Furfural and Chemical Routes for Its Transformation into Various Products

Vegetable biomass is basically made up of C₆ and C₅ sugars which constitutes of cellulose, hemicellulose and lignin along with other energy storage products like lipids and starches. The global interest and need to reduce the dependency on crude oil for energy have motivated and directed the researchers and scientists to explore the field of biomass as a source of energy especially for transportation fuels for vehicles. Gradual development of technology has shifted the interest to derive the conventional petroleum-based chemicals from biomass components with functional groups. Henceforth catalytic reactions, various chemical routes via heterogeneous catalysis, homogeneous processes, enzyme reactions for transformation and conversion of lignocellulosic biomass to various bio-based value-added chemicals have been extensively and widely explored, with special interests on developing environmentally friendly processes involving mineral acids, bases, etc.

Chemical transformation of sugars, which are made up of monosaccharide and disaccharides (glucose, fructose, xylose), is the most important and explored reaction pathway due to its availability in biomass primary compounds. Three important nonpetroleum-based chemicals, i.e. furfural (FUR), 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA), are derived via thermal dehydration of pentose and hexose sugars. FUR is one of the important chemicals derived from biomass and also one of the key derivatives for producing significant nonpetroleum-derived chemicals. The annual production of FUR is about 300,000tTonne/year. FUR is commercially produced by hydrolysis of pentosan polymers in biomass to pentose sugars (xylose) which undergo acid catalysis under high temperatures and successive dehydration. Furfuryl alcohol (FAL) is one such important product produced from catalytic hydrogenation of FUR. Cannizzaro reaction of FUR further produces furoic acid (FuA) which is an important feedstock for organic synthesis and an intermediate compound in the production of medicines and perfumes. Further, hydroxymethylation of FUR with formaldehyde is the commercial method for producing hydroxymethylfurfural (HMF). Commercial production of furan and tetrahydrofuran (THF) is also via catalytic decarbonylation and successive hydrogenation of FUR.

The different kinds and types of catalysts used in these processes of hydrogenation, alkylation and reduction by various researchers over the period of time also need to be properly combined in a single source, so as to create an updated library of various reaction pathways done so far with FUR to produce various kinds of value-added chemicals.