Chaoyue Zhao,Xianming Zhang,Ziting He,Qingxin Guan,Wei Li
For acetylene hydrochlorination, as a substitute for toxic mercury catalysts, Cu-based catalysts are probably the most promising and highly active non-noble metal catalysts. Here, density functional theory (DFT) was used to reveal the mechanism for how the NMP ligand significantly promotes the activity and stability of the Cu-catalyzed acetylene hydrochlorination reaction. According to the experimental and DFT results, the high activity of the NMP coordinated Cu-based catalyst is attributed to the catalyst–ligand and substrate–ligand interactions, which stabilize the substrate-Cu(II)-ligand complex in the catalytic cycle. Moreover, the most important two stages were investigated in detail: the reduction of (i) Cuα+ to Cu0 and (ii) Cu2+ to Cu+ during the reaction process. The results demonstrate that the NMP ligand prevents high valence Cu2+ from being reduced due to the geometric distortion influence and the hydrogen bond interaction between the catalysts and ligands. Also, NMP could inhibit the carbon deposition by avoiding the formation of Cu(0) and its strong adsorption of acetylene on the surface.
Ru-based catalysts have shown great potential for the environmentally friendly industrialization of acetylene hydrochlorination. However, the high cost and reduction of active sites in Ru catalysts have limited their practical applications. In this study, we propose a strategy to optimize the electronic structure of Ru single-atom catalysts by leveraging the strong coordination ability of ligands with the metal and apply this strategy to acetylene hydrochlorination. The experimental results verify that the performance of the catalyst increases with the increase of the ligand. Characterization results indicate that ligands not only optimize the electronic properties of Ru single atoms by forming a RuCl 2 -N structure, but also enhance the adsorption of reactants on the catalysts. DFT calculations reveal that the ligand-modified Ru species can efficiently adsorb and activate acetylene molecules, while the adjacent excessive ligand can adsorb and dissociate HCl molecules. This ultimately leads to an addition reaction between acetylene and HCl through a hydrogen overflow mechanism.
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