Abstract: The interfacial properties of the composite oxides have a significant relationship with the catalytic performance of CO₂ hydrogenation to methanol. Accordingly, the effects of various preparation methods including physical blending, impregnation, traditional co-precipitation and microfluidic continuous co-precipitation on the interfacial property and catalytic performance of Al₂O₃-CeO₂ composite oxides were investigated. Although the impregnation effect can moderately tune the interface properties of Al₂O₃/CeO₂, the insufficient oxygen vacancy defects resulted in inferior catalytic performance. The solid solution structure of co-precipitation sample enhanced the interfacial interaction of Al₂O₃/CeO₂ and the binding energy of the electron, forming sufficient oxygen vacancy defects to activate CO₂. The sample prepared by the microfluidic continuous co-precipitation has the excellent catalytic performance due to its smaller grain size, uniform composite structure and sufficient oxygen vacancy defects. Under the conditions of V(H₂)∶V(CO₂)∶V(N₂)=72∶24∶4, reaction temperature 320 ℃, reaction pressure 3 MPa and space velocity 9 000 mL·g^-1·h^-1, the CO₂ conversion, methanol selectivity and methanol space-time yield of the Al₂O₃-CeO₂ composite oxide can reach 15.3%, 86.4%, and 0.076 g·mL^-1·h^-1, respectively.

Key words: Al₂O₃-CeO₂ composite oxide, microfluidic continuous co-precipitation, oxygen vacancy, CO₂ hydrogenation, methanol