Styrene from Butadiene via 4-Vinylcyclohexene by the Dow Process

Published January 1996

Currently, more than 80% of the world's 1,3-butadiene (BD) is extracted from crude C₄ effluents made from the steam cracking of heavy hydrocarbon feedstocks such as naphtha in the production of ethylene. The growth rate of BD production in ethylene plants is estimated to be 28% greater than BD demand, which has resulted in a global BD surplus. Dow Chemical has introduced a new two-step process to produce styrene from BD via 4-vinylcyclohexene (VCH). The new process uses the crude C₄ stream from a steam cracker as the source of BD to convert into styrene monomer. The first step entails a liquid-phase dimerization reaction that converts the BD in the crude C₄ stream to VCH using a Dow proprietary copper-loaded zeolite catalyst. The second step converts VCH to styrene in a gas-phase oxidative dehydrogenation reaction using another Dow proprietary tin and antimony oxide catalyst. Since March 1994, Dow has operated an 18-40 lb/hr capacity pilot plant at its Freeport, Texas, facility using the styrene-from-BD-via-VCH process. Dow offers the new styrene technology for licensing.

In this review, we evaluate the Dow styrene-from-BD-via-VCH process at a production capacity of 250 million lb/yr (113,000 t/yr).

The Dow process offers an alternative to the conventional hydrogenation and cocracking methods employed for the crude C₄ stream when the market for pure BD does not justify extraction. Dow's process upgrades BD in the crude C₄ stream to the more valuable styrene monomer. Use of Dow's new technology seems most advantageous for the Asia/Pacific region where countries are net importers of styrene and long in BD supply because of recent naphtha-based ethylene plant expansions.