Process for Hydrogenating Unsaturated Compounds

1. Field of the Invention

The present invention relates to a process for hydrogenating an unsaturated organic compound which comprises contacting the same with hydrogen in the presence of a catalyst composed of a support containing alumina and aluminum phosphate carrying nickel thereon.

2. Description of the Prior Art

A support of the type employed herein is disclosed and claimed in U.S. Pat. No. 4,080,311 to William L. Kehl. The support is alleged to be useful as catalyst supports for various reactions, including polymerization of ethylene.

We have found, unexpectedly, that when unsaturated compounds are subjected to hydrogenation in contact with a catalyst composed of alumina and aluminum phosphate and carrying nickel thereon, effective nickel utilization as high, or higher, than when conventional supports are used as carriers, is obtained. In fact, when the support components are present in the preferred ranges, nickel utilization is substantially higher than with nickel catalyst on conventional supports.

The support used herein will be composed of (1) alumina and (2) aluminum phosphate, wherein the alumina is present in an amount ranging from about two to about 98 mole percent, preferably from about eight to about 40 mole percent, and aluminum phosphate in an amount ranging from about two to about 98 mole percent preferably from about 60 to about 92 mole percent, having an average pore radius of from about 10 A about 300 A, preferably from about 50 A to about 200 A, a surface area ranging from about 80 m.sup.2 /g to about 350 m.sup.2 /g, preferably from about 125 m.sup.2 /g to about 250 m.sup.2 /g, and a pore volume of from about 0.3 cc/g to about 1.5 cc/g, preferably from about 0.5 cc/g to about 1.2 cc/g. Preferably the support can be characterized after calcination for ten hours as being amorphous. The support will carry on the surface thereof, including the surfaces within the pores, a selected amount of nickel oxide and will constitute the catalyst used herein. The amount of nickel oxide carried on the support, as elemental nickel, will be in the range of about three to about 60 weight percent, preferably about five to about 25 weight percent.

The catalyst can be prepared in a number of ways, but preferably as follows. The support is initially prepared by admixing together an aqueous solution of aluminum nitrate and 85 percent aqueous phosphoric acid. The alumina-aluminum phosphate support can be conveniently precipitated from solution by the addition of ammonium hydroxide while maintaining the solution pH in the range of about 5 to about 10. After the support mixture is filtered and washed with water, it can then be mixed with a suitable nickel compound, preferably a nickel salt, such as nickel carbonate, nickel nitrate, nickel acetate, nickel formate, nickel hydroxide, etc., and blended to obtain a substantially homogeneous mixture. The resulting mixture is oven dried at about 120.degree. C. to about 130.degree. C. for about 16 to about 24 hours and then finally calcined at about 250.degree. C. to about 650.degree. C. for about ten hours to obtain the desired support carrying nickel oxide thereon. The nickel oxide deposited on the support will range in crystallite diameter from about ten to about 200 A, but generally will be in the range of about 30 to about 100 A. In preparing the above catalyst, the aluminum nitrate, phosphoric acid and nickel entity are used in molar amounts stoichiometrically corresponding to the amount of aluminum, nickel and phosphate components present in the desired catalyst.

The process defined and claimed herein can be used to hydrogenate unsaturated organic compounds having double and/or triple bonds, particularly those having double bonds. Of these aliphatic compounds having from two to 20 carbon atoms, particularly from two to 12 carbon atoms, and aromatic compounds having from six to 20 carbon atoms, particularly from six to 12 carbon atoms, are preferred. Especially preferred for the desired hydrogenation are aldehydes. The organic compounds can be either gaseous or liquid, at ambient pressure and temperature, but preferably are liquid. Examples of compounds that can be hydrogenated herein include ethylene, cyclohexene, acetylene, butadiene, benzene, toluene, naphthalene, anthracene, 2-ethyl-2 hexenal, heptanal, citral, cyclohexanone, 3-ene-1-pentyne, etc.

