HYDROTREATING CATALYSTS COMPRISING MIXTURES OF AN AMORPHOUS SULPHIDE OF TRIVALENT CHROMIUM AND MICROCRYSTALLITES OF MOLYBDENUM SULPHIDE OR TUNGSTEN

Abstract: A composition of matter comprising a mixture of (i) an amorphous sulfide of trivalent chromium and (ii) microcrys­ tallites of metal sulfide of a metal selected from Mo, W and a mixture thereof. These compositions have been found to be useful hydrotreating catalysts having nitrogen removal activ­ ity superior to that of commercial catalysts derived from cobalt molybdate on alumina.

Description: This invention relates to compositions containing an amorphous sulphide of trivalent chromium. The petroleum industry is increasingly turning to heavy crudes, resids, coal and tar sands as sources for future feedstocks. Feedstocks derived from these heavy materials contain more sulfur and nitrogen than feedstocks derived from more conventional crude oils. These feeds therefore require a considerable amount of upgrading in order to obtain usable products therefrom, such upgrading or refining generally being accomplished by hydrotreating processes which are wellknown in the petroleum industry. These processes require the treating with hydrogen of various hydrocarbon fractions, or whole heavy feeds, or feedstocks, in the presence of hydrotreating catalysts to effect conversion of at least a portion of the feeds, or feedstocks to lower molecular weight hydrocarbons, or to effect the removal of un wanted components, or compounds, or their conversion to innocuous or less undesirable compounds. Hydrotreating may be applied to a variety of feedstocks, e.g., solvents, light, middle, or heavy distillate feeds and residual feeds, or fuels. In hydrotreating relatively light feeds, the feeds are treated with hydrogen, often to improve odor, color, stability, combustion characteristics, and the like. Unsaturated hydrocarbons are hydrogenated. Sulfur and nitrogen are removed in such treatments. In the hydrodesulfurization (HDS) of heavier feedstocks, or residua, the sulfur compounds are hydrogenated and cracked. Carbon-sulfur bonds are broken, and the sulfur for the most part is converted to hydrogen sulfide which is removed as a gas from the process. Hydrodenitrogenation (HDN) , to some degree also generally accompanies hydrodesulfurization reactions. In the hydrodenitrogenation of heavier feedstocks, or residua, the nitrogen compounds are hydrogenated and cracked. Carbon-nitrogen bonds are broken, and the nitrogen is converted to ammonia and evolved from the process. Hydrodesulfurization, to some degree also generally accompanies hydrodenitrogenation reactions. In the hydrodesulfurization of relatively heavy feedstocks, emphasis is on the removal of sulfur from the feedstock. In the hydrodenitrogenation of relatively heavy feedstocks emphasis is on the removal of nitrogen from the feedstock. Albeit, hydrodesulfurization and hydrodenitrogenation reactions generally occur together, it is usually far more difficult to achieve effective hydrodenitrogenation of feedstocks than hydrodesulfurization of feedstocks. Catalysts precursors most commonly used for these hydrotreating reactions include materials such as cobalt molybdate on alumina, nickel on alumina, cobalt molybdate promoted with nickel, nickel tungstate, etc. Also, it is well-known to those skilled in the art to use certain transition metal sulfides such as cobalt and molybdenum sulfides and mixtures thereof to upgrade oils containing sulfur and nitrogen compounds by catalytically removing such compounds in the presence of hydrogen, which processes are collectively known as hydrotreating or hydrorefining processes, it being understood that hydrorefining also includes some hydrogenation of aromatic and unsaturated aliphatic hydrocarbons. Thus, U.S. Patent No. 2,914,462 discloses the use of molybdenum sulfide for hydrodesulfurizing gas oil and U.S. 3,148,135 discloses-¯the use of molybdenum sulfide for hydrorefining sulfur and nitrogen-containing hydrocarbon oils. U.S. 2,715,603, discloses the use of molybdenum sulfide as a catalyst for the hydrogenation of heavy oils. Molybdenum and tungsten sulfides have other uses as catalysts in reactions such as hydrogenation, methanation and water gas shift. In general, with molybdenum and other transition metal sulfide catalysts as well as with other types of catalysts, higher catalyst surface areas result