High-Efficiency Removal of NO_x Using a Combined Adsorption-Discharge Plasma Catalytic Process

Abstract

A combined adsorption-discharge plasma catalytic process was used for the removal of NO(x) using zeolites as catalysts without external heating. It was found that the types of plasma carrier gases exert great effect on the conversion of adsorbed NO(x). The conversion of adsorbed NO(x) is much lower in N(2) plasma than in Ar plasma, which is attributed to the reverse reaction, NO(x) formation reaction. The momentary increase of oxygen species derived from the decomposition of adsorbed NO(x) is considered to be the main cause as their collisions with nitrogen species can generate NO(x) again. Thus, solid carbon was added to the catalyst to act as a scavenger for active oxygen species to improve the conversion of adsorbed NO(x) in N(2) plasma. A NO(x) removal rate of 97.8% was obtained on 8.5wt.% carbon mixed H-ZSM-5 at an energy efficiency of 0.758 mmol NO(x)/W·h.

Non-thermal plasma enhanced NSR performance over Pt/M/Ba/Al2O3 (M = Mn, Co, Cu) catalysts

“…S2 [13,34]. Assuming that the concentration of NO x in combustion gas is 500 ppm, the energy consumption equals to an energy cost of 50.05 W·h to remove completely the NO x in 1 m 3 combustion gas.…”

“…The input electric discharge power was measured by voltage-charge Lissajous figures recorded with a 100 MHz digital oscilloscope (TDS 2012, Tektronix). The energy consumption is defined as follows [13]:…”

Pt-free, non-thermal plasma-assisted NO storage and reduction over M/Ba/Al2O3 (M = Mn, Fe, Co, Ni, Cu) catalysts

“…The input electric discharge power was measured by voltage-charge Lissajous figures recorded with a 100 MHz digital oscilloscope (TDS 2012, Tektronix). The energy efficiency was defined as follows [27]:…”

“…7), the transition metal containing catalysts show relatively low activity in NO x storagereduction catalysis. Based on the promise of non-thermal plasma (NTP) assisted chemistry [11,23,27,44,45], we opted to employ NTP in the rich phase to regenerate the catalysts. In the discharge stage, the regeneration of adsorbed NO x was investigated using 2% H 2 /Ar as the discharge gas (i.e., a H 2 -plasma was used).…”

“…Due to the lack of precious metal, the activity of the M/Ba/Al 2 O 3 was limited by its regeneration during the rich phase. In order to overcome this limitation, we attempted to employ non-thermal plasma (NTP) [11,[23][24][25][26][27][28] to facilitate rich-phase regeneration of the catalyst. Due to the activation of the reductant by NTP, a combination of plasma and catalysis was expected to result in regeneration of the LNT catalyst.…”