Acidity modification of ZSM-5 for enhanced production of light olefins from CO2

Utilization of multi-functional catalysis is fast becoming the method of choice to boost the production of valuable chemicals from CO2. Here, we present a possible route to increase selectivity to light olefins by modifying the acidity of the zeolitic component of a multi-functional catalyst. This is carried out via incorporation of Ca on the zeolite ZSM-5 by incipient wetness impregnation. This incorporation, while straightforward, leads to reduced Brønsted acidity and the formation of multiple Lewis acidic species inside the zeolite. NMR investigations point towards incorporation of CO/ketene into the zeolite leading to the creation of surface acetate species, which augments the production of light olefins. Additionally, the suppression of oligomerization due to the reduction of Brønsted acid sites also produces more light olefins at the expense of longer chain hydrocarbons.