Catalytic conversion of 2,5-furandicarboxylic acid production from hemicellulose

Abstract

2,5-furandicarboxylic acid (FDCA), one of the most important building blocks, has attracted tremendous concerns, and the routes for FDCA synthesis from non-edible hemicellulose are of vital importance from the views of the circular economy. Herein, a multistep process towards hemicellulose-to-FDCA conversion is proposed, including hemicellulose-to-furfural conversion and sequential oxidation to furoic acid (FA), following with cesium furoate (FA-Cs) preparation and its direct carboxylation with carbon dioxide (CO₂). The overall conversion yield of the targeted FDCA product towards the hemicellulose-to-FDCA pathway reaches 29.6%. Many efforts are made on the direct carboxylation reaction of FA-Cs with CO₂ using Cs₂CO₃ as a catalyst. Results show that FDCA with 56.47% yield is achieved via direct carboxylation of FA-Cs at 290 °C for 12 h with 40 mL/min of flowing CO₂. Different from the previous reports, it is demonstrated that drying methods of FA-Cs show significant effects on the yield and properties of the targeted FDCA product. It is found that the conventional drying method is more suitable than the vacuum drying method. From the putative reaction mechanism, the roles of CO₂ and Cs₂CO₃ are elucidated. CO₂ plays a direct role in carboxylation reaction, and excessive Cs₂CO₃ can deteriorate FDCA yield due to the occurrence of decomposition. Interestingly, biochar generated during carboxylation reaction is a promising potential adsorbent, which can efficiently adsorb methylene blue with a removal rate of 96% and an adsorption amount of 80 mg/g. This present work can provide an integrated strategy for both hemicellulose valorization and CO₂ utilization in future.