Fine tuning the dynamic PdCx formation for enhanced acetylene semi-hydrogenation: The role of gas environment and ZnO addition

Abstract

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 dynamic 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 identified 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.