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Dihydric alcohol
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Ethylene glycol is the simplest aliphatic dihydric alcohol with chemical properties of alcohols such as being capable of generating ether, ester, or being oxidized into acid or aldehyde as well as being condensed to form ether or being substituted by halogen. Its reaction with acyl chloride or acid anhydride generally forms di-esters. Under heating in the presence of catalyst (manganese dioxide, aluminum oxide, zinc oxide or sulfuric acid), it can be subject to intermolecular or intramolecular dehydration to form the cyclic ethylene acetals, which can react with nitric acid to generate glycol dinitrate (an explosive). Ethylene glycol is the raw material for production of polyester resins, alkyd resins and polyester fiber. It can also be used as the refrigerant agent for automobile and aircraft engines refrigerant. In 1980, the glycol amount used as refrigerant agent is equal to the amount consumption for producing polyester. In addition, it can also be used for synthesizing polymers such as polyester fibers. Ethylene glycol dinitrate, when used in combination with nitroglycerine can reduce the freezing point of explosives. Ethylene glycol can also be used as the raw material of pharmaceuticals and plastics and high-boiling solvents. Industry applied ethylene as a raw material with first converting it to ethylene oxide and then hydrolyzing to produce ethylene glycol.
This product is of fire and explosion hazards. It is irritating to skin and mucous membrane with inhalation of vapors or skin absorption producing a narcotic effect on the central nervous as well as causing kidney damage. Rat, through oral administration, has a LD50 of 8540 mg/kg. The maximal allowable concentration in the workplace is 5 × 10-6.
This information is edited by Xiongfeng Dai from Chemicalbook. |
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Poisoning and first aid
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This product is of low toxicity. Rat LD50: 5.5ml/kg~8.54ml/kg. People who is subject to oral administration by once has a LD50 of 80g~100g. The plasma concentration of ethylene glycol is 2.4g/L and can cause acute renal failure. It can be absorbed through the digestive tract, respiratory tract and skin. It can be discharged from the kidney in the form of prototype or ethanedioic acid (oxalate) from through oxidation. Glycol, after being oxidized into carbon dioxide, can be discharged from the respiratory tract.
Although ethylene glycol has a high toxicity but its volatility is small. Therefore, it is unlikely that the inhalation of it during production can cause severe poisoning. Inhalation poisoning is manifested as blurred consciousness, nystagmus and urine containing protein, calcium oxalate crystals and red blood cells. Oral toxicity in clinical practice can be divided into three stages: the first stage is mainly the central nervous system symptoms, such as the performance of ethanol poisoning; the second phase of the main symptoms mainly include shortness of breath, cyanosis, and various manifestations of pulmonary edema or bronchopneumonia; at the third stage, there may be significant renal disease, low back pain, kidney area percussion pain, renal dysfunction, proteinuria, hematuria, urine containing calcium oxalate crystals, as well as oliguria, anuria and even acute renal failure.
Patients mistakenly take it should be subject to the treatment based on the general principles of first aid for oral poisoning and can be given 600 mL of 1/6 mol of sodium lactate solution and 10 mL of 10% calcium gluconate through intravenous infusion. Patients of severe poisoning can subject to treatment of artificial kidney dialysis.
