Enhanced C─C coupling for syngas conversion to gasoline by Fe-substituted MFI in OXZEO catalysis published in Angewandte Chemie International Edition

Recently, a research team led by Prof. Xiulian Pan and Prof. Xinhe Bao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has made new progress in the direct synthesis of gasoline from syngas. They demonstrate that syngas conversion to gasoline is significantly improved using Fe-MFI zeolite in OXZEO catalysis.

Fisher–Tropsch synthesis (FTS) is the classic process for syngas conversion. Limited by the Anderson–Schulz–Flory (ASF) distribution, the selectivity of gasoline-range (C₅–C₁₁) hydrocarbons in FTS is less than 45%. The products are dominated by normal paraffins with low octane numbers. The OXZEO (oxide-zeolite) catalyst concept provides a bottom-up strategy to convert syngas to gasoline in one step, with the products enriched with isoparaffins and a high research octane number (Angew. Chem. Int. Ed., 2019; ACS Energy Lett., 2022; Appl. Catal. B, 2022; ACS Catal. 2023; J. Phys. Chem. C, 2024; Catal. Sci. Technol., 2024), which is unattainable via traditional FTS.

However, it remains a challenge to achieve a higher activity without degrading the C₅–C₁₁ selectivity. For instance, CO conversion can be readily increased by decreasing the Si/Al ratio in conventional aluminosilicate zeolite. It also caused strengthened acidity, which led to termination of chain growth and hence reduced C₅–C₁₁ selectivity.

We herein introduced ferric species to the MFI zeolite (Fe-MFI) and used it as the acidic component for OXZEO catalysis. Tetrahedrally coordinated ferric species are incorporated in the MFI framework, generating Brønsted acid sites (Si─OH─Fe). Thus, the transition states of reaction intermediates are better stabilized over Si─OH─Fe than those over Si─OH─Al, thereby making methylation kinetically more favorable over Fe-MFI, as confirmed by theoretical calculations. Meanwhile, the framework ferric species are resistant to reduction, thereby suppressing the hydrogenation of olefins. Thus, selective formation of C₅–C₁₁ is enhanced at a similar CO conversion compared to the conventional MFI zeolite. The resulting STY is among the highest reported for OXZEO catalysts.

This work was published in Angewandte Chemie International Edition with the title “Enhanced C─C coupling for syngas conversion to gasoline by Fe-substituted MFI in OXZEO catalysis”. This work was supported by the Ministry of Science and Technology of China and the National Natural Science Foundation of China. (Text/Picture by Yongzhi Zhao)

Article link: https://onlinelibrary.wiley.com/doi/10.1002/anie.5578716