Production Of Furfural From Xylose, Hemicelluloses And Lignocellulose Using Chlorides As Catalysts

Utilizing renewable biomass resources to produce fuels and high value-added chemicals can alleviate the problems of environmental pollution and energy crisis caused by fossil resources. Furfural is an important platform compound that can be obtained from lignocellulose biomass. However, the commercial furfural production process employing mineral acid as the catalyst will cause equipment corrosion, large amount of wastewater production and difficulty in separating mineral acids from the products. In view of these problems, new efficient methods for furfural production have been proposed. In this thesis, xylose, xylan-type hemicelluloses and xylose-rich lignocellulose were used as feedstock, and chlorides were employed as catalysts. The influences of chloride species, solvent systems and reaction conditions on furfural production were investigated under the different heating methods.Xylose was applied as the feedstock for the furfural production. The effect of different chlorides on furfural synthesis was studied in a homogeneous H2O-dimethyl sulfoxide(H2O-DMSO) system by heating in an oil bath. The results showed that Sn Cl4 was the most effective chloride for furfural synthesis from xylose, and the paired chlorides catalyst(Sn Cl4/Li Cl) can be further improved the furfural yield. Moreover, the effects of composition of catalyst, concentration of catalyst and xylose, reaction temperature and time, volume of DMSO on furfural production were also investigated by using Sn Cl4/Li Cl as catalysts. The highest furfural yield of 63.0% was obtained over Sn Cl4/Li Cl(4Sn Clχ = 0.8) at 130 oC for 6 h, with the concentration of catalyst of 0.33 mol/L and initial concentration of xylose of 0.05 g/m L in H2O-DMSO(5:5, V/V) system.Xylan-type hemicelluloses were used as the feedstock for the furfural production. The effect of different metal chlorides on furfural synthesis was studied in the aqueous system by the oven-heating method. It was found that Sn Cl4 showed the highest catalytic activity for transformation of beech xylan to furfural and the catalytic mechanism was proposed. In addtion, the effects of the single aqueous system and the biphasic system 2-methyltetrahydrofuran/H2O(2-MTHF/H2O) on furfural synthesis were investigated comparatively. The results showed that furfural yield obtained from the biphasic system was much higher than that from the aqueous system. The highest furfural yield of 78.1% was achieved at 150 °C for 2 h with the ratio of xylan: H2O: 2-MTHF of 1:50:20(g: m L: m L) and the amount of Sn Cl4 of 0.1 mmol. Morever, the influence of hemicelluloses with different chemical and structural features on the furfural synthesis was also discussed. The furfural yield to some extent was determined by the xylose content in hemicelluloses, and hemicelluloses with the high molecular weight and the high crystallinity could be favorable to synthesis furfural both in aqueous and biphasic systems.Lignocellulose(corncob and bagasse) rich in xylose were used as the feedstock. The process for furfural production was catalyzed by Sn Cl4 using microwave-assisted hydrothermal method. The effects of catalyst amount, reaction temperature and reaction time on the hydrolysate and solid residues were studied. The results showed that the addition of Sn Cl4 was also suitable for furfural synthesis from lignocellulose, Sn Cl4 can greatly promote the dissolution and hydrolysis of hemicelluloses, and further dehydration of pentose to furfural. The highest furfural yield of 9.0 wt% was achieved from the one-step conversion of corncob at 190 °C for 0 min with the amount of Sn Cl4 of 0.1 g and the solid-to-liquid ratio of1:20.