Ethylbenzene Dehydrogenation in the Presence of Carbon Dioxide over Alumina Supported Catalysts

摘要

Styrene (ST) is mainly used as the monomer of synthetic polymers. It is commercially produced by the dehydrogenation of ethylbenzene (EB) on the promoted iron oxide catalysts at 60O-700°C, just below the temperature where the thermal cracking becomes significant. Due to its high endothermic character, a large amount of superheated steam is used to supply heat, lower the partial pressure of the reactant, and avoid the formation of carbon deposits. However, much of the latent heat of steam is lost in the gas-liquid separator instead of recovering, which results in high energy consumption. Reaction coupling is proved to be one of the most promising processes for the dehydrogenation reactions. The coupling of EB dehydrogenation with reverse water-gas shift was carried out in the presence of carbon dioxide instead of steam. It was found that the equilibrium conversion could be greatly enhanced by the reaction coupling. When coupling with water-gas shift, the EB equilibrium conversion can be elevated to 82.4% from 25.2% for the single EB dehydrogenation at 550°C. Moreover, it is estimated that the energy required for producing per ton ST in the coupling process is 1.5-1.9x10~8 cal, compared with 1.5x10~9 cal in the current commercial process. Therefore, the new process could be an energy-saving and environmentally friendly one.