SUPPORTED COBALT-SILICA COPRECIPITATED HYDROGENATION CATALYST

Abstract: This invention relates to coprecipitated cobalt-silica hyd­ rogenation catalysts which are prepared by preparing an aqueous reaction mixture containing cobalt cations, silicate anions and solid porous carrier particles under agitation to form a coprecipitate of the cobalt and silicate ions onto said solid porous support particles; heating the aqueous reaction mixture; and adding an alkaline precipitating agent to precipi­ tate further the cobalt and silicate ions onto said solid porous carrier particles. The aqueous reaction mixture may addition­ ally include copper cations.

Description: This invention relates to coprecipitated cobalt silica catalysts and their use in hydrogenating organic com pounds. This invention also relates to the prep aration of supported coprecipitated cobalt-silica catalysts Furthermore, this invention relates to the use of the catalysts, in reduced form, to hydrogenate organic compounds. The catalytic reduction of organic compounds in tc-. presence of nickel and cobalt catalysts is known. nickel catalysts, especially supported nickel catalysts, have many commercial uses. For example, U.S. Patent 3,535,271 teaches the use of a nickel catalyst promoted by copper for dehydro genation, cracking, reforming, polymerisation, isomerisation, alkylation, as well as other treating processes. Other exam- ples of nickel catalysts and their use in reforming and other processes include U.S. Patent Nos 2,750,261; 3,205,182; 3,351,566; 3,417,029; 3,697,445; 3,859,370; 3,868,332; 4,088,603; and Belgian Patent No. 841, 812 (which generally corresponds to U.S. Application Serial No. 577,328). In all of these patents, the catalysts are prepared by copre cipitation or impregnation processes wherein the catalytic metal precursors are either precipitated from solution in the presence of a support material or solution containing said precursor or impregnated into the pores of a porous support material. In the British Patent No. 1,220,105, for example, aqueous solutions are employed in conjunction with a homogen eous precipitation procedure to give highly dispersed nickel catalyst. D.J.C. Yates, W.F. Taylor and J.H. Sinfelt (J. Am. Chem. Soc., 96,2996 [19641) described a chemisorption tech nique and its utility in correlating nickel particle size (and/or nickel surface area) with catalytic activity. in i- ure 3 of their publication, there is shown that a direct rcla tion exists between reduced nickel surface area (m2/g of catalyst) and initial reaction rate for ethane catalytically converted into methane (as mmoles C2H6 converted per hour gram of catalyst). It follows, then, that methods which in crease the nickel surface area of a nickel catalyst (other factors such as nickel content remaining constant) is a desir able feature, loading to a catalyst of: improved catalytic activity. Patentees of U.S Patent Mos. 3,697,445; 3,859,370 and 3,868,332 also appreciated tat by achieving a higher degree of dispersion of nickel in the catalyst results in a more active catalyst and indeed they obtain a fairly high degree of dispersions by their coprecipitation techniques wherein nickel cations were gradually precipitated from an aqueous solution in the presence of silicate anion and solid porous particles to obtain dispersion greater than 70 m"jg of reduced nickel metal per gram of catalyst. Belgian Patent No. 841,812 teaches that the addition of copper ions during the precipitation step provides a catalyst that can be reduced at temperatures of approximately 2000C. U.S. Patent o. 4,088,603 discloses an improved method of activating t coprecipitated nickel-copper-silica catalysts. A number of patents have dIsclosed cobalt cobalt ' nickel and cobalt-nickel-copper catalysts, e.g., U.S. Patent Nos. 3,166,491; 3,385,670; 3,432,443; ,547,830; 3,650,713; 3,661,798; 3,945,944; 4,014,933 and 4,026,823; and British Patent Nos. 1,000,826; 1,000,829; 1,095,996; 1,095,997 and 1,182,829. None of these patents, however, disclose copre cipitation of cobalt salts and silicate ions In the presence of the porous carrier particles.' In some of the above-mentioned patents, for example, U.S. Patent Nos. 3,697,445; 3,859,370; 3,868,332 and Belgian Patent No. 841,812 it is mentioned that cobalt or