Technology Type

Type: TDA Phosgenation
Process: Phosgenation
Abbreviation
: Most TDI produced in the world is from a three-step process. It begins with Nitration of Toluene, which is subsequently Hydrogenated to the Polyamine. The third and final step (apart from Distillation) is Phosgenation of the Toluene Diamine Isomers to Diisocyanates. It is generally accepted that the reaction to Isocyanate is a two-step process. First, Phosgene reacts with the Diamine to form a Dicarbamoyl Chloride. The Dicarbamoyl Chloride is not isolated and is directly converted to Diisocyanates at elevated Temperature (65-80°C) to form the Diisocyanates. The Acid is recovered by Distillation.
Link: https://ebrary.net/14339/environment/conventional_production