(6eq) Production of Furan-Based Products from Lignocellulosic Biomass

Lignocellulosic biomass has great potential for producing alternative fuels and chemicals. In particular, furan-based products such as HMF and furfural are attractive intermediates of biofuels and chemicals. Various conversion technologies for furan-based products have been investigated; however, there are still some challenges including low productivity, formation of by-products, complexity of reaction, high cost of catalysts, and difficulty of product separation. In order to overcome the aforementioned barriers, two novel processes for furan-based products were developed.

The first approach is a biphasic process for production of 5-bromomethyl furfural (BMF). BMF is a furan derivative with high reactivity and easy to be converted to other chemicals, and it is also an intermediate of furan-based biofuels. The reported in this study was a single step biphasic system including an aqueous phase of molten salt hydrate with mineral acid as catalyst and an organic phase of extracting solvent. The BMF was produced in the aqueous phase and immediately extracted into the organic phase to prevent the further decomposition and condensation. The production of BMF from different substrates including monosaccharides, polysaccharides, and real biomass was investigated. Under the optimum conditions, BMF yield from cellulose reached 90.3 %. The effects of reaction factors including acids loading, concentration of halide salt, and volume ratio of organic to aqueous phase were investigated. Different molten salt hydrates solutions (LiBr, LiCl and CaBr₂) were also compared to convert cellulose into halidemethyl furfurals (BMF/CMF). The application of biphasic system improved the products selectivity and prevented the formation of byproducts (humins).

The second approach for production of furan-based products from biomass is a one-pot process (HDA) integrating hydrolysis of polysaccharides to monosaccharides, dehydration of the monosaccharides to furans, and aldol condensation of the furans with acetone to produce furan acetone adducts as hydrocarbon precursors. The conversion was completed in a LiBr/acetone system without pretreatment or preprocessing of the biomass. Acetone was not only used as a solvent but also a reactant involved in aldol condensation reactions. Halide salt (LiBr) and hydrochloric acid (HCl) were used as catalysts in the process. According to the experimental results, halide salts play crucial roles in all three reactions above. A series of experiments were performed to optimize reaction factors for efficient conversion of corn stover. A product yield of 78% was obtained under the optimum conditions. In the meantime, lignin was significantly depolymerized and separated from other components during the process as a potential valuable co-product (HDA lignin). Most of LiBr and HCl (99%) were recyclable.