Styrene from gasoline

STEX [Styrene extraction] A process for extracting styrene from pyrolysis gasoline. Developed by Toray. 

FIGURE 3 Manufacture of styrene from a gasoline fraction. 

Application To directly recover styrene from raw pyrolysis gasoline derived from steam cracking of naphtha, gas oils and NGLs using the GT-Styrene process. 

All the styrene monomer (bpi.oia - 145.2 C, s/J == 0.906. ) produced throughout the world is obtained directly or indiiectly from etbylbenzeoe. Most is product by dehydrogenation, while a certain amount is also obtained as a co-product of Ae manu- ctuie of propylene oxide. Some attempts have been made to extract styrene from liyrolysis C5- gasolines (Stex process by Toray, deserflied in Section 4.2J), but they have. not culminated in commercial plants. 

Sato, M., Extract styrene from pyrolysis gasoline . Hydrocarbon Processing, 52 (51 141-144 (1973). Morimoto, H., Tatsumi, M., Tbe Stex process. Extraction of styrene from pyrolysis gasoline Bull, of Japan FePtdeiim IRSL, 16 ( ) 38-42 (1974). 

Application 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. 

GTC Technology Styrene Pygas Cg cut Extractive distillation process that directly recovers styrene from the raw pyrolysis gasoline derived from the steam cracking of naphtha, gasoils and NGL 3 2009... 

STEX [Siyrene Extraction] A process for extracting styrene from pyrolysis gasoline. Developed by Toray. Chem. Eng. News, 27 Aug 2001,79(35), 28-30. 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

The dominant share of styrene production comes from dehydrogenation of EB in plants like that shown in Figure 8-5. Some comes as a coproduct in propylene oxide/styrene plants. An even smaller amount is recovered from the gasoline fraction of olefins plants cracking heavy liquids. 

Benzene and para-xylene are the most sought after components from reformate and pygas, followed by ortho-xylene and meta-xylene. While there is petrochemical demand for toluene and ethylbenzene, the consumption of these carmot be discussed in the same way as the other four. Toluene is used in such a large quantity in gasoline blending that its demand as a petrochemical pales in comparison. Fthylbenzene from reformate and pygas is typically dealkylated to make benzene or isomerized to make xylenes. On-purpose production of petrochemical ethylbenzene (via ethylene alkylation of benzene) is primarily for use as an intermediate in the production of another petrochemical, styrene monomer. Ethylbenzene plants are typically built close coupled with styrene plants. 

Polymers with solubility parameters differing from those of the solvent by at least 2.0 H, will not dissolve in the solvent at room temperature. Thus although unvulcanized natural rubber (NR), unvulcanized styrene-butadiene elastomer (SBR), unvulcanized butyl rubber, and EPDM dissolve in gasoline or benzene, the vulcanized (cross-linked) polymers are swollen but will not dissolve due to the presence of the crosslinks. 

Gasoline hydrorefining is applied to remove polymerizable by-products (isoprene, cyclopentadiene, styrene and indene) from stream-cracked gasoline to prevent gum formation. Partial hydrogenation of dienes to monoalkenes and the hydrogenation of... 

Other methods, such as the direct reaction of benzene and ethylene (Fig. 2) or from pyrolysis gasoline (Fig. 3) are also used to manufacture styrene. 

Benzene found in the environment is from both human activities and natural processes. Benzene was first discovered and isolated from coal tar in the 1800s. Today, benzene is made mostly from petroleum sources. Because of its wide use, benzene ranks in the top 20 in production volume for chemicals produced in the United States. Various industries use benzene to make other chemicals, such as styrene (for Styrofoam and other plastics), cumene (for various resins), and cyclohexane (for nylon and synthetic fibers). Benzene is also used for the manufacturing of some types of rubbers, lubricants, dyes, detergents, drugs, and pesticides. Natural sources of benzene, which include volcanoes and forest fires, also contribute to the presence of benzene in the environment. Benzene is also a part of crude oil and gasoline and cigarette smoke. For more information on the nature and uses of benzene, see Chapters 3 and 4. 

The extractive-distillation column overhead can be further processed to recover a high-quality mixed xylene stream. A typical world-scale cracker could produce approximately 25,000 tpy styrene and 75,000 tpy mixed xylenes from pyrolysis gasoline. 

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