Phosgene, selective chlorination with

A similar type of mechanism was also proposed for carbon tetrachloride oxidation, important steps in both mechanisms were the adsorption of the chlorinated hydrocarbon on the Br-nsted acid sites and dissociative adsorption of molecular oxygen on Co cation sites. The formation of CO and CO2 products were via parallel reaction pathways, with little or no CO2 formed by sequential CO oxidation. The formation of phosgene as a reaction intermediate has been identified during CCL, oxidation at space velocities above 15,000 h 4n a wet feed stream and as low as 2,400 h Mn a dry stream. The selectivity of phosgene also increased with time on line as the catalysts deactivated from 99% conversion to ca. 10% conversion after 22.5 h use. 

The second example also involves catalysts development. The goal of this project, headed by Leo E. Manzer and Walter Cicha at the DuPont Central Research Station, was charged with developing a new highly selective catalyst for the manufacture of phosgene while reducing the amount of the undesired by-product, carbon tetrachloride. As a result of basic studies by the DuPont catalysts research team, it was recognized that carbon tetrachloride formation arose from chlorination of the carbon catalyst that is used in the commercial process to promote the reaction of carbon monoxide and chlorine. 

The following section highlights some selected recent applications of the use of phosgene equivalents in the preparation of Vilsmeier-type chlorinated derivatives of amides and ureas. Thionyl chloride, carbonyl bromides, phosphorus oxychloride, phosgene, triphosgene, oxalyl chloride, and p-toluenesulfonyl chloride are all efficient oxophilic promoters capable of generating Vilsmeier-type chloro imi-nium ion intermediate 1770 by reaction with formamides, particularly dimethyl-formaraide, and ureas. 

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