Effect of water vapour and ammonia on the solid-solid interaction of Cu oxide with Y-type zeolite: preparation of catalyst for reduction of nitric oxide with ammonia at low temperature.

TLDR: In this paper, a method is suggested for the preparation of highly active Cu-zeolite catalyst, which avoids the employment of a huge amount of water solution containing a Cu salt.

Abstract: The solid-solid interaction between copper oxide and NH4-Y zeolite has been followed to determine changes in the number of bridging framework OH groups, water evolved during the heating process, zeolite structural stability and changes in the state of the Cu ions, manifested in their reducibility and catalytic activity in the selective reduction of NO with ammonia. The interaction of CuO with NH4-Y results in copper oxide deaggregation and incorporation of single copper ions and/or Cu-O species into the zeolite cationic sites via their exchange with the zeolite bridging OH groups. The process is enhanced by increasing temperature and the presence of water vapour or ammonia in the gaseous phase, by coordination of water or ammonia molecules to copper ions, stimulating their movement into the zeolite bulk. These changes in the state of copper are reflected in the dramatic increase of the system's catalytic activity in the NO+NH3+O2 reaction. The catalytic activity of CuO/zeolite mixtures treated in this way, at temperatures above 470 K, approaches a high activity level of the Cu-exchanged Y zeolite containing single Cu ions. Thus, a method is suggested for the preparation of highly active Cu-zeolite catalyst, which avoids the employment of a huge amount of water solution containing a Cu salt.