Трихлороэтилен

Описание

Trichloroethylene (IUPAC), CHClCCl2, is a stable, low-boiling, colorless liquid with a chloroform-like odor. It is not corrosive to the common metals even in the presence of moisture. It is slightly soluble in water and is nonflammable. It is toxic by inhalation, with a TLV of 50 ppm and an IDLH of 1000 ppm in air. The FDA has prohibited its use in foods, drugs, and cosmetics. The four-digit UN identification number is 1710. The NFPA 704 designation is health 2, flammability 1, and reactivity 0. Its primary uses are in metal degreasing, dry cleaning, as a refrigerant and fumigant, and for drying electronic parts.

Химические свойства

Trichloroethylene, a colorless (often dyed blue), nonflammable, noncorrosive liquid that has the “sweet” odor characteristic of some chlorinated hydrocarbons. The Odor Threshold is 25-50 ppm.

Физические свойства

Clear, colorless, watery-liquid with a chloroform-like odor. Odor threshold concentrations determined in air were 21.4 ppm_v (Leonardos et al., 1969) and 3.9 ppm_v (Nagata and Takeuchi, 1990). The average least detectable odor threshold concentrations in water at 60 °C and in air at 40 °C were 10 and 2.6 mg/L, respectively (Alexander et al., 1982).

Использование

Trichloroethylene is used as a solvent, in drycleaning, in degreasing, and in limited use asa surgical anesthetic.

Методы производства

TCE has been in commercial use for almost 60 years. TCE has been used as a solvent because of its powerful ability to dissolve fats, greases, and waxes. It has been widely used in the dry cleaning industry and as a metal degreaser and in the electronic components industry where workers have been observed using it as a cleaning solvent without any protective equipment, thus allowing uncontrolled skin contact and inhalation exposures.

Определение

ChEBI: A member of the class of chloroethenes that is ethene substituted by chloro groups at positions 1, 1 and 2.

Общее описание

A clear colorless volatile liquid having a chloroform-like odor. Denser than water and is slightly soluble in water. Noncombustible. Used as a solvent, fumigant, in the manufacture of other chemicals, and for many other uses.

Реакции воздуха и воды

Slightly soluble in water.

Профиль реактивности

Trichloroethylene has been determined experimentally that mixtures of finely divided barium metal and a number of halogenated hydrocarbons possess an explosive capability. Specifically, impact sensitivity tests have shown that granular barium in contact with monofluorotrichloromethane, trichlorotrifluoroethane, carbon tetrachloride, Trichloroethylene, or tetrachloroethylene can detonate (ASESB Pot. Incid. 39. 1968; Chem. Eng. News 46(9):38. 1968). Trichloroethylene has been determined experimentally that a mixture of beryllium powder with carbon tetrachloride or with Trichloroethylene will flash or spark on heavy impact (ASESB Pot. Incid. 39. 1968). A mixture of powdered magnesium with Trichloroethylene or with carbon tetrachloride will flash or spark under heavy impact (ASESB Pot. Incid, 39. 1968).

Угроза здоровью

The toxic effects manifested in humansfrom inhaling trichloroethylene vapors areheadache, dizziness, drowsiness, fatigue, andvisual disturbances. A 2-hour exposure to a1000-ppm concentration affected the visualperception. Higher concentrations can pro duce narcotic effects. Heavy exposures maycause death due to respiratory failure or car diac arrest. A 4-hour exposure to 8000 ppmwas lethal to rats. Chronic exposure causedincrease in kidney and liver weights in testanimals.
The symptoms of poisoning from oralintake of trichloroethylene are nausea, vom iting, diarrhea, and gastric disturbances. Theacute oral toxicity, however, is low. Theoral LD50 value in mice is in the range2500 mg/kg. Trichloroethylene metabolizesto trichloroacetic acid, which is excreted inthe urine.
Although trichloroethylene exhibits lowtoxicity, its metabolite trichloroethanol, andoxidative degradation products phosgene,COCl2, and chlorine, can cause severe unex pected health hazards. Kawakami andassociates (1988) reported a case of Steven–Johnson syndrome in a worker in a printingfactory. In another case, fire on a stove in ametal-degreasing workplace produced phos gene and chlorine inhalation, which causeddyspnea, fever, and fatigue.
Trichloroethylene exhibited evidence ofcarcinogenicity in laboratory animals. Oraladministration produced liver tumors, whileinhalation caused lung and blood tumors inmice and rats.

Пожароопасность

Special Hazards of Combustion Products: Toxic and irritating gases are produced in fire situations.

Химическая реактивность

Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.

Контактные аллергены

Trichloroethylene is a chlorinated hydrocarbon used as a detergent or solvent for metals, oils, resins, sulfur, and as general degreasing agent. It can cause irritant contact dermatitis, generalized exanthema, Stevens-Johnson- like syndrome, pustular or bullous eruption, scleroderma, as well as neurological and hepatic disorders.

Возможный контакт

Trichloroethylene is used as a vapor degreaser of metal parts, as a solvent; and as a drug; It is also used for extracting caffeine from coffee, as a dry-cleaning agent; and as a chemical intermediate in the production of pesticides; in making waxes, gums, resins, tars, paints, varnishes, and specific chemicals; such as chloroacetic acid.

Канцерогенность

Trichloroethylene is reasonably anticipated to be a human carcinogen based on limited evidence of carcinogenicity from studies in humans, sufficient evidence of carcinogenicity from studies in experimental animals, and information from studies on mechanisms of carcinogenesis.

Метаболический путь

From the photooxidation reaction medium (1) of trichloroethylene, the formation of dichloroacetyl chloride, CO, phosgene, and pentachloroethane and their conversion to the final product, CO2, are identified. By the second TiO2 photocatalyst reaction (2), trichloroacetaldehyde, dichloroacetyl chloride, CO, and phosgene with the new identified intermediates oxalyl chloride, trichloroacetyl chloride, and trichloroacetic acid are observed.

Перевозки

UN1710 Trichloroethylene, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Методы очистки

Tricloroethylene undergoes decomposition in a similar way as CHCl3, giving HCl, CO, COCl2 and organic products. It reacts with KOH, NaOH and 90% H2SO4, and forms azeotropes with water, MeOH, EtOH, and acetic acid. It is purified by washing successively with 2M HCl, water and 2M K2CO3, then dried with K2CO3 and CaCl2, then fractionally distilled before use. It has also been steam distilled from 10% Ca(OH)2 slurry, most of the water being removed from the distillate by cooling to -30o to -50o and filtering off the ice through chamois skin: the trichloroethylene is then fractionally distilled at 250mm pressure and collected in a blackened container. [Carlisle & Levine Ind Eng Chem (Anal Ed) 24 1164 1932, Beilstein 1 IV 712.]

Несовместимости

Contact with strong caustics causes decomposition and the production of highly toxic and flammable dichloroacetylene. Violent reaction with chemically active metals; powders, or shavings, such as aluminum, barium, lithium, sodium, magnesium, and titanium. Violent reaction with aluminum in the presence of dilute hydrochloric acid. Thermal decomposition of trichloroethylene, due to contact with hot metal or UV radiation, forms hazardous products including chlorine gas, hydrogen chloride; and phosgene. Keep this chemical away from high temperatures, such as arc welding or cutting, unshielded resistance heating; open flames; and high intensity UV light. Slowly decomposed by light in presence of moisture, with formulation of hydrochloric acid.

Утилизация отходов

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration, preferably after mixing with another combustible fuel. Care must be exercised to assure complete combustion to prevent the formation of phosgene. An acid scrubber is necessary to remove the halo acids produced. An alternative to disposal for TCE is recovery and recycling.