Differences in bifunctionality of ZnO and ZrO2 in Cu/ZnO/ZrO2/Al2O3 catalysts in hydrogenation of carbon oxides for methanol synthesis.

• TOF MeOH increases with an increase in CO 2 content of the CO 2 /CO feed. • TOF MeOH ratio of (TOF) 5%CO2 /(TOF) 100%CO2 were 1.8 for Cu 6 Zn 3.0 Zr 0.0 Al 1. • TOF MeOH ratio of (TOF) 5%CO2 /(TOF) 100%CO2 were 10.4 for Cu 6 Zn 0.0 Zr 3.0 Al 1. • The role of ZrO 2 is enhanced by the reverse hydrogen spillover of Cu/ZnO. • The role of ZrO 2 is important only for high CO2 feed more than 50%. This work investigates the promotional roles of ZrO 2 and ZnO for methanol synthesis on five Cu 6 Zn 3.0-x Zr x Al 1 (x = 0.0, 0.5, 1.5, 2.5, 3.0) catalysts in the various CO 2 feed composition. TOF decreased with an increase in x of Cu 6 Zn 3.0-x Zr x Al 1 catalysts in the 5% CO 2 feed, while TOF is maximized over Cu 6 Zn 1.5 Zr 1.5 Al 1 in the 100% CO 2 feed. Both the effects of Zn (reverse spillover) and Zr (additional reaction sites) in the vicinity of Cu promote the CO 2 hydrogenation, maximizing the catalytic activity of Cu 6 Zn 1.5 Zr 1.5 Al 1 in the 100% CO 2 feed. The migration of hydrogen on ZrO 2 can be limited in little surface hydroxyls in 5% CO 2 feed, which can be a reason for the negative role of ZrO 2 in the 5% CO feed. The promotional effect of ZrO 2 on Cu/ZnO is important only for high CO 2 feed more than 50% CO 2. [ABSTRACT FROM AUTHOR]