Container of ethylene glycol should have "toxic agents" mark. The product, upon heating, should be sealed, vented to prevent inhalation of the vapor or aerosol. Avoid long-term direct skin contact with the product. |
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Chemical Properties
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It is colorless transparent viscous liquid with sweet taste and moisture absorption capability. It is also miscible with water, low-grade aliphatic alcohols, glycerol, acetic acid, acetone, ketones, aldehydes, pyridine and similar coal tar bases. It is slightly soluble in ether but almost insoluble in benzene and its homologues, chlorinated hydrocarbons, petroleum ether and oils. |
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Uses
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Glycol is mainly used as the antifreeze agent for preparation of the automobile cooling systems and the raw material for the production of polyethylene terephthalate (the raw material of polyester fibers and plastics material). It can also be used for the production of synthetic resins, solvents, lubricants, surfactants, emollients, moisturizers, explosives and so on. Glycol can often used as alternative of glycerol and can often be used as hydration agent and solvent in the tanning industry and pharmaceutical industry. Glycol has a strong dissolving capability but it is easily to be oxidized to toxic metabolic oxalic acid and therefore can’t be widely used as a solvent. The ethylene glycol can be supplemented to the hydraulic fluid and can be used for preventing the erosion of oil-based hydraulic fluid on the rubber of the system; the water-based hydraulic fluid with ethylene glycol as a main component is an inflammable hydraumatic fluid and can be applied to the molding machine in aircraft, automobiles and high-temperature operation. There are many important derivatives of ethylene glycol. Low molecular weight polyethylene glycol (mono-uret ethylene glycol, bi-uret ethylene glycol, tri-uret ethylene glycol or respectively called as diethylene glycol, triethylene glycol, tetraethylene glycol) is actually the byproduct during the hydration of ethylene oxide B for preparation of ethylene glycol. |
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Production method
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1. Direct hydration of ethylene oxide is currently the only way for industrial-scale production of ethylene glycol. Ethylene oxide and water, under pressure (2.23MPa) and 190-200 ℃ conditions, and can directly have liquid-phase hydration reaction in a tubular reactor to generate ethylene glycol while being with byproducts diethylene glycol, tripropylene ethylene gl]ycol and multi-uret poly ethylene glycol. The dilute ethylene glycol solution obtained from the reaction further undergoes thin film evaporator condensation, and then dehydration, refinement to obtain qualified products and by-products. 2. sulfuric acid catalyzed hydration of ethylene oxide; ethylene oxide can react with water, in the presence of sulfuric acid as the catalyst, at 60-80 ℃ and pressure of 9.806-19.61kPa for hydration to generate ethylene glycol. The reaction mixture can be neutralized by liquid alkaline and evaporated of the water to obtain 80% ethylene glycol, and then distilled and concentrated in distillation column to obtain over 98% of the finished product. This method is developed in early time. Owing to the presence of corrosion, pollution and product quality problems, together with complex refining process, countries have gradually discontinued and instead change to direct hydration. 3. Direct ethylene hydration; directly synthesize ethylene glycol from ethylene instead of being via ethylene oxide. 4. dichloroethane hydrolysis. 5. Formaldehyde method.
Industrial preparation of ethylene glycol adopts chlorine ethanol method, ethylene oxide hydration and direct ethylene hydration with various methods having their characteristics, as described below.
Chlorohydrin method
Take chloroethanol as raw materials for hydrolysis in alkaline medium to obtain it. The reaction is carried out at 100 ℃. First generate ethylene oxide. Then pressurize at 1.01 MPa pressure to obtain ethylene glycol.
Ethylene oxide hydration
Hydration of ethylene oxide contains catalytic hydration and direct hydration. The hydration process can be carried out under either normal pressure or under compression. Normal pressure method generally take a small amount of inorganic acid as catalyst for reaction at 50~70 ℃.
Pressurized hydration had a high demand for the molar ratio of ethylene oxide over water which is higher than 1:6, to reduce the side reaction of producing the ether with the reaction temperature being at 150 °C and the pressure being 147kPa with hydration generating ethylene glycol.
There are currently gas phase catalytic hydration with silver oxide being the catalyst and the alumina oxide being the carrier for reaction at 150~240 ℃ to generate ethylene glycol.
Direct hydration of ethylene
Ethylene, in the presence of catalyst (e.g., antimony oxide TeO2 with palladium catalyst) can be oxidized in acetic acid solution to generate monoacetate ester or diacetate ester with further hydrolysis obtaining the ethylene glycol.
