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 H-1 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.