In carrying out the hydrogenation herein, the compound to be hydrogenated and hydrogen are passed over the catalyst at a liquid hourly space velocity, measured at ambient temperature and pressure, of about 0.1 to about 20, preferably about 1 to about 12, while maintaining in the reaction zone a temperature of about 30.degree. to about 350.degree. C., preferably about 50.degree. to about 200.degree. C.; a hydrogen partial pressure of about 0 to about 1500 pounds per square inch gauge (about 0.1 to about 10.5 MPa), preferably about 100 to about 500 pounds per square inch gauge (about 0.8 to about 3.5 MPa); and total pressure of about 15 to about 2000 pounds per square inch gauge (about 0.2 to about 14.0 MPa), preferably about 115 to about 600 pounds per square inch gauge (about 0.9 to about 4.3 MPa). The recovery of the desired hydrogenated species is easily effected according to conventional procedures; for example, by release of gaseous material from the reaction product and subsequent fractionation of the desired species from the degassed reaction product.

A series of runs was carried out wherein a feed consisting of 15 weight percent 2-ethyl-2-hexenal and 85 weight percent 2-ethyl-1-hexanol was subjected to hydrogenation. The 2-ethyl-1-hexanol was present as diluent to inhibit excess temperature increases in the reaction zone. Other inert liquids, such as hexane, cyclohexane, decalin, methanol, ethanol, propanol, ethylene glycol, propylene glycol, etc., could be used in place of the 2-ethyl-1-hexanol. In each run, approximately five milliliters of a different hydrogenation catalyst, defined hereinafter, that had been crushed and sieved to about 20 to about 40 mesh, was placed in a stainless steel tube reactor having an inner diameter of 13 mm and a length of 1000 mm. Prior to the hydrogenation, the catalyst bed was pretreated as follows. The reactor was initially brought to 300.degree. C. while passing 28.3 liters of nitrogen per hour over the catalyst bed, after which the catalyst bed was maintained under such conditions for two hours. Over the next 100 minutes, while still maintaining the catalyst bed at 300.degree. C., hydrogen was bled into the nitrogen stream, with increasing amounts of hydrogen and decreasing amounts of nitrogen, until at the end of the period, solely hydrogen was passed over the catalyst bed. The total amount of gas during this period amounted to 28.3 liters per hour. The flow of hydrogen over the catalyst was maintained for one hour, after which the temperature of the catalyst bed was raised to 400.degree. C., while the hydrogen was continued to be passed thereover for an additional four-hour period. Hydrogenation, as discussed below, then proceeded. Pretreatment of the catalyst need not be done as indicated above, but can be carried out by passing hydrogen over the catalyst in a substantially inert atmosphere while maintaining the temperature in the catalyst bed between about 250.degree. to about 600.degree. C. and a hydrogen partial pressure of about 1.0 to about 1000 pounds per square inch gauge (about 0.007 to about 7.0 MPa) for about 0.5 to about 48 hours.

The desired hydrogenation was effected by passing 33 grams of the liquid feed per hour (as measured at ambient temperature and ambient pressure), that is, at a liquid hourly space velocity of 8.0 and four liters per hour of hydrogen while maintaining the temperature of the catalyst bed at 50.degree. C. and the hydrogen partial pressure at 100 pounds per square inch gauge (0.8 MPa). The reaction was permitted to proceed in each run for five hours. The results obtained are tabulated below in Tables I and II. In each of Examples I to VII, the runs were carried out using the catalyst defined hereinabove, namely a support comprising alumina and aluminum phosphate carrying nickel thereon, whereas in each of Examples VIII to XI, conventional, nickel-containing catalysts were used.

The catalysts used in Table I were prepared as follows.

