【作者】 何黎；

【导师】 杨儒；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2011， 硕士

【摘要】 纤维素是最丰富的生物质资源之一,纤维素的转化主要集中在酸水解和贵金属催化加氢,但酸水解容易产生环境问题,贵金属价格昂贵。因此寻找廉价的非贵金属催化剂绿色转化纤维素成为研究重点。过渡金属铜基催化剂是一种廉价的加氢催化剂,但其用于催化纤维素加氢反应方面鲜见报道。本论文以纤维素为原料,使用Cu基催化剂进行催化加氢反应,采用环境友好的方式转化纤维素。本课题以碳酸钠为沉淀剂,采用共沉淀法制备了Cu体系和Ni体系多元氧化物催化剂,采用化学吸附水解法制备了碱土金属氧化物负载CuO催化剂。着重研究了具有不同阴离子的铈盐(Ce(SO4)2、Ce(NO3)3)、CuO摩尔含量和Zn/Ce比例对CuO/ZnO/CeO2催化剂产物的影响。通过XRD、SEM、BET、TG、XPS、EDX以及TPR等表征手段分析了催化剂的物理结构、化学结构及还原性能,通过纤维素加氢反应对催化剂进行了活性评价,采用HPLC、ESI-MS和FT-IR等表征手段对加氢反应的液态产物进行了表征,研究了催化剂类型和反应条件对纤维素转化率和加氢产物产率的影响。实验表明,经共沉淀法制备的CuO/ZnO/CeO2催化剂前躯体为非晶态,煅烧后的物相主要是CuO, ZnO和Ce02,从TEM表征可以看出催化剂均为类球形,加入ZnO后,颗粒尺寸在10nm左右,ZnO和Ce02能促进CuO的分散,降低催化剂的还原温度。铈源的种类影响催化剂的物理结构和化学结构,采用硝酸铈为铈源时,催化剂比表面积为42.08m2·g-1～80.49m2·g-1,催化剂失重率为26%～29%,还原温度在250℃以下。采用硫酸铈为铈源,催化剂比表面积为7m2·g-1～28m2·g-1,催化剂失重率为13%～24%,还原温度在250℃以上。纤维素加氢反应中,催化剂种类、反应时间和反应温度均对纤维素转化率和产物产率造成影响。使用CZAl 361、CZCS 361、CMg-01和CSr-01作为催化剂时,6MPa H2,250℃反应120min,纤维素转化率可达100%。使用CuO/ZnO/CeO2作为催化剂,相同条件下以硫酸铈为铈源时,纤维素转化率较高,生成糠醇、乙酰丙酸以及其它小分子类化合物,而以硝酸铈为铈源时,纤维素转化率普遍低于硫酸铈铈源,但催化剂加氢效果较好,生成多元醇,如山梨糖醇和甘露糖醇及一些小分子化合物。更多还原

【Abstract】 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.更多还原