Dual Effect of Sulfation on the Selective Catalytic Reduction of NO with NH sub(3) over MnO sub(x)/TiO sub(2): Key Factor of NH sub(3) Distribution

The sulfation showed a dual effect on the selective catalytic reduction (SCR) reaction over MnO sub(x)/TiO sub(2). The activation of adsorbed NH sub(3) and the adsorption of NO sub(x) on MnO sub(x)/TiO sub(2) were both restrained after the sulfation. Therefore, the SCR reaction through the Eley-Rideal mechanism and that through the Langmuir-Hinshelwood mechanism were both restrained, resulting in an obvious decrease of NO conversion below 300 degree C. During NO reduction over MnO sub(x)/TiO sub(2) at higher temperatures, there was a competition among the SCR reaction, the nonselective catalytic reduction (NSCR) reaction and the catalytic oxidation of NH sub(3) to NO. The NSCR reaction and the catalytic oxidation of NH sub(3) to NO over MnO sub(x)/TiO sub(2) at higher temperatures were both restrained after the sulfation, so more NH sub(3) adsorbed on sulfated MnO sub(x)/TiO sub(2) was used to reduce NO to N sub(2). Therefore, the SCR activity and N sub(2) selectivity of sulfated MnO sub(x)/TiO sub(2) at higher temperatures were much higher than those of MnO sub(x)/TiO sub(2).