Decomposition and Reactivity of NH4HSO4 on V2O5/AC Catalysts Used for NO Reduction with Ammonia

Abstract The decomposition and reactivity of NH 4 HSO 4 deposited or in situ formed on various V 2 O 5 /AC and V 2 O 5 /TiO 2 catalysts are studied in detail using a temperature-programmed method. The results are correlated directly with the behavior of the catalysts in the NO reduction with NH 3 in the presence of SO 2 . The decomposition and reaction of NH 4 HSO 4 are easier on the V 2 O 5 /AC catalysts than on the V 2 O 5 /TiO 2 catalysts. On the V 2 O 5 /AC catalysts, the decomposition and reactivity of NH 4 HSO 4 are greatly dependent upon V 2 O 5 loading, the temperatures for the decomposition, and reaction increase with increasing V 2 O 5 loading. Most of the NH 4 HSO 4 deposited on the V 2 O 5 /AC can react with NO at 250°C when V 2 O 5 loading is below 5 wt%. The reactivity of NH 4 HSO 4 with NO, other than its decomposition, is associated with the behavior of the catalysts for the SCR reaction in the presence of SO 2 . During the SCR reaction on the V 2 O 5 /AC catalysts of low V 2 O 5 loading in the presence of SO 2 , the formed sulfate species stay on the catalyst surface and act as acid sites for NH 3 adsorption. Simultaneously, the ammonium ions react continuously with NO to avoid the surface deposition of excess ammonium–sulfate salts. Such a process effectively ensures the catalyst being promoted but not poisoned by SO 2 . The interaction between the AC and vanadium species results in synergism in the activation and reaction of ammonium ions linked to sulfate species. A bridge-type activated ammonia species is proposed and discussed.

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