Formic acid assisted synthesis of Cu-ZnO-Al2O3 catalyst and its performance in CO2 hydrogenation to methanol

The Cu/Zn/Al precursor by coprecipitation was treated with formic acid and then calcined in N2 to obtain Cu-ZnO-Al2O3 catalyst (CZA) for the CO2 hydrogenation to methanol. XRD, BET, TG-DSC, SEM, H2-TPR, N2O titration, XPS-AES and CO2-TPD characterization techniques were used to analyze the phase composition, structural properties of the catalyst, the Cu specific surface area, the dispersion and valence of the Cu species. The results showed that the formic acid treatment tuned the ratio of Cu+ and Cu0, increased the number of medium-strong base sites in the catalyst, and raised the selectivity of methanol. Under reaction conditions of W/F(H2/CO2=70/23)=10 g·h/mol, t=200 °C and p=3 MPa, using Cu-ZnO-Al2O3 treated under HCOOH/Cu/(molar ratio)=0.8, the CO2 conversion and the methanol selectivity were 6.7% and 76.3%, respectively.