Phosgene manufacture

Phosgene is a colorless gas at ambient temperature and pressure. Its odor has been described as similar to new-mown hay. Phosgene is manufactured from a reaction of carbon monoxide and chlorine gas in the presence of activated charcoal. The production of dyestuffs, isocyanates, carbonic acid esters (polycarbonates), acid chlorides, insecticides, and pharmaceutical chemicals requires phosgene. Manufacture of phosgene is approximately 1 million tons per year (y) in the United States, and more than 10,000 workers are involved in its manufacture and use. Manufacture of phosgene in the United States is... 

As an example, higher priority and more time and resources should be applied to a phosgene manufacturing process than a water filtration system. 

The dichlorine used for phosgene manufacture must be of a high degree of purity (ca. 99.8% [823b]). In particular, it must be dry and free of dihydrogen (to prevent corrosion), and free of dioxygen (to prevent burning of the carbon monoxide or the charcoal catalyst)... 

According to Atkinson et al., highly active charcoal effects the conversion of a mixture of CO and Cl 2 at a temperature below 50 "C [89]. Other workers, however, have found that commercial charcoals, supplied for phosgene manufacture, do not catalyse the CO/Clj reaction, even at temperatures as high as 100 "C. After treatment with dichlorine the catalyst was active above 80 C [ICI72]. 

W. Macnab, "Preliminary Studies for H.M. Factory, Gretna, and Study for an Installation of Phosgene Manufacture", Ministry of Munitions, Dept, of Explosive Supply, HMSO, London, 1926. 

At least five separate companies in Europe offer the process technology for phosgene manufacture under licence. These companies, and their particular processes, are described in Section 4.5.1. 

Preliminary Studies For H. M. Factory, Gretna and Study For An Installation of Phosgene Manufacture, Ministry of Munitions, Department of Explosive Supply, London. 

Phosgene manufactured from CO, CI2, and metal (Al, Ga) halide (Cl) catalyst. Low CCI4 contents of <1 ppm in batch process. 

Phosgene manufactured in the presence of an activated C catalyst, by the reaction of CI2 and CO containing <6.0 mol% H. Yellowing of the phosgene obtained is prevented by reducing the H content in CO. 

The problems between the military and the phosgene manufacturers, while clearly frustrating to both sides, were not so different from the kinds of production problems that might occur when undertaking the manufacture of any new difficult chemical process. The wartime pressure to produce quickly only highlighted the technical failures. Given the experience the military would have with the manufacturers of chlorpicrin and mustard gas, the problems in the phosgene plants appeared almost routine. 

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