Activity studies of vanadium, iron, carbon and mixed oxides based catalysts for the oxidative dehydrogenation of ethylbenzene to styrene: a review

Despite the enormous amount of research dedicated to the dehydrogenation of ethylbenzene to styrene over the last seven decades, there is still a great need to invent more efficient and cost-effective catalysts for the reaction process. It was found that an appropriate oxidation state of the active metal in a catalyst plays a vital role. For vanadium(V) based catalysts, the active phase of V was observed to be V5+ species for enhanced activity. In the iron-based catalyst systems, considerably better activities were found with the catalysts that involved the continuous oxidation of Fe2+ to Fe3+. On the other hand, the mixed oxide catalysts showed better performance than those of the individual oxides perhaps due to the increased acid-base bi-functionality. Various carbon-based catalysts, such as carbonaceous adsorbents, CNTs, carbon nanofoams, carbon fibers, and nanodiamond, have found to be active for the oxidative dehydrogenation of ethylbenzene. The prime cause for the deactivation of all these catalysts was coke formation on the surface of the catalyst, which needs to be minimized for better catalytic activity. In this review, various vanadium, iron, carbon and mixed-oxide based catalysts, which have been reported in the literature, are briefly surveyed for their activity towards the dehydrogenation of ethylbenzene to yield styrene.