Etherification and reductive etherification of 5-(hydroxymethyl)furfural: 5-(alkoxymethyl)furfurals and 2,5-bis(alkoxymethyl)furans as potential bio-diesel candidates

A low energy intensive process for the production of diesel fuel has been delineated from both 5-(hydroxymethyl)furfural (HMF) and its sugar precursor D-(–)-fructose. Alcoholic solutions of the above produced a mixture of potential bio-diesel candidates namely, 5-(alkoxymethyl)furfural, 5-(alkoxymethyl)furfural dialkylacetal, and alkyl levulinate, in the presence of solid acid catalysts. Sulfonic acid functionalized resins, Amberlyst-15 and Dowex DR2030 showed exceptional reactivity and selectivity for these reactions. Production of another potential diesel candidate 2,5-bis(alkoxymethyl)furan has been optimized through both sequential reduction/etherification and one-pot reductive etherification processes. During the metal catalyzed hydrogenation of HMF, platinum showed an exclusive selectivity for the reduction of the carbonyl functionality of HMF. Both Pt and Pt/Sn supported on Al2O3 catalysts have been optimized for the production of 2,5-bis(alkoxymethyl)furan from HMF. The reaction mechanisms of etherification and reductive etherification have been discussed in detail on the basis of intermediates observed during these processes.