Isolated Single-Atomic Cu Catalyst Supported on P-doped Carbon for Hydrochlorination of Acetylene

Abstract

As an environmentally friendly non-mercury catalyst for the hydrochlorination of acetylene, Cu-based catalysts have always attracted attention. In this study, a series of phosphorus-doped Cu-based catalysts supported on activated carbon were prepared by the wet impregnation method, the difference of them is that the calcination temperature of phosphorus-doped carrier is 200 ℃, 400 ℃, 600 ℃ and 800 ℃ respectively. In the test conditions of T = 150℃, GHSV(C2H2) = 90 h− 1 and V(HCl): V(C2H2) = 1.2, the highest acetylene conversion was 83.1%. The type of phosphorus configuration and the distribution on the surface of the carrier can be adjusted by changing the calcination temperature. Among the different phosphorus species formed by the phosphorus doping treatment at different temperatures, the P-C bond formed after the phosphorus element is incorporated into the carbon lattice also accounts for an increasing proportion with the increase of the calcination temperature,which is accompanied by a higher and higher acetylene conversion. It can be seen that the P-C bond plays a key role in the acetylene hydrochlorination reaction in this system. Meanwhile, Cu2+ was identified as the main active component in the catalyst by XPS. The representative HAADF-STEM image shows isolated copper species, confirming that the single-center copper species supported on the carbon support is the active center of the acetylene hydrochlorination reaction. The coordination structure formed by the interaction between the P-C bond and the atomically dispersed Cu2+ species is an effective and stable active site in the reaction. Density functional theory calculations indicate that the reaction is proposed to proceed according to the Langmuir-Hinshelwood (L-H) mechanism. This work is the first to identify which phosphorus species plays a role in the hydrochlorination of acetylene, which may provide some ideas for the design and optimization of phosphorus doping catalysts in the future.