Promoting Effect of Mn on In Situ Synthesized Cu-SSZ-13 for NH3-SCR

Abstract

The effect of Mn impregnation on the NH3-SCR (selective catalytic reduction of NOx by NH3) activity of in situ synthesized Cu-SSZ-13 was investigated in this work. It was found that Mn addition could efficiently improve the low-temperature activity of Cu-SSZ-13. The optimal amount of Mn was 5 wt.%, and NOx conversion was improved by more than 20% over a temperature range of 120 °C to 150 °C. SEM (scanning electron microscopy), XRD (X-ray diffraction), N2 adsorption-desorption, H2-TPR (temperature programmed reduction of H2), NH3-TPD (temperature programmed desorption of NH3) and in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) experiments were conducted to investigate the changes in the zeolite structure, active sites, acid sites and reaction mechanism. The impregnated MnOx species caused a decline in the crystallinity of Cu-SSZ-13 but markedly improved the redox ability. Nitrate and nitrite species were observed in the Mn-modified Cu-SSZ-13, and the formation of these species was thought to cause the observed increase in low-temperature NH3-SCR activity. The results show that the addition of Mn is a promising method for promoting the low-temperature catalytic activity of Cu-SSZ-13.

Investigation of Mn Promotion on HKUST‐1 Metal‐Organic Frameworks for Low‐Temperature Selective Catalytic Reduction of NO with NH3

“…For the HKUST-1-Mn2.5, -Mn3.75, and -Mn5.0 catalysts, very similar amount of Mn has been detected (in the range from 1.59 to 2.43 at.%), which implies that some Mn atoms were located inside the pores. [41] The calculated C/Cu atomic ratio was 9.1-10.0, in good agreement with those observed in other literature studies. [17,42] Mn/Cu atomic ratio ranged from 0.16 to 1.34, additionally highlights a difference with the other study on Mn@Cu 2 (BTC) 2 in which lower Mn loading was examined.…”

“…For the latter, a recovery was observed after the cycle in absence/ presence/absence of water vapor. [41,56] In our study, just before the water feeding, the NO and NH 3 conversions were 68 and 65 %, respectively. A rapid decrease was reported after the introduction of H 2 O with conversions found at the level of 25 % and 30 % for NO and NH 3 , respectively.…”

“…Our results, in terms of Mn content, agree well with those previously reported for Cu-SAPO-34 catalysts with 4 wt.% of Mn loading, or Cu-SSZ-13 catalysts, where the most promising catalysts have been ascribed to Mn content of 3 and 5 wt.% (depending on the temperature). [41,54,55] Despite small activity differences between HKUST-1-Mn2.5 and HKUST-1-Mn3.75 samples, we selected the latter to examine its resistance in the presence of H 2 O and SO 2 (separately).…”

One-Pot Three-Dimensional Printing Robust Self-Supporting MnO x /Cu-SSZ-13 Zeolite Monolithic Catalysts for NH 3 -SCR

“…15 The manganese compounds with varieties of valence states could enhance acid sites on the catalyst surface as well as inhibit the aggregation of Cu species, therefore the Mn-modified Cu-SSZ-13 zeolites perform outstanding low-temperature activity and excellent hydrothermal stability. [16][17][18] However, these multiple metal-doped zeolite catalysts are conventionally prepared through timeconsuming and relatively complex processes, such as ion-exchange and impregnating, which are unfavorable for future industrial application. 19 In addition, all these metal-optimized catalysts are based on zeolite powder and are required to be shaped into bodies with macro-size for use in the industrial reactor, which is a key step for the implementing of the laboratory-designed catalysts into scale-up forms.…”

Selective Catalytic Reduction: From Basic Science to deNOx Applications

“…He and coworkers [11] studied the promoting effect of Mn on a Cu-SSZ-13 catalyst. The authors discovered that impregnated MnOx species caused a decline in the crystallinity of Cu-SSZ-13 but markedly improved the redox ability.…”