Reaction‐Induced Formation of Stable Mononuclear Cu(I)Cl Species on Carbon for Low‐Footprint Vinyl Chloride Production

Abstract

Copper catalysts are attractive candidates for Hg-free vinyl chloride monomer (VCM) production via acetylene hydrochlorination due to their non-toxic nature and high stability. However, the optimal architecture for Cu-based catalysts at the nanoscale is not yet fully understood. To address this gap, the metal precursor and the annealing temperature are modified to prepare copper nanoparticles or single atoms, either in chlorinated or ligand-free form, on an unmodified carbon support. Evaluation in the reaction reveals a remarkable convergence of the performance of all materials to the stable VCM productivity of the single-atom catalyst. In-depth characterization by advanced microscopy, quasi in situ and operando spectroscopy, and simulations uncover a reaction-induced formation of low-valent, single atom Cu(I)Cl site motif, regardless of the initial nanostructure. Various surface oxygen groups promote nanoparticle redispersion by stabilizing single-atom CuCl x species. The anchoring site structure does not strongly influence the acetylene adsorption energy or the crucial role they play in stabilizing key reaction intermediates. A life-cycle assessment demonstrates the potential environmental benefits of copper catalysts over state-of-the-art alternatives. This work contributes to a better understanding of optimal metal speciation and highlights the sustainability of Cu-based catalysts for VCM production.

Advances in Single-Atom-Catalyzed Acetylene Hydrochlorination

“…This is particularly challenging for gold catalysts which require the use of aqua regia for stabilizing cationic gold species in the synthesis. Alternatively, restructuring of the active metal sites may occur under working conditions, as has been demonstrated on the various Cu/AC systems . The inspiring work suggests that the hydrochlorination reaction itself can be viewed as a tool to generate highly active catalysts, and thus deserves more explorations.…”

“…(g) Operando Cu K-edge XANES spectra of the Cu-based catalysts during the heating ramp (left) and under reaction conditions (right) with time on stream (tos). Adapted with permission from ref . Copyright 2023 Wiley.…”

“…Meanwhile, more extensive exploration of other replacing catalysts only came into the spotlight after 2013. Among the various active metals including Ru, − Cu, − Pd, − Pt, ,, Ag, , and Fe, − Ru and Cu have received more attention probably owing to the balanced activity and price. Albeit the earlier works on these metals being mainly focused on particle catalysts, more and more recent studies point to the great potential of single-atom catalysts ,,− ,− ,,,− in acetylene hydrochlorination, rivaling the performance of the well-recognized gold counterparts and thus signifying a bright future for a mercury-free technology for PVC manufacture.…”

Tailoring Asymmetric Cu-O-P Coupling Site by Carbothermal Shock Method for Efficient Vinyl Chloride Synthesis over Carbon Supported Cu Catalysts

“…Motivated by recent advances in controlling the atomic architecture of metal particles down to the single atom limit, heterogeneous catalysis has developed as one of the most crucial frontiers in nanoscience, with various applications in energy conversion and bulk and fine chemical synthesis. − Combining in-depth characterization and theoretical studies, enhanced synthetic control of the active site opens up new perspectives for solving long-standing challenges in heterogeneous catalysis, as recently exemplified by Pérez-Ramírez et al for nanostructured Au, Pd, Pt, Ru, Rh, and Ir systems in acetylene hydrochlorination. − ,, This provides us with the inspiration to design the optimal architecture for Cu-based catalysts at the nanoscale. Despite the fact that minimal research has shown the catalytic features and mechanisms affected by copper nucleation and chemical and electronic states, this highlights the need of understanding how these sites with diverse architectures catalyze reactions.…”

Hydrochlorination of acetylene catalyzed by mesoporous carbon with hierarchical assembly of polyimide nanosheets

“…In the past few decades, gold-based catalysts have been some of the most promising catalysts among the many transition metal catalysts, such as Au-based, 7–12 Pd-based, 13–15 Ru-based, 16–20 Bi-based 21 and Cu-based 22–26 catalysts, owing to their excellent catalytic activity and stability, but the high cost and low reserve prohibit the large-scale utilization of Au-based catalysts for acetylene hydrochlorination. Recently, carbonaceous materials have generally been employed in various reactions, such as the CO 2 reduction reaction, 27 the oxygen reduction reaction, 28 cellulose hydrolysis, 29 hydrazine oxidation, 30 and so on.…”