SELECTIVE HYDROGENATION OF STYRENE ON PD-HO GAMMA-AL2O3 AND PD/GAMMA-AL2O3 CATALYSTS/

Pd-Ho/gammaAl2O3 catalysts exhibit higher activity for styrene hydroge nation than Pd/gammaAl2O3 ones. The addition of holmium to Pd catalyst s changes the place of the palladium impregnation front depending on t he state of the supported palladium. As a consequence of the interacti on between holmium and Pd/gammaAl2O3 support, oxidized forms as holmiu m aluminate were formed. These forms are catalytically inactive but re present adsorption centers for styrene. On holmium containing catalyst s, hydrogenation takes place between the styrene adsorbed on basic cen ters and the hydrogen spilled over from palladium particles.