Mechanisms study of silicotungstic acid modified CeO2 catalyst for selective catalytic reduction of NOx with NH3: Effect of pH values

Abstract A series of silicotungstic acid modified CeO 2 (SC- x, x represents the pH value of solution that is used for the preparation of catalysts) were prepared for the selective catalytic reduction (SCR) of NO x with NH 3 . SC-9 showed the best catalytic activity among the samples. The monodentate nitrate, bidentate nitrate, bridging nitrate and NO 2 were detected over SC-9 and SC-10. Monodentate nitrate and bridging nitrate disappeared over SC-8. Furthermore, the monodentate nitrate and bridging nitrate could react with NH 4 + on Bronsted acid sites to generate NH 4 NO 3 , and then was reduced by NO to form NO 2 , accompanied with the fast reaction between NO 2 and coordinated NH 3 on Lewis acid sites in the presence of gaseous NO. Besides, the SCR reaction pathway of SC catalysts followed by the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism.