Unraveling the influence of CO2 and Ce loading over ZSM-5 for oxidative dehydrogenation of propane

Abstract

Utilization of CO2 as a soft oxidant for oxidative dehydrogenation of propane to propene (ODHP) is of great importance to attain net-zero carbon emissions and to reduce greenhouse gases contributing to global warming. Here, Ce was impregnated into ZSM-5 (denoted as CZ-5 catalyst) to enhance the C3H8 conversion and C3H6 selectivity due to the redox properties of Ce to activate CO2 into CO and O* and induce propane bond cleavage (C-H). After characterization of the catalyst’s physicochemical properties, NH3-TPD and pyridine IR analysis revealed that introducing Ce regulates the acidic properties of ZSM-5 catalysts by increasing the number of Lewis acid sites while simultaneously decreasing the amount of Brönsted acid sites. The increment in Lewis’s acid sites considerably improved the C3H6 selectivity. The oxygen transfer from Ce4+ to Ce3+ during the reaction also contributed to the outstanding performance of the 12 %CZ-5 catalyst. Regarding optimum conditions, 2 % CO2 concentration and 12 % Ce loading were the optimum amount of oxidant and Ce content that produce the highest C3H6 yield of 34.08 %. The catalytic effectiveness and stability were preserved despite several hours of propane conversions at 550 °C. Therefore, modifying ZSM-5 with Ce could be a feasible way for improving propene selectivity and catalyst stability for ODHP.