Catalytic transfer hydrogenation of sugarcane bagasse in ionic liquid and alcohol media for enhanced fructose and sorbitol production

Catalytic transfer hydrogenation (CTH) process and ionic liquids (ILs) are common methods for biomass transformation used to produce biochemicals from lignocellulosic biomass (LCB). This study employed an IL combined with a CTH process to valorize and transform sugarcane bagasse (SCB), aiming to co-produce fructose and sorbitol. This was achieved using a Paar reactor under various operating conditions optimized by a response surface methodology (RSM) using the Box-Behnken design (BBD). The two ILs, [1-Allyl-3-mim][Cl] and [1-Allyl-3-mim][HSO4], were tested for their catalytic potential in a CTH process using pure glucose and fructose in an alcohol medium. The [HSO4]-based catalyst showed higher activity than the Cl-based catalyst, stemming from its dual functionality namely efficient solvent and catalyst that can initiate the hydrolysis step. Specifically, 33.27% fructose and 61.08% sorbitol were obtained with 97.6% glucose conversion in 1,4-butanediol, while the Cl-based catalyst in 1,4-butanediol produced 28.6% fructose and 32.23% sorbitol at 99.56% glucose conversion. The [HSO4]-based ionic liquid (IL) was chosen for further optimization using SCB as the feedstock, and the results demonstrated how parameters (time, temperature, stock, and catalyst loading) affected yields of fructose and sorbitol, reaching 44.12% and 46.17%, respectively, under optimal conditions with [1-Allyl-3-mim][HSO4] + 1,4-butanediol system. The impact of these operating parameters, and the alcohol medium used were clear, as shown by the differences in yields when using SCB versus pure glucose, which can be attributed to the recalcitrant nature of SCB (comprising lignin, hemicellulose, and cellulose) which often influences the yields especially when the biomass is not pretreated. Overall, the production of both sorbitol and fructose from glucose strongly supports the potential of using SCB which contains convertible glucose units as a green feedstock for biochemical production. Graphical Abstract: