Studies of NO Reduction with Ammonia Over Copper Species Deposited on MCM‐41 Nanospheres ‐ Experimental Evidence of Reaction Mechanism

Abstract

AbstractNanospheres of MCM‐41 were modified with copper by template ion‐exchange (TIE) and cocondensation methods. In the samples modified by TIE, dispersion of copper was significantly improved by their post‐treatment in ammonia solutions. Highly dispersed copper species were significantly more active in low‐temperature NH3‐SCR than CuO aggregates. Copper dispersed on silica MCM‐41 catalytically operated at lower temperatures than copper deposited on silica‐alumina MCM‐41. The studies of reaction mechanism showed that ammonia and NOx species compete for these same adsorption sites (copper cations) and NH3 can remove NOx from such sites. Dispersed copper species are more active in NO to NO2 oxidation than CuO aggregates. Accumulation of oxidised NOx species in the absence of ammonia was more privileged on CuO aggregates. It is postulated that the main reaction pathway in the low‐temperature range is reaction of ammonia bounded to copper with NOx from gas phase or loosely bounded to the catalyst surface.