Highly selective hydrogenation of CO2 to propane over GaZrOx/H-SSZ-13 composite

Selective hydrogenation of CO2 into value-added hydrocarbons, particularly single products, is of great interest. However, this is a challenge because of the simultaneous occurrence of numerous competing elementary reactions. Here a GaZrOx/H-SSZ-13 composite is developed, which shows propane selectivity in hydrocarbons of 79.5%, along with butane selectivity of 9.9% and CO selectivity of 31.8%, at CO2 conversion of 43.4%. Such catalytic performance can be well maintained within 500 h. Incorporation of proper amounts of Ga into ZrO2 promotes methanol formation due to generation of high concentrations of surface oxygen vacancies with moderate CO2 adsorption strength. The large number of strong-acid sites of H-SSZ-13 seriously restricts conversion of generated methanol into aromatics at high H2 pressure, suppressing the aromatics-based cycle and favouring the alkene-based cycle instead. Accordingly, far more propene and butene are obtained than ethene, although they are rapidly hydrogenated to corresponding alkanes on the strong-acid sites of H-SSZ-13. The hydrogenation of CO2 into more valuable hydrocarbons is potentially attractive in the context of greenhouse gas removal schemes, although the efficiency of such processes is still limited. Now, a GaZrOx oxide catalyst working in combination with an H-SSZ-13 zeolite enables the highly efficient hydrogenation of CO2 to propane with minimal by-product production.