Styrene from Dilute Ethylene

Mobil and Badger have been developing their vapor-phase zeolite-catalyzed ethylbenzene (EB) process using dilute ethylene since the 1970s. In 1991, the first commercial installation, using dilute ethylene feedstock from a fluid catalytic cracking (FCC) unit, was on stream at Shell's Stanlow, U.K. plant. The process is based on Mobil/Badger's second-generation vapor-phase process.

The sources of dilute ethylene include coke-oven gas and FCC off-gas. The latter is often desulfurized and used as refinery fuel gas. When used as a feedstock for EB production, dilute ethylene must be dried and separated from propylene, in addition to sulfur removal. It is essentially upgraded from fuel value to a value equivalent to that of polymer-grade ethylene less the cost of purification.

In this review, we evaluate the use of dilute ethylene feed for EB production by the third-generation vapor-phase process, which has been offered by Mobil/ Badger since 1990, and present the economics of integrated EB/styrene production. We also compare the economics of EB/styrene production using three feeds: dilute ethylene, polymer-grade ethylene, and ethylene upgraded from dilute ethylene (upgraded ethylene).

The capacity of an EB/styrene plant using dilute ethylene is limited by the availability of dilute ethylene. EB/styrene production could be economically feasible only for plant sites located near large refineries with FCC capabilities or areas where a concentration of FCCs exists.