PROCESS OF PURIFYING WASTE GASES CONTAINING NITROGEN OXIDES BY OXIDATION

A process is described for the removal of nitrogen oxides from waste gases with the recovery of nitric acid or a nitrate solution. The waste gas is reacted with hydrogen peroxide in an amount appropriate to the desired degree of removal of nitrogen oxides, on a catalyst, at a temperature of less than 800 DEG C., preferably in the range of 20 DEG to 100 DEG C., to give the valuable product, nitric acid or a nitrate solution. This may be done in accordance with the invention by bringing the hydrogen peroxide as a solution, i.e., in the liquid phase, into contact with the catalyst through which the waste gas is flowing. The reaction product is either utilized in a gaseous form or processed to nitric acid or a nitrate solution. Alternatively, the hydrogen peroxide may be introduced in a gaseous form, using a honeycombed catalyst, and wherein the hydrogen peroxide is present in at least one half of the stoichiometrically determined amount. Regardless of whether the hydrogen peroxide is introduced in a liquid or vapor form, the resulting nitric acid solution may be scrubbed, preferably with a nitrate salt solution, to provide the concentrated product.