i-ron nay be used in place of nickel in the coprecipitation process. How ever, these patents only show nickel (in the examples) as the non-noble Group VIII catalytic metal used. It has been discovered that, contrary to the sug- gestions in the aforementioned prior art, the now noble Group VIII metals are not equivalent in terms of their catalytic properties and/or reduced metal surface area when prepared by cccrecipitation in the presence of silicate anions and solid carrier particles. In this connection, it has beeii found that when nickel is replaced by iron in the process of U.S. Patent No. 3,697,445, the resulting calcined and reduced catalyst does not appreciably catalyze the hydrogenation of benzene to cyclohexane while the initial argon B.E.T. 2 surface area of the catalyst was 256 m /g. However, quite surprisingly, when nickel is replaced by cobalt in the pro cess or U.S. Patent o. 3,697,445, the resulting catalyst follonting calcination and reduction at 400 C, has a rela -,tively low metal reduced surface area as detertnined by 2 hydrogen chemisorption (i.e., from 5 to 20 m /g of catalyst), but a high catalytic hydrogenation activity. The hydrogen- ation activity of the coprecipitate cobalt-silica catalyst is higher than anticipated in light of the low value of reduced metal surface area of the coprecipitateed catalyst relative to the nickel catalyst prepared by the same pro cedure. Surprisingly, the supported coprecipitation cobalt catalyst of the present invention has about twice the activity of the supported coprecipitated nickel-copper-silica catalyst of belgian Patent No. 841,812 even though it generally has less tan half of the reduced metal surface area of the nickel-copper-silica catalyst of said patent. In one embodiment of the invention, there is pro vided a supported cobalt-si lica coprecipitated hydrogenation catalyst characterized as having a B.E.T. total sur-ace area ranging from about 150 to about 350 n /g and a reduced cobalt surface area ringing from about 5 to about 20 m2/g as deter-- mined by hydrogen chemisorption, after reduction at 400 C, wherein the amount of cobalt in the catalyst ranges from about 25 wt.% to about 70 wt.t based on the total weight of the catalyst. Preferably, this catalyst will contain less than 0.1 wt. sodium based on the total eight of the activ catalyst. The catalyst of the present invention may addition ally include coprecipitated copper in an amount ranging from about 2 wt.t to about 10 wt.% based on the weight of the catalyst. The presence of the copper facilitates reduction of the catalyst at lower temperatures, i.e., 200 C. In another embodiment of the invention, there is provided a process for preparing a supported coprecipitated cobalt-silica catalyst comprising: (a) preparing a reaction mixture comprising an aqueous aqueous solution containing cobalt ions, silicate ions and solid porous carrier particles under agitation to form a copreclpitate of the cobalt and silicate ions onto said solid porous support particles; (b) heating the aqueous reaction mixture; and (c) adding an alkaline precipitatnng agent to fur- ther coprecipitate the cobalt and silicate ions onto said solid porous support particles. Preferably, the proportions of materials In the reaction mixture will be sufficient to provide from about . 25 wt.% to about 70 wt.% cobalt based on the total weight of the calcined and reduced catalysts. In this process copper ions may be added to the aqueous reaction mixture in an amount sufficient to provide from bout 2 wt.% to about 10 wt.% % of copper in the catalyst the weight percent being based on a total weight of the catalyst. Following preparation of the catalyst, the cat alyst :nay be calcined under oxidative conditions at a temp erature ranging from about 300 to about 450 C and reduced at temperatures ranging from about 75 C to 400 C. In still another embodiment of the present invention, there is provided a process for hydrogenating organic com pounds which comprises contacting at least one hydregenatable organic compound with a reducing agent such as hydrogen in the presence of the hereinabove described catalyst prepar ation in its calcined and reduced state. Typical organic compounds which may be reduced by the process of the in Invention include aromatic compounds, such