Effect of promoter TiO2 on the performance of CuO-ZnO-Al2O3 catalyst for CO2 catalytic hydrogenation to methanol

CuO-ZnO-Al2O3 was modified by co-precipitation, using TiO2 obtained from hydrolyzation of tetra-n-butyl titanate (C16H36O4Ti). The catalytic performances were investigated under the conditions of 260°C, 2.6 MPa, H2:CO2=3:1 (volume ratio) and SV of 3600 mL/(g·h). The modified samples showed a higher performance than CuO-ZnO-Al2O3 and 4% was the optimal dosage. XRD, H2-TPR, H2-TPD, NH3-TPD and CO2-TPD characterizations were performed. TiO2 improved CuO dispersion in the catalyst and enhanced the adsorption/activation of CO2 and H2 on the surface of catalyst, leading to easier reduction of CuO and lower concentration of strong acid sites on the surface of catalyst simultaneously.