Palladium Catalyst Passivation by Unsymmetrical Zn–N Metal–Organic Framework Boosting Acetylene Selective Hydrogenation

Developing a high-efficiency catalyst for the selective hydrogenation of acetylene to ethylene is of great importance for industrial polyethylene production to remove acetylene impurities. In this work, a passivation strategy for palladium catalyst has been developed by inducing strong electron metal–support interaction (EMSI) between the loaded Pd nanocatalyst and the nitrogen-containing metal–organic framework (MOF) support (ZIF-8-dia) to substantially improve the catalytic performance. Catalytic hydrogenation of acetylene demonstrates that the Pd/ZIF-8-dia exhibits ethylene selectivity above 83%, whether ethylene is cofed with acetylene and hydrogen or not. Mechanism studies reveal that the convenient transformation of Zn–N into Pd–N strengthens the EMSI to form a Pd nanocatalyst with a positively charged surface, substantially lowers its activity for hydrogen activation and the hydrogenation reaction, and favors the desorption of ethylene from the catalyst surface, therefore improving the performance of the ZIF-supported Pd catalyst for selective acetylene hydrogenation. The passivation strategy developed in this work opens up an opportunity for developing high-performance Pd catalysts for selective acetylene hydrogenation.