Removing nitric oxide from gas mixtures

Nitric oxide is removed from gas mixtures containing carbon monoxide, carbon dioxide, hydrogen, nitrogen and saturated and unsaturated hydrocarbons, which are to be subjected to low temperature treatment, by a process comprising adding oxygen in slight excess over that required for oxidation of the nitric oxide according to the reaction 2NO + O2 --> 2NO2 and forming and separating nitrogen dioxide and any secondary oxidation products such as dinitrogen trioxide and dinitrogen tetroxide simultaneously with the removal of carbon dioxide by washing with an aqueous washing liquid under a pressure of 8-40 atmospheres in a scrubber. The wash may be sodium or potassium hydroxide or sodium carbonate. Oxygen is supplied either in the gas phase or in dissolved form in the wash liquid, which is preferably at room temperature. Nitric oxide contents of 1 p.p.m. are thus reducible to 0.01 p.p.m.