Studying Methanol Conversion with NMR

Studying Methanol Conversion with NMR

Author: Angewandte Chemie International Edition

The methanol-to-hydrocarbons (MTH) reaction promises to be a major source for fuel and olefins in a post-oil society. Consequently, the reaction is under close scrutiny and more than 20 “direct” mechanisms, whereby methanol/dimethyl ether molecules are combined to form ethene, have been proposed for the initial C–C bond-forming step alone.

Zhongmin Liu, Yingxu Wei, and colleagues, Dalian Institute of Chemical Physics, China, have used in situ solid-state NMR spectroscopy to study methanol conversion over a zeolite catalyst (HZSM-5) at 300 ºC. Using solid-state cross-polarization magic angle spinning 13C NMR spectroscopy, the team detected a methyleneoxy analogue on the surface of HZSM-5, which originated from surface-activated dimethyl ether.

This finding provides evidence for a direct mechanism in the MTH reaction, where a C–H bond activation of adsorbed dimethyl ether or methanol by neighboring surface methoxy groups or trimethyloxonium cations is a prelude to the first C–C bond formation step of C1 reactants.


 

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