Electronic Promotion Effects of Metal Oxides: A Case Study of MnO Impact on Fischer–Tropsch Catalysis
S. S. Gupta, Prathamesh M. Shenai, Jurjen Meeuwissen, G. Leendert Bezemer, S. Shetty
Abstract
Fischer–Tropsch (FT) reaction is an industrially important process that relies on metal oxide promoters to significantly increase the activity and selectivity of the catalyst. Here, we investigate the role of MnO as a promoter for Co-based FT catalysts using experimental and computational tools. Experimental high-pressure data showed that MnO-promoted Co/TiO2 catalysts increased the activity by 70–80%, while liquid selectivity was increased by 2.7%, with a decrease in undesired methane. Using density functional theory calculations on Mn4O4 supported on Co(0001) surface, we showed that the MnO particle undergoes a redox cycle, activating the CO molecule in its vicinity. Promotion by MnO was observed through a reduction in the CO dissociation barriers of the direct and COH pathways by 41 and 60 kJ/mol, respectively, closely competing with the HCO pathway on bare Co(0001). These modeling results demonstrate that electronic promotion by MnO results in activity enhancement that is consistent with experiments. Finally, we discuss the insights from our calculations that could be relevant for understanding damped hydrogenation rates and increased long-chain selectivity and screening the next generation of electronic promoters.