Catalytic conversion of fructrose, glucose and cellulose to 5-(hydroxymethyl)furfural (HMF)

Abstract

The current dominant raw material for the energy and chemical sectors worldwide is crude oil. Within the last few years, petroleum prices have increased, geo-political stability has decreased, and supply has been threatened, driving a renewed interest across academic, government, and corporate centres to utilise biomass as an alternative raw material. The quest to make useful chemicals and fuels, which are potentially versatile intermediates between bio-based carbohydrate chemistry and petroleum-based organic chemistry, is among the most active research areas in chemistry. Many of the most promising alternatives for the sustainable supply of fuels and valuable chemicals are biomass resources. However, this process requires both economically and environmentally efficient methods before a biorefinery platform can be built on the basis of this route. In this research, the high-yield conversion of fructose, glucose and cellulose to the versatile intermediate 5-hydroxymethylfurfural (HMF) is described. The role of different transition metal salts in dithiocarbamate-based, hydrogensulfate-based and chloridebased ionic liquids in this process was investigated. Among all those investigated, the chromium(III) chloride catalyst system in hydrogensulfate-based ionic liquids was found to be the most effective method for conversion of fructose, giving an HMF yield of 96% whereas a chloride-based ionic liquid was found to be the most effective method for converting glucose to HMF, achieving a yield of 90%. Little or no side products (such as formic acid, levulinic acid, or humins) were observed, indicating the selectivity of the system. The activity of various catalysts for the conversion of fructose to 5-hydroxymethylfurfural (HMF) was investigated under different conditions including lower and higher temperatures and addition of co-solvents. The most challenging of the substrates investigated was cellulose, representing the closest substrate to untreated biomass. The best yield of HMF obtained from this substrate was 58% after one hour at 150 °C, which compares well with leading values in the literature. In these studies, the effects of temperature, substrate concentration, co-solvent addition and the nature of the ionic liquid were all investigated.