Styrene, also known as vinyl benzene and phenyl ethene, is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations confer a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers
Styrene is named for "styrax" (also called "storax Levant"), the resin from a Turkish tree, the Oriental sweetgum (Liquidambar orientalis), from which it was first isolated and not for the tropical Styrax trees from which benzoin resin is produced. Low levels of styrene occur naturally in many kinds of plants, as well as a variety of foods such as fruits, vegetables, nuts, beverages, and meats. Its density 0.909 g/cm³ , Melting point -30 °C, 243 K, -22 °F, Boiling point 145 °C, 418 K, 293 °F, Appearance is Colorless to yellow oily liquid, Penetrating odor and has a Negligible Solubility (< 0.1%).
Styrene was discovered in 1831. However, it did not become commercially important until 1942 when it was used in the synthesis of unsaturated polyesters and reinforced plastics. Styrene, a petroleum by-product, is the primary raw material from which polystyrene is made. Styrene, first commercially produced in the 1930s, played an important role during World War II in the production of synthetic rubber. After the war, much of the use of styrene shifted to the manufacture of commercial polystyrene products.
Americas Styrenics, Carville Styrenics Complex, Ineos Nova, LyondellBasell, Pars Petrochemical Co, Tabriz Petrochemical Co, Jubail Chevron Phillips Co, Shell Chemicals Canada Ltd, Integrated Refinery and Petrochemical Co, Siam Styrene Monomer Co, Saudi Petrochemical Co, Honam Petrochemical, LG Chem Ltd, Samsung Total Petrochemicals Co Ltd, Formosa Chemicals and Fibre Corp, Mitsubishi Chemical Corp, Sinopec Beijing Yanshan Petrochemical Co Ltd, Daqing Petrochemical Co are some of the leading producers of styrene in the world. In India there is no producer of styrene and the demand is being met by imports.
Styrene demand remains dominated by its main derivative, polystyrene (59%), which has reached maturity in most developed countries. Other styrene consumption is for the production of acrylonitrile-butadiene-styrene (ABS) and styrene-acrylonitrile (SAN) resins (16%), styrene-butadiene (S/B) copolymer latexes (6%) and unsaturated polyester, accounting for an additional 6% of world styrene demand, while SBR and SBR latexes production accounted for 4% of world demand.
Styrene is used in everything from food containers and packaging materials to cars, boats, computers, and video games.
The conventional method of producing styrene is alkylation of benzene with ethylene to produce ethylbenzene followed by dehydrogenation of the ethylbenzene to produce styene.
Two commonly used methods are employed for the production of EB. Both routes involve the alkylation of benzene with ethylene, but the difference comes in the catalyst systems that are used to promote the reaction. The traditional route involves the use of aluminium chloride as a catalyst and second involves the use of zeolite catalyst.
1. Mobil/Badger EB process: In this process, fresh and recycled benzene streams are vaporized and combined with an alkylaromatic recycle stream of mainly diethylbenzene and fresh ethylene before feeding to an alkylation reactor containing a fixed bed zeolite catalyst.
2. Lummus/UOP process: This process is the newest type of EB technology currently operated commercially. This process is based on zeolite catalyst developed by Unocal for other chemical processes and tailored for the needs of EB manufature.
3. Lummus CD Tech: The CDTECH EB technology is a fairly new entrant to the market. This method has only begun to proved commercially, but pilot plant tests have shown that it works well, and its basic principles are being used commercially in MTBE units. Like the previous EB processes described, the CDTECH design uses a zeolite catalyst system. Its major difference is that the reactor unit also incorporates the first stage distillation, which removes the light gases from the system.
4. Lummus/Sinopec Direct EB Process: The direct EB process is the newest technology available to produce EB through the direct recovery of ethylene from dilute ethylene feedstocks found in FCC offgas streams or steam cracker streams. It is similar to aforementioned EB process. The major difference is, in this case, the first reactor is designed to accommodate the variety of impurities that comprise the untreated dilute ethylene stream.
The major conventional styrene technologies via direct hydrogenationof EB that are available for license are held by the Lummus/UOP group and Badger licensing. In addition, there are privately held technologies operated by Dow, BASF, Enichem, and several producers in Japan.
In all of the conventional styrene processes, EB and steam are heated to high temperatures before being passed into a dehydrogenation reactor where EB is converted to styrene and hydrogen.
1. Badger-Total Styrene Process:
In this process, fresh and recycle EB (recovered in the distillation section) are mixed with steam upstream of the feed/effluent exchanger. In this exchanger the feed is first vaporized and then superheated. Next, the superheated EB/steam mixture is combined with additional superheated steam, bringing the entire feed mixture up to a reaction temperature prior to entering the primary reactor. In addition to styrene, small amounts of benzene, toluene and other trace impurities are produced.
2. Lummus/UOP Process:
The Lummus/UOP “Classic” styrene process employs the reaction fundamentals previously outlined in styrene production and can be compared to the Badger-Total process. Although some differences exist between the two processes, the essential reaction and separation theory is the same.
The Lummus/UOP “Smart” styrene process has some differences from other conventional processes. Its primary distinction is the introduction of an oxidative reheat step in the middle of the dehydrogenation reaction process.