One-pot conversion of fructose to levulinic acid over hydrothermally treated carbon from rice husk: adjustment of operating parameters

Abstract

A novel and environmentally benign solid catalyst was successfully synthesizedthrough hydrothermal treatment of rice husks with phosphoric acid for the efficientproduction of levulinic acid from fructose. The physicochemical properties of thesynthesized catalyst were investigated using nitrogen physisorption, X-ray diffraction, thermogravimetric analysis, potentiometric titration, temperature-programmedreduction, scanning electron microscopy, Fourier transform infrared spectroscopy,and energy-dispersive X-ray spectroscopy. Batch reactions for the transformation offructose into levulinic acid were carried out in a high-pressure Parr reactor undercontrolled conditions. The experiments were performed within a temperature rangeof 130–170 °C and over reaction times spanning from 1 to 7 h. Aqueous fructosesolutions at concentrations between 5 and 20 wt% were tested using a fructose-tocatalyst mass ratio between 2.8 and 11.1, with the system pressurized to 10 bar usingnitrogen to maintain an inert atmosphere and suppress undesired side reactions. Thecatalytic system demonstrated high efficiency in promoting the acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural, followed by its subsequent rehydration to levulinic acid. The results showed that a maximum levulinic acid yield of55% was achieved under optimal conditions: a 10 wt% fructose concentration, afructose-to-catalyst mass ratio of 3.7, a reaction temperature of 150 °C, and a reaction time of 5 h.