摘要
自1995年Maier首次应用酸催化溶胶凝胶法合成无定型多孔复合氧化物并用于应用过氧化氢的选择性氧化反应以来，多孔复合氧化物在催化领域的应用引起人们的关注，特别是随着用于制备催化材料的溶胶—凝胶技术的发展，制备不同组分的多孔复合氧化物，研究其制备规律及在非均相催化领域中的应用的报道屡见不鲜。苯乙烯是一种重要的有机化工原料，全世界苯乙烯的年产量约1300万吨，其中90％是由乙苯催化脱氢生产的，但该工艺受热力学的限制，具有能耗大的缺点。目前共氧化法、氧化脱氢法和脱氢—氢选择性氧化法等改进工艺均未实现工业化。近年来，在氧化脱氢工艺反应体系中应用CO_2取代氧气作为氧化剂，是一条利用CO_2资源和降低能耗的“绿色化学”途径．制备高性能的用于乙苯二氧化碳氧化脱氢(CO_2-EBDH)制苯乙烯的催化剂是一具有理论和实际应用价值的研究课题。
太原理工大学硕士学位论文
本文以酸催化溶胶一凝胶法合成多孔复合氧化物
MxTi为主线，以TIO:氧化物为基体进行了7种活性组分
的筛选;详细考察了制备条件对FexTi的织构、结构和二
氧化碳氧化乙苯脱氢反应活性的影响;对cOZ一EBDH反
应进行了工艺条件的优化选择;并与浸渍法制备的钦基
催化剂反应活性进行比较.采用XRD，TPR，SEM，TEM，
表面吸附，TGA等多种表征手段对FexTi催化剂研究，
为阐明多孔复合氧化物FexTi的催化剂体相结构，活性组
分负载量对COZ一EBDH产物选择性的影响和工业应用提
供有用信息，获得了以下凡点有意义的结果和结论.
1.活性组分的筛选结果表明，在同样的制备和反应
条件下，负载Fe的钦基复合氧化物催化剂的COZ一EBDH
反应活性明显优于负载V，Mg，C。，Ag，Ni，Zn的催
化剂.
2.FexTi55O复合氧化物催化剂对COZ一EBDH反应
具有非常高的活性，其中Fe3Ti55o在T=s23K，
P=0.IMPa，W/F=40geat·h/mol，COZ/EB=11的反应条件下，
乙苯转化率和苯乙烯选择性分别39.8%和98.0%.
5.复合氧化物FexTi55o比表面积为37一loomZzg，孔
体积0.15一0.25ml/g，Fe3+进入Tio:的晶格中形成
Fe一O一Ti键，具有高度分散的孤立Fe活性中心.
Porous mixed oxides were prepared in sol-gel process for the first time and applied on the reaction of selective oxidation with organic hydroperoxides by Prof. Maier in 1995. Since then, the application of AMM catalyst has received many concerns. Especially, along with the developing of sol-gel technology, many reports appeared on the preparation of different kinds of composition porous mixed oxides, for the investigation of the rule of preparing and the application of this kind catalyst on heterogeneous catalysis.
Styrene is one of the most important basic chemicals, about 13 million tons of styrene is annually produced all over the world, and 90% is commercially produced by the
dehydrogenation of ethylbenzene on Fe-K-based catalysts at 873-973K. However, EBDH is thermodynamically limited and, moreover, it is very energy consuming process because of the required excess of superheated steam. The process was improved in the ways of common oxidation, oxidation dehydrogenation of ethylbenzene,
dehydrogenation of ethylbenzene and oxidation of hydrogen. However, none of these processes has been commercially produced so far. Recently, the ethylbenzene dehydrogenation was coupled with the reaction of reverse water-gas shift, in which carbon dioxide instead of oxygen in the dehydrogenation. The process could be effective utilization of carbon dioxide resource, energy-saving and environmentally friendly. It is important in theory and practice to study new technology in preparation high capability catalyst of CO2-EBDH.
In this thesis, MxTi catalyst was prepared by acid-catalyzed sol-gel method and seven active components were screened. The preparation conditions were investigated in details especially their influence on the texture, structure and the CO2-EBDH of FexTi. The processed condition for hydrogenation of CO2-EBDH was optimized. The activity of FexTi was compared with the catalyst prepared with impregnation method. This research
provided useful information for the CO2-EBDH in selectivity and industry application, several significant results and conclusions were obtained as follows:
1. According to the result of active components screening, titanium-based mixed oxide doped with Fe shows better activity than that of doped with V, Mg, Co, Ag, Ni and Zn.
2. Mixed oxide FexTi550 revealed a very excellent activity in CO2-EBDH, the EB conversion and ST selectivity reached 39.8 % and 98.0% respectively over Fe3Ti550 with the reaction condition T=823K, P=0.1MPa, W/F=40gcat-h/mol, CO2/EB=11.
3. Mixed oxide FexTi550 has a specific surface area 37~100m2/g and a pore volume 0.15~0.25ml/g, highly-dispersed and isolated Fe centers embedded in Ti matrix, Fe3+ entered the crystal lattice of TiO2 and caused the formation of Fe-O-Ti bond in bulk structure.
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