Selective hydrogenation of acetylene over Pd-Sn catalyst: Identification of Pd2Sn intermetallic alloy and crystal plane-dependent performance

In Pd catalyzed acetylene semi-hydrogenation, high selectivity always comes at the expense of activity while improving both selectivity and activity is challenging. In this work, the performance of Pd alloy catalysts was enhanced by inserting Sn phase to modify both surface Pd ensembles and electronic structures. Compared with Pd/C, the optimal Pd2Sn/C catalyst exhibits higher selectivity at the same acetylene conversion level, with its selectivity increased from 10 % to nearly 95 % at ca 100 % acetylene conversion. Both experimental and DFT calculation results reveal that the specific performance is attributed to the redispersion of surface Pd ensembles by Sn insertion and down-shift of d-band center of catalysts, thus changing the adsorption behavior of the reaction gases. This design principle provides an efficient method for tailoring and optimizing durable Pd-based catalysts with desirable reactivity and ethylene selectivity for selective hydrogenation of acetylene.