草酸二甲酯气相法加氢制乙二醇催化剂研究进展

乙二醇是重要的化工原料，广泛应用于阻冻剂、燃料电池和聚酯工业等领域。传统制备乙二醇路线有基于石油路线的环氧乙烷水合法以及基于煤和天然气路线的C₁合成法。C₁路线合成乙二醇是CO氧化偶联生成草酸二甲酯，草酸二甲酯再催化加氢合成乙二醇。设计和制备高效草酸二甲酯加氢催化剂是实现煤制乙二醇工业化关键。草酸二甲酯加氢催化剂主要有Ru基均相催化剂和Cu基非均相催化剂，其中，无Cr的Cu基催化剂(Cu/SiO₂) 是研究重点。影响Cu/SiO₂ 催化性能的主要有载体、制备方法和助剂。载体类型不仅影响活性物种与载体之间的相互作用，而且影响活性物种分散度，具有高表面积和有序介孔结构的载体能够提高Cu物种分散度，从而显著提高催化剂活性。制备Cu/SiO₂催化剂的方法有蒸氨法、浸渍法、沉积沉淀法、离子交换法和溶胶-凝胶法等。蒸氨法制备的Cu/SiO₂形成铜氨络合离子，使Cu物种得到很好分散，还原后催化剂表面Cu+含量较高。Mo、Co、Ni和B等助剂的添加可以调变Cu物种的价态和分散度，提高催化剂性能。添加助剂时，要综合考虑助剂的引入对催化剂酸碱性质、活性物种分散度和载体孔径结构等的影响。研究认为，草酸二甲酯加氢机理是Cu⁰与Cu⁺的协同作用，Cu⁰是催化剂上的活性位点，活化H₂；Cu⁺起亲电子的L酸作用，激化CO键提高草酸二甲酯中酯基的反应。催化剂失活的主要原因是产物乙醇酸甲酯在催化剂表面较难脱附以及反应过程中催化剂烧结。Cu/SiO₂催化剂存在热稳定性差等缺陷，制备高稳定Cu基催化剂是今后发展方向。

Research progress in the catalysts for vapor phase hydrogenation of dimethyl oxalate to ethylene glycol

Ethylene glycol （EG） is an important fine intermediate, which is conventionally used in the fields of antifreeze,fuel cell and polyester manufacture,etc. There are two kinds of synthetic routes of ethylene glycol ： the hydration of ethylene oxide depended on the petroleum resource and the hydrogenation of oxalate based on the syngas route from the coal or natural gas. The latter route is suitable for the situation of China, and is the focus of this review. During the indirect synthesis of EG from syngas,dimethyl oxalates（DMO） are firstly synthesized via the coupling of CO with nitrite esters, and then are catalytically hydrogenated to EG. The designment and preparation of highly active catalysts for DMO hydrogenation are the key to realize the industrialization of coal to EG. The catalysts for DMO hydrogenation to EG mainly include homogeneous ruthenium-based catalysts and homogeneous copper-based catalysts. Cu/SiO2 catalysts, non-chromium Cu-based catalysts, are nowadays research focus of DMO hydrogenation catalysts. Three key factors affecting the catalytic performance of Cu/SiO2 catalysts are supports,assistants and preparation methods. The types of supports can affect not only the interaction between the active species and supports, hut also the dispersion of copper species. Supports with large surface areas and ordered mesoporous structure can improve the dispersion of copper species, and then greatly promote the activity and stability of Cu catalysts. The preparation methods of Cu/SiO2 catalysts include impregnation, deposition-precipitation, ammonia evapo- ration,and sol-gel method, etc. When CufSiO2 catalysts were prepared by ammonia evaporation method, copper-ammonia complex ions formed on the catalysts, which resulted in well dispersion of Cu species, and Cu ＋ contents on the surface of CufSiO2 catalysts after reduction were higher. The promoters, such as Mo, Co, Ni and B, etc, could modulate the valence and dispersion of Cu species greatly, and then improve the performance of the catalysts.