Preparation and characterization of Co mordenite coatings onto cordierite monoliths as structured catalysts

Abstract

Mordenite coatings onto the walls of cordierite monoliths were obtained by hydrothermal synthesis followed by cationic exchange. A battery of characterization techniques was used to describe the structured catalyst so obtained, and selective catalytic reduction (SCR) of NO with CH4 in excess O2 was used as a reaction test. A homogeneous distribution of the different components on the synthesized mordenite layer was obtained, with a Si/Al ratio lower than that of synthesis gel, suggesting aluminium transference from the substrate to the zeolite during the synthesis procedure; however, this effect was not observed for Mg. TPR results indicated that Co species in mordenite were exchanged Co2+, highly dispersed CoOx, and hydroxo-Co with a small contribution of Co3O4. The existence of different Co2+ sites is supported by NO desorption tests. Catalytic performance was fairly comparable to that of powdered Co-mordenite.