in more active catalysts than similar catalysts with lower surface areas. Thus, those skilled in the art are constantly trying to achieve catalysts that have higher surface areas. More recently, it has been disclosed in U.S. Patent Nos. 4,243,553, and 4,243,554 that molybdenum sulfide catalysts of relatively high surface area may be obtained by thermally decomposing selected thiomolybdate salts at temperatures ranging from 300-8000C in the presence of essentially oxygenfree atmospheres. Suitable atmospheres are disclosed as consisting of argon, a vacuum, nitrogen and hydrogen. In U.S. 4,243,554 an ammonium thiomolybdate salt is decomposed by heating at a rate in excess of 150C per minute, whereas in U.S. 4,243,553, a substituted ammonium thiomolybdate salt is thermally decomposed at a very slow heating rate of from about 0.5 to 20C/min. The processes disclosed in these patents are claimed to produce molybdenum disulfide catalysts having superior properties for water gas shift and methanation reactions and for catalyzed hydrogenation or hydrotreating reactions. Catalysts comprising molybdenum sulfide in combination with other metal sulfides are also known. Thus, U.S. Patent No. 2,891,003 discloses an ironchromium combination for desulfurizing olefinic gasoline fractions; 3,116,234 discloses Cr-Mo for HDS and 3,265,615 discloses Cr-Mo for HDN and HDS. The present invention relates to new compositions of matter comprising a mixture of (i) an amorphous sulfide of trivalent chromium and (ii) microcrystallites of a metal sulphide of a metal selected from Mo, W and mixture thereof. By amorphous is meant a compound which exhibits no detectable crystallinity when measured by X-ray diffraction. By microcrystallites is meant crystals whose major dimensions are less than about 0.1 microns by 0.01 microns, preferably less than 0.05 microns by 0.01 microns and still more preferably less than 0.015 microns by 0:-Q05 microns. These compositions have been found to be useful as hydroprocessing catalysts, such as hydrotreating catalysts having high activity and selectivity for nitrogen removal. The compositions of this invention are obtained by heating one or more catalyst precursors in the presence of sulfur and under oxygen-free conditions at a temperature of at least about 2000C for a time sufficient to form said catalyst. The catalyst precursor will comprise a mixture of (i) a hydrated oxide of trivalent chromium and (ii) a thiometallate salt of the general formula (L')(MOyWlyS4) , wherein y is any value ranging from 0 to 1, and wherein L' is the conjugate acid of one or more ligands, L, with a charge sufficient to balance the dinegative charge of the thiometallate anion. The ligBnd L is one or more neutral, nitrogen-containing ligands at least one of which is a chelating polydentate ligand. In a particularly preferred embodiment, the oxygen-free conditions will be an atmosphere comprising a gaseous mixture of hydrogen and hydrogen sulfide. Hydroprocessing catalyst is meant to include catalysts useful for any process that is carried out in the presence of hydrogen, including, but not limited to, hydrocracking, hydrodenitrogenation, hydrodesulfurization, hydrogenation of aromatic and aliphatic unsaturated hydrocarbons, methanation, water gas shift reactions, etc. These reactions include hydrotreating and hydrorefining reactions, the difference generally being thought of as more of a difference in degree than in kind, with hydrotreating conditions being more severe than hydrorefining conditions. Since as stated above, by amorphous is meant a compound which exhibits no detectable crystallinity when measured by X-ray diffraction, compositions of this invention analyzed by X-ray diffraction have exhibited no detect able.crystallinity for the chromium sulfide. Further, compositions of this invention analyzed by high resolution scanning transmission electron microscopy (HREM) with a microscope having a 42 point-to-point resolution revealed the presence of less than 5% of the total Cr2S3 in detectable crystalline form. By microcrystallites (of tungsten or molybdenum sulfide) is meant crystals whose major dimensions are less than about 0.1 microns by 0.01 microns, preferably less than 0.05 microns by 0.01 microns, and still more preferably less than 0.015 microns by 0.005 microns. Analysis of compositions of matter of this invention have revealed that