Oxidative Dehydrogenation of Ethylbenzene to Styrene

Global Styrenic Polymers Consumption Growth over 2008-2015 

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The well-established industrial dehydrogenation of ethylbenzene to styrene is carried out with a large excess of steam to overcome carbon deposition and the thermodynamic barriers of the reaction [49, 106]. However, the high endothermicity of the process causes a low conversion rarely exceeding 50 %. The occurrence of some side reactions such as production of toluene, benzene, and coke also affects the process yield and selectivity, and leads to catalyst deactivation [41]. A large excess of steam, a growing energetic and environmental issue, is often required to improve the catalytic selectivity to above 90 % and overcome the loss in selectivity and yield caused by irreversible coke formation [49, 107]. 

7 Carbon Dioxide Conversion in High Temperahjre Reactions 

Ceria-based iron oxide catalysts can form solid solutions (Cei Fex02) and were found to perform better than ceria-based Zr, Ti, Pr, and Y mixed oxides [117]. In order to stabihze the lattice structure of Ce02 and the oxygen diffusion capacity, the Cei xFex02 catalyst was prepared via the hydrothermal method and a highly dispersed Fe203 on the surface of the Cei solid solution was obtained 

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An efficient oxidation catalyst, OMS-1 (octahedral mol. sieve), was prepared by microwave heating of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with microwave radiation, and thus pronounced effects on the microstructure were expected. Their catalytic activity was tested in the oxidative dehydrogenation of ethylbenzene to styrene [25]. 

Selective partial oxidation of hydrocarbons poses considerable challenges to contemporary research. While by no means all, most catalytic oxidations are based on transition-metal oxides as active intermediates, and the oxidative dehydrogenation of ethylbenzene to styrene over potassium-promoted iron oxides at a scale of about 20 Mt/year may serve as an example [1]. Despite this... 

Kito and Hattori et al. have described INCAP (IN-tegration of Catalyst Activity Patterns [21-23]), an expert system which rates the applicability of catalyst components for the desired reaction based on known activity patterns for different catalyst properties. The system was successfully applied for the selection of promoter components for the oxidative dehydrogenation of ethylbenzene to styrene. An improved version INCAP-MUSE (INCAP for MUlti-Componcnt catalyst SElcction [24-26]) selects as many catalyst components until all required catalyst properties are present. Although the system was successfully applied to oxidation reactions, more recently better results have been obtained by neural network methods (Section 2.6.2.2). 

The oxidation of intracrystalline ammonium cations has been reported 3, 65), but most oxidations over zeolites featuring molecular oxygen-hydrocarbon systems have featured transition metal zeolites. The oxidative dehydrogenation of ethylbenzene to styrene and selective oxidation of benzyl alcohol to benzaldehyde over MnY at 250°-370°C were reported earlier 62). Propylene has been oxidized to formaldehyde, COo, and minor quantities or acrolein and acetaldehyde over Cu( II)-exchanged Y-type zeolite (39). 

The diversity of the important catalytic reactions used in industry and the difficulty of ensuring rigorous and detailed investigations for each reaction. In fact some important catalytic reactions have no published intrinsic kinetics (e.g. non-oxidative dehydrogenation of ethylbenzene to styrene) and others for which the literature offers only oversimplified power law kinetics. 

Recently, the remarkable properties of carbon nanotubes (CNTs) and related structures, such as carbon nanofibers (CNFs) and onionlike carbons, have attracted an increasing interest from the catalysis community [66], Although these materials are most often used as supports for active phases, some applications as catalysts have been reported, the oxidative dehydrogenation of ethylbenzene to styrene being the most frequently cited example [67-73], These reports basically confirm the mechanism proposed previously, based on a redox cycle involving the quinone surface groups. 

Grunewald, G. C., and R. S. Drago. 1990. Oxidative dehydrogenation of ethylbenzene to styrene over carbon-based catalysts. J. Mol. Catal. 58 227-233. 

Catalytic activity of carbon nanotubes and other carbon materials for oxidative dehydrogenation of ethylbenzene to styrene... 

Wang Q, Li X, Li W, Feng J (2014) Promoting effect of Fe in oxidative dehydrogenation of ethylbenzene to styrene with CO2 (I) preparation and performance of Cej xFcx02 catalyst. Catal Commun 50 21-24... 

Reddy BM, Jin H, Han DS, Park SE (2008) Oxidative dehydrogenation of ethylbenzene to styrene with carbon dioxide over Fe203/Ti02-Zr02 catalyst influence of chloride. Catal Lett 124 357-363... 

Oxidative dehydrogenation of ethylbenzene to styrene is catalyzed by various oxides containing phosphorous oxide. Aluminum phosphorous oxide shows the highest activity this is explained by the presence of both acid sites of Ho-1.5 to — 5.6 and base sites of H =17.2 to 25.6. Although the reaction itself is not an acid-base catalyzed reaction, the acid sites serve as adsorption sites for ethylbenzene while the base sites activate oxygen molecules to form O spedes which abstract the H from the intermediates. 

These few examples show an advantage of anaerobic oxidations for selected reactions, to minimize CO2 formation. A few other opportunities for further study should include the oxidation of o-xylene to phthalic anhydride, oxidative dehydrogenation of ethylbenzene to styrene, oxidation of isobutylene to methacrolein and methacrylic acid, and oxidative dehydrogenation of paraffins to olefins. 

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