Catalytic Conversion Of Biomass-derived Furfural And Levulinic Acid Into Chemicals And Oxygenated Fuels

Biomass resource is a carbon-neutral renewable resource. Because biomass resource is the only one which can be converted into conventional liquid, solid and gaseous fuels and other chemicals among the renewable resources, it has a unique advantage in the process of substitution of fossil resources. Biomass can be converted into the bulk but low value-added products, such as liquid fuels and high value-added chemicals such as succinic acid, sorbitol and glycerin through bio-refinery process. Biomass-based platform molecules are important bridges which linked the biomass feedstocks and target products such as fuels, fuel additives and chemicals. The development of simple and inexpensive process for the preparation of platform molecules and efficient conversion of platform molecules into fuels and chemicals are significant to improve the competitiveness of biomass resources to fossil resources.Furfural and levulinic acid are two important platform molecules in the biomass conversion process. Furfural can be obtained from the hemicellulose in the lignocellulosic biomass. At present, the catalysts in large-scale industrial production of furfural are inorganic acids. However, there are some problems of traditional inorganic acid catalysts, such as equipment corrosion and environmental pollution. In order to solve the above problems, we developed a tantalum hydroxide-based solid acid catalyst TA-p to catalytic convert D-xylose to furfural. On the basis of the conversion of D-xylose to furfural, we have established a multi-step catalytic conversion of furfural into poly(butylene2,5-furandicarboxylate)(PBF) for the first time.Levulinic acid could be cost-effectively produced from lignocellulosic materials via acid hydrolysis process in high yields. Additionally, the LA derivatives which feature with proper combustion properties and energy density have the potential to serve as fuel additives. Among them, valerate esters as novel oxygenated fuels could be blended in both gasoline and diesel. Currently the preparation of valerate esters has been reported, but there is still lack of the research on the efficient conversion of levulinic acid into valerate esters in one step. We have developed a bifunctional catalyst Ru/SBA-SO3H to achieve efficient catalytic one-step conversion of levulinic acid into valerate esters as oxygenated fuels.Chapter1presetned the concepts of biomass resources and biorefineries, then a brief overview of the use of biomass in several ways and biomass-based platform molecules was introduced. We reviewed of the preparation of furfural and the transformation of furfural and levulinic acid.Chapter2described the solid acid catalyst TA-p in water-organic solvent biphasic system for selective catalytic conversion of D-xylose to furfural. This process was performed both in a batch reactor and a continuous fixed-bed reactor. In the batch process, D-xylose conversion and furfural yield were significantly affected by the organic solvents, reaction temperature and time.1-butanol, which could be obtained through the fermentation of biomass-based carbohydrates, was selected as organic phase and the highest furfural yield of59%was achieved with D-xylose conversion of96%at180℃in the continuous process. Moreover, the long-time stability test for80h under the optimal conditions showed excellent stability of TA-p.Chapter3studied a multi-step route of catalytic conversion of furfural into2,5-furandicarboxylic acid-based polyester PBF with total carbon utilization. Catalytic oxidation of furfural into furoate could be easily achieved with a selectivity of93%at100%furfural conversion. The best results of catalytic disproportionation of furoate to furan and2,5-furandicarboxylate were obtained with the selectivity to2,5-FDCA of86%at61%furoate conversion. We have presented a new pathway of converting furfural which was a bulk biomass-based chemical into the key monomer2,5-FDCA of2,5-furandicarboxylic acid-based polyester with a good overall selectivity (80%for the two-step process). This route provides a hitherto important yet neglected strategy linking the platform molecule furfural from C5sugars and2,5-FDCA from C6sugars. It opens a new pathway for biorefinery and further study of the process is necessary. Moreover, furan was converted into1,4-BDO with the highest selectivity of70%at99%furan conversion. The furan-based polyester PBF was prepared from2,5-FDCA and1,4-BDO with total carbon utilization of furfural.Chapter4mainly discussed the hydrogenation of levulinic acid to valerate esters over supported Ru catalysts. The suitable acidity and proper hydrogenation activity of catalyst were the key factors for the reaction. A bifunctional catalyst Ru/SBA-SO3H was developed as active catalyst and characterized. The increase in the amount of acid sites on the support improved the selectivity to EV and VA, and the highest yield of94%to EV and VA was achieved. Probable reaction pathways were proposed and verified.Finally, we summaried the full paper and outlook the future work. In summary, this paper focused on two important platform molecules of furfural and levulinic acid in biomass conversion. The efficient conversion of D-xylose to furfural, a new route of conversion of furfural into2,5-furandicarboxylic acid-based polyester and the hydrogenation of levulinic acid to valerate esters in one-step with heterogeneous catalysis were achieved.