The evolution of single-site Pd1/AC catalyst during the process of acetylene dialkoxycarbonylation

Abstract

The stability of heterogeneous single-metal-site catalysts (HSMSCs) is always a challenging issue. Deactivation of HSMSCs often occurred and draw much intention. The investigation of the single-metal-site evolution during the deactivation process is great significance to maintain the stability of HSMSCs. Herein, a fundamental understanding of the deactivation process of an initially efficient single-Pd-site catalyst (Pd1/AC) for acetylene dialkoxycarbonylation was revealed from geometrical and electronic point of view via a series of characterizations. Synergistic effect of O2 and iodine ligands contributed to the stability of Pd1/AC catalyst to some extent. The valence of single Pd ions gradually changed from [Pdδ+] to [Pd0], leading to the formation of Pd nanoparticles (Pd black). In addition, the blockage of support microspores also worsened the deactivation of Pd1/AC.