Highly efficient CuO/ZnO/ZrO2@SBA-15 nanocatalysts for methanol synthesis from the catalytic hydrogenation of CO2

Abstract

Cu/ZnO@SBA-15 and Cu/ZnO/ZrO2@SBA-15 nanocomposites have been synthesized by an innovative impregnation-sol-gel autocombustion combined strategy and tested as catalysts for carbon dioxide hydrogenation to methanol. The composites, differing as to the active phase loading (20 and 35 wt.%) and Cu/Zn molar ratio (1.0-2.5 mol mol−1), have been characterized in terms of chemical, morphological, structural and textural features by a multi-technique approach. Characterization techniques revealed that the active phase is highly dispersed into/over the well-ordered mesoporous channels especially at low loading and low Cu/Zn molar ratio. In all the composites, the mesostructure of the support is retained together with a high surface area, large pore volume and uniform pore size. Catalytic results showed that the supported catalyst with the lowest Cu/Zn molar ratio (1.0 mol mol−1) exhibits the best catalytic performance with a space-time-yield of methanol of 376 mgCH3OH h-1 gcat-1, much more efficient than the unsupported catalyst (10 mgCH3OH h-1 gcat-1). The confinement of the active phase in the SBA-15 structure enhances its ability to interact with H2 and CO2, which results in improved performance. Moreover, the results show the influence of the active phase loading and the Cu/Zn molar ratio that lead to differences in the morphology and dispersion of the active phase, which in turn cause the composite to catalyse the reaction differently.