The Synthesis Of High-efficient Cu/ZrO₂ Catalyst And Its Application In The Hydrogenation Of Dimethyl Oxalate

Ethylene glycerol (EG), as an important chemical, which can be used in the synthesis of polyester, polyester fibre, hygroscopic, plasticizer and nonionic surfactant. As crude oil resource shrinks, traditional resource-based petroleum chemical industry should adjust its raw material route and product structure to the raw materials and products diversification direction.Traditionally, EG was synthesized from ethylene oxide which is excessively dependent on the petroleum resource, therefore the C1 route starting from dimethyl oxalate (DMO) to EG has attracted much attention,including the development of new catalyst in the gas-phase hydrogenation of DMO to EG, which is the key to the route of its industrialization. The reported catalysts are mostly restricted to metallic copper as a main active component, neutral silica as carrier, while the study of non-silica based materials is rare. Zirconia materials, which own excellent properties of high hardness, high toughness, high wear resistance, chemical resistance, acid-base and redox properties, become a new type of carrier with many interests. In this thesis, by constructing efficient copper-based zirconia catalyst, the synthesis of EG under mild conditions was made. Systematic investigations on the size effect as well as promoter effect of the copper based catalysts were performed.As carrier, acid sites on the surface of zirconia promote further etherification of ethylene glycol to 2-ME when using methanol as the solvent.2-ME, which has bothhydroxyl and ether group, has been extensively applied in industry. Current synthesis methods of 2-ME are based on ethylene, which is a petroleum-based raw material. The synthesis of 2-ME from DMO is therefore very important to the adjustment of Chinese energy structure and the reduction of dependence on oil resources.We choose the vapor selective hydrogenation of DMO as a probe reaction by optimizing the synthesis conditions, acid-base properties of the catalyst, active ingredient loading and bimetallic composition to obtain nanometer copper-based catalyst with high catalytic performance, which can also provide fundamental guidance for the future industrial applications. The main work and results of this thesis are as follows:1. Synthesis approach effect of Cu/ZrO2 catalyst and their influences on the catalytic performance of hydrogenation of DMO.Hydrogenation activities of Cu/ZrO2 catalysts with different zirconia as carrier and synthesized by different synthesis methods are coMPared, and the order of catalytic activity is:Cu/ZrO2(HMS)> Cu/Zr(1:1)-NaOH-NaC2O4> Cu/ZrO2 (Com). We also studied the influence of copper loading of the Cu/ZrO2 (HMS) catalyst on the catalyst composition, structure and catalytic activity. The result illustrates that the highest yield of EG (97%) can be obtained on the catalyst with 15 wt.% copper loading. Associated with the catalyst structure and catalytic properties, it can be found that the many highly dispersed copper species on this catalyst is one of the key factors.2. Promoter effect of CuCr/ZrO2 catalysts and their influence on catalytic behaviors of DMO hydrogenation reactionNano-zirconia synthesized by refluxing methodwas utilized as support, and the copper catalysts were prepared by the ammonia evaporation-precipitation. The iMPact of the copper load, calcination temperature and structural change after the introduction of Cr additives were investigated. The conversion of DMO and the selectivity to EG could be improved after the introduction of 1% Cr.3. Influence of acidification conditions of the support on the hydrogenation of DMO to EG and 2-METhe zirconium oxide synthesized by the reflux method after acidification was used as a carrier to improve the surface acidity of the catalyst, and further improve the yield of 2-ME. Research results showed that the zirconia acidified by 0.2 M sulfuric acid then calcined at 300℃ was used as carrier, and the highest yield of 2-ME (68%) was obtained over Cu/0.2SZ300 with 10% Cu loading. Products distribution of ethylene glycol and 2-ME can be tuned by modulating the surface acidity of the catalyst. The introduction of the acidification inhibits the crystallization of zirconia. Highly dispersed copper species and weak-medium surface acid sites of the catalysts promote the generation of 2-ME synergistically.