Selective oxidation of methanol over supported vanadium oxide catalysts as studied by solid-state NMR spectroscopy |
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| Authors: | Danlin Zeng Hanjun Fang Anmin Zheng Jun Xu Lei Chen Jun Yang Jiqing Wang Chaohui Ye Feng Deng |
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| Affiliation: | aState Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, PR China |
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| Abstract: | Methanol catalytic oxidation over VOx/Al2O3, VOx/ZrO2 and VOx/MgO catalysts has been studied by solid-state nuclear magnetic resonance (NMR) spectroscopy. It was found that stronger acid sites in VOx/Al2O3 result in almost the same selectivities for dimethoxymethane, paraformaldehyde and formic acid, and weaker acid sites in VOx/ZrO2 favor the formation of paraformaldehyde, while the VOx/MgO catalyst with the base support shows high selectivity for formate. Supporting VOx species on γ-Al2O3 and ZrO2 leads to the formation of Brønsted acid sites as revealed by the adsorption of probe molecules. The acid strength of Brønsted acid sites on the VOx/Al2O3 catalyst is found to be stronger than that of the VOx/ZrO2 catalyst which has the acid strength similar to zeolite HZSM-5's. The proposed bridging hydroxyl models accounting for the Brønsted acid sites formation were also confirmed by quantum chemical calculation. |
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| Keywords: | Methanol oxidation Vanadium oxide Solid-state NMR |
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