The above several methods takes ethylene oxide hydration as good with simple process and is suitable for industrialization. |
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Category
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Flammable liquid. |
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Toxicity grading
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Poisoning. |
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Acute toxicity
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Oral-rat LD50: 4700 mg/kg; Oral-Mouse LD50: 5500 mg/kg. |
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Irritation data
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Skin-rabbit 555 mg Mild; Eyes-rabbit 500 mg/24 hr mild. |
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Hazardous characteristics of explosive
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Being mixed with air can be explosive. |
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Flammability and hazard characteristics
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It is combustible in case of fire, high temperature and strong oxidant with burning releasing smoke irritation. |
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Storage characteristics
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Treasury: ventilation, low-temperature and dry. |
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Extinguishing agents
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Foam, carbon dioxide, water spray, sand. |
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Professional standards
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TWA 60 mg/m3; STEL 120 mg/m3. |
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Description
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Ethylene glycol was first synthesized in 1859; however, it did
not become a public health concern until after World War II. In
fact, the first published series of deaths from ethylene glycol
consumption involved 18 soldiers who drank antifreeze as
a substitute for ethanol. Despite the early recognition that
patients who drank ethanol in addition to ethylene glycol had
prolonged survival when compared to those drinking ethylene
glycol alone, antidotal treatment of ethylene glycol toxicity
with ethanol was not evaluated until the 1960s. Today,
ethylene glycol poisoning continues to be a public health
problem, particularly in the southeastern United States. In
2009, US poison control centers received 5282 calls about
possible ethylene glycol exposures, and the toxicology
community believes these exposures are underreported. |
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Definition
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ChEBI: A 1,2-glycol compound produced via reaction of ethylene oxide with water. |
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Production Methods
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Historically, ethylene glycol has been manufactured by
hydrolyzing ethylene oxide. Presently, it is also produced
commercially by oxidizing ethylene in the presence of acetic
acid to form ethylene diacetate, which is hydrolyzed to the
glycol, and acetic acid is recycled in the process . |
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Preparation
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Ethylene glycol is prepared by the hydration of ethylene oxide:
This reaction is carried out in a manner comparable to that described for the
preparation of propylene glycol from propylene oxide .
Ethylene glycol is a colourless liquid, b.p. 197°C. |
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Reactions
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Glycol reacts (1) with sodium to form sodium glycol, CH2OH · CH2ONa, and disodium glycol, CH2ONa·CH2ONa; (2) with phosphorus pentachloride to form ethylene dichloride, CH2Cl·CH2Cl (3) with carboxy acids to form mono- and disubstituted esters, e.g., glycol monoacetate, CH2OH·CH2OOCCH3, glycol diacetate, CH3COOCH2 · CH2OOCCH3; (4) with nitric acid (with sulfuric acid), to form glycol mononitrate, CH2OH·CH2ONO2, glycol dinitrate, CH2ONO2 · CH2ONO2; (5) with hydrogen chloride, heated, to form glycol chlorohydrin (ethylene chlorohydrin, CH2OH·CHCl); (6) upon regulated oxidation to form glycollic aldehyde, CH2OH·CHO, glyoxal, CHO · CHO, glycollic acid, CH2OH·COOH, glyoxalic acid, CHO·COOH, oxalic acid, COOH·COOH. |
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General Description
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Ethylene glycol is a clear, colorless syrupy liquid. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Since Ethylene glycol is a liquid Ethylene glycol can easily penetrate the soil and contaminate groundwater and nearby streams. |
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Reactivity Profile
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Mixing Ethylene glycol in equal molar portions with any of the following substances in a closed container caused the temperature and pressure to increase: chlorosulfonic acid, oleum, sulfuric acid, [NFPA 1991]. |
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Hazard
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Questionable carcinogen. Toxic by ingestion and inhalation. Lethal dose reported to be
100 cc. |
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Health Hazard
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Inhalation of vapor is not hazardous. Ingestion causes stupor or coma, sometimes leading to fatal kidney injury. |
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Fire Hazard
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Ethylene glycol is combustible. |
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Flammability and Explosibility
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Notclassified |
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Biochem/physiol Actions
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Ethylene glycol is a low toxicity molecule and is used for embryo cryopreservation in many domestic animals.Ethylene glycol 5M solution is an additive screening solution of Additive Screening Kit. Additive Screen kit is designed to allow rapid and convenient evaluation of additives and their ability to influence the crystallization of the sample. The Additive Kit provides a tool for refining crystallization conditions. |
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Safety Profile
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Human poison by
ingestion. (Lethal dose for humans reported
to be 100 mL.) Moderately toxic to humans
by an unspecified route. Moderately toxic
experimentally by ingestion, subcutaneous,
intravenous, and intramuscular routes.
