Ethylene glycol
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| General | ||||||||||||||||
| Surname | Ethylene glycol | |||||||||||||||
| other names |
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| Molecular formula | C 2 H 6 O 2 | |||||||||||||||
| Brief description |
colorless, viscous liquid with a sweetish taste |
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| properties | ||||||||||||||||
| Molar mass | 62.07 g mol −1 | |||||||||||||||
| Physical state |
liquid |
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| density |
1.11 g cm −3 (20 ° C) |
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| Melting point |
−16 ° C |
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| boiling point |
197 ° C |
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| Vapor pressure |
5.3 Pa (20 ° C) |
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| pK s value |
15.1 (25 ° C) |
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| solubility | ||||||||||||||||
| Refractive index |
1.4318 (20 ° C) |
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| safety instructions | ||||||||||||||||
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| MAK |
DFG / Switzerland: 10 ml m −3 or 26 mg m −3 |
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| Toxicological data | ||||||||||||||||
| Thermodynamic properties | ||||||||||||||||
| ΔH f 0 |
−460.0 kJ / mol (l) −392.2 kJ / mol (g) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C | ||||||||||||||||
(Mono-) ethylene glycol ( MEG , common name glycol ) is the simplest dihydric alcohol with the chemical name ethane-1,2-diol . It is the simplest vicinal diol . The common name is derived from sweet-tasting ( Greek glykys 'sweet').
The term glycols is also used for two classes of diols that are derived from ethylene glycol. On the one hand there are 1,2-diols such as 1,2-propanediol and on the other hand α, ω-diols, which are formed by the condensation of ethylene glycol: polyethylene glycols . Examples are diethylene glycol (DEG), triethylene glycol (TEG).
Extraction and presentation
Technical manufacturing
The large-scale production of ethylene glycol usually takes place through the catalyst-free hydration of ethylene oxide at temperatures of 150-200 ° C. and pressures of 20-40 bar.
The reaction is carried out in adiabatically operated tubular reactors. One works with a 10-20 fold molar excess of water to suppress the formation of higher glycols (especially diethylene glycol and triethylene glycol ). The components are usually worked up and separated from the product mixture by multi-stage distillation in rectification columns .
Furthermore, the hydration can also be carried out with acidic or basic catalysts at low temperatures (50–70 ° C) and without pressure.
Royal Dutch Shell's OMEGA process
A further development of this process is the Royal Dutch Shell's OMEGA process . Here, the ethylene oxide is first reacted with carbon dioxide in water to form ethylene carbonate . This then hydrolyzes with steam to form 2-hydroxyethyl hydrogen carbonate, which then breaks down by decarboxylation in water to form ethylene glycol and carbon dioxide. The latter is returned to the first reaction stage after processing.
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The yield of ethylene glycol in this process is approx. 99%. Mixtures of potassium iodide (KI) and potassium molybdate (K 2 MoO 4 ) serve as catalysts .
The global production capacity for ethylene glycol in 2010 was around 25 million tons per year.
properties
Ethylene glycol is a colorless, viscous liquid at room temperature. The melting point is −16 ° C. The compound boils at 197 ° C. under normal pressure. According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in Torr , T in ° C) with A = 9.6, B = 3225 and C = 283 in the temperature range from 53 ° C to 198 ° C.
Ethylene glycol has a viscosity of 20.81 mPas at 20 ° C. At 30 ° C the viscosity drops to 13.87 mPas.
Ethylene glycol forms flammable vapor-air mixtures above the flash point of 111 ° C. The ignition temperature is 410 ° C. The substance therefore falls into temperature class T2.
Ethylene glycol decomposes at the boiling point when exposed to air, releasing, among other things, glycolaldehyde , glyoxal , acetaldehyde , methane , formaldehyde , carbon monoxide and hydrogen . Unlike other glycol ethers, it does not form an azeotrope with water .
When used as a cooling liquid, the heat capacity varies from 2.4 to 4.2 kJ / (kg · K) for pure water, depending on the addition of water. A 50/50 mixture freezes at −40 ° C, boils at 108 ° C and reaches a heat capacity of 3.5 kJ / (kg · K).
Ethylene glycol is slightly corrosive to iron pipes.
use
It was developed in 1928 by IG Farben in Ludwigshafen as a frost-proof coolant for internal combustion engines and sold under the brand name Glysantin .
(Mono) ethylene glycol is mainly used today to produce polyester fibers and polyethylene terephthalate , a polyester made from stoichiometric amounts of terephthalic acid and ethylene glycol with a 100% degree of esterification. 45% of the amount produced worldwide is processed in China.
Because of its hydrophilic properties, it is used as an absorbent for the removal of water vapor from natural and refinery gas or cycle gases from hydro refining. Glycol-water mixtures are used as de-icing agents for aircraft and traffic areas at all commercial airports .
In research, ethylene glycol is used as a solvent and reducing agent for the liquid phase synthesis of one-dimensional metal nanostructures.
safety instructions
- The skin permeability of ethylene glycol is similar to that of ethanol and glycerin . Ethylene glycol is very difficult to absorb through intact skin. Reddening or inflammation may occur, and irritation effects may be felt when the eyes or mucous membranes come into contact.
