BEHAVIOR OF HIGHLY DISPERSED PLATINUM CATALYSTS IN LIQUID-PHASE HYDROGENATIONS

Group VIII metals are found to present good behavior as hydrogenation catalysts when supported on highly porous materials such as alumina. A series of highly dispersed platinum catalysts supported on alumina has been prepared by means of adsorption from solution, with platinum contents varying from 0.5 to 3.0 wt %. The kinetic behavior of the catalysts has been analyzed for the liquid-phase hydrogenation of benzene in a stirred tank reactor, assuring a chemically-controlled regime for stirring speed above 600 rpm and catalyst particle size below 0.08-0.16 mm in the studied conditions. For a constant dispersion, a certain amount of surface platinum has been found to remain inactive, either due to inaccessibility of the reagents or due to poisoning. As hydrogen pressure increases, the reaction order shifts from 1 to 0. The apparent activation energy resulted in 72 kJ mol-1.