A Computational Chemical Investigation of the Dehydration and Dehydrogenation of Ethanol on Oxide Catalysts

Yuji SHINOHARA*, Tsuyoshi NAKAJIMA, Satoshi SUZUKI, Shozi MISHIMA*1 and Hideaki ISHIKAWA*2

* Graduate School of Science and Technology, Shinshu University, Wakasato 500, Nagano-shi, 380 Japan
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*1 Cooperative Research Center, Shinshu University, Wakasato 500, Nagano-shi, 380 Japan
*2 Superconductivity Research Laboratory, International Superconductivity Technology Center,
1-10-13 Shinonome, Koto-Ku, Tokyo, 135 Japan

(Received: June 11, 1997; Accepted for publication: October 13, 1997 ; Published on Web : November 26, 1997)

A computational chemical investigation has been made into the mechanisms of the dehydration and the dehydrogenation of ethanol on six oxide catalysts (SiO2, TiO2, ZnO, MnO, MgO and CdO) using the DV-Xa method. Transition state models of the consecutive mechanism including ethoxide formation and the concerted mechanism proposed by Eucken and Wicke were computed.
By comparing the computed results with experimental ones published in the literature, it was concluded that the consecutive mechanism is more reasonable than the concerted one. It was also concluded that the rate-determing step of the ethanol dehydration is for a b-hydrogen shift to a surface oxide ion and that the ease of the shift is a factor controlling the dehydration/ dehydrogenation selectivities of oxide catalysts.

Keywords: DV-Xa method, Ethanol, Dehydration, Dehydrogenation, Oxide catalyst, Reaction mechanism

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