they can be expressed by the illustrative, but non-limiting general formula [x(Mo or W)Sa](Cr2Sb) wherein 1.5 < a < 3.5, 1.5 < b < 4.5 and O < x < 4. It is preferred that 1.8 < a < 2.4 and 2.7 < b < 3.2. Chemical analysis of the composition prepared in Example 1, below, revealed it to be Cur0,811 MoS3 15 which can be written in the general form as (2.47 MoS2)(Cr2S3). The chemical analysis, performed at high spatial resolution in the electron microscope, also indicated microcrystallites of MoS2 as highly dispersed on or in the amorphous Cr2S3. As stated above, the catalysts of this invention may be prepared from one or more catalyst precursors which will comprise a mixture of (i) a hydrated oxide of trivalent chromium and (ii) a thiometallate salt of the general formula (L')(MoyWl¯ys4) wherein y is any value ranging from 0 to 1 and L' is the conjugate acid of one or more ligands, L, with a charge sufficient to balance the dinegative charge of the thiometallate anion. Ligand L will be one or more neutral, nitrogen containing ligands wherein at least one of said ligands is a multidentate chelating ligand. The ligand, in its conjugate acid form, forms a cation [L'2+. Thus, the catalytic metal Sulfide anion (MoyWl-ys4)2- will be ionically bound to the cation. By neutral is meant that the ligand itself does not have a charge. Those skilled in the art know that the term "ligand" is used to designate functional coordinating groups which have one or more pairs of electrons available for the formation of coordinate bonds. Ligands that can form more than one bond with a metal ion are called polydentate while ligands that can form bnly one bond with a metal ion are called monodentate. Monodentate ligands are not capable of forming chelates. Hence, if one uses one or more species of monodentate ligands in the precursor molecule, then one must also use more than one polydentate chelating ligand. Preferably L will be one or more polydentate chelating ligands. The total denticity of the ligand species comprising L will be six. Thus, L will be three bidentate ligands, two tridentate ligands, a mixture of a bidentate and a quadridentate ligand, a hexadentate ligand or a mixture of a polydentate ligand with monodentate ligands as long as the combination has a total denticity of six. As has heretofore been stated, it is preferred to use chelating bidentate and tridentate alkylamine ligands. In general, the ligands useful in this invention include alkyl and aryl amines and nitro gen heterocycles. Illustrative but non-limiting examples of ligands useful in the catalyst precursors of this invention are set forth below. Monodentate ligands will include NH3 as well as alkyl and aryl amines such as ethylamine, dimethyl amine, o-phenylene diamine and nitrogen heterocyclic amines such as pyridine, etc. Useful chelating bidentate amine ligands are illustrated by ethylenediamine, 2,2'-bipyridine, o-phenylene diamine, tetramethylethylenediamine and propane-1,3 diamine. Similarly, useful chelating tridentate amine ligands are represented by terpyridine and diethylenetriamine, while triethylenetetramine is illustrative of a useful chelating quadridentate amine ligand. Useful chelating pentadentate ligands include tetraethylene pentamine while sepulchrate (an octazacryptate) is illustrative of a suitable chelating hexadentate ligand. As a practical matter it will be preferred to use chelating, polydentate alkyl amines. Illustrative, but not limiting examples of alkyl amines that are useful in the catalyst precursor of this invention include ethylenediamine, diethylenetriamine, and tetraethylenetetramine. It is particularly preferred to use bidentate and tridentate alkyl amines such as ethylenediamine(en) and diethylenetriamine(dien). The conjugate acid of ligand L, referred to as L', will have a charge sufficient to balance the dinegative charge of the thiometallate anion. For example, if L is ethylenediamine (en), L' will be [H2en]2+ and the corresponding thiomolybdate salt, for example, will be [H2en}3(MoS4). For diethylene triamine, (dien), the corresponding salt will be [H2 dien]2(MoS4). In general, the precursors useful for forming the compositions of this invention may be prepared by mixing a slurry of a hydrated oxide of trivalent chromium Cr(OH)3 xH2O, with one or more of the thiometallate salts containing the conjugate acid of one or more ligands, precipitating