Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
55689 | Catalysis Today | 2011 | 6 Pages |
The activity, selectivity and stability of Pd/H-MOR and Ce–Pd/H-MOR catalysts for the selective catalytic reduction of NO with CH4 (SCR-CH4) were studied in O2 excess (4.1%) in the absence and presence of H2O (5%). The reaction was carried out in a 300–650 °C temperature range with a S.V. of ≅33,000 h−1. The characterization of fresh and used catalysts by FTIR spectroscopy of adsorbed CO and NO showed that the loss of NO conversion in H2O presence was due to a decreasing concentration of Pd2+ sites and to the parallel formation of PdO particles that enhanced CH4 combustion under dry conditions. This behavior was modified by Ce addition. Under wet conditions the Ce–Pd/H-MOR catalyst was very active (XNO = 76% at 550 °C), selective (100% of N2) and stable. The FTIR spectrum of CO adsorbed on used samples demonstrated that Ce inhibited the transformation of active Pd2+ into PdO particles. However, Ce presence also enhanced CH4 combustion under wet conditions. At low temperatures (<500 °C) H2O presence inhibited N2O formation and 90% selectivity to N2, which improved with Ce addition, was obtained.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (155 K)Download as PowerPoint slideHighlights► Pd/H-MOR and Ce-Pd/H-MOR catalysts were characterized by FTIR of adsorbed CO and NO. ► The catalysts's activity for SCR-CH4 was studied in the presence and absence of H2O. ► On Pd/H-MOR water lowered the amount of Pd2+ sites and the activity for NO reduction. ► Ce addition stabilized the active Pd2+ sites and enhanced the activity for NO reduction.