Reduction of nitrogen oxides by ozonization-catalysis hybrid process

Abstract

Treatment of nitrogen oxides (NOx) by using a hybrid process consisti ng of ozonization and catalysis was investigated. The ozonization method may be an alternative for the oxidation of NO to NO 2. It was found that nitric oxide (NO) was easily oxidized to nitrogen dioxide (NO 2) in the ozonization chamber without using any hydrocar - bon additive. In a temperature range of 443 to 503 K, the decomposition of ozone into molecular oxygen was not sig- nificant, and one mole of ozone approximately reacted with one mole of NO. A kinetic study revealed that the oxidation of NO to NO2 by ozone was very fast, almost completed in a few tens of milliseconds. When the amount of ozone added was less than stoichiometric ratio with respec t to the initial concentration of NO, negligible NO 3 and N2O5 were formed. The oxidation of a part of NO to NO 2 in the ozonization chamber enhanced the selective reduction of NO x to N2 by a catalyst (V 2O5/TiO2), indicating that the mixture of NO and NO 2 reacts faster than NO.