Fast and continuous synthesis of 2,5-furandicarboxylic acid in a micropacked-bed reactor

Oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) is of great importance for the production of biopolymer. It is regarded as a representative of the heterogeneous process, in which the reactant in the gas phase and liquid phase interact with each other over the solid catalysts. Due to the low mass-transfer efficiency and co-existence of O2 and organic compounds in the batch reactor, low catalytic efficiency and safety concerns hiders the commercial application. Herein, a micropacked-bed reactor was used to realize the efficient and ultrafast continuous-flow synthesis of FDCA. Au/CeO2 was used as a catalyst and O2 was used as a green oxidant. Owing to the enhanced gas − liquid mass transfer efficiency, an HMF conversion of 100% and an FDCA selectivity of 90 % were achieved within only 41 s, which represents a space–time-yield of 1–2 orders of magnitude higher than that of traditional reactors. By virtue of the minimized internal and external mass transfer resistances, kinetic parameters of the reaction were determined. The rate constants were more than one order of magnitude higher than those of other strategies. In addition, the oxidation of HMFCA to FFCA was determined to be the rate-controlling step. Overall, this work not only delineates an efficient strategy for synthesizing FDCA from HMF, but also opens a new avenue for enhancement of heterogeneous reactions suffering from limited mass transfer.