Universal increase in catalytic hydrogenation performance for lanthanide-modified Pd/Al2O3 catalysts by hydrogen transfer

Hydrogen spillover phenomenon can significantly impact the activity in hydrogenation reaction, but the spillover is limited in a very short range on non-reducible Al2O3, a most widely used industrial support. Herein, Al2O3 doped with different lanthanides (ln) was prepared by co-precipitation, which was then used to produce Pd/lnAl2O3 catalysts. These catalysts display much higher hydrogenation activity towards alkylated anthraquinone than undoped Pd/Al2O3 catalyst and those modified by non-lanthanide elements. After the introduction of lanthanides, the reaction order of H2 decreases from 1 to 0. Further characterization and DFT calculation show that H2 storage ability is increased for ln-doped catalysts due to the low activation energy of H transfer and low adsorption energy of H on O(-ln) sites. In addition, a reasonable relationship between reducibility of ln3+ in catalysts and the catalytic performance is found.