Abstract
The emerging oxide–zeolite bifunctional catalysis for direct syngas conversion has drawn extensive interest, both academically and industrially, with further exploration urging a clear mechanistic understanding of this complex catalytic network. Herein, using a specially designed quasi-in situ, solid-state nuclear magnetic resonance-gas chromatography/gas chromatography-mass spectrometry analysis strategy, this reaction is fully monitored from the very early induction period to steady-state conversion under high-pressure flow-reaction conditions, using ZnAlOx/H-ZSM-5 composites as model catalysts. We identify abundant critical and/or transient intermediates in dynamic evolution, including carboxylates, alkoxyls, acid-bounded methyl-cyclopentenones and methyl-cyclopentenyl carbocations, providing direct evidence of vigorous regulation by unique, oxygenate-based pathways of the reaction network. This proposed mechanism overturns the general cognition of oxide–zeolite reactions as simple tandem catalysis, and highlights the many roles (both positive and negative) of CO and H2 molecules via oxygenate-based routes, thus dictating the final product. The current characterization technology and its mechanistic understanding would benefit further exploration in bifunctional catalysis.
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Data availability
Data supporting the findings of this study are available within this paper and its Supplementary Information or from the corresponding author upon reasonable request. The datasets for catalytic performance tests of syngas conversion are available in the figshare repository (https://doi.org/10.6084/m9.figshare.19722955.v1).
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Acknowledgements
This work was financially supported by the National Key R&D Programme of China (no. 2021YFA1502803), National Natural Science Foundation of China (grant nos. 21773230, 91945302, 21902158 and 22002165), LiaoNing Revitalization Talents Programme (no. XLYC1807207), China National Postdoctoral Programme for Innovative Talents (no. BX20190321) and the China Postdoctoral Science Foundation (nos. 2019M651161 and 2019M651154). P.G. thanks the Special Assistant Funding of the Chinese Academy of Science. The authors thank Y. Ding for NH3-TPD measurements and S. Li for help in the operation of SEM.
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G.H. conceived the project. G.H., P.G. and Y.J. designed the experiments, analysed the data and wrote the paper. Y.J. and P.G. prepared the catalysts, conducted catalytic tests and carried out NMR measurements. Y.J. carried out structural characterization of catalysts. Z.Z. and K.C. participated in experiment design. D.X. carried out partial NMR measurements. Q.H. and H.C. prepared partial catalysts. Q.H. participated in TEM measurement. All authors participated in the analysis of experimental data and discussion of the results.
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Ji, Y., Gao, P., Zhao, Z. et al. Oxygenate-based routes regulate syngas conversion over oxide–zeolite bifunctional catalysts. Nat Catal 5, 594–604 (2022). https://doi.org/10.1038/s41929-022-00806-2
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DOI: https://doi.org/10.1038/s41929-022-00806-2
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