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鉴于我国“富煤缺油少气”的资源结构特点,煤制乙二醇作为现代煤化工五大示范工程之一,已于2009年列入国家石化产业振兴规划中。因此研究以煤为原料经合成气中CO氧化偶联合成草酸酯随后再加氢制乙二醇的工艺具有重要的研究价值及应用前景。基于本工艺的关键步骤草酸酯加氢反应中面临的铜基催化剂构效关系和活性位不明确等问题,本文对铜催化剂中铜物种的结构和价态形成的关系,及草酸二甲酯加氢的活性位等科学问题进行了研究。通过对蒸氨水热法制备Cu/SiO2催化剂的过程进行系统表征,发现制备过程中形成的铜氨络合离子能与混合液中的氧化硅表面的羟基以及带负电的氧原子分别发生脱水反应或静电吸附,能够有效的均匀负载铜物种在载体表面,从而增强载体与金属的相互作用。焙烧后的催化剂结构中主要存在层状硅酸铜和高分散的纳米CuO两种铜物种,在一定条件下还原4h后,在其表面分别形成Cu+和Cu0物种。通过改变Cu/SiO2催化剂的铜负载量的方式进一步调控结构中的层状硅酸铜和纳米CuO的相对含量,可调控还原后表面的Cu0和Cu+的相对量,从而获得了催化剂结构与加氢反应性能的构效关系规律。通过定量表面的Cu0和Cu+,并将其与目标产物的转化频率关联,得出Cu0在加氢反应中作为主要的活性位,而Cu+物种主要促进乙醇酸甲酯等中间产物的转化。同时关联Cu0/(Cu++Cu0)与反应速率发现草酸二甲酯加氢反应存在适宜的Cu0与Cu+比例,两者显示出协同作用。
In view of the resource structure of our country, “rich in coal, less fuel and less gas”, coal-to-ethylene glycol has been included in the revitalization plan of the national petrochemical industry in 2009 as one of the five major demonstration projects of modern coal chemical industry. Therefore, it is of great research value and application prospect to study the process of synthesis of oxalate by CO oxidative coupling in synthesis gas and subsequent hydrogenation of ethylene glycol to coal. Based on the key steps of this process oxalate hydrogenation reaction facing the structure-activity relationship of copper-based catalyst and the active site is not clear and so on, this paper on the copper catalyst copper species structure and valence state formation, and dimethyl oxalate Hydrogenation of active sites and other scientific issues have been studied. The results showed that Cu (superscript 2 +) and Cu (superscript 2 +) formed during the preparation of Cu / SiO 2 catalyst could be dehydrated with the hydroxyl groups on the surface of silicon oxide and the oxygen atom with negative charge respectively. Or Electrostatic adsorption, can effectively uniform load copper species in the carrier surface, thereby enhancing the carrier and the metal interaction. After calcination, there are two kinds of copper species, layered copper silicate and highly dispersed nano CuO. After reduction for 4 h under certain conditions, Cu + and CuO species are formed on the surface of the catalyst. By changing the Cu loading of Cu / SiO2 catalyst, the relative contents of CuO and CuO in the structure can be further controlled by adjusting the relative content of CuO and CuO in the structure. The catalytic structure and hydrogenation Reactive properties of the structure-activity relationship. By quantifying Cu0 and Cu + on the surface and correlating them with the conversion frequency of the target product, Cu0 was found to be the predominant active site in the hydrogenation reaction while Cu + species mainly promoted the conversion of intermediate products such as methyl glycolate. At the same time, Cu0 / (Cu + + Cu0) and the reaction rate were found to have suitable Cu0 and Cu + ratio in the hydrogenation of dimethyl oxalate, which showed synergistic effect.