Effects of supports on bimetallic Pd-Cu catalysts for CO2 hydrogenation to methanol

Lab-synthesized and commercial materials, TiO2 , ZrO2, CeO2, Al2O3 and SiO2 , were employed to investigate the effects of support on bimetallic Pd-Cu catalysts for CO2 hydrogenation to methanol. SiO2 was used as a benchmark with negligible MSI (metal-support interaction) and adsorption capacity. TiO2 P25 (TiO2-P1) with coexistence of anatase/rutile phase exhibited the optimal supports among TiO2 serial supports. TiO2-P1, ZrO2, and Al2O3 exhibited significant promotional effects than SiO2 support, and the methanol synthesis activity decreased as: TiO2-P1(similar to)ZrO(2) > Al2O3 > CeO2-D-similar to SiO2. Pd-Cu/TiO2-P1 and Pd-Cu/ZrO2 yielded 1.6-time more CH3OH than Pd-Cu/SiO2. Detailed characterizations demonstrated that methanol formation was mainly correlated to PdCu3 alloy and H-2/CO2 adsorption. Pd-Cu/CeO2-D possessed the strongest MSI, but with alloy restructuring to form PdCux, lowered weakly adsorbed ratio of CO2 and surface adsorption ratio of H-2/CO2, therefore exhibiting worse catalytic performance. Pd-Cu/TiO2-P1, Pd-Cu/ZrO2 , and Pd-Cu/Al2O3 possessed moderate MSI and desirable performance.