Zp. Zhu et al., Decomposition and reactivity of NH4HSO4 on V2O5/AC catalysts used for NO reduction with ammonia, J CATALYSIS, 195(2), 2000, pp. 268-278
The decomposition and reactivity of NH4HSO4 deposited or in situ formed on
various V2O5/AC and V2O5/TiO2 catalysts are studied in detail using a tempe
rature-programmed method. The results are correlated directly with the beha
vior of the catalysts in the NO reduction with NH3 in the presence of SO2.
The decomposition and reaction of NH4HSO4 are easier on the V2O5/AC catalys
ts than on the V2O5/TiO2 catalysts. On the V2O5/AC catalysts, the decomposi
tion and reactivity of NH4HSO4 are greatly dependent upon V2O5 loading, the
temperatures for the decomposition, and reaction increase with increasing
V2O5 loading. Most of the NH4SO4 deposited on the V2O5/AC can react with NO
at 250 degreesC when V2O5 loading is below 5 wt%. The reactivity of NH4HSO
4 with NO, other than its decomposition, is associated with the behavior of
the catalysts for the SCR reaction in the presence of SO2. During the SCR
reaction on the V2O5/AC catalysts of low V2O5 loading in the presence of SO
2, the formed sulfate species stay on the catalyst surface and act as acid
sites for NH3 adsorption. Simultaneously, the ammonium ions react continuou
sly with NO to avoid the surface deposition of excess ammonium-sulfate salt
s. Such a process effectively ensures the catalyst being promoted but not p
oisoned by SO2. The interaction between the AC and vanadium species results
in synergism in the activation and reaction of ammonium ions linked to sul
fate species. A bridge-type activated ammonia species is proposed and discu
ssed. (C) 2000 Academic Press.