Fine tuning the dynamic PdCx formation for enhanced acetylene semi-hydrogenation:The role of gas environment and ZnO addition
Palladium carbide(PdCx)has been extensively reported as active phase in acetylene semi-hydrogenation that can be dynamically formed during reaction.However,fine tuning of dy-namic PdCx formation towards enhanced acetylene semi-hydrogenation is of great challenge and the dynamic insights remain elusive.In this paper,the state-of-the-art in situ characterizations have been adopted to elucidate the dynamic PdCx formation for acetylene semi-hydrogenation.The role of hydrogen atmosphere and ZnO addition in tuning the carburization process were clearly identi-fied by in situ spectroscopies.The hydrogen in the gas environment assisted the carbon infiltration via PdHx hydrides,while the addition of ZnO suppress the carburization by the surface Zn alloy.As a result,the carbon content in PdCx can be precisely modulated by altering the hydrogen atmosphere and ZnO additives,and exhibits a linear correlation with the activity of acetylene semi-hydrogenation.The carbon insertion enriched the electron state of Pd sites in PdCx that favors the activation of hydrogen for acetylene semi-hydrogenation.This work thus provides a new route for the design of Pd catalyst for high-performance acetylene semi-hydrogenation by fine tuning the reaction environment and the degree of carburization during dynamic PdCx formation.
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