Abstract
The interaction of NO with Co2+/Co3+ redox sites in CoAPO-18 and CoAPO-5 catalysts was studied by means of FTIR and diffuse reflectance UV-Vis spectroscopy both at 298 and 85 K. Two families of Co2+ sites were found in the CoAPO-18 structure. (A) Ions in framework [Co2+(OH)P], associated with Brønsted acid sites which adsorb NO to produce dinitrosyls absorbing at 1903 and 1834cm-1; these dinitrosyl complexes are reactive, in that Co2+ is oxidized to Co3+ and N2O is formed. (B) Structural defects Co2+ (Lewis acid sites) which stabilize dinitrosyls absorbing at 1900 and 1813 cm-1. The NO adsorption both on reduced and, more significantly, on oxidised CoAPO-18 also leads to the formation of NO2δ+ adsorbed species. It was found that the two kinds of dinitrosyl complexes have different reactivity in presence of oxygen. Both families of sites are also present in CoAPO-5 catalysts on which, however, the redox reaction upon NO adsorption does not occur significantly.
| Lingua originale | Inglese |
|---|---|
| pagine (da-a) | 547-552 |
| Numero di pagine | 6 |
| Rivista | Catalysis Today |
| Volume | 54 |
| Numero di pubblicazione | 4 |
| DOI | |
| Stato di pubblicazione | Pubblicato - 17 dic 1999 |
| Evento | Proceedings of the 1998 2nd World Congress on Environmental Catalysis 'Environmental Catalysis - Fundamental and Applied NOx Control Studies' - Miami, FL, United States Durata: 15 nov 1998 → 20 nov 1998 |