Facile Synthesis of Palladium-Silver Dilute Alloy Catalyst for Acetylene Hydrogenation
Graphical Alloy catalyst for acetylene hydrogenation: A palladium-silver dilute alloy catalyst (Pd x Ag/Al 2 O 3 ) was fabricated and showed an outstanding performance for acetylene hydrogenation, which contains the Pd 1 Ag single-atom-alloy (SAA) and Pd 2 Ag dimer-alloys (DA) species. Selective hydrogenation of acetylene (C 2 H 2 ) to ethylene (C 2 H 4 ) 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 (Pd x Ag/Al 2 O 3 ), which contains the Pd 1 Ag single-atom-alloy (SAA) and Pd 2 Ag dimer-alloy (DA) species. This catalyst exhibits a high ethylene (C 2 = ) yield of 90.1 % even after 100 hours at 60 °C, which is 11.9 times higher than that of the PdAg/Al 2 O 3 alloy catalyst. Based on in-situ spectroscopic investigations and theoretical calculations, both Pd 1 Ag SAA and Pd 2 Ag DA species in Pd x Ag/Al 2 O 3 are easier to desorb C 2 H 4 compared with PdAg/Al 2 O 3 , and they experience the possible hydrogenation paths with the low energy barriers to yield C 2 = . Furthermore, Pd x Ag/Al 2 O 3 is beneficial to restraining coking due to the endothermic C−H bond cleavage. Thus, these combined merits contribute to the superior catalytic performance for Pd x Ag/Al 2 O 3 .
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