Small Molecules Effective for Conversion of Lignocellulosic Biomass to Furfural and Its Derivatives

This review summarizes recent applications of small organic and inorganic molecules as catalysts or solvents (chemical hands and scissors) in the production of furfural (FA), 5-(hydroxymethyl)furfural (HMF), and 5-(chloromethyl)furfural (CMF). The possible transformation of lignocellulosic biomass into a one-pot configuration and two-step technique based on the preliminary separation of hemicellulose, lignin and cellulose with the subsequent hydrolysis of separated polysaccharides is compared and discussed. Interestingly, these rather simple and cheap molecules are catalytically active and enable a high rate of conversion of polysaccharides into furfural and its derivatives. Usually, elevated pressure and reaction temperatures above 150 °C are necessary for effective hydrolysis and dehydration of in situ formed monosaccharides; nevertheless, ionic liquids or deep eutectic solvents enable a significant decrease in the reaction temperature and performance of the discussed process at ambient pressure.