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 ha s been prepared by means of adsorption from solution, with platinum co ntents varying from 0.5 to 3.0 wt %. The kinetic behavior of the catal ysts has been analyzed for the liquid-phase hydrogenation of benzene i n a stirred tank reactor, assuring a chemically-controlled regime for stirring speed above 600 rpm and catalyst particle size below 0.08-0.1 6 mm in the studied conditions. For a constant dispersion, a certain a mount of surface platinum has been found to remain inactive, either du e to inaccessibility of the reagents or due to poisoning. As hydrogen pressure increases, the reaction order shifts from 1 to 0. The apparen t activation energy resulted in 72 kJ mol-1.