the thiometallate salt onto the slurried particles of hydrated chromium oxide and recovering the,precursor. The hydrated chromium oxide may be freshly precipitated from an aqueous solution of a trivalent chromium salt. Alternatively, the source of hydrated chromic oxide may be a sol or colloidal, aqueous suspension of same. Intone method of preparation the hydrated chromium oxide will be precipitated from an aqueous solution of trivalent chromium salt by contacting said salt solution with one or more basic amine chelating agents. In one embodiment, a water soluble trivalent chromium compound is dissolved in water and hydrated chromium oxide is precipitated by addition of a ligand, L, or a mixture of ligands, L. This procedure produces a slurry or suspension of very fine particles of a hydrated oxide of trivalent chromium in the aqueous phase, which also contains some free ligand L, and some of the conjugate acid of the ligand L, LI. When the conjugate acid is a strong acid, that is if the ligand L is a weak base, than a quantity of ammonium hydroxide may be added to precipitate the chromium. The water soluble chromium salt may be any water soluble salt that is convenient to use such as halide, sulfate, nitrate, etc. The hydrated chromium oxide slurry is then mixed with a solution of the thiometallate prepared by dissolving ammonium thiometallate in an excess of the ligand or mixture of ligands. A small amount of water may be added if desired. On mixing the slurry with the thiometallate solution an orange-red colored precipitate forms which is recovered by filtration. This precipitate will be a precursor of a composition of this invention. The salts (L') (MOyWlyS4) may generally be prepared by dissolving the ammonium thiometallate in excess of the ligand L. The salt is recovered as a precipitate by addition of water or some other suitable antisolvent such as methanol or acetone. The compositions or catalysts of this invention will be prepared by heating one or more precursors, in an oxygen-free environment in the presence of sulfur at a temperature of at least about 2000C for a time sufficient to form the catalyst. Although the sulfur required during the formation of the catalyst may be present in the precursor, it is preferred that the sulfur be present in an amount in excess of that contained in the precursor. Thus, it is preferred that the composition be formed by heating the precursor in the presence of excess sulfur in the form of a sulfur bearing compound. Mixtures of hydrogen and H2S have been found to be particularly suitable. Preferably the temperature will range between from about 250-6000C, more preferably from about 250-5000C and still more preferably from about 300-4000C. The oxygen-free environment may be gaseous, liquid or mixture thereof. The compositions of this invention were established using a number of analytical techniques briefly described below. X-ray diffraction (XRD) analysis was done by grinding a sample to fine powder and packing it into an alumina tray, containing a cylindrical recess 25 mm in diameter and 1 mm in depth. The top surface of the sample was flat and co-planar with the top of the aluminum tray after this preparation. Measurements were made in ambient atmosphere using a Siemens D500 X-ray diffractometer in G-2G reflection (Bragg Brentano) geometry. The incident X-ray beam was taken from a fixed anode copper target with a wavelength of 1.54178 i. The diffracted beams were monochromated using a graphite monochromator to minimize fluoresence and were detected using a proportional counter detector. Data were collected by stepping the detector in angular increments of 0.020 2G and counting at each step for two seconds. The intensity and angular information were stored in a PDP 1103 computer and subsequently plotted as detected counts in 2 seconds versus 20. The morphology and crystal structure determination of the constituent phases were carried out using high resolution and analytical electron microscopy. In this procedure, described in P.C. Flynn et al., J. Catal., 33, 233-248 (1974), the transition metal sulfide powder is prepared for the Transmission Electron Microscope (TEM) by crushing in an agate mortar and pestle to produce powder fragments through which an electron beam can pass. The crushed powder is ultrasonically dispersed in hexane and a drop of this suspension is allowed to