The Preparation And Characterization Of Cu-Based Catalyst And The Study On Catalytic Hydrogenation Of Cellulose

Cellulose is the most abundant resources of raw materials, the main convert methods of cellulose are acid hydrolysis and hydrogenation catalyzed by noble metals. The acid hydrolysis may cause environmental problems and the high cost, limited supply of noble metals will suppress their applications towards industrial production. Therefore, it is urgent to develop new materials to convert cellulose environment-friendly. In this case, non-noble metal materials such as copper-based catalysts which are typical hydrogenation catalysts have been studied as promising alternative candidates. Up to now, there is few study reported on their applications in catalytic hydrogenation of cellulose. In our work, we use cellulose as the raw material, the no-noble Cu-based multiple oxides catalysts were used towards hydrogenation of cellulose.The Cu-based and Ni-based catalysts were prepared by co-precipitation method using sodium carbonate as the precipitating agent and the CuO supported on alkaline earth metal oxides catalysts were prepared by the chemisorption-hydrolysis method. The focus is on the different hyrogenation products catalyzed by CuO/ZnO/CeO2 catalysts which is caused by different sources of cerium (Ce(SO4)2, Ce(NO3)3), the molar content of Cu and the molar ratio of Zn/Ce. The physical structure, chemical structure and reduction performance of catalysts were characterized by XRD, SEM, BET, TG, XPS, EDX and TPR. The hydrogenation activities of catalysts were evaluated by hydrogenation of cellulose. Liquid reaction products were characterized by HPLC, ESI-MS, FT-IR and so on. Influences of the kind of catalysts and reaction conditions on the conversion of cellulose and the yield of hydrogenation products were discussed.Experiment results indicated that the main phase of CuO/ZnO/CeO2 catalysts prepared by precipitation method was CeO2, ZnO and CuO. It can be obseved from the TEM images that the catalysts were spherical with the particle size about 10 nm. ZnO and CeO2 can promote the dispersion of CuO and reduce the reduction temperature of the catalysts. The sources of Ce affected on the physical and chemical structure of catalysts. When using cerium sulfate as source, the catalysts surface area were 7 m2·g-1-28 m2·g-1, weight loss of the catalysts were 13%-24%, the reduction temperature of the catalysts were higher than 250℃. While using cerium nitrate as source, the surface area of catalysts were 42.08 m2·g-1-80.48 m2·g-1, weight loss of the catalysts were 26%-29%, the reduction temperature of the catalysts were mostly lower than 250℃.In the hydrogenation reaction, the conversion of cellulose and the yield of products were influenced by the kind of the catalysts, reaction time and reaction temperature. When using CZA1 361, CZCS 361, CMg-01 and CSr-01 as catalysts and 6 MPa H2,250℃,120 min as the reaction condition, the conversion of cellulose can reach 100%. Under the same reaction conditions, when using CuO/ZnO/CeO2 as catalyst, the catalysts produced by cerium sulfate source had higher conversion of cellulose, the hydrogenation products were furfural, levulinic acid and other small molecule compounds. While using catalysts produced by cerium nitrate source, the conversion of cellulose was generally lower, but a better hydrogenation product of polyols, such as sorbitol, mannitol and other small molecule compounds, were obtained.