Abstract: The effect of the combination way of dielectric barrier discharge (DBD) stage filled with fused silica pellets and a CuZSM-5 catalyst on NOx removal was investigated by one-stage plasma-over-catalyst (POC) and two-stage plasma-followed-by-catalyst (PFC) reactors. In the NO/N2 or NO/C2H4/N2 system, there was a small synergistic effect between DBD plasmas and CuZSM-5 using the one-stage POC and the two-stage PFC reactors. The NOx conversion from the one-stage POC reactor or the two-stage PFC reactor decreased in the NO/O2/N2 system. Under the conditions of the reaction mixture of NO, C2H4, O2, and N2, gas hourly space velocity of 12 000 h–1, the input discharge energy density (Ein) of 155 J/L, and 250 ºC, the NOx conversions in the systems of pure catalyst, pure plasma, plasma-catalyst combination in a one-stage POC reactor, and a two-stage PFC reactor were 39%, 1.5%, 79%, and 52%, respectively. The observed moderately plasma-enhanced NOx conversion in the two-stage reactor was attributed to the stable species such as NO2, CO, and CO2 formed in its first discharge stage. Both short-lived active species (such as N2*, NO*, CH, and CN) and stable species formed from the plasma-induced or plasma-catalytic process in the one-stage reactor may be responsible for the significant synergistic effect between the DBD plasmas and CuZSM-5 catalyst.

Key words: nitrogen oxide;dielectric barrier discharge, emission spectroscopy;synergistic effect;copper;ZSM-5 zeolite