Selective oxidation of ethylhenzene to styrene with carbon dioxide

The dehydrogenation process for the production of styrene ( ST) based on the selective oxidation of ethylbenzene (EB) with the major global warming gas CO2, is reviewed. The usage of CO2 instead of steam could provide several advantages such as reduction of the reaction temperature, remarkable energy saving in the distillation process of ST, restraining deactivation of catalysts to some degree, and so on. The iron-oxide-based catalysts and the vanadium-oxide-based catalysts are highly active and promising catalysts for the new reaction system. The mechanism of CO2 oxidation is also discussed. It can be concluded that the remarkable promoting effect of CO2 on the dehydrogenation of EB is due to both redox cycle of oxide catalyst and coupling of EB with reversed water gas shift reaction. Although the application of CO2 is very effective, the catalysts deactivation mechanism, suitable measures to enhance their catalytic stability and the economic evaluation on the new process must be further investigated.