Experimental and modeling studies on the acid-catalyzed conversion of inulin to 5-hydroxymethylfurfural in water

Inulin is considered as an attractive feed for the synthesis of 5-hydroxymethylfurfural (HMF), an important biobased platform chemical with high application potential. We here report a systematic study to optimize the HMF yield from inulin in a batch reactor for reactions in water using sulphuric acid as the catalyst. The latter was selected on the basis of a screening study with seven organic- and inorganic Brönsted acids (H2SO4, HNO3, H3PO4, HCl, trifluoroacetic acid, maleic acid and fumaric acid). The effect of process conditions such as temperature (160-184 °C), inulin loading (0.05-0.17 g/mL), sulphuric acid concentration (0.001-0.01 M) and reaction time (0-60 min) on HMF and levulinic acid (LA) yields were determined experimentally and subsequently modeled using non-linear multivariable regression. The highest experimental HMF yield was 39.5 wt% (50.6 mol%) and was obtained at 170 °C, an inulin loading of 0.17 g/mL, a sulphuric acid concentration of 0.006 M and a reaction time of 20 min. Agreement between experiments and model for both HMF and LA yield was very satisfactorily.