Assessment of ion exchange resins as catalysts for the direct transformation of fructose into butyl levulinate

[Display omitted] •Butyl levulinate synthesis from fructose in aqueous 1-butanol is feasible at moderate temperature on ion-exchange resins.•Gel-type resins with low crosslinking degree are suitable to catalyze the production of butyl levulinate from D-fructose.•An indicator of humins formation is the fact that the amount of formic acid is higher than that of levulinic acid.•A relationship between activity of the resins and their morphology in a swollen state is found. The transformation of fructose into butyl levulinate in aqueous 1-butanol (initial molar ratio 1-butanol/fructose 79, and butanol/water 1.19) has been studied in a discontinuous reactor at 80−120 °C and 2.0 MPa over 8 sulfonic polystyrene-DVB ion exchange resins as catalysts (catalyst loading 0.85–3.4 %). Resins swell greatly in the reaction medium and the reaction takes place mainly in the swollen gel-phase. Swollen resins in water have been characterized by analysis of ISEC data, and spaces originated in the gel phase upon swelling are described in terms of zones of different polymer density. A relationship has been found between the morphology of swollen resins and ester production. Swollen resins with low polymer density show the highest butyl levulinate yield. Dowex 50Wx2 was the most effective because it creates the largest and widest spaces in the gel-phase when swelling. Consequently, it better accommodates the proton-transfer-reaction mechanisms.