(239h) Understanding the Alcohol Dehydration On Metal Oxides

A fundamental understanding on the dehydration of simple alcohols can help us elucidate and eventually control the selective dehydration of polyols and complicated biomass molecules to value-added chemicals. Herein, we use Density Functional Theory (DFT) calculations to study the alcohol dehydration on group XIII oxides, including γ-Al₂O₃ which is a commonly used support in heterogeneous catalysis. Both E1 and E2 type of dehydration mechanisms for primary (ethanol, 1-propanol), secondary (2-propanol), and tertiary (2-methyl-2-propanol) alcohols were investigated. In addition, we considered possible coupling reactions between reactants, products and dehydration intermediates. A key finding is that the dehydration barriers of the alcohols correlate linearly with the corresponding carbenium ion stability (alcohol property) [1]. This is because the transition state of the alcohol dehydration has carbenium characteristics. By accounting for the acid strength of the active site, the basic strength of the surface oxygens and the substitution degree of the alcohol, structure-property relationships were developed. Our results explain several experimental observations.

[1] Roy S., Mpourmpakis G., Hong D.-Y., Vlachos D.G., Bhan A. and Gorte R.J., ACS Catal. 2, 1846−1853 (2012)