Dual Effect of Sulfation on the Selective Catalytic Reduction of NO with NH₃ over MnO_x/TiO₂: Key Factor of NH₃ Distribution

Abstract

The sulfation showed a dual effect on the selective catalytic reduction (SCR) reaction over MnO x /TiO 2 . The activation of adsorbed NH 3 and the adsorption of NO x on MnO x /TiO 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 °C. During NO reduction over MnO x /TiO 2 at higher temperatures, there was a competition among the SCR reaction, the nonselective catalytic reduction (NSCR) reaction and the catalytic oxidation of NH 3 to NO. The NSCR reaction and the catalytic oxidation of NH 3 to NO over MnO x /TiO 2 at higher temperatures were both restrained after the sulfation, so more NH 3 adsorbed on sulfated MnO x /TiO 2 was used to reduce NO to N 2 . Therefore, the SCR activity and N 2 selectivity of sulfated MnO x /TiO 2 at higher temperatures were much higher than those of MnO x /TiO 2 .

MnO supported on Fe–Ti spinel: A novel Mn based low temperature SCR catalyst with a high N2 selectivity

“…TPR profile of 5% Mn-10% Fe/TiO 2 showed four obvious reduction peaks. The peak at 331 o C was assigned to the reduction of highly dispersed MnO x [22], the peak at 417 o C was probably assigned to the reduction of Fe 2 O 3 and Mn 3 O 4 [22], and the reduction peaks above 500 o C was probably attributed to the reduction of FeO to Fe [20]. Fig.…”

A review of Mn-containing oxide catalysts for low temperature selective catalytic reduction of NOx with NH3: reaction mechanism and catalyst deactivation

“…It is reported widely that the NH 3 -SCR of the NO reaction when comparing the stoichiometric conditions follows both the Langmuir-Hinshelwood (L-H) mechanism and the Eley-Rideal (E-R) mechanism. 52,53 Through the L-H mechanism, both NH 3 and NO are adsorbed on the surface of catalysts. However, via the E-R mechanism, adsorbed NH 3 reacts with gaseous NO.…”

“…NH 3 is consumed mainly via N 2 and N 2 O formation and the oxidation of the catalyst to NO x . 52 The wastage of NH 3 is a huge additional cost of the deNO x process. To decrease the wastage of NH 3 , an appropriate NH 3 /NO ratio is necessary.…”

A novel dual layer SCR catalyst with a broad temperature window for the control of NO emission from diesel bus

“…Both the SCR reaction and the NSCR reaction contributed to NO x reduction, while the C-O reaction contributed to NO x formation. Therefore, NO x conversion can be described as [15]:…”

“…Meanwhile, the contribution of the NSCR reaction can be calculated according to the formation of N 2 O, and it can be calculated as follows [15]:…”