(793b) On the Fructose Dehydration Kinetics in Aqueous HCl: An Integrated Experimental and Physics-Based Modeling Approach
Furans are a class of chemicals readily obtained from biomass that can be used as intermediates for the production of valuable fuels and chemicals. In particular, 5-hydroxymethylfurfural (HMF) can be derived from fructose through Brønsted acid catalyzed dehydration. However, several side reactions also occur in this same acidic medium: fructose can degrade to humins and HMF can rehydrate to formic and levulinic acids or polymerize to humins. Understanding the effect of process parameters on these reactions is therefore important for designing processes. There have been several efforts to study the kinetics of fructose dehydration at varying temperatures or pH values1-8. These efforts have relied heavily on a phenomenological approach using lumped models for fructose dehydration using empirical expressions for the effect of pH and ignoring the tautomeric composition of fructose.9-11 In the present work, a two-step reaction model is formulated and used to represent fructose dehydration. This model is based on prior computational work in our group11as well as on insights from kinetic isotope experiments carried out in order to identify the rate limiting step of the dehydration mechanism. We conducted 45 different kinetic experiments with varying concentrations of either fructose or HMF comprising over 1500 data points in total over a range of temperatures and pH values. These data are fitted simultaneously using least-squares nonlinear regression to determine the pre-exponentials and activation energies of all reactions considered with constraints from our prior first-principles modeling. In summary, the present work brings together for the first time a comprehensive experimental data set and physical insights to develop a model that describes the production of HMF from fructose while accounting for experimental and computational advances in the field.
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