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Ethylene Glycol (MEG) is a toxic, colorless, practically odorless, low-volatility, low-viscosity, hygroscopic liquid. It is completely miscible with water and many organic liquids. The hydroxyl groups on glycols undergo the usual alcohol chemistry, giving a wide variety of possible derivatives. This chemistry permits ethylene glycol to act as an intermediate in a wide range of reactions. Especially significant is resin formation, including the condensation with dimethyl terephthalate or terephthalic acid resulting in a polyester resin (PET) for soft drinks and food packaging.
The widespread use of ethylene glycol as an antifreeze is based on its ability to lower the freezing point when mixed with water. The physical properties of ethylene glycol-water mixtures are therefore extremely important. Ethylene glycol has numerous end uses that include the production of polyester fibers and resins, as an additive in chilled water air-conditioning systems, geothermal heating/cooling systems, and as an important precursor to polyester fibers and resins in the plastics industry.
Ethylene Glycol (MEG) is an organic compound widely used as an automotive antifreeze and the precursor to polymers. In its pure form, it is an odorless, colorless, syrupy liquid. Ethylene glycol is toxic, and ingestion can result in death.
Ethylene glycol is produced from ethylene, via the intermediate ethylene oxide. Ethylene oxide reacts with water to produce ethylene glycol according to the chemical equation:
This reaction can be catalyzed by either acids or bases, or can occur at neutral pH under elevated temperatures. The highest yields of ethylene glycol occur at acidic or neutral pH with a large excess of water. Under these conditions, ethylene glycol yields of 90% can be achieved. During the process some by-products are formed: Diethylene Glycol (DEG) and Triethylene Glycol (TEG). These by-products are separated from MEG through distillation.
The major end uses of ethylene glycol are as an antifreeze, which accounts for over 50% of ethylene glycol’s commercial uses, and as raw material in the production of polyester fibers and plastics, mainly PET, which accounts for 40% of total ethylene glycol consumption. Because this material is cheaply available, it finds many Applications.
Ethylene Glycol’s major end uses are as an antifreeze, which accounts for more than 50% of ethylene glycol’s commercial use, and as raw material in the production of polyester fibers and plastics, mainly PET, which accounts for 40% of total ethylene glycol consumption. Because this material is cheaply available it finds many niche applications.
Ethylene glycol is a medium for convective heat transfer in automobiles and liquid cooled computers. It is also commonly used in chilled water air-conditioning systems that place either the chiller or air handlers outside, or systems that must cool below the freezing temperature of water. In geothermal heating/cooling systems, ethylene glycol is the fluid that transports heat through the use of a geothermal heat pump. The ethylene glycol either gains energy from the source, or dissipates heat to the source, depending if the system is being used for heating or cooling.
Due to its low freezing point, ethylene glycol resists freezing. A mixture of 60% ethylene glycol and 40% water does not freeze until temperatures drop below -45°C (-49° F).
In the plastics industry, ethylene glycol is an important precursor to polyester fibers and resins. Polyethylene terephthalate (PET) resins used to make plastic bottles for soft drinks is prepared from the reaction of ethylene glycol with terephthalic acid.
Because of its high boiling point and affinity for water, ethylene glycol is a useful desiccant. Ethylene glycol is widely used to inhibit the formation of natural gas hydrates in long multiphase pipelines that convey natural gas from remote gas fields to an onshore processing facility. Ethylene glycol can be recovered from the natural gas and reused as an inhibitor after purification treatment that removes water and inorganic salts.