CATALYSIS OF REDUCTION OF SUPPORTED NICKEL OXIDE

Small amounts of metallic platinum or palladium, incorporated in alumina-supported nickel oxide catalysts, have been observed to enhance activation of the catalysts by hydrogen. By contrast, small amounts of gold and silver, which do not readily adsorb hydrogen as atoms, also do not enhance activation of the catalysts. Hydrogenolysis, isomerization, and aromatization reactions of n-heptane with hydrogen, used for characterizing catalytic activity, were carried out in a pulse-flow reactor coupled with a gas chromatograph. Platinum or palladium, in atom ratios to nickel (as oxide) as low as 5 × 10-3 were sufficient to cause large increases in conversion over the nickel component, while gold and silver, in atom ratios to nickel as high as 1 × 10-1 produce no such effect. There is now a preponderance of evidence favoring reduction by surface-diffusing hydrogen atoms as the mechanism for activation of supported nickel oxide by platinum and palladium.