Study On Mixed Oxides Catalysts Applied In Ethylbenzene Dehydrogenation In The Presence Of Carbon Dioxide

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 thedehydrogenation 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 researchprovided 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.