Facile Synthesis of Palladium-Silver Dilute Alloy Catalyst for Acetylene Hydrogenation

Selective hydrogenation of acetylene (C2H2) to ethylene (C2H4) has been recognized as an important strategic reaction for the removal of trace acetylene from ethylene. Palladium-based alloys are one of the most commonly used catalysts for this reaction but bear a high price and unsatisfactory catalytic performance. Here, we develop a feasible strategy toward the synthesis of a palladium-silver dilute alloy catalyst (PdxAg/Al2O3), which contains the Pd1Ag single-atom-alloy (SAA) and Pd2Ag dimer-alloy (DA) species. This catalyst exhibits a high ethylene (C-2(=)) yield of 90.1 % even after 100 hours at 60 degrees C, which is 11.9 times higher than that of the PdAg/Al2O3 alloy catalyst. Based on in-situ spectroscopic investigations and theoretical calculations, both Pd1Ag SAA and Pd2Ag DA species in PdxAg/Al2O3 are easier to desorb C2H4 compared with PdAg/Al2O3, and they experience the possible hydrogenation paths with the low energy barriers to yield C-2(=). Furthermore, PdxAg/Al2O3 is beneficial to restraining coking due to the endothermic C-H bond cleavage. Thus, these combined merits contribute to the superior catalytic performance for PdxAg/Al2O3.