Highly efficient Cu-based catalysts via hydrotalcite-like precursors for CO2 hydrogenation to methanol

A series of Cu–Zn–Al–Zr precursor materials are prepared by coprecipitation at different pH values (6.0–11.0) and treated under hydrothermal condition. Zincian malachite is formed as the main phase at the low pH of 6.0 and 7.0, and is replaced by hydrotalcite-like phases with increasing the pH. After calcination and reduction of precursors, Cu/ZnO/Al2O3/ZrO2 catalysts are obtained and tested for methanol synthesis from CO2 hydrogenation at the reaction temperature of 463 K. With increasing pH, the Cu particle size first increases until pH 9.0 and then decreases. Compared with the sample resulting from well-crystallized zincian malachite (pH 7.0), the catalysts derived from phase-pure hydrotalcite-like precursors (pH ≥ 9.0) exhibit lower BET specific surface area and lower specific Cu surface area. In addition, due to the smaller of Cu particle size and the stronger interaction among Cu and ZnO, the catalytic activity for the Cu/ZnO/Al2O3/ZrO2 catalysts via the hydrotalcite-like precursors is higher than that for the catalysts derived from zincian malachite precursors at low reaction temperature. A maximum CH3OH yield of 0.087 g gcat−1 h−1 with the CO2 conversion of 10.7% and the CH3OH selectivity of 81.8% at 463 K and 5.0 MPa is obtained over the Cu/ZnO/Al2O3/ZrO2 catalyst prepared at pH 9.0.