Interactions between atomically dispersed copper and phosphorous species are key for the hydrochlorination of acetylene

Abstract

Vinyl chloride, the monomer of polyvinyl chloride (PVC), is industrially synthesized via acetylene hydrochlorination. Thereby, easy to sublimate but toxic mercury chloride catalysts are widely used. It is imperative to find environmentally friendly non-mercury catalysts to promote the green production of PVC. Low-cost copper-based catalysts are promising candidates. In this study, phosphorus-doped Cu-based catalysts are prepared. It is shown that 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, the formed P-C bond plays a key role. The coordination structure formed by the interaction between P-C bonds and atomically dispersed Cu2+ species results in effective and stable active sites. Insights on how P-C bonds activate the substrate may provide ideas for the design and optimization of phosphorus-doped catalysts for acetylene hydrochlorination.

Construction of Highly Dispersed Cu–P/Cl Active Sites Using Methyldiphenyloxophosphine for Efficient Acetylene Hydrochlorination

“…This indicates an average valence state between Cu 1+ and Cu 2+ in both Cu-based catalysts, 61 S5). However, apart from the Cu−Cl (2.27 Å) characteristics derived from the CuCl 2 precursor, 47 Cu−O with a bond length of 1.95 Å was observed for the benchmark catalyst 15% Cu/AC, which may stem from the coordination of Cu precursors with Ocontaining groups on the support. Similarly, the slightly augmented Cu−O coordination number and the potential P− O−Cu species observed in the P 2p XPS spectrum of the 15% Cu 8 MDPO 1 /AC catalyst demonstrate that most of the Cu−O bonds still derived from the interaction of Cu species with Ocontaining groups on the support surface, and perhaps some of them stemmed from the coordination of Cu species with the O atom of the ligand.…”

“…Notably, the P�O stretching vibration and the inplane bending vibration of the benzene rings are red-shifted by 18 and 29 cm −1 in CuCl 2 -MDPO due to electron aggregation and electron feeding, further demonstrating the generation of a local active domain as a result of the coordination between the MDPO ligand and CuCl 2 precursors, as was verified by the appearance of peaks attributable to P−O/P−O−Cu and P−Cu species in the P 2p XPS spectrum of the 15% Cu 8 MDPO 1 /AC catalyst (Figure 4). 41,47 Structural Properties of the Cu Catalysts. The pore structure was analyzed via N 2 adsorption−desorption isotherms to determine the effect of the MDPO ligand on the texture properties of the Cu-based catalysts.…”

Tunable Redox Cycle and Enhanced π-Complexation in Acetylene Hydrochlorination over RuCu Catalysts

“…Thus, the search for alternative methods to achieve the stable operation of Rubased catalysts is ongoing. 11,25 Achieving a high electron density on the Ru centers through electron transfer from Cu atoms can improve the electron complementary redox cycles, which is considered a promising stabilization strategy. 5,9,26 It has been confirmed that the high electron density of Cu can break and activate the carbon− carbon triple bond (CC) of C 2 H 2 by forming π−σ coordination bonds, thus accelerating the catalytic reaction with a lower energy barrier.…”

“…Ru-based catalysts exhibit high activity for HCl activation, but the active sites (Ru­(III) or Ru­(IV)) are always deactivated by the induced thermodynamic autoreduction. Also, excessive reductive C 2 H 2 or HCl gas could also lead to the reduction of the Ru­(III)/Ru­(IV) pair to inactive Ru(0) species and cause coke deposition. − As reported, the formation of inactive Ru(0) species occurred at any stage of the simultaneous or stepwise hydrochlorination reaction. , Thus, rationally eliminating or slowing down the generation of Ru(0) is a vital issue to improve the stability of Ru-based catalysts further. To address the problem, extensive efforts have focused on catalyst carrier design and modification of the Ru coordination environment.…”

“…Based on this, some emerging bimetallic catalysts (e.g., Ru–Co and Ru–Bi catalysts) have been synthesized by forming specific coordination bonds with Ru atoms. − Despite the aforementioned methods for mitigating Ru(0) generation being partially successful, it still remains a great challenge to develop long-term stable Ru-based catalytic systems. Thus, the search for alternative methods to achieve the stable operation of Ru-based catalysts is ongoing. , …”