Unveiling the effect of Al2O3 on PbCl2 resistance over Mn-Ce/AC catalyst for low-temperature NH3-SCR of NO

Background: Lead salts, as a heavy metal species, caused serious damage for the activity and operation lifetime of SCR catalysts. Methods: Al-decorated Mn-Ce/AC catalyst was synthesized using the impregnation method to investigate the anti-Pb poisoning ability of Al2O3 on Mn-Ce/AC catalyst.Significant Findings: The addition of Al expressed a significant promotion on activity of MC/AC catalyst in both fresh and poisoned states. XRD analysis confirmed that Al oxide confined the crystallization of active MnO2 over the poisoned catalysts, contributing to the dispersion of components. From the morphology, Al doping increased the aggregation of PbCl2, which released more active sites and further restrained the negative effect of PbCl2. More abundant of Mn4+ and surface oxygen with adding Al was in favor of the redox circle and the activation of reactants. The enhanced surface acidity and redox property served as the chemical motivations for the anti-PbCl2 ability of catalysts. In situ DRIFTS demonstrated that all catalysts followed both E-R and L-H pathways, and the E-R played a dominant role in the reaction activity. PbCl2 did not change the reaction pathways but made the reaction more difficult to happen. Finally, a possible mechanism model of Al2O3 on PbCl2 resistance over MC/AC catalyst was proposed.

Automated summary

In this study, an Al2O3-modified Mn-Ce/AC catalyst was synthesized using the impregnation method. The addition of Al significantly improved the catalytic activity of the MC/AC catalyst. XRD analysis confirmed that Al oxide inhibited the crystallization of active MnO2 on the poisoned catalysts, leading to better component dispersion. Al doping increased the aggregation of PbCl2, releasing more active sites and mitigating the negative effect of PbCl2. The presence of more Mn4+ and surface oxygen with Al addition promoted the redox cycle and activation of reactants. The enhanced surface acidity and redox property played important roles in the catalyst's ability to resist PbCl2. In situ DRIFTS analysis revealed that both E-R and L-H pathways were followed by all catalysts, with E-R being the dominant pathway. PbCl2 did not change the reaction pathways but hindered the occurrence of the reaction. A possible mechanism model of Al2O3's resistance to PbCl2 over the MC/AC catalyst was proposed.