Control of nitrogen oxide reactions in off-gases from the diazotization/coupling of aromatic amines

Abstract From the Canadian patent

The deposition of an aromatic diazonium nitrate on the walls of a pipeline through which is conducted a residual gas produced in the diazotization of a primary aromatic monoamine is prevented by heating the walls of the pipeline limiting the residence time of the gas in the pipeline or, providing for the absence of nitrogen dioxide in the gas. Nitrogen dioxide can form in the pipeline when nitric oxide and molecular oxygen are present, but the deposition of the diazonium nitrate, formed from the nitrogen dioxide via a reaction with the monoamine, is prevented by the hot pipeline walls and/or short residence time.