Preparation of Cu–Al2O3–TiO2–Ti3C2/HZSM-5 Catalysts for Catalytic CO2 Hydrogenation to Dimethyl Ether

Abstract

To develop efficient catalysts for CO₂ hydrogenation to dimethyl ether, Cu–Al₂O₃–TiO₂–Ti₃C₂/HZSM-5 bifunctional catalysts were prepared by the surfactant PVP-assisted coprecipitation. The influence of Ti₃C₂ on Cu–Al₂O₃-based catalysts was investigated. The characterization results revealed that slight oxidation of the Ti₃C₂ surface generated highly dispersed TiO₂ nanoparticles that the doping of TiO₂‒Ti₃C₂ in the Cu‒Al₂O₃ catalyst increased the specific surface area of the catalyst and promoted the formation and growth of Cu nanoparticles, and that strong interactions occurred between TiO₂‒Ti₃C₂ and the Cu components. The number of oxygen vacancies at the interface between TiO₂‒Ti₃C₂ and Cu increased by 17%, and the electronic kinetic energy of Cu⁰ decreased by 0.1 eV, with the electron-rich oxygen vacancies transferring electrons to Cu²⁺ ions and maintaining more Cu species in lower oxidation states. Reactions were carried out at 260 °C and 3.0 MPa with a gaseous hourly space velocity (GHSV) of 1500 cm³‧g⁻¹‧h⁻¹ using Cu–Al₂O₃–TiO₂–Ti₃C₂/HZSM-5 with 5.0 wt% Ti₃C₂ as the hydrogenation catalyst, which provided a CO₂ conversion of 26.8% with 57.8% selectivity for DME.

Graphical Abstract