Washcoating of cordierite honeycomb with Ce–Zr–Mn mixed oxides for VOC catalytic oxidation
Résumé
The application of monolithic catalysts to the VOC removal is a crucial issue for practical applications in order to minimize the pressure drop in the reactor. In this study, cordierite monoliths coated with Mn, Ce and Zr elements were synthesized, characterized and tested in n-butanol oxidation. The “one-pot synthesis” (Ce, Mn and Zr nitrates mixed together) leads to a homogeneous distribution of Mn species whereas the impregnation of Mn over the Ce–Zr washcoated phase does not. Ultrasound experiments used to evaluate the coating adherence show that the washcoated mixed oxide is well anchored on the cordierite. The introduction mode of Mn species is crucial for catalytic activity. The specific reaction rates of n-butanol oxidation are slightly increased when Mn species are impregnated over the Ce–Zr washcoated phase. In comparison with this sample huge catalytic activity improvement is observed in the presence of Mn–Ce–Zr washcoated phase, i.e. when the one pot synthesis procedure is used for the Mn species introduction. The high specific surface area, good dispersion and reducibility of the mixed oxides coated as a thin layer over the cordierite led to the catalytic activity enhancement observed in n-butanol oxidation.