Styrene

In the styrene monomer (SM) unit, the reversible, endothermic dehydrogenation reaction is carried out over an iron oxide-based catalyst. Steam is the diluent and heat carrier used in commercial reactors. The reactors typically operate under vacuum conditions as diluent steam reduces the partial pressure of the reactants. The steam also acts as a catalyst decoker via water-gas-shift reactions. A very small amount of ethylbenzene (EB) is thermally converted, with most thermal reactions resulting in by-products, such as benzene and toluene. Other by-products include C9s, such as alpha-methylstyrene and cumene. 

The styrene distillation section typically consists of a 3- or 4-column configuration, including a superfractionator for the EB/SM split. The superfractionator is commonly called the EB Recycle column or EB/ SM splitter. With commercial designs of 100+ theoretical stages in 6 to 7 packed beds and tower diameters of up to 39 ft [12 m], the splitter is one of the largest commercial applications of distillation and performs a critical separation. Structured packing is ideally suited for styrene columns and was first used in the 1980s. Because styrene is a reactive monomer, a low bottom temperature, achieved through a low column pressure drop and low liquid residence times, is desirable. Many plants have conventional FLEXIPAC® structured packing installed. For revamps and also new plant construction, FLEXIPAC® HC® structured packing and high-performance tower internals are preferred.

The last section of the distillation train is styrene recovery from residue. Because of fouling potential, structured packing typically is not used in this step. For improved fouling resistance and to handle concentrated heavies and polymers, sieve trays and dual flow trays are most often used in the stripping section. As an alternate unit operation, flash drums and wiped film evaporators are also used. 

A second commercial route for styrene production is propylene oxide/styrene monomer (PO/SM), but it accounts for a much smaller share of global styrene production. This process also uses EB as the intermediate and produces both PO and SM as co-products. Although the distillation configuration and separations are significantly different, the mass transfer products used are the same due to similar design considerations.

Key Offerings

• High-Performance Structured Packing: Designed to minimize pressure drop and maximize separation efficiency.
• Advanced Mist Eliminators: Prevent product loss and support regulatory compliance. 

Benefits for Styrene Producers

By integrating our innovative solutions, styrene producers benefit from:

• Improved process efficiency and product yield
• Lower operating costs through energy savings
• Enhanced equipment reliability and longevity
• Consistent production quality to meet market demands