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.
You Han,Yulian Wang,Yan Wang,Yubing Hu,Yao Nian,Wei Li,Jinli Zhang
A series of Cu-pyrrolidone/spherical activated carbon (SAC) catalysts were prepared via a simple incipient wetness impregnation method and then assessed in acetylene hydrochlorination, and the catalytic evaluation result indicated that the 1-methyl-2-pyrrolidinone (NMP) ligand was found to be the most effective one to significantly improve the activity and stability of Cu catalyst. The catalyst with the optimal molar ratio of NMP/Cu = 0.25 showed 94.2% acetylene conversion at 180°C and an acetylene gas hourly space velocity of 180 h −1 . Moreover, the acetylene conversion of Cu-0.25NMP/SAC remained stable over 99.1% for about 220 h under the industrial condition. Transmission electron microscopy (TEM) analyses proved that NMP ligand improved the dispersion of Cu species. In addition, hydrogen temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), and Brunner–Emmet–Teller (BET) indicated that the additive of NMP was preferential to stabilize the catalytic active Cu + and Cu 2+ species and inhibit the reduction of Cu α+ to Cu 0 during the preparation process and reaction, hence restraining the coke deposition. Furthermore, the steady coordination structure between Cu and NMP was confirmed by Fourier-transform infrared spectra (FT-IR) and Raman combining with density functional theory (DFT) calculation, which could effectively lower the adsorption energy of catalyst for C 2 H 2 and inhibit the serious carbon deposition caused by excessive acetylene self-accumulation. Our findings suggest that the efficient, well-stabilized cost-effective, and environmentally friendly Cu catalyst has great potential in acetylene hydrochlorination.
危险品化学品经营许可证（带存储）