Identifying the catalytic active site of durable Ru-based liquid-phase catalyst for acetylene hydrochlorination

Abstract

A comprehensive understanding of the structure and dynamic evolution of catalytic active sites is vital for advancing the study of liquid-phase acetylene hydrochlorination. Here, we successfully developed a Ru-DIPEA/TMS catalyst optimised through systematic composition and condition tuning, demonstrating exceptional performance with 95.5 % C₂H₂ conversion and sustaining over 91.1 % activity along with nearly 100 % selectivity for VCM during a continuous 900-h test. Using a combination of characterisation techniques, including UV–vis spectroscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, single-crystal X-ray diffraction, and X-ray absorption spectroscopy, along with density functional theory (DFT) calculations, the structure and dynamic behaviour of the active sites were thoroughly investigated under the synergistic influence of ligands and HCl. The results revealed that HCl activation induces a significant structural transformation of the active sites, leading to the formation of a hexacoordinate complex, Ru(CO)₂C_l2(C₆H₁₅N·HCl)₂. DFT calculations further elucidated the mechanism underlying active site formation, revealing that an increased electron density around the Ru centre and corresponding changes in its coordination environment play critical roles in enhancing catalyst stability and activity. This study contributes to a deeper understanding of the structural basis of active site evolution during acetylene hydrochlorination, offering both practical insights into industrial applications and foundational knowledge for advancing liquid-phase catalysis.