Selective hydrogenation of CO2 and CO over potassium promoted Co/ZSM-5

The utilization of CO2 as a C-1 feedstock for synthesis of value-added chemicals and fuels could both mitigate the negative effects associated with increasing CO2 emissions and decrease dependence on fossil fuels as part of a future circular carbon economy. Co-based catalysts have been well-developed for Fischer-Tropsch synthesis (FTS), but replacing the CO reactant with CO2 (CO2-FTS) typically results in low selectivity toward desirable light olefins. To better understand the structure-property relationships of Co-based catalysts, and extend promising FTS results to CO2-FTS, we have studied the effect of a potassium promoter and acidic properties of ZSM-5 on catalytic performance. The selectivity of FTS and CO2-FTS is shown to be a strong function of Si/Al ratio in co-impregnated catalysts, with findings supported by in situ XAFS and FTIR, demonstrating light olefin selectivity can be tuned by Si/Al ratio and the method of introducing the K promoter.