Styrene
Encyclopedia : S : ST : STY : Styrene
| Styrene | |
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| General | |
| Systematic name | Phenylethene |
| Other names | Vinyl benzene, cinnamene, styrol |
| Molecular formula | C8H8 |
| SMILES | c1ccccc1C=C |
| Molar mass | 104.15 g/mol |
| Appearance | colourless oily liquid |
| CAS number | |
| Properties | |
| Density and phase | 0.9 g/cm3 |
| Solubility in water | < 1% |
| Melting point | -30 °C (243.15 K) |
| Boiling point | 145 °C (418.15 K) |
| Acidity (pKa) | ? |
| Basicity (pKb) | ? |
| Chiral rotation | ? ° |
| Viscosity | ? cP at ? °C |
| Structure | |
| Molecular shape | ? |
| Coordination geometry | ? |
| Crystal structure | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | [MSDS] |
| Main hazards | flammable |
| Flash point | 31 °C |
| R/S statement | R: 10-36 S: 38-20-23 |
| RTECS number | ? |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas
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| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related styrenes | Polystyrene Stilbene |
| Related aromatics | Ethylbenzene |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Styrene dissolves in many organic liquids but does not dissolve significantly in water. Millions of tonnes per day are produced to make products such as rubber, plastic, insulation, fiberglass, pipes, automobile parts, food containers, and carpet backing.
Most of these products contain styrene linked together in a long chain (polystyrene) as well as unlinked styrene. Low levels of styrene also occur naturally in a variety of foods such as fruits, vegetables, nuts, beverages, and meats.
Production
Styrene is most commonly produced by the catalytic dehydrogenation of ethylbenzene. Ethylbenzene is mixed in the gas phase with 10–15 times its volume in high-temperature steam, and passed over a solid catalyst bed. Most ethylbenzene dehydrogenation catalysts are based on iron(III) oxide, promoted by several percent potassium oxide or potassium carbonate. On this catalyst, an endothermic, reversible chemical reaction takes place.
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Steam serves several roles in this reaction. It is the source of heat for powering the endothermic reaction. It limits carbon deposition (coking) inside the reactor, which would otherwise degrade the catalyst's performance. It also dilutes the concentration of the reactant and products in the reaction mixture, shifting the position of chemical equilibrium towards products. A typical styrene plant operates several reactors in series, injecting fresh steam into the reaction mixture between each reactor. Each steam injection reheats the reaction mixture and shifts the position of chemical equilibrium further towards the products, making higher conversion possible. Typical per-pass conversions are on the order of 65%. The separation of styrene from the remaining ethylbenzene requires tall distillation towers, because styrene and ethylbenzene have similar boiling points (145 °C for styrene, 136 °C for ethylbenzene). Improving conversion and so reducing the amount of ethylbenzene that must be separated is the chief impetus for researching alternative routes to styrene.
Health effects
Inhaling high levels of styrene in a short amount of time can cause nervous system effects such as depression, concentration problems, muscle weakness, tiredness, nausea and possibly eye, nose and throat irritation.Animals inhaling styrene vapour in short-term studies damaged their nasal lining. Long-term exposure damaged the liver. There is no information on human health effects of inhaling low levels for a long time, but effects are likely to be similar.
Some information is available of the human health effects from eating or touching styrene. Animal studies show that ingestion of high levels of styrene over several weeks can cause damage to the liver, kidneys, brain, and lungs. When styrene was applied to the skin of rabbits, it caused irritation.
No information is available as to whether breathing, ingesting, or touching styrene affects fetal development (making it teratogenic) or human reproduction. In animal studies, short-term exposure to very high levels resulted in some reproductive and developmental effects.
The International Agency for Research on Cancer (IARC) has determined that styrene is a potential carcinogen to humans. Several studies of workers have shown that inhaling styrene may result in developing leukemia. No information exists as to the carcinogenicity of styrene in people who either swallow it or get it on their skin. Studies in animals that inhaled or ate styrene suggest that it is mildly carcinogenic.
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