2567. OWEN, J. R. (Phillips Petroleum Co.). Catalyst. United States Patent 2,606,159, Aug. 5, 1952. Chem. Abs., vol. 47, 1953, pp. 799-800.

A catalyst of superior activity is obtained when the minor component or promoter is concentrated at or near the surface of the catalyst pellet, with the inner part of the pellet substantially free of the minor component. Active Al₂O₃, obtained by precipitating hydrous Al₂O₃ gel and drying, or by other methods, is finely ground, mixed with a volatile or combustible binder, and pelletted. The pellets are then calcined in such a manner that a predetermined amount of the binder, preferably 50-75% is removed. This may be accomplished by heating the pellets in air at 204°-593° for 3-15 min. The cooled pellets are impregnated with a solution of a metal salt that is converted to the desired minor component by ignition. When Cr₂O₃ is desired, aqueous solutions of CrO₃ and Cr(NO₃)₂ are suitable. The impregnated pellets are finally ignited at 204°-593°, ordinarily in an oxidizing atmosphere, to convert the dissolved salt to the oxide and to remove substantially all the remaining binder. Instead of combustion, solvent extraction may be used to remove the binder from the outer parts of the pellets, and finally the residual solvent is evaporated. The process is particularly applicable to the preparation of hydrogenating-dehydrogenating catalysts, which consist of metals, metal oxides, and mixtures of metals and oxides. In an example, 2 catalysts consisting of Ni₂O₃ were deposited on Al₂O₃, 1 completely impregnated and the other shell-impregnated, but both containing 9.0% Ni₂O₃. After impregnation, the catalysts were calcined in air for several hours at 538°. They were then reduced at 343° and tested before exposure to air in the hydrogenation of C₂H₄ with a 1:1 ratio of C₂H₄:H₂ and a space velocity of 10,000 vol. (standard conditions) total gas per catalyst vol. per hr. The extent of hydrogenation was measured by comparing the thermal condition of the charge and effluent gas in a thermal-condition cell, previously calibrated with known mixtures of H₂ and C₂H₄ during each test. After reducing for 4 hr., the completely impregnated catalyst showed –1.0% average hydrogenation in 60 min. at 0°. The shell-impregnated catalyst, after reducing for 4 hr., had an average hydrogenation of 74.1% in 60 min. at 0°.