Study on the regulation of Fischer-Tropsch synthesis catalytic performance by mixing oxides with iron-based catalysts

Abstract

In Fischer-Tropsch synthesis (FTS), iron-based catalysts are prone to deactivation due to carbon deposition. To address this challenge, we developed a simple physical powder-mixing strategy by mechanically mixing iron-based FTS catalysts with oxides such as SiO₂, MgO, ZnO, ZrO₂, MnO₂, Al₂O₃, and graphene oxide (GO). Experimental results demonstrate that oxide incorporation significantly suppresses carbon deposition in a composition-dependent manner, thereby enhancing catalytic stability. Notably, after mixing with SiO₂ or MgO powder, the CO conversion reached 96.6% and 97.6%, respectively, maintaining stability for more than 20 h. In contrast, catalyst mixed with quartz sand particles underwent rapid deactivation within 20, with a decrease in CO conversion from 93.0% to 14.6%, accompanied by a sharp rise in CH₄ selectivity. By combining various characterization methods such as XRD, Mossbauer spectroscopy, TGA, XPS and CO-TPD, the promoting mechanism of oxides on reaction stability was deeply studied. The results indicate that the catalyst mixed SiO₂ powder reduced the content of active χ-Fe₅C₂ phases from 97% to 52.1% and effectively suppressed carbon deposition. This enhancement is attributed to the strong interfacial interactions between SiO₂ and the iron-based catalyst, which moderately inhibited CO adsorption and dissociation kinetics, decelerated carbonization, and prevented rapid accumulation of carbon species on the catalyst surface. Similar mechanisms were observed over MgO additives, further validating the role of oxide-iron interactions. This work elucidates the mechanism of the interaction between iron-based catalysts and mixed oxides on carbon deposition behavior in Fischer-Tropsch synthesis reactions, providing an innovative strategy and theoretical foundation for designing highly active and stable catalysts.