The role of MgO during CO2 hydrogenation to methanol over Pd/ZnO catalyst

Abstract

Selective hydrogenation of CO₂ to methanol over Pd nanoparticles supported on MgO promoted ZnO oxide catalyst was investigated in a fixed bed continuous downflow reactor at 3 MPa pressure and temperature between 200–280 °C. The synthesized catalyst showed exceptionally high selectivity (>90%) for methanol production via CO₂ hydrogenation at low temperature (220 °C) and pressure (3 MPa). 2wt%Pd loaded on ZnO catalyst showed very less activity but the addition of MgO on the ZnO led to a higher dispersion of Pd, which directly influences catalyst activity and methanol production. The addition of 10 wt% MgO over 2wt%Pd/ZnO catalyst improved the catalyst activity, where we observed ∼ 8.2% CO₂ conversion with ∼ 90.6% methanol selectivity. Density Functional Theory (DFT) calculation shows the addition of MgO at the Pd/ZnO catalyst promotes the adsorption of CO₂, as well as reaction intermediates HCOO and COOH. The long-term stability of MgO-promoted Pd-ZnO was tested, and it was found that catalyst showed no deactivation even after 80 h time-on-stream.