Vol. 9, Special Issue 4, Part A (2023)

Abstract
Furfural and 5-hydroxymethylfurfural (5-HMF) have been recognized as valuable biomass-derived platform chemicals and bridges between biomass raw materials and the biorefinery industry, utilizing as a building-blocks for the production of many chemicals and fuels. Biorefinery refers to a facility that integrates biomass conversion to produce fuels, power, heat and value-added chemicals from biomass. The biorefinery concept is thus analogous to today’s petroleum refinery which produces multiple fuels and products from oil. Furfurals are important intermediates in the chemical industry. They are produced by homogeneous catalysis in an aqueous solution. The elimination of homogeneous mineral acids makes the reaction mixtures less corrosive, produces less waste and facilitates easy separation and recovery of the catalyst. Furfural is produced in the dehydration of xylose and HMF is formed from glucose and fructose. They are formed only in the presence of an acidic catalyst. Bases are not active in dehydration reactions but do catalyze the isomerization of monosaccharides which are favourable when using glucose as a raw material. Lignocellulosic biomass, a cheap and plentiful resource could play a key role in the production of sustainable chemicals. The simple sugar contained in the renewable lignocellulosic biomass can be converted into commercially valuable products such as 5-hydroxymethylfurfural (5-HMF). Finding an active and stable water-tolerant solid acid catalyst still poses a challenge for the production of furfural (furan-2-carbaldehyde) and 5-(hydroxymethyl)-2-furaldehyde (5-HMF). This review summarizes catalytic conversion approaches, focusing on the heterogeneously catalyzed formation of furfural. The attractiveness of catalytic concepts is evaluated, keeping in mind productivity, sustainability and environmental footprint. The study is targeted at gaining an understanding of the key aspects of catalyst design and development for sugar chemistry and therefore attention is also given to heterogeneous catalysis related to HMF.