用于加氢制备二醇反应中的高效纳米铜基及镍基催化剂的合成及其性能研究

【作者】 郭秀英；

【导师】 戴维林；

【作者基本信息】 复旦大学 ， 物理化学， 2010， 硕士

【摘要】 乙二醇(EG)是一种重要的有机化工原料,主要用来生产聚酯纤维、防冻剂、不饱和聚酯树脂、非离子表面活性剂、乙醇胺以及炸药等。传统的制备乙二醇路线是基于石油路线的环氧乙烷水合法,七十年代世界石油危机的冲击,使人们认识到石油资源的有限性,因此开发利用我国丰富的煤和天然气资源,发展碳一化工具有重要的战略意义和经济意义。非石油路线的碳一路线合成乙二醇是指经由CO氧化偶联生成草酸二甲酯(DMO),DMO再加氢合成乙二醇(EG),其中草酸二甲酯加氢制备乙二醇是实现工业化的关键步骤,具有重要的经济价值。目前,介孔材料由于其具有较大的孔径、较高的比表面积及高的热稳定性,常常用来作为催化剂载体。与普通载体相比,介孔材料负载的催化剂由于其能更好的分散和稳定活性物种,因此常常具有较高的活性、选择性以及稳定性。1,2-丙二醇(1,2-PDO)的用途十分广泛,可用于食品添加剂和药物溶剂,还可以用来生产不饱和树脂、药品、化妆品、涂料和防冻剂等。1,2-丙二醇的普遍合成路线是环氧丙烷水合法,但存在着成本偏高、环境污染和石油枯竭的问题。随着生物柴油的广泛兴起,甘油作为大量的副产物出现了,因此利用甘油氢解制备二醇,取代石油路线具有重要意义。本论文研究了铜基催化剂上草酸二甲酯加氢制备乙二醇和铜、镍基催化剂上甘油氢解制备二醇(即乙二醇和1,2-丙二醇),关键是催化剂的制备和结构与其催化性之间的能关系。取得的主要结果如下：采用简单的蒸氨法一步制备了负载量分别为20-60wt%的Cu／SBA-15催化剂,具有较高的比表面积及高的热稳定性,TEM表征发现其仍保留介孔SBA-15的长程有序结构,XRD表征其颗粒较小为17.2-27.5 nm。将这些Cu／SBA-15催化剂用于DMO加氢,发现50wt%的Cu／SBA-15催化剂的活性和EG的选择性最佳,在473 K、3 MPa、H2／E=100以及DMO LHSV=0.6 ml/gcat.h的时候,DMO转化率为100%,EG的得率为99%。作为对比,采用传统的浸渍方法制备了含量为50wt%Cu／SBA-15催化剂发现CuO的颗粒较大,为40.3 nm左右,这表明部分CuO以较大的颗粒分布在载体的外表面,几乎没有催化活性。我们首先用共沉淀法制备了不同Cu：A1比例的Cu／Al2O3催化剂,发现在Cu：Al为1：1的时候氢解活性最高。加入适量的Zn之后,得到高活性的Cu／ZnO／Al2O3催化剂,其中摩尔比Cu：Zn：Al2O3为4：2：4时候具有最高活性：在甘油92%的转化率条件下,乙二醇的选择性高达99%。通过BET、XRD、TEM和TPR系列表征了催化剂的物理化学性质。Raney Ni催化剂(骨架Ni)具有类似海绵形貌的结构,表现出较高加氢反应活性。表征结果显示,Raney Ni催化剂主要由金属态的Ni组成,颗粒大小为4.64 nm。系统研究了一种新的反应条件下Raney Ni催化剂催化甘油氢解制备二醇(EG和1,2-PDO)。反应条件温和,不需要氢气气氛,常压反应：在10wt%的甘油水溶液在453 K,0.1 MPa N2条件下极短的时间内就可以达到100%甘油转换率和58.5%的二醇得率。更多还原

