Ethylbenzene is an organic compound with the formula or . It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as a reaction intermediate in the production of styrene, the precursor to polystyrene, a common plastic material. In 2012, more than 99% of ethylbenzene produced was consumed in the production of styrene.
Occurrence and applications
Ethylbenzene occurs naturally in coal tar and petroleum. Used in the recovery of natural gas, ethylbenzene may be injected into the ground.
Production
Ethylbenzene is produced on a large scale by combining benzene and ethene in an acid-catalyzed chemical reaction:
:
In 2012, more than 99% of ethylbenzene was produced in this way.
Small amounts of ethylbenzene are recovered from the mix of xylenes by superfractioning, an extension of the distillation process.
In the 1980s a zeolite-based process using vapor phase alkylation offered a higher purity and yield. Then a liquid phase process was introduced using zeolite catalysts. This offers low benzene-to-ethylene ratios, reducing the size of the required equipment and lowering byproduct production.
Industrial accidents
On June 3, 2014, an explosion occurred in the Dutch Moerdijk industrial area. This happened in a chemical reactor operated by Shell which overheated due to an exothermal runaway reaction between the metal oxide catalyst and ethylbenzene.
Health effects
The acute toxicity of ethylbenzene is low, with an LD<sub>50</sub> of about 4 grams per kilogram of body weight. The longer term toxicity and carcinogenicity is ambiguous. Eye and throat sensitivity can occur when high level exposure to ethylbenzene in the air occurs. At higher level exposure, ethylbenzene can cause dizziness. A study conducted in 2012 found that in country air the median concentration was found to be 0.01 ppb and indoors the median concentration was 1.0 ppb. It can also be released into the air through the burning of coal, gas, and oil. The use of ethylbenzene in the industry contributes to ethylbenzene vapor in the air. After about three days in the air with the help of sunlight, other chemicals break down ethylbenzene into chemicals that can be found in smog. Generally, ethylbenzene is not found in drinking water, however it can be found in residential drinking water wells if the wells are near waste sites, underground fuel storage tanks that are leaking, or landfills.
Biodegradation
Certain strains of the fungus Cladophialophora can grow on ethylbenzene. The bacterium Aromatoleum aromaticum EbN1 was discovered due to its ability to grow on ethylbenzene.
References
- National Toxicology Program. Toxicology and Carcinogenesis Studies of Ethylbenzene (CAS No. 100-41-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). TR No. 466. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1999.
External links
- National Pollutant Inventory - Ethybenzene Fact Sheet
- NLM Hazardous Substances Databank – Ethylbenzene
- EPA Chemical database
- Intox Chemical database
- Agency for Toxic Substances and Disease Registry
- CDC - NIOSH Pocket Guide to Chemical Hazards