Although styrene is present in the pyrolysis gasoline by-product from steam cracking, it cannot be purified by conventional distillation because of the presence of many other components or isomers with close boiling points. GTC Technology Inc. (formerly Glitsch Technology Corporation) has developed a process to recover styrene from untreated pyrolysis gasoline using extractive distillation. The GT-Styrene process uses a proprietary solvent system, called Techtiv-200, which changes the relative volatility of the pygas components and allows styrene to be selectively extracted. Styrene is produced at high purity, suitable for polymerization, at a significant upgrade over its alternate value as gasoline blending component.
The GT-Styrene process has been successfully tested in a pilot plant, but has not yet been demonstrated on a commercial scale. According to GTC, a multi-unit license of the technology has been established with a major Asian company. The first plant is currently under design, and will have a capacity of 27,000 t/yr of styrene.
In this review, we present a conceptual design and preliminary economics for a process to recover 55 million lb/yr (25,000 t/yr) of styrene from pygas. Our analysis indicates that the extraction technology provides profitable production of styrene at small capacities, although the economics of the process are largely dependent on the price differential between styrene and hydrotreated pygas. Prime targets for the technology are ethylene producers that can generate sufficient pygas feedstock to produce at least 20,000 t/yr of styrene. This would include major naphtha-based steam crackers in Asia, Europe, and the Americas.