Impact of Sulfur-Oxides on the Ammonia Slip Catalyst Performance 2014-01-1545

The ammonia slip catalyst (ASC), typically composed of Pt oxidation catalyst overlaid with SCR catalyst, is employed for the mitigation of NH₃ slip originating from SCR catalysts. Oxidation and SCR functionalities in an ASC can degrade through two key mechanisms i) irreversible degradation due to thermal aging and ii) reversible degradation caused by sulfur-oxides. The impact of thermal aging is well understood and it mainly degrades the SCR function of the ASC and increases the NH₃ conversion to undesired products [1]. This paper describes the impact of sulfur-oxides on critical functions of ASC and on NH₃ oxidation activity and selectivity towards N₂, NOx and N₂O. Furthermore impact of desulfation under selected conditions and its extent of ASC performance recovery is explained.