as benzene, olefins, aldehydes and nitriles. As generally discussed above, the catalysts of the present invention are prepared by preparing a reaction mix ture comprising an aqueous solution containing cobalt cations (which may optionally include copper cations), silicate anions and solid porous carrier particles as the support material such as kieselguhr. Preferably a solution contain ing the cation(s) is uniformly comingled with the silicate anion solution with solid porous carrier particles slurried therein, by the addition of the catian-containing solution to the support-containing silicate solution over a period of approximately 5 to 40 minutes. Alternatively, the solution containing silicate anions may bo added to the solution of cobalt cations with the solid porous support particles slurrieo therein. By comingling the previously prepared solutions, the amount of dissolved cobalt (and optionally with the copper cations) in the reaction mixture may be kept exceed ingly low and in general well below 0. 60 moles/liter of the aqueous reaction mixture. This dilute on of the dissolved cobalt ions is preferred in obtaining high catalytic activity. Also, the addition should !be made at a sub- stantially constant rate accompanied by vigorous mixing to increase uniformity in the catalyst formation. The mix ture is then heated, preferably to its boiling point at at mospheric pressure, and a precipitating agent is added to further coprecipitate the remaining dissolved cobalt and optionally copper with the silicate anions onto the porous support particles. During catalyst preparation, water is added to the f" reaction mixture to maintain a nearly constant volume so that water loss by evaporation is. continually replaced. The aque ous reaction mixture is preferably kept at its boiling point ., (at atmospheric pressure) for a period of one to five hours (al though heating at a temperature bestow the boiling point of the solution, i.e., 60-99 C, may be employed to minimize evaporation); it is then filtered and the resulting product is washed repeatedly with boiling water to remove alkali metals and other impurities. (Generally the washings will be four or more times). Then, the catalyst is dried at temperatures ranging from 90-200 C, for one to five hours and calcined in an oxygen source, e.g., an oxygen-containing gas such as air to a tenlperature ranging from 300-4500C, for a period of 2-8 hours, preferably 3-5 hours. The finished catalyst can then be charged directly (or subsequent to shaping or extruding such as in the form of tablets or pellets) into the reaction vessel, without activation, and activated in the reaction vessel with a gaseous reductant, usually flowing hydrogen. As stated previously, the cobalt-containing solution and the silicate-containing solution are preferably comingled under conditions of dilution such that the amount of dis- solved cobalt ions in the resultant reaction mixture is maintained exceedingly low thereby providing for a high catalytic activity. Additionally, however, it is preferred that in preparing the catalyst oZ this invention, the coprecipi- tation of the catalyst is made from dilute solutions, i.e, the cobalt-containing solution should have a cobalt concentration no greater than 1.0 moles/liter and the other solution a silicate ion (e.g., alkali metal metasilicate) concentration no greater than 0.4 moles/liter. en copper cations are included in the reaction mixture the copper con- centration is determined by the desired amount of copper in the catalyst. The most preferred solution used in preparing the catalyst has no more than 0.75 moles/liter of cobalt, more preferably less than 0.6 moles/liter and 0.26 moles/ liter of silicate ions, e.g., sodium metsilicate. This is contrasted with a more concentrated precipitation in witch the solution contains up to twice as much solute. The mole ratio of cobalt to silicate employed rancos from about 0.3:1 to about 2.5:1 in the calcined and reduced catalyst. In the case of the silicate-porous silica based catalysts about 30 to 90 wt.