Human systemic effects by ingestion and
inhalation: eye lachrymation, general
anesthesia, headache, cough, respiratory
stimulation, nausea or vomiting, pulmonary,
kidney, and liver changes. If ingested it
causes initial central nervous system
stimulation followed by depression. Later, it
causes potentially lethal kidney damage.
Very toxic in particulate form upon
inhalation. An experimental teratogen.
Other experimental reproductive effects.
Human mutation data reported. A skin, eye,
and mucous membrane irritant.
Combustible when exposed to heat or
flame; can react vigorously with oxidants. Moderate explosion hazard when exposed
to flame. Iptes on contact with chromium
trioxide, potassium permanganate, and
sodium peroxide. Mixtures with ammonium
dichromate, silver chlorate, sodium chlorite,
and uranyl nitrate ipte when heated to
100°C. Can react violently with
chlorosulfonic acid, oleum, H2SO4, HClO4,
and Pass. Aqueous solutions may ignite
silvered copper wires that have an applied
D.C. voltage. To fight fire, use alcohol foam,
water, foam, CO2, dry chemical. When
heated to decomposition it emits acrid
smoke and irritating fumes. |
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Potential Exposure
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Ethylene glycol is used in antifreeze (especially as car radiator antifreeze) and in production of polyethylene terephthalate fibers and films; in hydraulic fluids; antifreeze and coolant mixtures for motor vehicles; electrolytic condensers; and heat exchangers. It is also used as a solvent and as a chemical intermediate for ethylene glycol dinitrate, glycol esters; resins, and for pharmaceuticals. |
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Environmental Fate
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Ethylene glycol is considered an inert ingredient in pesticides. It
typically enters the environment through waste streams after
use of deicing products, where it is highly mobile in soil and
contaminates groundwater. Ethylene glycol is considered
‘readily biodegradable.’ It biodegrades relatively quickly; its
half-life (t1/2) is 2–12 days in soil.
Ethylene glycol is biodegraded in water under both aerobic
and anaerobic conditions within a day to a few weeks. In the
atmosphere, ethylene glycol photochemically degrades with
a t1/2 of approximately 2 days. |
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Shipping
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UN3082 Environmentally hazardous substances,
liquid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required |
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Purification Methods
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It is very hygroscopic, and also likely to contain higher diols. Dry it with CaO, CaSO4, MgSO4 or NaOH and distil it under vacuum. Dry further by reaction with sodium under nitrogen, reflux for several hours and distil. The distillate is then passed through a column of Linde type 4A molecular sieves and finally distil under nitrogen, from more molecular sieves. Then fractionally distil it. [Beilstein 1 IV 2369.] |
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Toxicity evaluation
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Ethylene glycol has low toxicity but it is metabolized to
a variety of toxic metabolites. Ethylene glycol and glycolaldehyde
have an intoxicating effect on the central nervous
system that can lead to ataxia, sedation, coma, and respiratory
arrest similar to ethanol intoxication. However, the profound
metabolic acidosis reported in toxicity is secondary to accumulation
of acid metabolites, especially glycolic acid. The
oxalic acid metabolite complexes with calcium and precipitates
as calcium oxalate crystals in the renal tubules, leading to acute
renal injury. Further, oxalate’s ability to chelate calcium may
cause clinically relevant serum hypocalcemia. |
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Incompatibilities
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Reacts with sulfuric acid, oleum, chlorosulfonic acid; strong oxidizing agents; strong bases; chromium trioxide; potassium permanganate; sodium peroxide.
Hygroscopic (i.e., absorbs moisture from the air) |
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Waste Disposal
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Dissolve or mix the material
with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal,
state, and local environmental regulations must be
observed. Alternatively, ethylene glycol can be recovered
from polyester plant wastes |
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Who Evaluation
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Evaluation year: 1998 |
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EXPOSURE ROUTES
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inhalation, ingestion, skin and/or eye contact
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FIRST AID
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(See procedures)
Eye:Irrigate immediately
Skin:Water wash immediately
Breathing:Respiratory support
Swallow:Medical attention immediately
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Consumer Uses
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ECHA has no public registered data indicating whether or in which chemical products the substance might be used. ECHA has no public registered data on the routes by which this substance is most likely to be released to the environment. |
