Multifunctional catalyst of Cu/ZnO and molecular sieve for low temperature CO2 conversion to methanol

Abstract

Carbon dioxide (CO2) conversion to methanol is a promising way to mitigated CO2 emission. the Cu/ZnO catalyst applied with molecular sieves was tested on alcohol assisted methanol synthesis at 423 K and 5 MPa. The Cu/ZnO was synthesized by coprecipitation at optimal parameters (precipitation temperature = 333 K, pH = 8) in two different aging time (30min and 1h). The formation of Cu/ZnO was confirmed by XRD technique. The physiochemical properties of Cu/ZnO were analysed by SEM-EDX, N2-adsorption and desorption, and H2-TPR. the Cu/ZnO_1h with a longer aging time showed a larger specific surface area (100.58 m2/gcat) and well dispersion. The effect of molecular sieve was investigated. The molecular sieve only adsorbed the target compounds and did not involve as catalyst in the reaction. Methanol yield increased from 8.5% to 33.6% when Cu/ZnO was loaded with molecular sieve 3Å. The adsorption of water shifted the reaction equilibrium toward to more methanol yield. In contrast, when Cu/ZnO with molecular sieve 5Å was used, methanol yield decreased to 4%. It was likely that methanol product was adsorbed by molecular sieve 5Å and was separated from ethyl acetate which is a by-product.