Hydrogen cyanide (HCN) is an important chemical with over a million tons produced globally each year. The watery liquid or gas is used in a variety of syntheses including the production of adiponitrile (for nylon), methyl methacrylate, sodium cyanide and chelating agents. Most hydrogen cyanide is consumed at its production site, forming other higher-value products.
The method which has proved successful for HCN manufacture is based on that described by Andrussow in 1930 which employs methane, ammonia and air at high temperatures (1100-1200°C). Apart from the greater complexity of the recovery arrangements, the operating characteristics of the processes that are being used today are closely similar to those established by Andrussow.
The various modifications of the process differ in their sources of methane, in the proportions of reacting gases, in the nature of the platinum metal catalyst, and in the means of collecting and purifying the product, and recovering or recycling the excess ammonia. Commonly, unreacted ammonia is removed by washing with sulfuric acid. Hydrogen cyanide is then obtained as an aqueous solution by washing with water and followed by distillation and condensation. These steps are represented in figure 1