Molecular Routes of Dynamic Autocatalysis for Methanol-to-Hydrocarbons Reaction
- 28 July 2021
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 143 (31), 12038-12052
- https://doi.org/10.1021/jacs.1c03475
Abstract
The industrially important methanol-to-hydrocarbons (MTH) reaction is driven and sustained by autocatalysis in a dynamic and complex manner. Hitherto, the entire molecular routes and chemical nature of the autocatalytic network have not been well understood. Herein, with a multitechnique approach and multiscale analysis, we have obtained a full theoretical picture of the domino cascade of autocatalytic reaction network taking place on HZSM-5 zeolite. The autocatalytic reaction is demonstrated to be plausibly initiated by reacting dimethyl ether (DME) with the surface methoxy species (SMS) to generate the initial olefins, as evidenced by combining the kinetic analysis, in situ DRIFT spectroscopy, 2D 13C–13C MAS NMR, electronic states, and projected density of state (PDOS) analysis. This process is operando tracked and visualized at the picosecond time scale by advanced ab initio molecular dynamics (AIMD) simulations. The initial olefins ignite autocatalysis by building the first autocatalytic cycle—olefins-based cycle—followed by the speciation of methylcyclopentenyl (MCP) and aromatic cyclic active species. In doing so, the active sites accomplish the dynamic evolution from proton acid sites to supramolecular active centers that are experimentally identified with an ever-evolving and fluid feature. The olefins-guided and cyclic-species-guided catalytic cycles are interdependently linked to forge a previously unidentified hypercycle, being composed of one “selfish” autocatalytic cycle (i.e., olefins-based cycle with lighter olefins as autocatalysts for catalyzing the formation of olefins) and three cross-catalysis cycles (with olefinic, MCP, and aromatic species as autocatalysts for catalyzing each other’s formation). The unraveled dynamic autocatalytic cycles/network would facilitate the catalyst design and process control for MTH technology.Keywords
Funding Information
- National Natural Science Foundation of China (21703239, 21991092, 22032005, 22072148)
- DICP (DICP I202121)
- the High Level Talents Innovative Support Plan of Dalian (2019RQ031)
- The Key Research Program of Frontier Sciences, Chinese Academy of Sciences (QYZDY-SSW-SC024)
- International Partnership Program of Chinese Academy of Sciences (121421KYSB20180007)
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