New Insight into the Hydrocarbon‐Pool Chemistry of the Methanol‐to‐Olefins Conversion over Zeolite H‐ZSM‐5 from GC‐MS,Solid‐State NMR Spectroscopy,and DFT Calculations |
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| Authors: | Dr. Anmin Zheng Dr. Jun Xu Dr. Qiang Wang Pan Gao Guodong Qi Prof. Yanjun Gong Prof. Dr. Feng Deng |
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| Affiliation: | 1. Wuhan Center for Magnetic Resonance, State Key Laboratory, Magnetic Resonance and Atomic Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (P.R. China), Fax: (+86)?27‐87199291;2. State Key Laboratory of Heavy Oil Processing, CNPC Key Laboratory of Catalysis, China University of Petroleum‐Beijing, Beijing 102249 (P.R. China) |
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| Abstract: | Over zeolite H‐ZSM‐5, the aromatics‐based hydrocarbon‐pool mechanism of methanol‐to‐olefins (MTO) reaction was studied by GC‐MS, solid‐state NMR spectroscopy, and theoretical calculations. Isotopic‐labeling experimental results demonstrated that polymethylbenzenes (MBs) are intimately correlated with the formation of olefin products in the initial stage. More importantly, three types of cyclopentenyl cations (1,3‐dimethylcyclopentenyl, 1,2,3‐trimethylcyclopentenyl, and 1,3,4‐trimethylcyclopentenyl cations) and a pentamethylbenzenium ion were for the first time identified by solid‐state NMR spectroscopy and DFT calculations under both co‐feeding ([13C6]benzene and methanol) conditions and typical MTO working (feeding [13C]methanol alone) conditions. The comparable reactivity of the MBs (from xylene to tetramethylbenzene) and the carbocations (trimethylcyclopentenyl and pentamethylbenzium ions) in the MTO reaction was revealed by 13C‐labeling experiments, evidencing that they work together through a paring mechanism to produce propene. The paring route in a full aromatics‐based catalytic cycle was also supported by theoretical DFT calculations. |
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| Keywords: | carbocations olefins reaction mechanisms solid‐state NMR spectroscopy zeolites |
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