Catalytic dehydration of C6 carbohydrates for the production of hydroxymethylfurfural (HMF) as a versatile platform chemical

Interest in utilizing biorenewable feedstocks to produce fuels and chemicals has risen greatly in the past decade due to the economic, political and environmental concerns associated with diminishing petroleum reserves. A fundamental challenge lying ahead in the development of efficient processes to utilize biomass feedstock is that, unlike their petroleum counterparts, biomass contains an excess amount of oxygen. Therefore, catalytic strategies such as dehydration and hydrogenolysis amongst others have been extensively studied as platform technologies for deoxygenation. In this review, we primarily discuss the catalytic dehydration of C6 carbohydrates to 5-hydroxymethylfurfural, which has attracted much attention due to the versatility of using furanic compounds as an important platform intermediate to synthesize various chemicals. The emphasis is on the fundamental mechanistic chemistry so as to provide insights for further catalyst/catalytic system design. After separately discussing fructose and glucose dehydration, this review summarizes recent progress with bi-functional catalyst systems for tandem glucose/fructose isomerization and subsequent fructose dehydration, thereby realizing highly selective HMF production directly from the more abundant and cheaper C6 sugar feedstock, glucose.