【作者】 赵彦巧；

【导师】 张继炎；

【作者基本信息】 天津大学 ， 工业催化， 2004， 硕士

【摘要】 二氧化碳是主要的温室气体之一。二甲醚是重要的有机化工产品。随着工业的发展，空气中的二氧化碳含量日益增多，大大加剧了人类生存环境的恶化，通过二氧化碳加氢合成二甲醚是有效利用二氧化碳的一条重要可能途径。二氧化碳加氢合成二甲醚反应过程中主要包括二氧化碳加氢合成甲醇、甲醇脱水生成二甲醚和二氧化碳与氢的逆水煤气变换反应。本研究分别以工业C207催化剂和自制CuO-ZnO-Al2O3作为甲醇合成催化剂，以HZSM-5分子筛作为脱水催化剂，二者经机械混合制成二氧化碳加氢一步法合成二甲醚的复合催化剂。采用BET、XRD、H2-TPR、NH3-TPD、IR和实验室固定床反应活性评价等研究方法，系统地考察了HZSM-5分子筛的硅/铝比、C207 与HZSM-5两种组分的质量配比、自制甲醇合成催化剂的沉淀剂种类、沉淀顺序、沉淀方法及铜锌组分的比例等因素对复合催化剂物化性质和催化反应性能的影响。同时，本文还对反应温度、压力、空速等反应条件对催化剂反应性能的影响规律进行了探索研究，获得了在不同条件下二氧化碳加氢反应中二氧化碳转化率和甲醇、二甲醚选择性的变化规律，初步确定了在本研究范围内的最佳反应条件。根据催化剂反应性能评价和NH3-TPD表征结果可以推测，HZSM-5分子筛的强酸中心可能是甲醇脱水的活性中心。硅/铝比为25 的HZSM-5分子筛作脱水组分的复合催化剂的强酸中心数目最大，而H2-TPR测试结果表明其还原活化温度较低，所以硅/铝比为25 的HZSM-5分子筛作为脱水组分用于制备二氧化碳加氢合成二甲醚复合催化剂效果较好。在自制的CuO-ZnO-Al2O3催化剂中，以碳酸钠水溶液作沉淀剂、用两步共沉淀法得到的甲醇合成组分效果较好。实验结果表明，在H2/CO2(mol/mol)=3、反应温度518K、压力3MPa、空速（GHSV）1600h-1的反应条件下，复合催化剂具有较好的反应活性和选择性：以C207作为甲醇合成催化剂组分的复合催化剂，二氧化碳转化率达19.82％，甲醇和二甲醚的总收率为11.79％；以共沉淀法自制的CuO-ZnO-Al2O3作为甲醇合成催化剂组分的复合催化剂，二氧化碳转化率达26.48％，甲醇和二甲醚的总收率为17.95％。更多还原

【Abstract】 Carbon dioxide is one of the main greenhouse gases. Dimethyl ether is a important organic chemical product. Carbon dioxide in the atmosphere is more and more increasing with the industrial development, so the environment we live in are aggravated. Synthesis of dimethyl ether from carbon dioxide hydrogenation is an important way of using carbon dioxide efficiently. The reactions studied is a composite system, which involves three reactions i.e. synthesis of methanol from carbon dioxide hydrogenation, dehydration of methanol to dimethyl ether and the reversed water-gas shift reaction. Experiments had been carried out over the hybrid catalysts, which were prepared by the mechanical mixing of C207 commercial catalyst or CuO-ZnO-Al2O3 catalyst prepared with co-precipitation method (as methanol synthesis catalyst) and HZSM-5 (as dehydration catalyst). Using the technologies of BET, XRD, H2-TPR, NH3-TPD, IR and activity-evaluation in a laboratory fixed-bed reactor, the effects of Si/Al ratio in HZSM-5, the mass ratio of C207 to HZSM-5, precipitation agents, precipitation orders, precipitation methods and Cu/Zn ratio in CuO-ZnO-Al2O3 catalyst on the physico-chemical properties and reaction performance of catalysts were systemically investigated. And the effects of reaction conditions including temperature, pressure and space velocity on the reactivity over the optimized catalyst were also tested. Through the experimental results, the feasible reaction conditions were suggested. According to the results of activity-evaluation and NH3-TPD, it was concluded that the stronger acidic sites could be active for methanol dehydration. The hybrid catalyst with 25 of Si/Al ratio in HZSM-5 was of larger amount of stronger acidic sites, and showed lower reduction temperature, thus demonstrated the best dehydration performance for synthesis of dimethyl ether. Among the CuO-ZnO-Al2O3 catalysts prepared by co-precipitation method, the one by two-step co-precipitation in the solution of sodium carbonate showed ideal catalytic activity.Good catalytic activity and dimethyl ether selectivity had been obtained on the hybrid catalysts under the reaction conditions of H2/ CO2=3, 518K, 3Mpa and GHSV＝1600h-1. With the hybrid catalyst of C207 as methanol synthesis catalyst, the conversion of CO2 is 19.82％, the overall yield of methanol and dimethyl ether is 11.79％. With the hybrid catalyst of CuO-ZnO-Al2O3 prepared by co-precipitation method as methanol synthesis catalyst, the conversion of CO2 is 26.48％, the overall <WP=5>yield of methanol and dimethyl ether is 17.95％.更多还原