<br/><br/>Understanding the role of water on acid catalyzed water elimination from primary and secondary alcohols is key for designing active catalysts for the selective conversions bio-derived molecules. The impact of increasing concentrations water on hydronium ion catalyzed elimination reactions of primary and secondary alcohols has been explored kinetically, spectroscopically and by computational chemistry. In the absence of water alcohol dehydration to alkenes and ethers occurs via monomeric and dimeric adsorbed species. The stronger adsorption of the alcohols compared to water shows quantitatively that the reduced dehydration rates in the presence of water rate are not the consequence of the competitive adsorption between 1-propanol and water. The impact of water to reduce the dehydration rate is caused by the water-induced differences in stabilization of reactants and transition states. Water stabilizes the adsorbed state of the alcohol significantly more than the transition state, leading to the higher activation barrier for elimination step. This gradually changes as the concentration of water increases making the size of the hydronium ion a key parameter in the rates of reaction. The quantification of the elementary steps in this catalytic chemistry allows separating the impact of the environment in stabilizing ground and transition states from the role of the size of the hydronium ion. The parameters to select zeolite catalysts for the highest rates of elimination reactions will be discussed.<br/>

Impact of water on dehydration of alcohols on molecular sieves

251st National Meeting (2016)

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