Title : Catalysts for Ethylbenzene to Styrene: Challenges & break through
Abstract:
Styrene is one of the major commodity chemicals/monomers used for the production of different polymeric materials such as polystyrene (PS), acrylonitrile-butadiene-styrene (ABS) and styrene-butadiene rubber, which find their use in several segments including packing materials, automotive, construction and tires [1]. At present the world styrene production is over 35,000 kta, which is expected to reach over 50,000 kta in 10 years with a consumption growth rate of around 2% per annum. Styrene is predominantly produced by conventional dehydrogenation of ethylbenzene (EB) route in the presence of steam over Fe-based catalysts with different promoters [2] using processes licensed by Badger or Lummus Technology. Being an endothermic process, selectivity to styrene and ethylbenzene conversion are controlled by heat, which is supplied through super-heated steam.
In the conventional process, steam-to-hydrocarbon feed weight ratio (sometimes referred to as steam-to-oil ratio) is typically in the range of 1.0-2.0 with ethylbenzene conversion over 60% and styrene selectivity of more than 93%, where the by-products are mainly benzene and toluene due to the dealkylation reaction. Clariant Corporation is a styrene catalyst leader who offers a wide range of catalysts based on end use requirements. In this process, steam plays a crucial role such as in the removal of carbonaceous deposit (coke), as a diluent to shift equilibrium towards higher conversion. Steam, as an oxidizing agent, renders the iron oxide to remain in an appropriate oxidation state, and it supplies the needed heat for the reaction. However, the energy to produce the steam is expensive, resulting in a high operating expense. Therefore, Clariant endeavors to develop new-generation catalysts, which can be used at low steam-to-oil ratio of 1.0 or below. Loss or redistribution of promoter like potassium, building of carbonaceous deposits are major challenges while developing new commercial catalysts for low-steam operation. It is a real technical challenge to the catalysis community to develop a robust catalyst that works at this low steam-to-oil ratio, apart from other engineering challenges as it creates heat exchange limitations [3]. Developing commercial scale catalyst production, which meets customer expectations, is a formidable scientific question.
Some of the mechanistic aspects of the EB-to-styrene reaction and current challenges will be discussed along with our latest catalyst solutions.
