【Frontiers in HaiChuan Chemical Technology】Dalian Institute of Chemical Physics uncovers the mechanism by which the accessibility of acid sites on molecular sieves regulates the conversion efficiency of syngas

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The mechanism by which the accessibility of acid sites on molecular sieves regulates the conversion efficiency of syngas has been revealed. Publication date: 2025-03-10. Recently, the Research Group on Carbon-Based Energy Catalytic Conversion (Group 522) at the Nanoscale and Interface Catalysis Research Center, part of the **Key Laboratory of Catalytic Fundamentals** in our institute, led by researchers Jiao Feng, Pan Xiulian, and Academician Bao Xinhe, made new progress in the study of direct syngas conversion. They uncovered the mechanism by which the accessibility of acid sites on molecular sieves influences the conversion efficiency of syngas, providing new insights into the mechanisms governing mass transfer in molecular sieves and aiding in the design of high-performance molecular sieve catalysts. Zeolite molecular sieves are widely used in the field of energy chemistry due to their unique pore structure and excellent shape-selective catalytic properties. However, this inherent advantage also leads to diffusion limitations, making it difficult for target molecules to effectively reach the internal active sites and thereby hindering an increase in catalytic efficiency. Although researchers have conducted extensive studies on the mass transfer mechanisms within molecular sieves, there is still a lack of quantitative understanding regarding the relationship among the morphological structure of molecular sieves, mass transfer efficiency, and catalytic activity. Mordenite (MOR) molecular sieves possess a unique pore structure, in which the acidic sites within the 8-membered rings serve as active sites for syngas conversion, while the 12-membered ring pores act as pathways for molecule transport. In this study, the research team used MOR molecular sieves as model catalysts to conduct an in-depth analysis of the mass transfer effects of MOR with different 12-membered ring pore lengths (2L) in syngas conversion, and established a quantitative relationship between the accessibility of active sites and catalytic performance. By analyzing the relationship between the effective diffusion length (2𝑙), the Thiele modulus, and the effective factor of reaction rate, the research team determined that in the syngas conversion reaction, a 12MR pore length of 60 nm is close to the critical threshold for eliminating diffusion limitations. Based on this, the research team optimized the ZnAlOx-MOR bifunctional catalyst, achieving excellent performance with a carbon monoxide (CO) conversion rate of 33% and an ethylene selectivity of 69%. In 2016, this team proposed the design concept of a dual-functional OXZEO® catalyst that combines metal oxides with molecular sieves, enabling the high-selective production of C2–C4 alkenes (Science, 2016). Following breakthroughs in basic research, the team collaborated with Academician Liu Zhongmin’s team at our institute as well as Shaanxi Yanchang Petroleum (Group) Co., Ltd. to complete, in 2020, a kiloton-scale industrial test of the world’s first innovative technology for directly producing low-carbon olefins OXZEO®-TO from coal via syngas. At the same time, the team conducted systematic research on the catalytic mechanisms of metal oxides and molecular sieves, as well as the dual-function matching and coupling mechanisms, and achieved a series of advancements (Angew. Chem. Int. Ed., 2018) ； Angew. Chem. Int. Ed., 2019 ； Angew. Chem. Int. Ed., 2020 ； Nat. Commun., 2022 ； Natl. Sci. Rev., 2022; J. Am. Chem. Soc., 2022; Science, 2023 ； Angew. Chem. Int. Ed., 2023; J. Am. Chem. Soc., 2024; J. Am. Chem. Soc., 2024). The OXZEO® concept offers new approaches for the resource utilization of coal, natural gas, and carbon dioxide, and has attracted widespread attention and research (Chem. Rev., 2021). The relevant research findings, titled “Maximizing the Accessibility of Acid Sites Within Zeolite Catalysts for Syngas Conversion,” were recently published in Angewandte Chemie International Edition and selected as a VIP (Very Important Paper) article. The first author of this work is Dr. Wang Haodi, a graduate from Group 522 of my institute. This research was supported by projects such as the **Key R&D Program**, the National Natural Science Foundation, the Liaoning Provincial Natural Science Foundation, the Dalian Science and Technology Innovation Fund, and the innovation fund of our institute.