Supramolecular active center model (left), 13C-27Al double resonance NMR spectrum of "Carbon pool" species (right)

The Deng Feng research group of Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, has made new progress in the research of "supramolecular active centers" for the reaction of methanol to olefins with zeolite molecular sieves. The results of the research are published in the "German Applied Chemistry".

The MTO (methanol-to-olefins) reaction of zeolites catalyzed by methanol to ethylene, propylene and other light olefins has become the core technology in the petrochemical field instead of petroleum production bulk chemicals, low-carbon olefins. However, the reaction mechanism of the MTO process is still not very clear, which restricts the development of high-efficiency catalysts to some extent. A unique phenomenon in the MTO reaction is that the “hydrocarbon pool” species (such as carbocation and polytoluene) limited in the pores of the molecular sieves have a catalytic effect, and the role of the acid sites of the molecular sieves is also indispensable, which is considered in the MTO reaction. There may be a "supramolecular active center" composed of the "hydrocarbon pool" species and the framework acid sites of the molecular sieve, but there is no direct experimental evidence for the existence of the "supramolecular active center" and its mechanism of action in the MTO process.

Recently, the research team's Xu Jun, Wang Chao, and Wang Qiang used 13C-27Al double-resonance solid state NMR technology developed in the previous period to directly observe the 13C (“hydrocarbon pool” organics) in the study of the MTO reaction of the zeolite molecular sieve ZSM-5. The interaction between the species) and 27Al (inorganic molecular sieve framework aluminum) confirmed the existence of "supramolecular active sites"; the use of 12C/13C isotope exchange NMR experiments clarified the role of "supramolecular active centers" in the MTO reaction: The "hydrocarbon pool" species that have strong interactions with the molecular sieve framework aluminum and are spatially adjacent exhibit high reactivity, and the "hydrocarbon pool" species far from the framework aluminum of the molecular sieve has lower reactivity. This result is of great significance for the development of methanol chemistry and revealing the MTO reaction mechanism. The research work was supported by the National Natural Science Foundation of China.

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