Catalytic DeNO_x activity of cobalt and copper ions in microporous MeALPO-34 and MeAPSO-34

A combined spectroscopic and catalytic study of the NO reactivity on microporous aluminophosphates, with chabasite-related structure, CoAPO-34, CuAPO-34 and CuAPSO-34, is reported. NO and CO adsorption were monitored by FTIR spectroscopy, and revealed that Co²⁺ /Co³⁺ and Cu⁺ /Cu²⁺ redox couples, the sites responsible for the catalytic activity, are present in these catalysts. CoAPO-34 catalysts showed exceptionally high performances in the oxidation of NO to NO₂, and poor activity in other DeNO_x reactions. Copper-based aluminophosphates and silico-aluminophosphates, besides good performances in the NO oxidation to NO₂, showed good activity in the N₂O decomposition even in the presence of oxygen or water in the feed. The presence of silicon has beneficial effects both on the thermal and hydrothermal stability of the zeolitic structure, as well as on the catalytic performances of the metal-aluminophosphates.