Effect of operating parameters on H2/CO2 conversion to methanol over Cu-Zn oxide supported on ZrO2 polymorph catalysts: Characterization and kinetics

Abstract

Kinetic aspects of the operating parameters for the catalytic conversion of H2/CO2 to methanol over two novel catalysts were evaluated to understand the effect of the polymorphic ZrO2 phase composed of Cu0/+-ZnO sites at the atomic level and its impact on the reaction mechanism. The catalysts were characterized by in situ and ex-situ XRD, N2 adsorption/desorption isotherms, FRX, TPR, TPD-N2O, in situ XANES, TPD-CO2, and in situ DRIFTS techniques. The influence of different reaction variables such as the GHSV, temperature, pressure, and H2/CO2 ratio were studied using a fixed bed continuous plug flow reactor. The Cu-ZnO catalyst supported on the tetragonal zirconia polymorph exhibited the highest methanol yield due to the lower activation energy when compared to the catalyst with a greater amount of the monoclinic phase. In addition, the catalysts were reused for 8 cycles of 6 h to evaluate their stability, which can translate into lower costs for large-scale methanol production. The estimation of the kinetic parameters for the Cu-Zn oxide catalysts supported on ZrO2 polymorphs was important to understand the reaction mechanism, as well as to provide useful information for scaling up the process.