% of the total silica content of the activated catalyst is derived from precipitated silicate ions when the solid porous particles comprise silica. Preferably, however, 50 to 70 wt.t or the total silica content is derived from the silicate ions when the solid porous particles comprise silica. The remaining steps in prepl2,-lng and activating the catalyst are identical to those described above. In a preferred aspect of the invention the catalyst of the invention is formed by coprec ritating, cobalt (and op tionQlly including copper) and silicate ions onto a porous solid particulate support preferably solid porous silica particles from an aqueous solution. In this preferred enl- bodiment cf the inventiun, two distinct solutions are pre- pared with solid porous particles slurried in one of them. In one of these solutions is a siiic-L'e ion source such as alkali metal silicates, i.e., sodium and potassium silicates sodium metasilicate, etc. or silicic acid ion source which is preferably slurried in an aqueous mixture containing solid porous particles. A second solution, containing a source of cobalt cation (and optionally copper cation) is also prepared; the source of the cobalt cation may be any of the following: cobaltous nitrate, cobaltous chloride and cobaltous bromide. The source of the copper cation may be also copper nitrate, copper chloride and copper bromide. Other sources cf cobalt any copper cations and silicate ions ay be utilized and ac e obvious to one skilled in the art. The salLs of the metal are the water soluble compounds, e.g., nitrates, halides, formates, or oxalates. As discussed above, the solid porous particles, preferably silica particles, will be slurried in either the silicate ion solution or the cobalt containing solution. In particular, kieselguhr, infusorial earth, diatomaceous earth, siliceous earth, silica or alumina will be the source of the porous particles. The concentration of the porous solid particles can be expressed as percent of total silica in the catalyst and should be from 10 to 70 wt.%, preferably from 30 to 50 wt.%. The solution containing the cation(s) and the other solution containing the silicate ions, with one containing the solid porous particles, are comingled at a slow rate to effect maximum mixing. Typically, the cobalt (which may optionally include copper ions) solution would be added to a sodium metasilicate solution, with kieselguhr slurried there in uniformly over approximately a 5 to 40 minute period, preferably 10 to 30 minute period. Alternatively the solution containing sodium metasilicate may be added to the cobalt solution, which has the kieselguhr slurried therein. The mixture is then heated. Coprecipitation is completed by various methods knoam in the art, but it is most preferred that the coprecipitation cf the cobalt (and optionally the addition of copper) and silicate ions in the aqueous solution containing the solid porous particles be completed by the addition of a water-soluble alkaline precipitating agent. The alkaline ammonium precipitants are most suitable for minimizing the amount of alkali metal residue which has to be removed by washing to avoid poisoning action on the fin ished catalyst. In some instances, the potassium precipi- tants may be nosed where the potassium acts as a promoter rather than a poison. Sodium carbonate is still another e- ample of a suitable water-soluble alkaline precipitating compound. Various oranic alkaline materials may be used to complete the precipitation such as urrea, primary and secon dary amines. However, a preferred precipitating agent is ammonium bicarbonate. The precipitated catalyst is preferably washed to remove impuritIes, particularly sodiu... If it is desired to remove the trace levels of sodium in the catalyst, c.e may wash the filter cake with a washing liquor comprising a mixture of water and a small amount, i.e., about 100 ppm of a filtering aid such as sodium or potassium carbonate or nitrate or 200 ppm of ammnium carbonate. In this connection reference is made to U.S. patent No. 4,105,591, tho dis closure of which is incorporated herein by reference. After the washing, drying and calcining iS com pleted, the catalyst must be reduced in order to activate it. Reduction is carried out in the presence of a reducing gas which is preferably hydrogen. The recucing gas is passed over the catalyst at ambient tenrnAatures at a rate of 5/1hr/gm to 30 l/hr/gm and then the temperature is raised to a range of from 750C to 4000C. In the case of the