- Because of the low vapor pressure , it can practically only be inhaled as an aerosol or vapor from hot products containing ethylene glycol.
- When ingested 30 ml or more is a serious, if more than 100 ml of a life-threatening intoxication . The BfR specifies a toxic dose of 0.1 ml / kg body weight for humans.
Oral toxicity
The symptoms are similar to those of methanol poisoning ("adulterated alcohol"). The breakdown products, however, are completely different. Because of the sweet taste of water-diluted antifreeze, ethylene glycol poisoning is not uncommon. For adults, immediate consumption of drinking ethanol is recommended as an antidote (150 ml whiskey or brandy); clinically, 4-methylpyrazole ( fomepizole ) or ethanol is given iv.
It is not the ethylene glycol itself that is toxic to the cells, but its metabolites with aldehyde functions, glycolaldehyde , glyoxal and glyoxylic acid . These react with all thiol and amino functions of enzymes and proteins. The enzyme alcohol dehydrogenase (ADH) catalyzes these oxidation steps (alcohol → aldehyde). The recommended antidotes act as competitive inhibitors of alcohol dehydrogenase. The enzyme aldehyde oxidase (AO) controls the slow oxidation step (aldehyde → carboxylic acid).
If left untreated, the poisoning progresses in three stages from initial symptoms (dizziness, drunkenness, impaired consciousness), damage to the heart and liver (after 12–24 hours) to uremic coma with acute kidney failure . Typical degradation and secondary products such as glycolic acid , hippuric acid and oxalic acid are detected.
See also
Web links
Individual evidence
- ↑ entry to GLYCOL in CosIng database of the European Commission, accessed on February 26 2020th
- ↑ a b Entry on ethylene glycol. In: Römpp Online . Georg Thieme Verlag, accessed on November 10, 2014.
- ↑ a b c d e f g h i j k Entry for CAS no. 107-21-1 in the GESTIS substance database of the IFA , accessed on March 19, 2017(JavaScript required) .
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Dissociation Constants of Organic Acids and Bases, pp. 8-42.
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-232.
- ↑ Entry on Ethane-1,2-diol in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on August 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 107-21-1 or ethylene glycol ), accessed on November 2, 2015.
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 89th edition. (Internet version: 2009), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-22.
- ↑ a b c d Manfred Baerns, Arno Behr, Axel Brehm, Jürgen Gmehling, Kai-Olaf Hinrichsen, Hanns Hofmann, Regina Palkovits, Ulfert Onken, Albert Renken: Technische Chemie . 2nd Edition. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013, ISBN 978-3-527-33072-0 .
- ↑ Manfred Fedtke, Wilhelm Pritzkow, Gerhard Zimmermann: Technical organic chemistry - basic materials, intermediate products, final products, polymers . 1st edition. German publishing house for basic industry, Leipzig 1992, ISBN 3-342-00420-7 .
- ↑ a b Entry on ethylene glycol. In: Römpp Online . Georg Thieme Verlag, accessed on February 17, 2019.
- ↑ a b E. Brandes, W. Möller: Safety-related parameters - Volume 1: Flammable liquids and gases. Wirtschaftsverlag NW - Verlag für neue Wissenschaft GmbH, Bremerhaven 2003.
- ↑ Nikos G. Tsierkezos, Ioanna E. Molinou: Thermodynamic Properties of Water + Ethylene Glycol at 283.15, 293.15, 303.15, and 313.15 K . In: Journal of Chemical & Engineering Data . tape 43 , no. 6 , November 1, 1998, pp. 989-993 , doi : 10.1021 / je9800914 .
- ↑ The explosion range is between 3.2% by volume (80 g / m³) as the lower explosion limit (LEL) and 43% by volume (1090 g / m³) as the upper explosion limit (UEL).
- ↑ schmidtler.de: Antifreeze
- ↑ Glycosol N data sheet (PDF; 689 kB) at glykolundsole.de
- ↑ Wolfgang Stichel: Use of antifreeze in heating systems: Aging of glycol / water mixtures. Federal Institute for Materials Research and Testing , 125 Years of IKZ Haustechnik, issue 21/1997, p. 32ff.
- ↑ BASF-History 1924–1944 ( Memento from February 28, 2017 in the Internet Archive )
- ^ Report on the world market situation by PTA and MEG, 2007 ( Memento from August 31, 2011 in the Internet Archive )
- ↑ a b c BASF Medical guidelines for acute exposure to ethylene glycol, information and recommendations for paramedics / emergency doctors / doctors on site. (Status: 2012; PDF; 36 kB)
- ↑ The minimum lethal dose for humans is given as around 100 ml (GESTIS) and 1.4 g / kg body weight (Agency for Toxic Substances and Disease Registry: Toxicological Profile for Ethylene Glycol , p. 50). In individual cases and with optimal medical therapy, the intake of about 1000 ml (GESTIS) ethylene glycol was survived.
- ↑ BfR - Medical reports in the event of poisoning, p. 41 (2005)
- ↑ Merck Veterinary Manual - Overview of Ethylene Glycol Toxicity (rev. May 2013) .
- ↑ G. Eisenbrand, M. Metzler: Toxikologie für Chemiker, Georg Thieme Verlag Stuttgart ISBN 3-13-127001-2 , p. 207.