SYNTHESIS OF PHOSGENE FROM CARBONACEOUS MATERIALS

The chlorination of a powdered coal analysis C, 61.5 H, 1.4 N, 1.3 Cl, 2.9% with liquid dichlorine at 490 C and 40 atmospheres pressure in a Carius tube (16 h) in the absence of air was found to produce phosgene in a yield (carbon-based) of about 6%. CCl., and large amounts of HCl were also formed [ICI103]. The formation of phosgene was also noted during the gaseous chlorination (in the absence of air) of petroleum cokes in the temperature ranges of 500-850 C [1786] and of 800-1000 C [717]. A maximum yield of 

In view of the dissociation of phosgene at such high temperatures this reaction appears to be very unlikely. 

An early patent describes the preparation of phosgene and calcium carbide by heating a mixture of calcium oxide, calcium chloride (or NaCl or MgClj) and carbon in an electric furnace [1289a]. The phosgene is formed from the combination of CO and Clj (in the presence of coke) released by heating the mixture. The overall stoicheiometry corresponds to  

Passage of the off-gases through a mass of bone-black, coke, or pumice results in the dismutation of the phosgene into tetrachloromethane and carbon dioxide (see Section 8.2). 

Phosgene has been formed at the graphite anode during the electrolysis of commercial calcium aluminates (for the production of aluminium-calcium alloys) when the aluminate content of the molten bath became low relative to the chloride-containing melt [233]. 

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