【作者】 张云；

【导师】 陈久岭； 李永丹；

【作者基本信息】 天津大学 ， 工业催化， 2007， 硕士

【摘要】 本文采用沉淀法制备了水滑石母体,煅烧后获得了镁铝复合氧化物MgO-Al₂O₃（MA）催化剂,用X光衍射、热重-差热分析和CO₂程序升温脱附研究了催化剂的性质和结构,在间歇式釜式反应器中全面考察了反应条件如催化剂预处理、反应温度以及不同镁铝配比对大豆油和甲醇酯交换反应制备生物柴油产率的影响,进而研究了镁铝为3:1的MA负载醋酸钾煅烧后获得催化剂的催化活性。结果表明,煅烧后所得的MA中铝离子分布在MgO的晶格中,MA表面有弱碱中心和强碱中心,随MgO含量的升高有增强的趋势,在酯交换反应中起催化作用的主要应为弱碱中心。研究条件下,大豆油精制过程和反应温度对生物柴油的产率影响不大,反应前N₂气氛处理可以活化表面碱中心位,提高生物柴油产率,MA中镁铝比例对催化活性也有明显的影响。在镁铝复合氧化物上通过等体积浸渍法负载醋酸钾煅烧后获得的碳酸钾均匀分布在MA中,二者发生的强相互作用使催化剂表面形成大量的强碱中心。负载KAc的MA的反应活性明显比未负载的高,并且随着醋酸钾负载量的增加,大豆油和甲醇的酯交换反应活性升高,但反应过程中负载的碳酸钾会从镁铝氧化物表面流失。更多还原

【Abstract】 Mg-Al composite oxide （MA） with different atomic ratios of Mg and Al were obtained from the calcinations of hydrotalcite precursor by precipitation. The property and the structure of MA were investigated using X-ray diffraction, thermogravimetry, differential thermal analysis and temperature-progammed desorption of carbon dioxide. The activity of MA in the transesterifiacation of soybean oil and methanol to biodiesel was measured in a batch reactor mounted with a stirrer. The influence of the conditions on the yield of biodiesel, such as catalyst pretreatment, reaction temperature and the composition of MA was studied. Additionally, potassium carbonate supported on MA was prepared by calcination of potassium acetate that was loaded on the surface of MA by dry impregnation method and their activity was also observed.The results showed that the Al ions were distributed in the lattice of MgO crystal in the system of MA and there existed abundant base sites of different strength. The strength of the corresponding base sites tended to increase with MgO content. In the transesterification reaction of the soybean oil with methanol, the base sites of low strength may take in a more important role than those of high strength. There was not clear influence of the refining process of soybean oil and the reaction temperature on the biodiesel yield on MA, however, the pretreatment of MA in N₂ could improve the activity greatly.Potassium carbonate produced after the calcinations of the supported potassium acetate on MA could be dispersed uniformly on the surface of MA and many base sites of high strength were formed in this catalyst system. The activity of the transesterification reaction was increased effectively after the loading of potassium carbonate on MA and the activity was also increased with the content of loading potassium acetate. However, the loss of potassium carbonate in the catalyst system could cause the decrease of the catalytic activity in the transesterification reaction process.更多还原