Removal of nitrogen oxides by using a nonthermal plasma-assisted catalytic process in the presence of ammonia

This study investigates the removal of nitrogen oxides (NOx) by a nonthermal plasma reactor (dielectric-packed bed reactor) combined with a monolithic V2O5/TiO2 catalyst using NH3 as a reducing agent. The effect of initial NOx concentration, feed gas flow rate, humidity, oxygen content, and reaction temperature on the removal of NOx was examined in simulated exhaust gas mixtures. Increasing the fraction of NO2 in NOx, which is the main role of the plasma reactor, largely enhanced the NOx removal efficiency. In the presence of plasma discharge, the temperature dependence of catalytic removal of NOx, was very small. However, according to the scanning electron microscope images of the used catalysts, ammonium nitrate causing catalyst deactivation was observed to form below 443 K, indicating that the plasma-catalytic process should be operated at temperatures higher than 443 K. The results obtained from the parametric study show that the present system is not so sensitive to the changes in such variables as water vapor content, oxygen content and initial NOx concentration.