(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 values^1-8. 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.

References

1          Kuster, B. F. M. The influence of water concentration on the dehydration of d-fructose. Carbohydr. Res. 54, 177-183 (1977).

2          Kuster, B. F. M. & Temmink, H. M. G. The influence of pH and weak-acid anions on the dehydration of d-fructose. Carbohydr. Res. 54, 185-191 (1977).

3          Kabyemela, B. M., Adschiri, T., Malaluan, R. M. & Arai, K. Glucose and Fructose Decomposition in Subcritical and Supercritical Water:  Detailed Reaction Pathway, Mechanisms, and Kinetics. Ind. Eng. Chem. Res. 38, 2888-2895 (1999).

4          Khajavi, S. H., Kimura, Y., Oomori, T., Matsuno, R. & Adachi, S. Degradation kinetics of monosaccharides in subcritical water. J. Food Eng. 68, 309-313 (2005).

5          Girisuta, B., Janssen, L. P. B. M. & Heeres, H. J. Green Chemicals: A Kinetic Study on the Conversion of Glucose to Levulinic Acid. Chem. Eng. Res. Des. 84, 339-349 (2006).

6          Girisuta, B., Janssen, L. P. B. M. & Heeres, H. J. A kinetic study on the decomposition of 5-hydroxymethylfurfural into levulinic acid. Green Chem. 8, 701-709, (2006).

7          Asghari, F. S. & Yoshida, H. Kinetics of the decomposition of fructose catalyzed by hydrochloric acid in subcritical water: Formation of 5-hydroxymethylfurfural, levulinic, and formic acids. Ind. Eng. Chem. Res. 46, 7703-7710, (2007).

8          Kuster, B. F. M. & Van Steen, H. J. C. D. Preparation of 5-Hydroxymethylfurfural Part I. Dehydration of Fructose in a Continuous Stirred Tank Reactor. Starch - Stärke 29, 99-103 (1977).

9          Kimura, H., Nakahara, M. & Matubayasi, N. Solvent effect on pathways and mechanisms for D-fructose conversion to 5-hydroxymethyl-2-furaldehyde: in situ 13C NMR study. J. Phys. Chem. A 117, 2102-2113, (2013).

10        Caratzoulas, S. & Vlachos, D. G. Converting fructose to 5-hydroxymethylfurfural: a quantum mechanics/molecular mechanics study of the mechanism and energetics. Carbohydr. Res. 346, 664-672, (2011).

11        Nikbin, N., Caratzoulas, S. & Vlachos, D. G. A First Principles-Based Microkinetic Model for the Conversion of Fructose to 5-Hydroxymethylfurfural. Chemcatchem 4, 504-511, (2012).