dry onto a standard 3 mm TEM grid, which is covered with a thin ( < 200 i) amorphous carbon film. Samples were analyzed in a Philips 400T FEG TEM at 100 KV by bright field imaging, energy dispersive X-ray microanalysis, and microdiffraction. Quantitative chemical analysis was obtained by the thin foil ratio method, as described in G. Cliff and G. W. Lovimer; J. Microscopy, 1975, Volume 103, Page 203, and absorption effects were analyzed and corrected using the procedure described by Goldstein, et al. in "Introduction to Analytical Electron Microscopy", J. J. Hren, J. I. Goldstein, and D. C. Joy eds, Plenum Press, New York, NY 1979, Page 83. X-ray fluorescent spectra was generated from the excited volume of a sample defined by a cylinder of 100 probe size and the thickness of the sample (typically 1ooo R). As mentioned previously, molybdenum and tungsten sulfide catalysts have many uses, including hydrotreating. Hydrotreating conditions vary considerably depending on the nature of the hydrocarbon being hydrogenated, the nature of the impurities or contaminants to be reacted or removed, and, inter alia, the extent of conversion desired, if any. In general however, the following Table illustrates typical conditions for hydrotreating a naphtha boiling within a range of from about 250C to about 2100C, a diesel fuel boiling within a range of from about 1700C to 3500C, a heavy gas oil boiling within a range of from about 3250C to about 4750C, a lllbricating oil feed boiling within a range of from about 290 to 5500C, or residuum containing from about 10 percent to about 50 percent of a material boiling above about 5750C. Typical Hydrotreating Conditions Space Hydrogen Pressure Velocity Gas Rate Feed Temp., C psig V/V/Hr SCF/B Naphtha 100-370 150-800 0.5-10 100-2000 Diesel Fuel 200-400 250-1500 0.5-4 500-6000 Heavy Gas Oil 260-430 250-2500 0.3-2 1000-6000 Lube Oil 200-450 100-3000 0.2-5 100-10,000 Residuum 340-450 1000-5000 0.1-1 2000-10,000 It should be noted that the compositions of this invention are useful catalysts litricating oil refining processes where it is desirable to remove oxidation initiating nitrogen compounds from lubricating oil feeds. The invention will be further understood by reference to the following examples. Example 1 Precursor Preparation A chromium thiomolybdate catalyst precursor was prepared by dissolving 40 grams of ammonium thiomolybdate into 82 ml of diethylenetriamine in al liter flask which formed a dark red solution. The sides of the flask were washed with distilled water and the flask was cooled to OOC. In a separate flask 27.56 grams of CrC13.6H2O was dissolved into 250 ml of distilled water. Diethylenetriamine(dien), 25 ml, was added to form a precipitate. The resulting slurry was allowed to stand for 2-3 hours and then added slowly, with agitation, to the (NH4)2MoS4/dien solution. This resulted in the formation of a bright orange precipitate which was then stirred while on the ice bath for a half hour after the addition was completed. The precipitate was then separated by filtration, washed with water and ethanol and dried at ambient temperature under vacuum. Ninety-one grams of precursor were recovered as an orange colored precipitate. The precursor had the approximate (calculated) formula [Cr(OH)3.l.5H20] (H2dien)11(MoS4)11. Elemental analysis of the precursor is set forth below in wt.%. Cr Mo S C H N O Precursor 10.0 20.1 28.0 12.3 4.8 10.5 14.3 Catalyst Preparation The precursor was pelletized using a 4% aqueous solution of polyvinyl alcohol as a binder, loaded into a stainless steel¯reactor and purged for one hour under nitrogen at 1000C and atmospheric pressure. Ten percent of hydrogen sulfide in hydrogen was introduced into the reactor at a rate of 0.75 SCF/hr for each lOcc of catalyst in the reactor. The temperature in the reactor was then raised to 3250C and held at this temperature for three hours to form the catalyst after which the temperature in the reactor was lowered to 1000C, the H2S/H2 gas flow was stopped and the reactor was purged with nitrogen and allowed to cool to room temperature. Elemental analyses of the catalyst or composition of this invention formed by sulfiding the precursor is set forth below in wt.