Experimental Investigation on the Two-Sided Effect of Acidic HZSM-5 on the Catalytic Performance of Composite Fe-Based Fischer-Tropsch Catalysts and HZSM-5 Zeolite in the Production of Aromatics from CO2/H2

A negative effect of an HZSM-5 zeolite was observed for CO2 hydrogenation toward the production of aromatics when combined with Fe-based Fischer-Tropsch synthesis (FTS) catalysts in an improper manner. The conversions of CO2 and CO were seriously hindered due to suppression in the formation of Fe carbides. With various especially designed experiments, it is confirmed that the Bronsted acid sites in the zeolite serving as an electron acceptor should be the major factor influencing the electron transfer from the Fe phase to CO molecules, resulting in the suppression of CO dissociation. Additionally, we suggested a practical way to eliminate the negative effect of the acidic HZSM-5 zeolite by coating an inert layer on either the Fe-based catalyst or the zeolite. With these observations, it is beneficial to design a multifunctional catalyst system that can be scaled up by paying more attention toward the two-sided effect of zeolites.