CO2 hydrogenation to methanol over PdZn catalysts on bimetallic modified dendritic mesoporous silica nanospheres

Abstract

Catalysts with the CeTi bimetallic modified dendritic mesoporous silica nanospheres (CTD) as supports, and the PdZn as active metal phase, PdZn/CTD catalysts with higher Pd metal dispersion and more oxygen vacancies were synthesized for efficient CO2 hydrogenation to methanol (MeOH). The modification of PdZn/CTD using CeTi metals can increase the dispersion of PdZn and improve the Ce3+/Ce4+ ratios. Higher active metal dispersion of PdZn/CTD catalyst is conducive to more H2 adsorption and to the expose of activation sites. Higher Ce3+/Ce4+ ratio of PdZn/CTD is beneficial to generate more oxygen vacancies, which can adsorb and activate CO2 molecules efficiently. The optimized PdZn/CTD catalysts exhibit superior CO2 conversion (33.6 %), MeOH selectivity (32.9 %), MeOH yield (11.1 %), TOF value (22.5 h−1), space–time yield (STY) (4.44 molMeOH kg-1 h−1) and 100 h long-term stability. Besides, through in-situ DRIFTS, HCOO* and CH3O* species are found to be the primary intermediates of the CO2 hydrogenation to MeOH reaction over the PdZn/CTD catalysts.