%. Cr Mo S C H N 15.6 33.5 37.6 3.5 0.81 1.16 Reaction Conditions About 20 g of the catalyst was loaded into a fixed-bed reactor. Hydrotreating was carried out at the conditions set forth below: Temperature 3250C Pressure 3.15 MPa Hydrogen rate 3000 SCF/bbl LHSV 3.0 V/V/Hr. Liquid product was analyzed for total sulfur by X-ray fluorescence and for nitrogen by combustion analysis. The feedstock used was a light catalytic cycle oil (LCCO) that was about 20 wt.% paraffinic having nominal properties set forth in Table 1. Hydrotreating Experiment In this experiment, the results obtained from the catalyst composition of this invention was compared to results obtained from a commercial hydrotreatng catalyst comprising nickel molybdate on 6-A1203. This catalyst contained 18 percent molybdenum oxide and 3.5 percent nickel oxide supported on gamma alumina. The commercial catalyst was sulfided employing the same procedure used to form the catalysts of this invention, except that the temperature was 3600C for one hour. The results of these experiments are shown in Tables 2 and 3 and show that the catalyst of this invention is not only a useful hydrotreating catalyst but has higher selectivity for hydrodenitrogenation than the commercial nickel molybdate on alumina catalyst. Table 1 LCCO Feed Gravity ( API) 18.6 Sulfur, wt. % 1.4 Nitrogen, ppm 292 GC distillation Wt. % Temp., C 5 231 10 --251 50 293 70 321 90 352 95 364 Table 2 Hydrotreating Activity for Commercial Nickel Molybdate on Alumina Catalyst Hours on Stream %HDS %HDN 49 80.0 32.3 71 80.8 38.6 75 80.0 37.6 Table 3 Hydrotreating Activity for Catalyst Prepared From Chromium Promoted Thiomolybdate Precursor Catalyst Hours on Stream %HDS %HDN 66 50.2 78.8 The catalyst of this invention was inspected by a number of analytical techniques, as described briefly above. Electron microscopy of the fresh catalyst prepared in this example has revealed that the molybdenum microcrystallite sizes generally had dimensions less than about 0.1 microns by 0.01 microns. The chromium sulfide was present as distinct regions of amorphous material in which less than 5% of crystalline forms were discernable with the 4 point-to-point resolution instrument used. After the catalyst had been on stream for three days, as shown in Tables 1 and 3, it was removed from the reactor for analysis. Examination of electron micrographs of this composition, taken at a magnification of 680,000X, revealed the presence of many lines 6.2A apart and generally not more than 150A in length. It is well known in the art [see, for example, R. R. Chianelli, International Reviews in Physical Chemistry, (1982), 2(127-165)] that such lines with the 6.2A spacings are characteristic of MoS2. MoS2 occurs in layers which are seen to be highly disordered and occurring singly or stacked but in the micrograph the degree of stacking is generally not more than eight stacks and usually not more than four stacks. The Cr2S3 phase was observed to be completely amorphous. In some cases a small amount of crystalline Cr2S3 phase was detected, but only as a minority phase. The predominant material, which is the catalytically active composition of this invention, is a mixture of microcrystalline MoS2 or WS2 or mixture thereof with amorphous Cr2S3. The catalyst composition of this Example was also analyzed by X-ray diffraction, both fresh and after being on stream for three days. There was no discernable difference in the diffraction patterns. The diffraction patterns obtained were consistent with MoS2 microcrystallites of the size observed by the electron microscope. The X-ray diffraction patterns contained a broad peak between approximately 10 and 15' 20 which is indicative of stacks of MoS2 crystallites with a stack number of about 4. There was no evidence in the X-ray diffraction (XRD) patterns for any crystalline chromium sulfide phase. The XRD thus supports the electron microscopy results in indicating that the chromium sulfide is amorphous. Example 2 In this experiment a chromium molybdenum sulfide on alumina catalyst was prepared using the procedure set forth in Example 4 of U.S. Patent 3,265,615. Thus, 24.2 grams of (NH4)6Mo7024 4H2O(APM) were dissolved in 150 ml of water. One-half of this solution was used to impregnate 26.6 grams of a re forming gradeA1203 that had been calcined to remove water. The impregnate was dried overnight at 1000C and reimpregnated with the other half of the APM solution. The resulting impregnate was again dried overnight at 1000C and then calcined in air for four hours at 5500C. To the calcined