Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I. It is also a valued industrial reagent and building block in synthesis of pharmaceuticals and other organic compounds. In low concentrations, its odor resembles freshly cut hay or grass.
• Phosgene is a major industrial chemical used to make plastics and pesticides.
• At room temperature (70°F), phosgene is a poisonous gas.
• Phosgene itself is nonflammable (not easily ignited and burned).
• Phosgene is also known by its military designation, “CG.”
PHYSICAL PROPERTIES
At room temperature, phosgene is a a white or pale yellow gas with, at low concentrations, the odor of newly mown hay or corn. It is, by itself, nonflammable (#CDC). It is four times denser than air.
Phosgene is also known as carbonyl chloride (COCL2). It is formed when chlorinated hydrocarbon compounds are exposed to high temperatures.
PROCESS
Industrially, phosgene is produced by passing purified carbon monoxide and chlorine gas through a bed of porous activated carbon, which serves as catalyst.
CO + Cl2 → COCl2 (ΔH
rxn = −107.6kJ/mol)
The reaction is exothermic and therefore, the reactor must be cooled. Typically, the reaction is conducted between 50 and 150 deg.C. Above 200 deg. C, phosgene reverts to carbon monoxide and chlorine. Because of safety issues, phosgene is often produced and consumed within the same plant and extraordinary measures are introduced to ensure safe handling of the product.
USES
•sPhosgene is a widely used chemical intermediate, primarily manufactured in the preparation of many organic chemicals. Phosgene is used for the synthesis of isocyanate-based polymers, carbonic acid esters, and acid chlorides. It is also used in the manufacture of dyestuffs, some insecticides, and pharmaceuticals and in metallurgy. (1,6)
• In the past, phosgene was used as a chemical warfare agent (in WWI and WWII). (1,3,5)
PHOSGENE INDUSTRY
The phosgene industry has been showing continuous growth in the past which is expected to continue in the near future. Western Europe has been the leading consumer of this compound followed by North America and China. China and the Middle East are expected to grow at a better pace due to the increasing demand for phosgene derivatives mainly toluene diisocyanate and methylene diphenyl diisocyanate. Phosgene has its application in a number of industrial sectors that include insecticides, pharmaceuticals, cosmetics and many others. Growing economies and growth in various industrial sectors mainly in the Asia Pacific region is expected to be a major driver for the phosgene industry. The growing demand for chemicals that use phosgene as an intermediate chemical is also expected to trigger the demand for phosgene.
