Reduction of nitrogen oxides from simulated exhaust gas by using plasma–catalytic process

Removal of nitrogen oxides (NOx) using a nonthermal plasma reactor (dielectric-packed bed reactor) combined with monolith V2O5/TiO2 catalyst was investigated. The effect of initial NOx concentration, feed gas flow rate (space velocity), humidity, and reaction temperature on the removal of NOx was examined. The plasma reactor used can be energized by either ac or pulse voltage. An attempt was made to utilize the electrical ignition system of an internal combustion engine as a high-voltage pulse generator for the plasma reactor. When the plasma reactor was energized by the electrical ignition system, NO was readily oxidized to NO2. Performance was as good as with ac energization. Increasing the fraction of NO2 in NOx, which is the main role of the plasma reactor, largely enhanced the NOx removal efficiency. In the plasma–catalytic reactor, the increases in initial NOx concentration, space velocity (feed gas flow rate) and humidity lowered the NOx removal efficiency. However, the reaction temperature in the range up to 473 K did not significantly affect the NOx removal efficiency in the presence of plasma discharge.