ФОСГЕН

Описание

Phosgene is a colourless, reactive, non-flammable gas that is heavier than air with a musty hay odour. Phosgene is commonly stored under high pressure as a liquid. Phosgene reacts with water to form corrosive acids, reacts with most metals in the presence of moisture, liberating hydrogen, an extremely flammable gas, and reacts violently with alkalis. As an industrial and commercially important chemical, phosgene is a precursor material/chemical intermediate, and has extensive application in the manufacture of a wide range of products such as polymers – polyurethanes and polycarbonates – pesticides, medicines, dyestuffs, some insecticides, pharmaceuticals, and in metallurgy.

Химические свойства

Phosgene, COCL2, also known as carbonyl chloride and chlorofonnyl chloride, is a colorless,poisonous gas produced by the action of chlorine and carbon monoxide. It condenses at 0 °C (32 OF) to a fuming liquid. Phosgene was used as a war gas, but is now used in the production of metal chlorides, pharmaceuticals, isocyanate resins,and perfumes.

Физические свойства

Colorless gas at ambient temperature; strong, pungent odor; density of the gas 4.045 g/L at 25°C; density of the liquid 1.392 g/mL at 4°C; liquefies to a light yellow fluid at 8.2°C; freezes at -128°C; critical temperature 182°C, critical pressure 55.96 atm, critical volume 190 cm³/mol; slightly soluble in water with slow hydrolysis; soluble in benzene, toluene and acetic acid.

Использование

PHOSGENE is an intermediate in organic synthesis, especially production of toluene diisocyanate and polymethylene polyphenylisocyanate; in metallurgy to separate ores by chlorination of the oxides and volatilization; occurs as a product of combustion whenever a volatile chlorine compound comes in contact with a flame or very hot metal; originally manufactured as an agent for chemical warfare during World War I.

Подготовка

Phosgene is prepared by the reaction of carbon monoxide and chlorine. The mixture of these gases is passed over activated carbon:
CO + Cl2 → COCl2
Alternatively, phosgene can be made by reacting carbon monoxide with nitrosyl chloride, or by treating carbon tetrachloride with oleum.

Определение

ChEBI: An acyl chloride obtained by substitution of both hydrogens of formaldehyde by chlorine.

Методы производства

Phosgene is manufactured in many facilities in the United States and in many other countries. Typical production processes involve the reaction of carbon monoxide with nitrosyl chloride, or the reaction of carbon tetrachloride with oleum.

Реакции воздуха и воды

Decomposes slowly in water or moist air (or when inhaled) to form very corrosive hydrogen chloride gas (hydrochloric acid) and carbon monoxide.

Профиль реактивности

PHOSGENE is water reactive. Incompatible with strong oxidizing agents, alcohols, amines, alkali. May react violently with aluminum, alkali metals (lithium, potassium, sodium), alcohols (isopropyl alcohol, 2,4-hexadiyn-1,6-diol), sodium azide [Bretherick, 5th ed., 1995, p. 134]. May react vigorously or explosively if mixed with diisopropyl ether or other ethers in the presence of trace amounts of metal salts [J. Haz. Mat., 1981, 4, 291]. PHOSGENE reacts with phosphate or silicate salts, yielding water-reactive and toxic POCl3 with phosphates (Dunlap, K.L. 2005. PHOSGENE. In Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc.).

Опасность

Phosgene is a strong irritant to the eyes, is highly toxic by inhalation, and may be fatal if inhaled. The TLV is 0.1 ppm, and the IDLH is 2 ppm in air. The boiling point is 46°F, and it is noncombustible. When carbon tetrachloride comes in contact with a hot surface, phosgene gas is evolved, which is one of the main reasons that carbon tetrachloride fire extinguishers are no longer approved. The four-digit UN identification number is 1076. The NFPA 704 designation is health 4, flammability 0, and reactivity 1. It is shipped in steel cylinders, special tank cars, and tank trucks.

Угроза здоровью

PHOSGENE is a lung toxicant that causes damage to the capillaries, bronchioles and alveoli of the lungs, by decomposition to hydrochloric acid. There is little immediate irritant effect upon the respiratory tract, and the warning properties of the gas are therefore very slight. Pulmonary edema, bronchopneumonia and occasionally lung abscesses develop. Degenerative changes in the nerves have been reported as later developments. A concentration of 25 ppm is dangerous for exposures lasting 30-60 minutes and 50 ppm is rapidly fatal after even short exposure.

Пожароопасность

When heated to decomposition or on contact with water or steam, PHOSGENE will react to produce toxic and corrosive fumes. Reacts violently with aluminum; tert-butyl azido formate; 2,4-hexadiyn-1,6-diol; isopropyl alcohol; potassium; sodium; hexafluoro isopropylidene; amino lithium; lithium. Stable in steel containers if dry. Avoid moisture.

