Effects of trifluoromethanesulfonic acid ligand on the Zinc-based catalysts for the acetylene hydration

Abstract

Developing an efficient Zn-based catalyst modified with Trifluoromethanesulfonic acid (TfOH) ligand is extremely desirable for the acetylene hydration reaction. In this paper, with the use of a simple impregnation method, a series of Zn-TfOH/AC catalysts were synthesized, and the Zn-1.5TfOH/AC catalyst demonstrated the optimal catalytic performance with 96% acetylene conversion in the hydration of acetylene. The X-ray absorption fine structure (XAFS) spectra of the fresh Zn-1.5TfOH/AC catalysts demonstrated the establishment of the Zn-O4 coordination structure. According to the characterization results, TfOH ligands effectively inhibited carbon accumulation and Zinc loss, improved acidic sites and the dispersion of active metal, and produced more catalytic active site. Furthermore, the hydration reaction mechanism of Zn-TfOH/AC catalyst with Zn(OTf)2, TfO-ZnCl, and TfO-ZnOH complex configurations was explored by the Density Functional Theory (DFT) method, which showed that the activation barrier increased sequentially TfO-ZnOH < Zn(OTf)2 < TfO-ZnCl. Importantly, the OH− in TfO-ZnOH is involved in the reaction and regenerated by the dissociation of H2O, which lowers the energy barrier. This will provide a reference to design more efficient nonmercury catalysts for acetylene hydration.