Preparation Of Cerium Zirconium Catalyst And Its Application To Liquid Phase Hydrogenation Of Cellulose

With the rapid development of economy and technology,severe energy shortage and environmental issues have been brought.To seek a kind of environment-friendly renewable energy has been became an improtant task of sustainable develpoment strategy.Biomass resources have become a hot topic because of their renewbility and rich reserves.Cellulose is an important component of biomass resources in nature,which has large content and wide contrubition.The production of hydrolysis of cellulose has high value-add,and their utilization not only can reduce environmental pollution,but also can mitigate the energy crisis.Ethylene glycol?EG?is an important chemical intermediate,which is mainly prepared through the hydration of ethylene oxide in the lower reaches of ethylene.The price varies with the fluctuation of the price of crude oil.The application of its production and subsequent products has been seriously affected.The new production route of EG has become one of the key points of the people's attention.Due to the complexity of the production of cellulose hydrolysis,single target product yield was low.To obtain high yield of EG,a high efficiency,inexpensive catalyst is necessary.In this paper,cellulose was selectively converted to EG by research suitable Ru/CeO2 catalyst,and modified CeO₂ to obtaine higher yield of EG.Different morpgologies of CeO₂ were prepared by hydrothermal method and the deposition of noble metal Ru on CeO₂ via reduction of the metals salt precursor by NaBH₄.To study the physicochemical properties of the ctalysts,XRD?SEM?TEM and XPS were used to characterize the catalysts.The catalysts were applied to the catalytic hydroliquefaction of cellulose.The effects of reaction conditions such as reaction temperature?reaction time?initial H₂ pressure and Ru loading et al.on the catalytic hydrogention of cellulose were also investigated.The results showed that the optimum process conditions for the preparation of ethylene glycol by catalytic hydrogention of cellulose were as follows:the reaction temperature was 240?,the reaction time was 2 h,the initial H₂ pressure was 4.0 MPa and the load of Ru was 1.0%of the mass of the carrier,and the morpgology of CeO₂ was nanorods.Under these conditions,the conversion of cellulose and the yield of ethylene glycol were 100%and 44.80%,respectively.In addition,the liquid products of catalytic hydrogention of cellulose were analyzed,the results showed that in this catalyst system,the product of polyol mainly included ethylene glycol,and a small amount of 1,2-propanediol and glycerol.At the same time,metal Zr modified CeO₂ catalysts were also prepared by hydrothermal method and the different Ce/Zr mole ratios of 1.0%Ru/Ce_xZr_1-xO₂ were obtained.To compare with pure 1.0%Ru/r-CeO₂ catalyst,the results showed that under the optimum reaction conditions,when Ce/Zr=8/2,the modified catalysts demonstrated best catalytic performance,that the cellulose was completely converted and the yield of ethylene glycol increased to56.79%.Under this catalytic system,the process of catalytic hydrogention of cellulose:in the high-temperature water,cellulose was hydrolyzed to glucose with H⁺,The existense of Ce³⁺was benificial to C-O of glucose,and the existense of Zr⁴⁺was benificial for glucose tetro-aldol condensation reaction,then obtained the final product EG.Metal Zr modified CeO₂ catalysts Ru/Ce_xZr_1-xO₂,was used to catalyze the hydrogenation of cellulose,the result showed that the catalysts could increase the yield of EG to 58.23%,and the total yield of polyols was 73.81%.