MANUFACTURE OF DINITROGEN TETROXIDE Russian patent published in 2015 - IPC C01B21/36 

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry, in particular to inorganic synthesis, and can be used for the manufacture of N₂O₄ in self-contained plants. The manufacture of N₂O₄ comprises a step of compressing gas stream to at least 0.4 MPa (a) and oxidising the residual nitrogen oxide (NO) to produce nitrogen dioxide (NO₂) and accumulating the feed nitrogen tetroxide (N₂O₄), comprising along with the liquid nitrogen tetroxide (N₂O₄) a nitric acid 3HO₃, by cooling the gas stream down to at least minus 10°C; a step of feed nitrogen tetroxide (N₂O₄) distillation maintaining the reflux ratio in the column within 1…2; a step of washing tail gases with dilute nitric acid in a contact countercurrent and concentrating the nitric acid to achieve up to 50-58%; a step of concentrating of feed dilute nitric acid of 50-58% in a concentration column to achieve 80-85% superazeotropic nitric acid by accumulating in the middle of liquid phase multilyer the excess of nitrogen tetroxide (N₂O₄) compared to the amount stoichiometrically required for the formation of acid by the reaction between mass flows passing in countercurrent to each other, with the oxygen fed into the bottom zone, introducing nitrogen tetroxide (N₂O₄) along with concentrated nitric acid into the middle of liquid phase multilayer, maintaining the pressure within 0.7 to 0.9 MPa (a) and three temperature levels in three zones throughout the height of the column; cooling the gas mixture stream, comprising nitrogen dioxide (NO₂) and nitrogen tetroxide (N₂O₄) separated from the nitric acid vapours, down to the temperature of not below minus 10°C, required for the condensation of nitrogen tetroxide vapours (N₂O₄) and polymerisation of nitrogen dioxide (NO₂) in gas phase into the liquid nitrogen tetroxide (N₂O₄). Besides, the off-spec product (N₂O₄) is introduced into the accumulating nitrogen tetroxide feed (N₂O₄) while maintaining the reflux ratio in the column within 0.6…2.

EFFECT: improved quality of the manufactured N₂O₄, process safety and utilisation of the off-spec product (N₂O₄).

2 cl, 1 dwg