【Abstract】 Ethylene glycol (EG), an important chemical widely used in antifreeze and polyester manufacture, is universally produced from petroleum-derived ethylene via its epoxidation in the present industrial approach. However, this process is greatly restricted by the dwindling petroleum resource. In this respect, the indirect synthesis of EG from syngas via the coupling of CO with nitrite esters to obtain oxalates and then hydrogenation of oxalates to EG has huge potential both in the economic and environmental persistent development.It is well known that mesoporous materials which possess high surface area, large pore volume, regular structure, uniform pore size distribution, and relative high thermal stability have drawn much attention in the field of separation, adsorption, and drug delivery. Immobilization of nanoscopic materials in such high-surface area supports with improved catalytic activity and product selectivity is a task of great economic and environmental importance in the chemical industries.Propylene glycol (PG), used as high value-added speciality chemical intermediates, are widely used for manufacturing polyester fibers, unsaturated polyester resins, antifreeze, pharmaceuticals and other important products. At present, PG is mainly produced from the hydration of corresponding epoxy alkanes, which are commonly derived from a petrochemical approach. However, as crude oil resource shrinks, synthesis of the two diols from biomass glycerol attracts more and more interest. In this work catalytic hydrogenation of dimethyl oxalate to glycerol and catalytic hydrogenalysis of glycerol to diols on Cu catalyst and Ni catalyst has been studied in details. Through characterizations, the effect of bulk structure and surface component of catalysts on the catalytic performance were investigated.Ultra-high (50%) copper contented mesoporous Cu/SBA-15 catalysts were successfully prepared through the simple ammonia-driving deposition-precipitation method. The catalyst shows high copper dispersion and perfect activity in the selective hydrogenation of DMO to EG, much better than that of the catalyst prepared by the traditional impregnation method. The catalyst with a copper content of 50 wt% also exhibited the best catalytic performance at 0.6 h-1,while the conversion of DMO was kept at 100% and the selectivity to EG was above 99%. Such promotion can be ascribed to the much smaller particle size, much higher dispersion of copper species, and more resistance to sintering. With the rapid development of the bio-diesel industry by transesterification of seed oils with methanol, glycerol of renewable origin, as a by-product of bio-diesel production, seems to be an attractive option as a new feedstock. Catalysts containing an active copper compound such as Cu-chromite, Cu-ZnO, Cu-SiO2 or Cu-Al2O3 are active in glycerol hydrogenation. Cu/Al2O3 and Cu/ZnO/Al2O3 catalysts with high copper content and high copper dispersion were successfully synthesized via the simple co-precipitation method that can efficiently catalyze the hydrogenolysis of glycerol to 1,2-propanediol in an autoclave. Cu/Al2O3 (molar ratio:1/1)proved as effective for the production of 1,2-propanediol because of the high selectivity (about 90.1%),but the conversion of glycerol is relative low (about 71.3%). As addition of ZnO, Cu/ZnO/Al2O3 (molar ratio:4/2/4) catalyst shows higher conversion of glycerol (about 92.5%) and keeps high selectivity (about 99.0%). The physical and chemical properties of these catalysts have been studied through various characterization methods such as BET, XRD, TEM and TPR.Raney-Ni catalysts (skeletal catalysts) with a ponge-like structure are one kind of well-known catalyst used in several hydrogenation processes. The prepared Raney-Ni catalysts mainly contains of metal Ni, about 4.64 nm. A new and efficient catalytic route for the production of PG and EG by catalytic combination of glycerol aqueous reforming and hydrogenation of glycerol has been developed using the Raney Ni catalyst. The reaction conditions are much milder than those previously reported, since no hydrogen was needed and the reaction can be conducted under ambient pressure. At 453 K,0.1 MPa of N2 conditions the reaction can get 58.5% diols yield and the 100% conversion of glycerol solution(10wt%).更多还原