Catalytic Hydroconversion Of Cellulose To Polyols Over The Al₂O₃and Ru/C Combination Catalyst

Cellulose is one of the most abundant biomass resources in nature. The effectiveand clean conversion of cellulose to sorbitol and C2~C3polyols is of significantimportance for the utilization of biomass energy. In order to achieve the effectiveconversion of cellulose, this thesis focuses on selection of the appropriatecombination catalysts and modification of Al2O3mesoporous materials.The combination of various nanosized acid metallic oxides and Ru/CMK-3catalysts were used in the hydrolytic hydrogenation of cellulose to sorbitol. Thecombination of nanosized γ-Al2O3and Ru/CMK-3catalyst showed a relatively higherconversion of cellulose and better sorbitol selectivity. The acid sites and thehydrogenation sites of various combination catalysts and the distributioncharacteristics of the reaction products were also discussed. The results showed thatthe balance between the acid sites and the hydrogenation sites was crucial to obtainthe high selectivity of sorbitol. When the acid function was excess, the selectivity ofsorbitol would reduce. The effects of the ratio of γ-Al2O3and Ru/CMK-3and reactiontime were examined further. The results showed that a cellulose conversion of49.8%with a sorbitol selectivity of91.2%was obtained within10h at200°C over nanosizedγ-Al2O3and Ru/CMK-3catalysts with a weight ratio of40:1.Ordered mesoporous alumina materials doped with tungsten were synthesized bya sol-gel copolymerization route in the presence of non-ionic surfactants (F127),silicotungstic acid as the source of tungsten. The state of W specie and acid propertyin the materials were characterized by several analysis methods. The results showedthat when the theoretical molar ratio of W/Al was less than0.06, the W specie inW-Al2O3was highly dispersed. When the theoretical molar ratio of W/Al wasbetween0.12to0.24, some WO3crystal could be detected in W-Al2O3material. Andwhen the molar ratio of W/Al was0.24, weak Br nsted acid active sites were detected.The combination of W-Al2O3materials and Ru/C catalysts were used in the catalytichydrogenation of cellulose. The distribution characteristics of the reaction productswere also discussed. And glucose as a probe molecule was used to test the catalyticactivity of the W-Al2O3and Ru/C combination catalysts and the corresponding reaction mechanism was proposed. The results showed that the WO3crystal couldcatalyze the cleavage of the C-C bonds to form ethylene glycol.Mesoporous tungsten aluminium oxide materials were synthesized by adjustingcalcination temperature in the synthesis process of ordered mesoporous W-Al2O3materials. The combination of tungsten aluminium oxide materials and Ru/C catalystswere used in the catalytic hydrogenation of cellulose. The results showed thatsynthetic tungsten aluminium oxide materials at800°C could efficiently catalyze theconversion of cellulose to ethylene glycol. And the effects of reaction time andamount of catalysts were examined further. The results showed that a celluloseconversion of100%and a ethylene glycol yield of42.8%were obtained within1h at245°C over WMA(0.24)-800and Ru/C catalysts with the weight ratio of5:1.