Influence of copper content on structural features and performance of pre-reduced LaMn1-xCuxO3 (0≤x<1) catalysts for methanol synthesis from CO2/H2

A series of pre-reduced LaMn1-xCuxO3 (0≤x<1) catalysts for methanol synthesis from CO2 hydrogenation were prepared by a sol-gel method. The catalytic performances were strongly dependent on the copper content. XRD investigation revealed that the single perovskite structure could be preserved after being reduced, when the substitution for Mn by Cu was less than 50%. The Cu-doped (x=0.5) LaMnO3 was much more active than the other catalysts for reaction, showing CO2 conversion up to 11.33% and methanol selectivity close to 82.14%. The structural features of samples (x≤0.5) were studied. It was determined that copper existed as Cu+ species under reduction conditions. H2 was adsorbed on Cu+ sites and CO2 was activated on the medium CO2 active species in the lattice. The strong interaction between Cu+ and Mn inhibited the further reduction from Cu+ to Cu0 and made the fine dispersion of medium basic site to adsorb CO2, contributing to reactivity.