impregnate was added a hot (80-1000C) solution of 20 g of Cr2(SO4)3 in 50 ml of water, followed by drying overnight at 1000C to form 58.7 g of a green colored, chromium molybdate precursor. This precursor was then pelletized and screened to -20 to +40 mesh. The screened precursor was placed in the reactor and contacted with flowing hydrogen at room temperature. The temperature was then raised to 2880C and held there for one-half hour, followed by raising the temperature to 4500C, holding for one-half hour and then raised to 5100C and held at 5100C for one-half hour. The reactor temperature was then lowered to 3160C, and the hydrogen replaced with a 10% H2S in H2 mixture. The flowing H2S/H2 mixture contacted the precursor for three hours at 3160C. The LCCO feed was then introduced employing the procedure set forth above, again at an LHSV of 3.0 V/V/hr. The results are set forth below in Table 4. Table 4 Catalyst Hours on Stream %HDS %HDN 48 23.8 5.8 70 24.4 5.2 These results are much different from the results obtained for a chromium molybdenum sulfide catalyst of this invention employing the same feed and reaction conditions set forth in Table 3. Thus, the chrom ium promoted catalyst of this invention is much superior in both HDS and HDN activity to the chromium promoted catalyst disclosed and claimed in U.S. 3,265,615. These comparative results also established that the catalyst of this invention is a different catalyst from that of U.S. 3,265,615. Example 3 In this example, the composition of this invention was prepared by precipitating the thiomolybdate of (dien) onto colloidal Cr203, drying and sulfiding. The resultant solid was tested as a hydrotreating catalyst. The amount of Cr203 used was in excess of that amount needed to form the unsupported species of this invention so that the excess Cr203 served as a support. 5.207 g of (NH4)2MoSg (0.02 m) was dissolved in 50 ml of diethylenetriamine (dien) in an ice bath. A 22 wt.% (0.09 m) aqueous dispersion of colloidal Cr203 (Nyacol) containing 13.69 g of Cr2O3 was diluted to 200 ml with water and transferred to a 100 ml round bottom flask provided with a mechanical stirrer. The thiomolybdate solution was added slowly with agitation, stopping occasionally to break up any gel formed with a spatula. The slurry was filtered, the solid washed with acetone and dried in a vacuum at 500C. A sample of the solid was ground and sieved to 20/40 mesh. This catalyst precursor had the following composition: Element S Mo Cr C H N wt.% 3.26 3.18 19.0 18.77 6.14 14.80 The material was sulfided as described in Example 1. It is believed that the final catalyst contained about 60 wt.% chromia. Evaluation of the composition as a catalyst was carried out in an automated, continuously stirred tank reactor unit consisting of a one liter autoclave, calibrated feed burrete, pump, gas-liquid separator, and product liquid collector. In a typical experiment, 20 cc of catalyst were charged in a stainless steel basket which was placed inside the autoclave. Operating conditions and hydrotreating results are listed in Table 5. Table 5 Operating Conditions and Hydrotreating Results Feed LCCO Temperature, OC 325 Pressure, MPa 3.15 Hydrogen Rate, SCF/Bbl 3000 LHSV, V/V/hr 1 %HDS 38 %HDN 46 Example 4 A 34 wt.% suspension of colloidal silica, 147 g, was diluted with 100 g of distilled water. A solution of 26.4 g of Cr(NO3)3 9H2O in 35 g of dis tilled water was added to this colloidal suspension. A solution of 25.8 g of (NH4)2MoS4 in 100 ml ethylenediamine was added dropwise to the silica suspension with constant agitation, and the stirring continued for 20-30 minutes after-all the en solution had been added. A precipitate formed which was filtered and dried in a vacuum oven at 500C, sulfided as in Example 1 and rescreened to 20/40 mesh. Reaction Conditions The same reaction conditions were employed as in Example 1. the results shown in Table 6 were obtained. Table 6 Hydrotreating With Supported Catalyst Run Length, hrs. %HDS %HDN 48 36.9 35.3 69 32.1 24.9 140 33.3 25.4 While desulfurization level is much lower than that achieved with a commercial catalyst (see Table 2, Example 1) the denitrogenation obtained with this supported catalyst is about the same order as with commercial catalyst. This shows that the ratio of HDN/HDS activity of the supported catalyst of this invention is higher than that of commercial catalyst.