cobalt-copper- silica supported catalyst of the invention lower temperatures of reduction may be employed, i.e., 80 C to 250 C. The reduction (activation) is preferably carried out after the catalyst has been loaded into the reaction vessel (in the case of the cobalt-copper-containing catalyst) where the hydrogenation will be carried out, which may be either batch or continuous. The nature of the reactor will be obvious to one skilled in the art. The activation pro cedure cf U.S. Patent No. 4,088,603 may be used with the catalyst of the present invention. The activated catalyst is sensitive to deactivation and may not be stored in the presence of oxygen at ordinary temperatures without first being passivated. The passivaticn step may consist of purging the reactor at a temperature greater than 3000F with an inert gas preferably nitrogen, cooling to ambient temperature and then passing the iner gas over the catalyst while an air bleed is introduced into the inert gas so as to have approximately 1-2 moi percent oxygen present. This procedure will passivate the catalyst .. by putting a surface oxide coating on it. Preferably, the catalyst will be passivated by the process of U.S. Patent No. 4,090,980. The resulting catalyst preferably is capable O±r having a cobalt surface area ranging from about 5 to about 20 m2/g as determine by hydrogen chemisorption after rn,duo- tion at 400 C. The cobalt surface area as referred to herein is determined by hydrogen chemisorption after reduction at 4000C unless otherwise specified, in the manner described b Yates, Taylor and Sinfelt in J. Am. Chem. Soc., 86, 2996 (1964), the disclosure of which is incorporated herein by reference. The cobalt surface area is reported as square meters per gram of total catalyst. The B.E.T. total surface area of the catalyst of the invention will range from about 150 to about 350 mê/g, preferably from about 225 2 to about 300 m /g. The method for measuring the total cat- alyst surface area known as the B.E.T. method is described in E;nmet, P.H. Advances in Catalysis, I, 65 (1948). Also, the catalyst preferably contains about 0.1 wt.% or less of sodium and preferably from 25 wt.% to about 60 wt.% of cobalt. The catalysts of the present invention are usefu in hydrogenating hydrogenatable organic compounds. In this connection the catalysts of the present invention may be used to hydrogenate aromatic containing compounds as typi- ed by the hydrogenation of benzene to cyclohexane, the hydrogenation of aldehydes, both saturated and unsaturated to the alcohols as razz in the well-known oxo process, the hydrogenation of the double bonds in edible fats and oils as well as other olefins both straight and branched chain, the hydrogenation of aro matics in white oil base stock to produce high-grade white oil, the hydrogenation of nitro compounds tc aninea and the hydrogenation of nitriles to amines. Indeed, olefins as used herein signify unsaturated compounds having at least one multiple bond and contemplates polyunsaturated compounds as well. The conditions for the hydrogenation reactions have been discussed very widely and are well known to those skilled in the art; broadly the following conditions may be utilized temperatures ranging from about 250C to 30000, preferably from 750C to 2500C; pressures ranging from 1 at rnosphere to 800 atmospheres, preferably from 1 atrosphere to 50 atmospheres; feed rates or from 0.2 to 100 volumes per hour per volume of catalyst and hydrogen addition of from 500 to 10,000 standard cubic feet per barrel (SCF/B) of feed may be used. In the case of the oxo procss, i.e., the addition of carbon monoxide and hydrogen to alkene e to produce alco hols, aldehydes and other oxygenated organic compounds, one would typically employ conditions such that the temperatures would range from about 700C to 1750C an use a hydrogen-to- hydrocarbon mole ratio of 0.5 to 10 and a pressure of 100 to 1000 psig. The alkenes used in such a process would t';pi- cally contain 2. to 20 carbon atoms. The product of such a carbonylation process generally consists of aldehydes, ace tals, unsaturated oxygenated materials and the like which require hydrofinishing in a second or urther hydrogenation stage. It is to the treatment of the aldehyde product, in particular, that the present invention