To one liter of distilled water having dissolved therein 375 grams of Al(NO.sub.3).sub.3.9H.sub.2 O there was added 92.24 grams of 85 percent aqueous phosphoric acid. Into a mixing container there was placed one liter of distilled water. There was then added to the well-mixed container from separate burets the solution prepared above and a 1:1 volume mixture of water and ammonium hydroxide (containing 28 weight percent ammonia) while maintaining the pH of the resulting mixture at 8.0. The resulting slurry was filtered and washed with five liters of distilled water. The solids content of the filter cake was found to be 11.3 weight percent using an ohaus moisture balance. A portion of the filter cake (205 grams) was thoroughly mixed with 5.9 grams of nickel carbonate. The resulting catalyst was dried at 120.degree. C. for 18 hours; sized to 20-40 mesh; and calcined at 350.degree. C. for 10 hours. The catalyst carried 10 weight percent nickel, as nickel oxide. The pertinent information relating to the preparation of the catalyst used in Example I is set forth in Table III. The catalyst used in Examples II to VII were prepared following the procedure of that of Example I, except as noted in Table III.

The catalyst used in Example VIII is a proprietary catalyst sold by Harshaw Chemical Company, Cleveland, Ohio, composed of a silica-based non-phosphate-containing support carrying 50 weight percent nickel.

The catalyst used in Example IX was prepared as follows: Forty grams of kieselguhr (98 weight percent solids) were dry blended with 26.13 grams of nickel carbonate and then mixed with 130 cc of distilled water. The resulting paste was dried at 120.degree. C. for 18 hours, sized to 20-40 mesh and calcined at 350.degree. C. for 10 hours. The resulting catalyst carried 20 weight percent nickel, as nickel oxide.

The catalyst used in Example X was prepared according to the following procedure: Forty-five grams of silica gel (94 weight percent solids), which had been sized to -100 mesh, were dry-blended with 28.2 grams of nickel carbonate and then mixed with 130 cc of distilled water. The resulting paste was dried at 120.degree. C. for 18 hours, sized to 20-40 mesh and calcined at 350.degree. C. for 10 hours. The resulting catalyst contained 20 weight percent nickel, as nickel oxide.

The catalyst of Example XI was prepared as follows: Forty grams of alumina (85 weight percent solids) were dry-blended with 22.67 grams of nickel carbonate and then mixed with 140 cc of distilled water. The resulting paste was dried at 120.degree. C. for 18 hours, sized to 20-40 mesh and calcined at 350.degree. C. for 10 hours. The resulting catalyst contained 20 weight percent nickel, as nickel oxide.

Referring to Tables I and II, by "nickel utilization" we mean the weight percent of charge hydrogenated to useful and desired product per gram of elemental nickel in the catalyst. In this case that means 2-ethyl-2-hexenal converted to the corresponding hydrogenated species.; that is, a mixture of 2-ethylhexanal and 2-ethylhexanol. In each example, except Example XI, total conversion was substantially solely to a mixture of 2-ethylhexanal and 2-ethylhexanol. In Example XI, in addition to a conversion of 52 weight percent of the charge to the desired mixture, there was an additional conversion of 27 percent of the charge to undesirable degradation and decomposition products.

The data in Tables I and II show the uniqueness of the catalysts used herein. It will be noted that in each of Examples II, III, IV and VII that the catalysts used herein resulted in a nickel utilization value about as high, or even higher, than with nickel catalysts using conventional supports therefor. Thus in Example VIII, even when a silica-based catalyst carried 50 weight percent nickel thereon, nickel utilization was only 30, and in Example IX with a kieselguhr support, nickel utilization was but 11. In Example X with nickel on silica, a nickel utilization of 72 was achieved. While a nickel utilization of 86 was obtained with the alumina support in Example XI, as noted, 27 weight percent of the charge was converted to undesired product, resulting in a selectivity of 66 percent. In each of the remaining runs we obtained 100 percent selectivity to desired product.

Special note should be taken, however, of Examples I, V and VI, wherein the catalyst support was composed of alumina and aluminum phosphate in the preferred ranges and carried nickel thereon in the preferred range. In each case the nickel utilization was at least 100.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.