Воспламеняемость и взрывоопасность

Noncombustible.

Промышленное использование

The common name for carbonyl chloride, COCl₂, a colorless, poisonous gas made by the action of chlorine on carbon monoxide. It was used as a poison war gas. But it is now used in the manufacture of metal chlorides and anhydrides, pharmaceuticals, perfumes, isocyanate resins, and for blending in synthetic rubbers.
Because of its toxicity, most phosgene is produced and employed immediately in captive applications. The biggest use of the material is for toluene diisocyanate (TDI), which is then reacted into polyurethane resins for foams, elastomers, and coatings. Polycarbonate is used for making breakresistant housings, signs, glazings, and electrical tools. Phosgene also is a reactant for the isocyanates that are used in pesticides, and the di- and polyisocyanates are adhesives, coatings, and elastomers.

Профиль безопасности

A human poison by inhalation, A severe eye, skin, and mucous membrane irritant. In the presence of moisture, phosgene decomposes to form hydrochloric acid and carbon monoxide. This occurs in the bronchioles and alveoli of the lungs, resulting in pulmonary edema followed by bronchopneumonia and occasionally lung abscess. There is little immediate irritating effect upon the respiratory tract, and the warning properties of the gas are therefore very slight. There may be no immedate warning that dangerous concentrations are being inhaled. After a latent period of 2 to 24 hours, the patient complains of burning in the throat and chest, shortness of breath, and increasing dyspnea. Where the exposure has been severe, the development of pulmonary edema may be so rapid that the patient dies within 36 hours after exposure. In cases where the exposure has been less, pneumonia may develop several days after the occurrence of the accident. In patients who recover, no permanent residual disability is thought to occur. A common air contaminant. Under the appropriate conditions it undergoes hazardous reactions with Al, tertbutyl azido formate, 2,4-hexadiyn-l,6-diol, isopropyl alcohol, K, Na, sodium azide, hexafluoroisopropylideneamino lithium, lithium. When heated to decomposition or on contact with water or steam it will react to produce toxic and corrosive fumes of CO and Cl-. Caution: Arrangements should be made for monitoring its use

Возможный контакт

Phosgene can be deadly at a concentration as low as 2 ppm. Phosgene is used as an intermediate in the manufacture of many industrial chemicals, including dyes and plastics; in the making of dyestuffs based on triphenylmethane, coal tar, and urea. It is also used in the organic synthesis of isocyanates and their derivatives, carbonic acid esters (polycarbonates); and acid chlorides. Other applications include its utilization in metallurgy; and in the manufacture of some insecticides and pharmaceuticals. Exposure to phosgene may occur during arc welding and in fires involving vinyl chloride; released from household paint removers and degreasers when they are used in the presence of heat. Phosgene (CG) has been used as a military choking, pulmonary agent since WW I, and has become a staple of chemical arsenals in many countries

хранилище

In particular, work with phosgene should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Containers of phosgene solutions should be stored in secondary containers, and phosgene cylinders should be stored in a cool, wellventilated area separate from incompatible materials.

Перевозки

UN1076 Phosgene, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material, Inhalation, Hazard Zone A. 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. Military driver shall be given full and complete information regarding shipment and conditions in case of emergency.AR 50-6 deals specifically with the shipment of chemical agents. Shipments of agent will be escorted in accordance with AR 740-32

Методы очистки

Dry the gas with Linde 4A molecular sieves, de-gas it and distil it under vacuum at low temperature. This should be done in a closed system such as a vacuum line. It is hydrolysed by H2O but does not fume in moist air. It is available in cylinders and as a ~20% solution in toluene. It is HIGHLY TOXIC and should not be inhaled. If it is inhaled, the operator should lie still and, be made to breathe in ammonia vapour which reacts with phosgene to give urea. [Pope et al. J Chem Soc 117 1410 1920, Beilstein 3 IV 41.]

Несовместимости

Moisture, alkalis, ammonia, alcohols, copper. Reacts slowly in water to form corrosive hydrogen chloride and carbon dioxide. Violent reaction with strong oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alcohols, alkaline materials, strong acids, strong bases, alcohols, ammonia, amines, aluminum, alkali metals. Attacks many metals in presence of water. Phosgene (CG) reacts violently with strong oxidants, amines, alkalis, and many metals. Above 300C, phosgene decomposes in the presence of moisture to form hydrochloric acid and carbon dioxide. In the presence of moisture, phosgene attacks plastic, rubber, coatings and many metals.