applies. Hydrogenation conditions in this further reaction stage follow those gen erally employed in the first stage. Another useful improved hydrogenation is the con version of aromatics in white spirits to yield high quality solvents. The upgrading of white spirits by the process of the instant invention is an improvement in the treatment of such materials. Still another useful improved hydrogenation of the invention is the conversion of olefins in paraffin solvents such as denonenizer bottoms and deoctanizer overheads. Two especially useful hydrogenation processes in cluded within the scope of the invention include the hydro- genation of aromatics such as benzene to cyclohexane and the production of amines from nitro compounds and nitriles. ror example, the invention is useful 'in converting C12 to C24 nitriles to the corresponding fatty acid amines. Also, aro matic nitro compounds may be converted to amines, e.g., nitrobenzene to aniline or the conversion of aromatic amines to cycloaliphatic amines, e.g., aniline to cyclohexyl aminc. The following examples more fully describe the manner of making and using the above-described invention as ell as to set forth the best modes contemplated for carrying out various aspects of the invention. EYAIPLE 1 Catalyst A was prepared as follows: 62.7g of Co(NO3)2#6H2O was dissolved in 280 ml of distilled water, then 21.36 of Na2SiO3.9H20 was dissolved in another 280 ml of distilled water and 2.8g of acid washed kieselguhr was slurried in the first solution containing the cobaltous salt. The first solution with the kieselguhr scurried therein was stirred vigorously while the second solution containing the sodium metasilicate was added at a uniform rate over a 20-minute period. This mixture was then heated to the boiling point of the solution (at atmospheric pressure) and 44.7g of NH4 RC03 was added at a uniform rate oxter a 20- minute period. This mixture was kept at the boiling point of the solution for 3 hours while stirring was continued. It was then filtered and washed 2 times with boiling distilled water, each wash consisting of 1 iiter of the distilled water. The filter-cake was then dried at 12000 and calcined in air for 4 hours at 400 C. The reduced cobalt surface area of catalyst A was determined by hydrogen chemisorption, after reduction at 400 C to be 10.4 m2/g of catalyst and the cobalt content based on the total weight of the calcined and reduced catalyst, will be found to be between 25 wt% and 70 wt%. The catalyst t the above procedure had a B.E.T. total surface area of 170 m2/g. EXAMPLE 2 Catalyst B was prepared in the same manner as Catalyst A except tl.at the first solution containing the cobalt contains 3.8g of Cu(NO3)2#3H2O dissolved therein. Atter reduction at 400 C the reduced Co surface area, as determined by hydrogen chenlisorptioll, will be found to be between 5 and 20 m2/g and the wt.% of cobalt based on the total eight of calcined and reduced catalyst will be found to be between 25 and 70 wt%. The B.E.T. total surface area ill be found to be between 150 and 350 m2/g. Comparative Example I Catalyst C was prepared as follows: 112g of Ni(No3)2-6H2O was dissolved in 500 ml of distilled water, then 38g of NaSiO3 # 9H2O was dissolved in another 500 ml of water and 5g of acid washed kieselguhr was slurried in the second solution. The second solution with kieselguhr slur- ried therein was stirred vigorously while te first solution containing the nickel salt was added at a uniform rate over a 20-minute period. This mixture was then heated to the boiling point of the mixture (at atmospheric pressure) and 80 gm. of NH4HCO3 was added at a uniform rate over a 20 minute period. The mixture was kept at the boiling point of the reaction mixture for 3 hours white stirring continue. It was then filtered and washed 5 times with boiling water, each wash consisting of 500 ml of distilled water. The filter-cake was then dried at 120 C and calcined in air for 4 hours at 400 C. The reduced nickel surface area was det ermined by hydrogen chemisorption, after reduction at 400 C to be 65 m2/g and it had a B.E.T. total ure area of 292 m2/g. Comparative Example II Catalyst D was prepared as follows: 8.75gm of Cu(NO3)2 # 3H2O and 112 gm of Ni(NO3)2 # 6H2O were dissolved in 500ml of distilled