5-hydroxymethylfurfural and furfural production in biphasic systems: kinetic studies of autocatalytic operation and using EDTA as thermoresponsive catalyst

Abstract

5-hydroxymethylfurfural (HMF) and furfural are highly praised chemicals in the biofuel context, derived from fructose (Fruc) and xylose (Xyl), respectively. Here a H2O/MIBK biphasic system is used as a green approach to extract in situ the furans generated in each reaction, thereby mitigating undesired reactions of rehydration and/or self-condensation to humins. The production of HMF and furfural is performed through two approaches: an autocatalytic reaction and using a thermoresponsive catalyst, hence facilitating recycling. Ethylenediaminetetraacetic acid (EDTA) was identified as a thermoresponsive organic acid with high recyclability (>97 % catalytic activity recovery after 5 cycles and regeneration) acting as homogeneous catalyst under reaction conditions. After proving the lack of mass transfer limitations and considering the reaction networks and mass balances for HMF and Fur production, macrokinetic models were proposed to describe the two reactions in a biphasic medium. In the autocatalytic regime, the values of the activation energy of the dehydration of Fruc to HMF and Xyl to furfural were 155.72 ± 12.84 kJ mol−1 and 138.09 ± 7.45 kJ mol−1, respectively, whereas in the presence of EDTA as catalyst, the dehydration of Fruc to HMF showed a value of 139.12 ± 8.40 kJ mol−1 and that of Xyl to furfural of 130.33 ± 9.49 kJ mol−1.