Effects of SO2 Treatment of Commercial Catalysts on Selective Catalytic Reduction of NOx by NH3

Nitrogen oxide(NOx), which is emitted from stationary and mobile sources, is a major air pollutant that causes environmental problems, such as photochemical smog, acid rain and greenhouse effect. Selective catalytic reduction(SCR) of NOx is a principal technology for the reduction of NOx from stationary sources. CeO2, MnOx and zeolite catalysts have been investigated for SCR of NOx. However, these catalysts are still in the experimental stage. In practical SCR projects, V2O5-WO3(MoO3)-TiO2 catalyst is a widely used traditional catalyst for De-NOx of power plants. Fuels, such as coal containing sulfur, are widely used in practical applications. In particular, SO2 is present in exhaust gas during combustion. Generally, SO2 can be oxidized to SO3, which then reacts with NH3 in steam atmosphere to generate sulfides or sulfates. An SCR catalyst used for practical applications would be deactivated in the SO2 atmosphere.