Direct conversion of furan into levulinate esters via acid catalysis

This study developed a method for the direct conversion of the biomass-derived furan to the methyl levulinate, a platform molecule, via acid-catalysis in dimethoxymethane/methanol. Dimethoxymethane acted as the electrophile to transform furan into 2-methoxymethyl-furan (the ether of furfuryl alcohol). The following step of acid catalysis converted 2-methoxymethyl-furan to methyl levulinate. No hydrogenation catalyst or hydrogen was used in the process, which was the new reaction route for the conversion of furan to the value-added levulinic acid/ester. Polymerization was the main challenge in this reaction route, which could be suppressed but to some limited extent with methanol as a co-reactant/solvent in the reaction medium. The polymerization of furan and cross-polymerization reactions between dimethoxymethane (the reactant) and methyl levulinate (the targeting product) via Aldol condensation were the important reasons for the decreased production of methyl levulinate. The DRIFTS and TG-MS studies showed that the coke formed from the polymerization of furan contained more aliphatic structure, more carboxylic groups and methyl groups, while the coke from methyl levulinate contained more carbonyl groups and more conjugated A-bonds, projecting the structural difference of furan and methyl levulinate.