CO2 hydrogenation to methanol and dimethyl ether by Pd–Pd2Ga catalysts supported over Ga2O3 polymorphs

Abstract The production of methanol and dimethyl ether (DME) via CO 2 hydrogenation was studied using Pd catalysts supported on α-Ga 2 O 3 , α-β-Ga 2 O 3 and β-Ga 2 O 3 polymorphs. The formation of a Pd 2 Ga intermetallic compound was observed using XRD and XPS. The catalytic activity improves with an increase in the content of the Pd 2 Ga intermetallic compound. The content of Pd 2 Ga on Pd/Ga 2 O 3 depends on the Ga 2 O 3 crystalline phase of the catalyst. A slight catalytic deactivation was observed for all samples studied. The Pd/α-β-Ga 2 O 3 catalyst displayed the largest deactivation. The deactivation appears to be caused by a loss of basic sites. The selectivity to dimethyl ether is not dependent on the Pd 2 Ga content, but depends on the catalyst acidity. This assertion was tested by adding niobia to the catalysts, thus increasing the DME selectivity from 0 to 53%. The content of Pd 2 Ga over Pd/Ga 2 O 3 catalysts was identified to be a crucial parameter for CO 2 hydrogenation to methanol.