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Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes: as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odorless, colorless, flammable, viscous liquid. It has a sweet taste but is toxic in high concentrations. This molecule has been observed in outer space.
This reaction can be catalyst by either 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. The major byproducts are the oligomers diethylene glycol, triethylene glycol, and tetraethylene glycol. The separation of these oligomers and water is energy-intensive. World production of ethylene glycol was ~20 Mt in 2010.
A higher selectivity is achieved by the use of Shell's OMEGA process. In the OMEGA process, the ethylene oxide is first converted with carbon dioxide () to ethylene carbonate. This ring is then hydrolyzed with a base catalyst in a second step to produce mono-ethylene glycol in 98% selectivity.Scott D. Barnicki, "Synthetic Organic Chemicals", in Handbook of Industrial Chemistry and Biotechnology edited by James A. Kent, New York: Springer, 2012. 12th ed. . The carbon dioxide is released in this step again and can be fed back into the process circuit. The carbon dioxide comes in part from ethylene oxide production, where a part of the ethylene is completely oxidation.
Ethylene glycol is produced from carbon monoxide in countries with large coal reserves and less stringent environmental regulations. The oxidative carbonylation of methanol to dimethyl oxalate provides a promising approach to the production of -based ethylene glycol. (PDF; 5.4 MB), 2011 Prospectus. Dimethyl oxalate can be converted into ethylene glycol in high yields (94.7%) and H. T. Teunissen and C. J. Elsevier, Ruthenium catalyzed hydrogenation of dimethyl oxalate to ethylene glycol, J. Chem. Soc., Chem. Commun., 1997, 667–668), . by hydrogenation with a copper catalyst:S. Zhang et al., Highly-Dispersed Copper-Based Catalysts from Cu–Zn–Al Layered Double Hydroxide Precursor for Gas-Phase Hydrogenation of Dimethyl Oxalate to Ethylene Glycol, Catalysis Letters, Sept. 2012, 142 (9), 1121–1127, .
Because the methanol is recycled, only carbon monoxide, hydrogen, and oxygen are consumed. One plant with a production capacity of of ethylene glycol per year is in Inner Mongolia, and a second plant in the Chinese province of Henan with a capacity of was scheduled for 2012. , four plants in China with a capacity of each were operating, with at least 17 more to follow.
In the United States, semicommercial production of ethylene glycol via ethylene chlorohydrin started in 1917. The first large-scale commercial glycol plant was erected in 1925 at South Charleston, West Virginia, by Carbide and Carbon Chemicals Co. (now Union Carbide Corp.). By 1929, ethylene glycol was being used by almost all dynamite manufacturers. In 1937, Carbide started up the first plant based on Lefort's process for vapor-phase oxidation of ethylene to ethylene oxide. Carbide maintained a monopoly on the direct oxidation process until 1953 when the Scientific Design process was commercialized and offered for licensing.
Pure ethylene glycol has a specific heat capacity about one-half that of water. So, while providing freeze protection and an increased boiling point, ethylene glycol lowers the specific heat capacity of water mixtures relative to pure water. A 1:1 mix by mass has a specific heat capacity of about 3140 J/(kg·°C) (0.75 BTU/(lb·°F)), three-quarters that of pure water, thus requiring increased flow rates in same-system comparisons with water.
The mixture of ethylene glycol with water provides additional benefits to coolant and antifreeze solutions, such as preventing corrosion and acid degradation, as well as inhibiting the growth of most microbes and fungi. Mixtures of ethylene glycol and water are sometimes informally referred to in the industry as glycol concentrates, compounds, mixtures, or solutions.
Table of thermal and physical properties of saturated liquid ethylene glycol:Frank P. Incropera, David P. Dewitt, heodore L. Bergman, Adrienne S. Lavigne (2025). 9780471457282, John Wiley and Sons, Inc.. ISBN 9780471457282
| 0 | 1130.75 | 2.294 | 0.242 | 615 | |||
| 20 | 1116.65 | 2.382 | 0.249 | 204 | |||
| 40 | 1101.43 | 2.474 | 0.256 | 93 | |||
| 60 | 1087.66 | 2.562 | 0.26 | 51 | |||
| 80 | 1077.56 | 2.65 | 0.261 | 32.4 | |||
| 100 | 1058.5 | 2.742 | 0.263 | 22.4 |
There is a difference in the mixing ratio, depending on whether it is ethylene glycol or propylene glycol. For ethylene glycol, the mixing ratios are typically 30/70 and 35/65, whereas the propylene glycol mixing ratios are typically 35/65 and 40/60. The mixture must be frost-proof at the lowest operating temperature.
Because of the depressed freezing temperatures, ethylene glycol is used as a de-icing fluid for and aircraft, as an antifreeze in automobile engines, and as a component of vitrification (anticrystallization) mixtures for low-temperature preservation of biological tissues and organs.
The use of ethylene glycol not only depresses the freezing point of aqueous mixtures but also elevates their boiling point. This results in the operating temperature range for heat-transfer fluids being broadened on both ends of the temperature scale. The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower vapor pressure than pure water.
Natural gas is dehydrated by ethylene glycol. In this application, ethylene glycol flows down from the top of a tower and meets a rising mixture of water vapor and hydrocarbon gases. Dry gas exits from the top of the tower. The glycol and water are separated, and the glycol is recycled. Instead of removing water, ethylene glycol can also be used to depress the temperature at which are formed. The purity of glycol used for hydrate suppression (monoethylene glycol) is typically around 80%, whereas the purity of glycol used for dehydration (triethylene glycol) is typically 95 to more than 99%. Moreover, the injection rate for hydrate suppression is much lower than the circulation rate in a glycol dehydration tower.
It serves as a protecting group in organic synthesis for the manipulation of ketones and aldehydes. (1999). 9780471160199, John Wiley & Sons. ISBN 9780471160199 By reacting with the carbonyl to form an acetal product, it reduces the likelihood of nucleophilic attack at that carbonyl carbon. After the desired reaction is completed, the carbonyl can be regenerated using acid-catalyzed hydrolysis. In one example, isophorone was protected using ethylene glycol:
The glycol-derived dioxalane of ethyl acetoacetate is a commercial fragrance fructone. (2025). 9783527306732 ISBN 9783527306732
Antifreeze products for automotive use containing propylene glycol in place of ethylene glycol are available. They are generally considered safer to use, as propylene glycol is not as palatable and is converted in the body to lactic acid, a normal product of metabolism and exercise.
Australia, the UK, and seventeen US states (as of 2012) require the addition of a bitter flavoring (Denatonium) to antifreeze. In December 2012, US antifreeze manufacturers agreed voluntarily to add a bitter flavoring to all antifreeze that is sold in the consumer market of the US.
In 2022, several hundred children died of acute kidney failure in Indonesia and The Gambia because the paracetamol syrup made by New Delhi-based Maiden Pharmaceuticals contained ethylene glycol and diethylene glycol, ingredients that have been linked to child deaths from acute kidney injury in The Gambia. In December 2022, Uzbekistan's health ministry said children died as a result of ethylene glycol in cough syrup made by Marion Biotech, which is based at Noida, near New Delhi.
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