Oxygen vacancies prompt the formation of hydrated hydroxyzinc in Zn-based catalysts to enhance acetylene hydration

Abstract

Herein, the Zn-based catalysts with oxygen vacancies were obtained via the simple and effective method, and the oxygen-vacancy (Ov)-rich anatase TiO2 was as carrier, which was introduced oxygen-vacancy through heat treatment. The catalysts performance test results showed that the Zn/TiO2-300-10 with oxygen-vacancy (Ov)-rich exhibited excellent catalytic performance (acetylene conversion >89 % for 30 h) at the reaction temperature of 260 °C. Electron paramagnetic resonance spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy revealed the formation of oxygen-vacancy in treated TiO2 carriers. Subsequently, all the Zn-based catalysts were characterized by a series of characterization techniques. The results showed that the Zn/TiO2-300-10 catalyst with Ov-rich could produce more hydroxyl‑containing Zn species and improve Zn dispersion than that of the untreated Zn/c-TiO2 catalysts. Meanwhile, the DFT calculation results showed that, for the oxygen-vacancy-rich Zn-based catalysts, the OH− species from (ZnOH)+ species participated in acetylene hydration, thereby reducing the activation energy of acetylene hydration, and allowing the regeneration of (ZnOH)+ species via water cleavage. While, the reactant C2H2 was directly reacted with water dissociation with higher activation energy for the Zn/TiO2 catalyst without oxygen-vacancy. This study lays the foundation for further developing other Ov-rich carriers more suitable for Zn loading.