Study of the NO Adsorption Capacity on Co Ion Exchanged Mordenite

LAURA B. GUTIERREZ, ANDREA FESER, EDUARDO E. MIRÓ, MARÍA A. ULLA

Costa Verde, Río de Janeiro, Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering . h Mercosur Congress on Process Systems Engineering. ENPROMER 2005; 2005

UFRJ - Universidade Federal do Rio de Janeiro, IME - Instituto Militar de Engenharia, UERJ - Universidade do Estado do Rio de Janeiro, UFF - Universidade Federal Fluminens, UFRRJ - Universidade Federal Rural do Rio de Janeiro

 Co,H-Zeolites have been extensively studied for the SCR of NOx with CH4 in excess oxygen. However, there are some aspects that have not been elucidated yet. In order to study the effect of the Co species on the NO adsorption capacity of Co,H-mordenites, experiments were performed on different cobalt-containing catalysts with different treatments (heated on He, O2 and H2). Solids with 8.85, 2.91, 2.45 and 1.15 %w of cobalt were prepared by ion exchange over NH4-mordenite, catalytically studied and characterized by TPR, NO-TPD and FTIR with NO as probe molecule.The Co8.85H-MOR reduction profile presented three peaks at 350, 680 and 850°C, attributed to Co3O4, Co oxo-ions and to Co2+ at exchange positions in the zeolitic matrix respectively. Co2.45H-MOR and Co1,15H-MOR showed that almost all the Co is in the zeolitic matrix. Besides, the Co2.91H-MOR profile showed two peaks at 295 and 505°C indicating the presence of a low amount of Co oxide species. The NO adsorption capacity not only depended on the Co/Al ratio and pretreatments but also on the presence of Co oxides. In fact, for similar Co/Al ratios, Co2.91H-MOR showed a lower NO/Co ratio than Co2.45H-MOR. The presence of high concentration of Co3O4 negatively affected both the NO to N2 conversion and the NO adsorption capacity for all pretreatments. These species probably blocked the main Mordenite channels and/or produce the formation of some Co island on the zeolite surface, lowering the amount of surface Co.The main NO surface species detected were dinitrosyl and mononitrosyl. Their stability and relative amount depended on the cobalt species and the pretreatments. Heating in He or H2 induced the stabilization of exchanged Co in sites less accessible to gases, whereas the calcination with O2 involved the mobilization of Co to More external sites.