Selective Oxidation of Furfural to Succinic Acid over Lewis Acidic Sn-Beta

Selective production of succinic acid from furfural with H2O2 over Sn-Beta, a pure Lewis acid catalyst, is reported. Under optimized reaction conditions, 53% yield of succinic acid was obtained, and the catalyst was recyclable. 2(3H)-Furanone was detected as an intermediate using 1H nuclear magnetic resonance (NMR), HH correlation NMR spectroscopy, liquid chromatography–mass spectrometry (MS) and gas chromatography–MS. Kinetic modeling revealed that Baeyer–Villiger oxidation of furfural to 2(3H)-furanone was accelerated in comparison to other competing reactions in the presence of the pure Lewis acidic Sn-Beta catalyst. The Lewis acid density of the Sn-Beta catalyst was directly correlated to the formation rate of products, confirming a Lewis acid-catalyzed mechanism. Detailed characterization showed that Sn-Beta activates furfural by coordinating to the carbonyl group and does not activate H2O2. On the other hand, the parent HBeta-38 zeolite produced activated H2O2 in solution, which caused side reactions to produce maleic acid. Selectivity of Sn-Beta was also compared with that of TS-1, another Lewis acid zeolite, which produced maleic acid because of the ability of TS-1 to activate H2O2 as a hydroperoxy species. Therefore, Sn-Beta is a selective and reusable catalyst for succinic acid synthesis from biomass-derived furfural.