Catalytic Performance of Various Zinc-Based Binary Metal Oxides/H-RUB-13 for Hydrogenation of CO2

Direct formation of light olefins (C-2(=)-C-4(=)) from CO2 hydrogenation is attractive because it decreases the greenhouse effect and gives value-added chemicals concurrently. Although it has been extensively studied and significant progress has been made, controllable regulation of light olefin distribution remains a challenge. Herein, the bifunctional catalysts composed of various zinc-based binary metal oxides and H-RUB-13 zeolite were prepared, including ZnZrOx/H-RUB-13, ZnAlOx/H-RUB-13, ZnGaOx/H-RUB-13, and ZnCrOx/H-RUB-13, and the C2-4 olefin selectivity in hydrocarbons reaches 64.7-83.2% at a CO2 conversion of 10.2-15.5%. ZnZrOx/H-RUB-13 shows the highest CO2 conversion as a result of the presence of larger amounts of oxygen vacancies that promote CO2 adsorption and activation. More interestingly, propene and butene are the dominant hydrocarbons, and C-3(=) + C-4(=) accounts for > 90% of light olefins. This confirms the potential of H-RUB-13 zeolite to suppress ethene formation. However, the distribution of light olefins also depends on the global acidic property of the bifunctional catalyst. ZnCrOx/H-RUB-13 with strong acidity shows higher ethene selectivity because of the promotion of the aromatic-based cycle.