stage hydrocracking test, measured as described in the article by Carruthers and DiCamillo, "Pilot Plant Testing of Hydrotreating Catalysts," Applied Catalysts, 43 (1988) 253-276. The relative volume activity is determined utilizing as the standard a catalyst commercially available (as of May 1994) under the trade designation HC-H from Unocal Corporation, Brea, Calif. RWA relative weight activity, determined in accordance with the aforementioned article. |
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