water, then 38gm of Na2Si039H20 was dissolved in another 500ml of distilled water and 5gm of acid washed kieselguhr was slurried in the second solution. The second solution with the kieselguhr slurried therein was stirred vigorously while the first solution containing the copper and nickel salt was added at a uniform rate over a 20-minute period. This mixture was t1.en heated to the boiling point of the reaction mixture and 80ym of NH4HCO3 was added at a uniform rate over a 20-minute period. This mixture was kept at the boiling point of the mixture for 3 hours while stirring continued. It wZs ten filtered and washed 5 times with boiling water, each wash consisting of 500ml of distilled water. The filter-cake was then dried at 1?.00C and calcined in air for 4 hours at 4000C. The reduced nickel surface area of Catalyst D was determined by hydrogen chemisorption, after reduction at 100 C, to be 61.3 mê/g and it had a B.E.T. total surface area of 259 m2/g. Each of Catalysts A, B, C and D was use to hydrogenate benzene to cyclobexane to ascertain their rel ative hydrogenation catalytic capabilities. The results of this comparison are shown in Table I. 1 TABLE I 2 Catalytic Conversion of Benzene to Cyclohexane(a) 3 Catalyst A (Co/SlO2) Catalyst B (Co/Cu/SlO2) Catalyst C (Nl/SiO2) Catalyst D (Ni/Cu/SiO2) 4 Time Benzene Time Benzene Time Benezene Time Benzene 5 (min) Conversion % (min) Conversion % (min) Conversion % (min) Conversion % 6 35 84.5 30 21.7 30 63.1 30 40.6 43.4 7 60 84.6 60 18.4 60 61.8 60 42.6 8 90 81.4 90 17.7 90 61.1 90 - 105 40.0 9 170 78.0 120 16.5 120 57.4 120 -10 180 16.0 180 54.1 11 240 74.0 240 14.7 210 58.5 240 38.5 12 240 57.7 13 (a) Reaction Conditions: Pressure: 1 atmosphere; Temperature: 76-77 C; Feed: 90% 14 n-hexane, 10% benzene; Feed rate: 20 cc/hr; H2 rate: 20.4 1/hr; Catalyst 15 charge: 0.25gm (catalyst reduced 16 hr at 400 C) The data in Table I sho that Catalyst A, the co balt/SiO2 catalyst had a higher activity for hydrogenating benzene than does the corresponding nickel-silica sopreci pitated catalyst (Catalyst C). was prepared iii accordance with U.S. Patent No. 3,697,445, even though the latter catalyst, when reduced at 400 C, has a relatively higher metal surface area than the cobalt-silica coprecipitated catalyst of the instant invention The data in Table 1 also shows that the nickel-copper-silica coprecipitated catalyst has a higher activity for hydrogenation of benzene than does Catalyst B (the cobalt-copper-silica coprecipitated catalyst) which is believed to be attributed to the copper concentrating in the surface and since the copper itself has very low hydrogenation activity the catalyst has a low activity. EXAMPLE 3 Catalyst E was prepared in me same manner as Catalyst B except that t was reduced t 200C for 16 hours instead of at 4000C for 16 hours. The reduced Co surface area (determinea by hydrogen chemisorption) will be found to be between 5 and 20 m2/g and the wt of Co based on the total weight of calcined and reduced catalyst will be found to be between 25 and 70 wt%. The BEI total surface area will be found to be between 150 and 350 m2/g. Comparative Example III Catalyst F was prepared in the save manner as Catalyst D except that the catalyst was reduced at 2000C for 16 hours instead of at 400 C for 16 hours. TABLE II Ctalytic Conversion of Benzene to Cyclohexane (a) Catalyst E (Co/Cu/SiO2) Catalyst F (Ni/Cu/SiO2) Time Benzene Time Benzene (min) Conversion % (min) Conversion % 60 46.6 60 79;2 7 90 44.4 90 77.8 1 120 44.0 150 78.0 240 77.3 (a) Reaction Conditions: Pressure: 1 atmosphere; Temperature: 76-770C; Feed: 90 n-hexane, 10% benzene; Feed Rate: 20 cc/hr; H2rate: -20.4 l/hr Catalyst charge: 0.25gm (catalyst -reduced -16 hrs &commat; 2000C) Comparative Example IV Catalyst G was prepared as follows: 91.2gm of Fe(NO3)3#9H2O was dissolved in 500ml of distilled water. - To this solution there was added 2.8gm of -kieselguhr fol lowed by the addition under conditions of vigourous mixing 200 ml of an aqueous solution containing 21.26 gm of Na2SiO3.9H2O. Mixing of this comingled solution was con tinued and followed by heating to about 80 C. The coprec' pitation was completed by the addition of 67.2gm of ammonium bicarbonate. The mixture was mixed for an additional 30 minutes after the last addition, and