Cobalt-Exchanged Mordenite onto a Cordierite Honeycomb for SCR-NO

Abstract

Structured catalysts were prepared by deposition of cobalt-exchanged mordenite films on the walls of cordierite monolith channels either by wash coating or by hydrothermal synthesis. The aim of this work is to analyze different deposition techniques and their influence on the catalytic activity. The catalytic activity of the structured materials is compared with that of zeolite powder. The hydrothermal synthesis was performed in situ in a pressured autoclave reactor varying the reaction conditions (time, stirring degree). This technique consists in the crystallization of mordenite on the cordierite honeycombs employed as a substrate. In order to analyze the stirring effect, some of the samples were synthesized by stirring while others were treated in a stagnant medium. The influence of time on reaction was estimated by sampling at regular time intervals. Deposition by impregnation (wash coating) was also performed by immersing the monolith into a suspension (20-40 wt.%) with Co-exchanged mordenite. The wash coating was performed under different conditions (suspension concentration, incorporation of agglutinants, number of immersions) to obtain a zeolite coating active and selective as catalyst for nitric oxide selective reduction with hydrocarbons. The samples obtained by either method were characterized by scanning microscopy, TPR, XRD, and catalytic activity for the SCR of NOx with propane.