Thermal decomposition phosgene

Stabilized tetrachloroethylene, as provided commercially, can be used in the presence of air, water, and light, in contact with common materials of constmction, at temperatures up to about 140°C. It resists hydrolysis at temperatures up to 150°C (2). However, the unstabilized compound, in the presence of water for prolonged periods, slowly hydrolyzes to yield trichloroacetic acid [76-03-9] and hydrochloric acid. In the absence of catalysts, air, or moisture, tetrachloroethylene is stable to about 500°C. Although it does not have a flash point or form flammable mixtures in air or oxygen, thermal decomposition results in the formation of hydrogen chloride and phosgene [75-44-5] (3). 

Phosgenes Thermal decomposition of chlorinated hydrocarbons, degreasing, manufacture of dyestuffs, pharmaceuticals, organic chemi- Metal fabrication, heavy chemicals Damage capable of leading to pulmonary edema, often delayed... 

Highly toxic perfluoroisobutylene (PFIB) poses a serious health hazard to the human respiratory tract. PFIB is a thermal decomposition of polytetrafluo-roethylene (PTFE), e.g., Teflon. PFIB is approximately lOx as toxic as phosgene. Inhalation of this gas can cause pulmonary edema, which can lead to death. PFIB is included in Schedule 2 of the Chemical Weapons Convention (CWC), the aim of the inclusion of chemicals such as PFIB was to cover those chemicals, which would pose a high risk to the CWC. 

Moist phosgene is very corrosive it decomposes in the presence of moisture to form hydrochloric acid and carbon monoxide thermal decomposition may release toxic and/or hazardous gases. 

Processes are under development to manufacture methylene diphenyl diisocyanate (MDI) without using toxic and corrosive phosgene. The proposed process schemes usually consist of three steps alkoxycarbonylation of nitrobenzene or aniline with CO and an alcohol to alkyl plienylcarbamate, condensation of the carbamate, and then thermal decomposition of the resulting urethane to MDI. For example, the condensation of methyl N—phcnylcarbamate (MPC), and IICHO into methylene diphenyl diurethane (MDU) is carried out in the presence of an acid catalyst. 

The decomposition of mandelic acid (70),62 the elimination of CO2 from the intermediate in the reaction of phosgene with carboxylic acids,64 the thermal decomposition of haloacetic acids (74),65 and the hydrolysis of aryl carbazates (140)119 were discussed earlier. 

Phosgenes Thermal decomposition of chlorinated Metal fabrication, heavy chemicals Damage capable of leading to pulmonary... 

Disulfuryl fluoride is a clear colorless liquid with a boiling point of 51°. Its vapor pressure over the temperature range —28 to 43° follows the equation logioP(mm.) = 8.015— 1662/T. It has an inhalation toxicity of the same order as that of phosgene, and should be handled only in a well-ventilated area. Its thermal decomposition to sulfur trioxide and sulfuryl fluoride is not very appreciable below 200° but is rapid at 400-500°. In the presence of metal fluorides such as ceaum or sodium fluoride, however, its decomposition point is considerably low er. It hydrolyzes rather slowly to give fluorosulfuric acid. It is not very soluble in cold concentrated sulfuric acid or fluorosulfuric acid, but is soluble in acetonitrile, ethyl ether, carbon tetrachloride, monofluorotrichloromethane, and benzene. 

This process was elaborated as a heterogeneously catalyzed variation by Asahi Chemicals (Japan) in order to open a new route to diisocyanates, not depending on the use of phosgene [120, 134]. Ethyl phenylcarbamate, which in a first step is obtained by catalytic oxidative carbonylation of aniline, CO, oxygen, and ethanol (eq. (17)), is condensed with aqueous formaldehyde to yield methylene diphenyl diurethane. Thermal decomposition leads to methylene diphenyl diisocyanate (MDI), which is one of the most important intermediates for the industrial manufacture of polyurethanes (eq. (18)). The yields and selectivities of the last reaction step seem to be the main reasons why this process is still inferior to the existing ones. 

Although the employment of tetrachloromethane (carbon tetrachloride) in fire extinguishers has now largely been superseded by more efficient and inherently safer materials, this type of extinguisher is undoubtedly still in use, despite the fact that phosgene is a major product of its oxidative thermal decomposition. 

Phosgene was detected, by g.c.-m.s. and n.m.r. spectroscopy, in a commercial solvent mixture of trichloroethene and tetrachloroethene (80 20) [1254]. Such contamination is likely to arise as a result of photochemical decomposition. The primary product of the oxidation of trichloroethene under ultraviolet radiation is trichloroepoxyethane cf. the thermal decomposition product, structure (3.4), which rearranges to dichloroethanoyl chloride and chloral. Secondary decomposition of one of these compounds occurs to give CO, COj, HCl and COCI2 [ICI55]. 

CO were estimated at 126 and 63 p.p.m., respectively [1178]. The quantity of phosgene formed from the thermal decomposition of 1 g of CHj=CHCl in a CH,=CHCl-air mixture between 100 and 1000 "C is illustrated in Table 3.9 [1178] phosgene generation would therefore not be an important factor in a road tanker fire [ICI38]. 

The reaction of carbon monoxide with lead(II) chloride is illustrated in Table 5.2 [168]. Thermal decomposition of the lead salt to give dichlorine, followed by reaction with carbon monoxide, could be responsible for the phosgene formation [781]. 

Thermal decomposition of C jCl g in the hot detonation gases of nitrocellulose also yields some phosgene [1814]. 

In contrast, if plutonium(IV) oxide is prepared in an active form (by thermal decomposition of plutonium(IV) oxalate at 3(X) C [1683b,2042], or by calcination of a plutonium nitrate solution [261]), it will react with phosgene at between 350 and 400 C [2042]. Kinetic studies (between 425 and 525 C) have shown the reaction to be first order in PuOj, with an activation energy of 72.0 kJ mol [1924]. Moreover, it was demonstrated conclusively that the smaller the PuOj particles, the greater the reaction rate [1924], even... 

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