Kinetics of the decomposition of fructose catalyzed by hydrochloric acid in subcritical water: Formation of 5-hydroxymethylfurfural, levulinic, and formic acids

This paper deals with the dehydration of fructose (F) to 5-hydroxymethylfurfural (HMF) and the rehydration of HMF to levulinic acid (LA) along with formic acid (FA) in subcritical water (sub-CW) in the presence of HCl as catalyst. The experimental conditions were 483-543 K, 4-15 MPa, and residence times of 0.5-300 s. The pressure (in the range of 4-15 MPa) did not affect the decomposition reactions. This differed from other operating variables. The main products were found to be HMF, 2-furaldehyde (2FA), LA, FA, and soluble polymers. The HMF, LA, and FA were also individually subjected for decomposition at the same condition. We found that, during the sub-CW reaction, byproducts (soluble polymers) were produced not only from F but also from HMF. However, we distinguished between two different polymers (i.e., produced from the decomposition of F or HMF) in a proposed reaction model. The kinetics of the sub-CW reaction was developed by considering not only F, HMF, LA, and FA but also soluble polymers. The kinetic constants obtained from the proposed reaction pathway showed good agreement with experimental results.