Tuning the morphology of CoMn2O4 for efficient alkali-resistant catalytic reduction of NOx

Abstract

To improve the NH3-SCR catalytic performance of CoMn2O4, we altered their geometric morphological and structural characteristics, developing the hollow spherical and hollow cubic morphologies of CoMn2O4 by employing hard-templating and self-templated strategy. The influence of catalyst morphology on NH3-SCR activities and alkali metal resistance was discussed specifically, and the physicochemical properties of fresh and used catalysts poisoned by alkali metals were investigated by XRD, FTIR, N2 physisorption, H2-TPR, NH3-TPD, XPS and in situ DRIFTS. Interestingly, the CoMn2O4 hollow spherical (CoMn2O4-S) outperformed hollow cubic (CoMn2O4-C) and the reference solid sphere with much better low-temperature activity, the widened temperature window and higher poisoning-resistant ability. Loss of acid sites, drop of active oxygen species and reducibility accounted for the poor low-temperature activity of alkali poisoned catalysts. CoMn2O4-S catalysts with abundant acid sites and hollow configuration can decelerate the process of alkali metal poisoning. With the aid of in situ DRIFTS investigation, it was confirmed that the SCR reaction over fresh or poisoned CoMn2O4 catalysts follows an Eley-Rideal (E-R) mechanism.