dilute to 4 liters with 'water, washed by decantation 2 times witch 4 liter washes, filtered and dried at 1200C. The catalyst was cal timed for 3 hours at 4000C. The catalyst had a 2 B.E.T. total surface area after evacuation at 260 C of 256 mê/g. after overnight reduction at 400 C the catalyst had a metal surface determined by hydrogen chemisorption to be less than one m2/g catalyst, tand a B.E.T. surface area or only 132 m2/g of catalyst. An attempt was made to convert benzene to cyclohex ane using the iron catalyst prepared above. The reaction conditions were as follows: Pressure: 1 atni.; Temperature: 76-770C; Feed: 90% N-hexane, 10% benzene; Feed rate: 20 cc/hr; H2 rate: 20.4 liters/hour; Catalyst charge: 0.2sums of catalyst which had been reduced 16 hours at 4O0"C. Samples of product were taken at 15 minutes, 30 minutes and 60 min utes and there was no sign of benzene conversion in eithcr of these samples. The temperature was raised to 112"C and the product was sampled to find no conversion of benzene to cyclohexane. The above tests demonstrate that the non-noble metal silica coprecipitated compositions are not equivalent in their hydrogenation catalytic properties. The above examples show tilat by increasing the reduced nickel surface area one also increases the hydrogenation capability of the catalyst. However, the cobalt-containing catalyst having a substantially lower reduced metal. surface area has a higher selective cata lytic activity than the corresponding nickel catalyst. The iron containing composite prepared by the process of U.S. Patent No. 3,697,445 had substantially no detectable cataly tic activity with respect to converting benzene to cyclo hexane, whereas the cobalt-containing catalysts of the present invention have good hydrogenation catalytic activity.

Claims: CLAJMS 1. A supported coprecipitated cobaJt-silica catalyst having a B.h.T. total surface area ranging from 150 to 350 mê/g and a reduced cobalt surface area ranging from 5 to 20 m2/g as determined by hydrogen chemisorption, after reduction at 4000C, wherein the amount of cobalt in the catalyst ranges from 25 wtZ to 70 wt.% based on t5e total weight of the calcined and reduced catalyst, wherein said cat.]yst has been prepared by coprecipitating cobalt and silicate ions oltto solid porous particles. 2. A catalyst according to claim 1 wherein the catalyst contains about 0.1 wt.% or less sodium based on the Lotal weight of the active catalyst. 3. A catalyst according to either of claims 1 and 2 wherein the solid porous particles are infusorial earth. diatomaceous ear;h, siliceous earth, silica or alimina. 4. A catalyst according to either of claims 1 and 2 wherein the solid porous particles are kieselguhr. 5. A catlayst according to any one of the preceding claims which additionally includes from 2 wt.% to 10 wt.% of coprecipitated copper based on the total weight of th catalyst. 6. A catalyst according to any one of the preceding claims wherein the amount of solid porous particles ranges from 10 wt.% te 70 wt.% based on the total silica in the catalyst. 7. A catalyst according to claim 6 wherein the amount of the porous solid particles ranges from 30 wt.f to 50 wt.% based on the total silica in the catalyst. 8. A catalyst according to any one of the preceding claims which has been reduced to an active state. 9. A process fcr preparing a supported coprecipitated cobalt-silica catalyst according to claim 1 which comprises: (a) preparing a reaction mixture containing cobalt icns, silicate ions and solid porous carrier particles under agitation to form a coprecipitate of the cobalt and silicate ions onto said solid porous support particles; (b) heating the aqueous reaction mixture; and (c) adding an allSaline precipitating agent to coprecipitate further the cobalt and silicate ions onto said solid porous support particles. 10. A process for hydrogenating organic compounds which comprises contacting at least one hydrogetiatable organic compound with hydrogen in the presence of the catalyst according to claim n.

Inventors: BARNETT, ALLAN EMERSON, CARTER, JAMES LESLIE
Applicants: EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1980
Main classification: B01J23
IPC codes: C07C5, C07C1, B01J21, C07C67, B01J35, C07B31, C07C209, C07B61, B01J23, C07C13, B01J37