Synergy Study for Plasma-Facilitated $\hbox{C}_{2} \hbox{H}_{4}$ Selective Catalytic Reduction of $\hbox{NO}_{x}$ Over $\hbox{Ag}/\gamma\hbox{-}\hbox{Al}_{2}\hbox{O}_{3}$ Catalyst

Synergy study is of great importance to optimize the two-stage plasma-facilitated catalysis system and also necessary to gain a mechanistic understanding of the overall reaction process. In this paper, the effects of the long-lived chemical products of plasma pretreatment on the subsequent selective catalytic reduction (SCR) of NO
_x
at fixed and changed energy density of dielectric-barrier-discharge plasma reactor were investigated, respectively, for the aim of the synergy study of plasma- facilitated C
₂
H
₄
-SCR (PF-SCR) of NO
_x
over Ag/gamma-Al
₂
O
₃
catalyst at lower temperature. For comparison, C
₂
H
₄
-SCR of NO
_x
over Ag/gamma-Al
₂
O
₃
catalyst alone was also considered. Results showed that PF-SCR for NO
_x
removal exhibited obvious synergistic effect at 240degC, and the NO
_x
removal efficiency for plasma alone, C
₂
H
₄
-SCR alone, and PF-SCR were 43.6%, 6.7%, and 90.1%, respectively. In the NO/NO
₂
/C
₂
H
₄
/O
₂
/N
₂
system, the long-lived chemical products of plasma pretreatment for the synergistic link between plasma and catalysis included NO
₂
, aldehyde (formaldehyde and acetaldehyde), and nitrogen-contained organic compounds (methyl nitrate, nitro methyl, and ethyl nitrate). Among the nitrogen-contained chemical products of plasma pretreatment, the major synergistic link between plasma and catalysis was NO
₂
at lower input energy density, transferred to the mutual action of NO
₂
and nitrogen-contained organic compounds over catalyst at higher input energy density.