GT-Styrene is an extractive distillation process that directly recovers styrene from the raw pyrolysis gasoline derived from the steam cracking of naphtha, gasoils and natural gas liquids (NGLs). The produced styrene is high purity and suitable for polymerization at a very attractive cost compared to conventional styrene production routes. The process is economically attractive for pygas feeds containing more than 15,000 tpy of styrene.
Raw pyrolysis gasoline is prefractionated into a heartcut C8 stream. The resulting styrene concentrate is fed to an extractive distillation column and mixed with a selective solvent, which extracts the styrene to the tower bottoms. The rich solvent mixture is routed to a solvent recovery column, which recycles the lean solvent back to the extractive distillation column and recovers the styrene overhead. A final purification step produces a 99.9% styrene product containing less than 50 ppm phenyl acetylene. The extractive distillation column overhead can be further processed to recover a high-quality mixed-xylene stream. A typical world-scale cracker can produce approximately 25,000 tpy of styrene and 75,000 tpy of mixed xylenes from pyrolysis gasoline.
Process advantages:
• Produces polymer-grade styrene at 99.9% purity
• Allows the recovery of isomer-quality mixed xylenes for paraxylene production
• Upgrades pygas stream components to chemical value
• Debottlenecks pygas hydrotreater and extends cycle length
• Reduces hydrogen consumed in hydrotreating
• Optimized solvent system and design provide economical operating costs.
Licensor: GTC Technology
