Hydrogenation of CO2 into hydrocarbons over bifunctional system Cu–ZnO/Al2O3 + HZSM-5: Effect of proximity between the acidic and methanol synthesis sites

Abstract

A one-step CO2 hydrogenation reaction into hydrocarbons (HC) using a bifunctional system constituted by a methanol synthesis catalyst [Cu–ZnO–Al2O3 (CZA)] and a zeolite (HZSM-5) has been studied. The influence of the catalyst bed configuration on activity, selectivity, and HC yield has been evaluated. The results obtained at TR = 623 K, PR = 3.0 MPa and WHSV = 6000 h−1 show that CO2 hydrogenation and hydrocarbon selectivity were strongly influenced by the proximity between oxide and zeolite, whatever the disposition of the two catalytic active sites. Indeed, the highest conversion and the best yield of hydrocarbons (mainly C2) were obtained with the M1 bifunctional catalysts in which the oxide–zeolite proximity is the lowest. This is ascribed to the hydrogen spillover phenomenon, which does not promote the carbon chain growth.