Understanding the reaction kinetics of fructose dehydration is important to selectively produce 5-hydroxymethyl furfural (HMF). We conduct kinetic studies of fructose dehydration at temperatures between 75-150 oC with pH values between 0.7 and 1.6 to gain insight into the reaction system. We seek to incorporate known physical phenomena into our kinetic model, including fructose tautomerization and the correct rate-limiting step. Kinetic isotope effect (KIE) experiments using deuterium-labeled fructose confirm that the correct rate-limiting step in fructose dehydration is an intra-hydride transfer. A pseudo-equilibrated protonation and dehydration of fructose followed by the rate-limiting intra-hydride transfer can capture the experimental kinetics and KIE experiments well. We use this information to develop a skeleton dehydration mechanism that integrates the fundamental kinetic experiments and accounts for the KIE, as well as the distribution of fructose tautomers, which changes significantly with temperature. These insights are incorporated in a larger model for dehydration presented in forthcoming work, including a flow reactor model that shows higher temperatures improve the optimum yield of HMF.

Experimental and computational study of Br�nsted acid-catalyzed fructose dehydration kinetics

247th National Meeting (2014)

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