дихлордифторметан

Описание

Dichlorodifluoromethane is known as CFC-12, also called R-12, or Freon-12. R-12 is a general name for Refrigerant-12. Freon is a trade name for DuPont. CFC stands for chlorofl uorocarbons, which are nontoxic, nonfl ammable, synthetic chemicals containing atoms of carbon, chlorine, and fluorine.CFC use climbed steadily worldwide as it was incorporated in refrigeration and air conditioning, as well as being used as propellants, blowing agents, and solvents.

dichlorodifluoromethane structure

Химические свойства

Dichlorodifluoromethane is a liquefied gas and exists as a liquid at room temperature when contained under its own vapor pressure, or as a gas when exposed to room temperature and atmospheric pressure. The liquid is practically odorless and colorless. The gas in high concentrations has a faint etherlike odor. Dichlorodifluoromethane is noncorrosive, nonirritating, and nonflammable. Ethereal odor at .20% by volume. Shipped as a compressed gas.
Dichlorotetrafluoroethane is a colorless, nonflammable liquefied gas with a faint, ethereal odor.
Trichloromonofluoromethane is a clear, volatile liquid at room temperature and atmospheric pressure. It has a characteristic carbon tetrachloride-like odor and is nonirritating and nonflammable.

История

CFCs were developed in the 1930s as coolants for refrigerator, freezer, and motor vehicle air conditioners.they subsequently found use as metal cleaners, degreasers, propellants, solvents, and blowing agents in the production of foams. CFCs have received widespread environmental attention because of their potential to deplete stratospheric ozone.

Использование

Refrigerant, aerosol propellant.
Dichlorodifluoromethane is used as a refrigerant gas in refrigerators and air conditioners.
Dichlorodifluoromethane is also used in aerosol sprays, in plastics, and as an aid in detecting leaks.
Dichlorodifluoromethane harms the ozone layer, which protects the earth from the sun’s ultraviolet radiation.

Методы производства

Dichlorodifluoromethane is prepared by the reaction of hydrogen fluoride with carbon tetrachloride in the presence of a suitable catalyst, such as polyvalent antimony. The dichlorodifluoromethane formed is further purified to remove all traces of water and hydrochloric acid as well as traces of the starting and intermediate materials.
Trichloromonofluoromethane is also obtained by this process.
Dichlorotetrafluoroethane is prepared by the reaction of hydrogen fluoride with chlorine and perchloroethylene in the presence of a suitable catalyst such as polyvalent antimony.

Общее описание

A colorless gas having a faint ethereal odor. Shipped as a liquid confined under its own vapor pressure. Contact with the unconfined liquid can cause frostbite. Both components are noncombustible. Can asphyxiate by the displacement of air. Exposure of the closed container to prolonged heat or fire can cause Dichlorodifluoromethane to rupture violently and rocket.

Реакции воздуха и воды

The liquefied gas poured into water can be violently explosive. This is due to the phase transition from superheated liquid to vapor.

Профиль реактивности

The reaction of aluminum with various halogenated hydrocarbons produces a self-sustaining reaction with sufficient heat to melt aluminum pieces, examples of other halogenated hydrocarbons are fluorotrichloromethane, Dichlorodifluoromethane, chlorodifluoromethane, tetrafluoromethane. The vigor of the reaction appears to be dependent on the combined degree of fluorination and the vapor pressure, [Chem. Eng. News 39(27):44(1961)].

Угроза здоровью

INHALATION: some narcosis when 10% in air is breathed.

Профиль безопасности

Dichlorodifluoromethane is a colorless, non-flammable gas that can affect you when breathed in. Acute (short-term) exposure to dichlorodifluoromethane can cause dizziness, lightheadedness, and trouble with concentration. Exposure to high concentrations of the gas can cause the heart to beat irregularly or to stop. The health effects of chronic (long-term) exposure to dichlorodifluoromethane are unknown at this time. There is no evidence of an increase in cancer risk due to exposure to dichlorodifluoromethane.

Возможный контакт

Dichlorodifluoromethane is used as an aerosol propellant, refrigerant and foaming agent

Канцерогенность

There was no evidence of carcinogenicity when groups of 50 male and 50 female rats were given oral doses of 15 or 150 mg/kg of CFC 12 daily for 2 years. As described above, there was no evidence of carcinogenicity when groups of 90 male and 90 female rats and of 60 male and 60 female mice were exposed by inhalation to levels of 1000 and 5000 ppm, 4 h/day, 5 days/ week.

Экологическая судьба

Surface Water. Estimated half-lives of dichlorodifluoromethane from an experimental marine mesocosm during the spring (8–16 °C) and winter (3–7 °C) were 20 and 13 d, respectively (Wakeham et al., 1983).

хранилище

Chlorofluorocarbon propellants are nonreactive and stable at temperatures up to 5508℃. The liquefied gas is stable when used as a propellant and should be stored in a metal cylinder in a cool, dry place.

Перевозки

UN1028 Dichlorodifluoromethane or Refrigerant gas R-12, Hazard class: 2.2; Labels: 2.2-Nonflammable compressed gas. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner

Методы очистки

Pass the gas through saturated aqueous KOH then conc H2SO4, and a tower packed with activated copper on Kielselguhr at 200o removed CO2 and O2. A trap cooled to -29o removed a trace of high boiling material. It is a non-flammable propellant.

Несовместимости

The presence of greater than 5% water in solutions that contain trichloromonofluoromethane may lead to hydrolysis of the propellant and the formation of traces of hydrochloric acid, which may be irritant to the skin or cause corrosion of metallic canisters. Trichloromonofluoromethane may also react with aluminum, in the presence of ethanol, to cause corrosion within a cylinder with the formation of hydrogen gas. Similarly, alcohols in the presence of trace amounts of oxygen, peroxides, or other free-radical catalysts may react with trichloromonofluoromethane to form trace quantities of hydrochloric acid.
Both dichlorodifluoromethane and dichlorotetrafluoroethane are compatible with most ingredients used in pharmaceutical aerosols. Because of their poor miscibility with water, most MDIs are formulated as suspensions. However, solution MDIs can be prepared through the use of ethanol as a cosolvent for water and propellant, resulting in a clear solution (provided the water content is less than 5%).

Утилизация отходов

Return refillable compressed gas cylinders to supplier. 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. Because of potential ozone decomposition in the stratosphere, R-12 should be released to the atmosphere only as a last resort. 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

Регуляторный статус

Included in the FDA Inactive Ingredients Database (aerosol formulations for inhalation, nasal, oral, and topical applications). With few exceptions for existing MDIs, the FDA and EPA have banned the use of CFCs in the USA after 31st December 2008, with all CFCs to be phased out by 2010–2015. Included in nonparenteral medicines licensed in the UK.