Fructose Dehydration to 5-HMF over TiO2 acid catalysts

The valorization of the biomass is, nowadays, considered an eco-sustainable approach for the production of biofuels and added value platform molecules. 5-HydroxyMethylFurfural (5-HMF) can be considered one of the most important molecule [1] obtained from the cellulosic part of biomass, starting from which various intermediates as polymer feedstocks, chemicals and fuels can be derived by mean of a thermal/acid catalysed process. In the present work, we investigated different solid sulfonic catalysts based on titania support on the hydrothermal dehydration of fructose to 5-HMF (Fig.1). The catalytic performance of the synthesized materials were evaluated in hydrothermal conditions leading to the formation of 5-HMF. The reaction was carried out at different temperature both in water and 50:50 water/organic solvent mixture (3:7 sec-BuOH/MIBK) biphasic batch during 3h of reaction. According to preliminary results, the best catalytic activity was achieved when the sulfonic group is directly linked to the titania support. For this catalyst a total fructose conversion with a yield in 5-HMF of 65 % was reached when water/organic solvent mixture was used as reaction medium. Interestingly, in the presence of the most performant catalyst, a very good yield of 5-HMF (ca. 50%) was reached also by using only water as solvent. The surface and structural properties of the catalysts were investigated by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermo-gravimetrical analysis (TGA), N2 adsorption isotherms and acid capacity measurements performed on both fresh and spent materials. These material characterizations allowed to correlate the physical and chemical catalysts properties with their activity versus the reaction of fructose dehydration to 5-HMF.