Claims: CLAIMS: 1. A composition of matter comprising a mixture of (i) an amorphous sulfide of trivalent chromium and (ii) microcrystallites of a metal sulphide of a metal selected from Mo, W and & mixture thereof in which said composition exhibits no crystallinity for the chromium sulfide when measured by X-ray diffraction. 2. A composition according to claim 1 comprising a mixture of (i) a single phase, amorphous metal sulfide of trivalent chromium and (ii) microcrystallites of metal sulfide of a metal selected from Mo, W and mixture thereof. 3 A composition according to either of claims 1 and 2 which exhibits less than 5% of the chromium sulfide in detectable crystalline form when measured with an electron microscope having a 4 X point-topoint resolution and wherein said microcrystallites Of a metal sulfide of Mo, W or amixture thereof have major dimensions of less than about 0.1 microns by 0.01 microns. 4. A process for preparing the composition of any one of the preceding claims comprising heating one or more precursors at a temperature of at least about 2000C, in the presence of sulfur and under oxygen-free conditions for a time sufficient to form said catalyst, wherein said precursor is formed by mixing a slurry of particles of a hydrated oxide of trivalent chromium with one or more salts containing a thiometallate anion of Mo, w or amixture thereof and a cation containing the conjugate acid of one or more neutral, nitrogen-containing ligands, at least one of which is a chelating polydentate ligand, to precipitate the thiometallate salt or salts onto the particles of hydrated chromium oxide and recovering the precursor. 5. A process according to claim 4 wherein said precursor is prepared by mixing a slurry of particles of hydrated chromium oxide with a solution of thiometallate salt prepared by dissolving an ammonium thiometallate of Mo, W or mixture thereof in an excess of one or more neutral, nitrogen-containing ligands, at least one of which is a chelating polydentate ligand to form a precursor precipitate and recovering said precursor. 6. A process according to either of claims 4 and 5 wherein said precursor comprises a mixture of (a) a hydrated oxide of trivalent chromium and (ii) a thiometallate salt of the general formula (L') (MoyWl¯ys4) wherein y is any value ranging from 0 to 1, wherein L' is the conjugate acid of one or more ligands, L, with a charge sufficient to balance the dinegative charge of the thiometallate anion and wherein L is one or more neutral, nitrogen-containing ligands, at least one of which is a chelating polydentate ligand. 7. A process according to claim 6 wherein said catalyst is formed in the presence of excess sulfur in the form of a sulfur-bearing compound and wherein ligand L is selected from alkyl amines, aryl amines, nitrogen heterocycles and mixtures thereof. 8. A process according to claim 7 wherein ligand L is one or more chelating polydentate amines and preferably one or more alkyl amines. 9. A hydroprocessing process comprising contacting a hydrocarbon feed at elevated temperature of at least about 100 C and in the presence of hydrogen, with a catalyst according to any one of claims 1, 2 and 3 or with a catalyst prepared by the process according to any one of claims 4 to 8. 10. Process according to claim 9 wherein said feed is upgraded by contacting said feed at an elevated temperature of at least about 1000C and in the presence of hydrogen with said catalyst for a time sufficient to upgrade at least portion of said feed. 11. A process according to claim 10 wherein a hydrocarbon feed is hydrotreated, the contacting temperature is at least about 150 C and the contacting occurs for a time sufficient to hydrotreat at least a portion of said feed. 12. A process for removing nitrogen from a nitrogen-containing hydrocarbon feed which comprises contacting said feed at an elevated temperature of at least about 1500C and in the presence of hydrogen with a catalyst according to any one of claims 1, 2 and 3, or with a catalyst prepared according to the process of any one of claims 4 to 8 said contacting occurring for a time sufficient to remove nitrogen from at least a portion of said feed. 13. A process according to claim 12 wherein said feed is a lubricating oil feed. 14. A process for improving the oxidation stability of a nitrogen and sulphur containing lubricating oil feed which comprises contacting said feed at an elevated temperature of at least about 150 C and in the presence of hydrogen with a catalyst according to any one of claims 1, 2 and 3 or with a catalyst prepared by the process according to any one of claims 4 to 8 said contacting occurring for a time sufficient to improve the oxidation stability of said oil.

Inventors: CHIANELLI, RUSSELL ROBERT, HO, TEH CHUNG, JACOBSON, ALLAN JOSEPH, MONTAGNA, ANGELO ANTHONY, STEGER, JOHN JOSEPH
Applicants: EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1985
Main classification: B01J27
IPC codes: C10G45, B01J31, B01J27, C10G49