Mechanism of the Catalytic Reduction of Nitric Oxide by Ammonia over Cobalt-Amine Complexes in Na-Y Zeolite

Article abstract of DOI:10.1021/j100225a029

The mechanism of the NO-NH3 reaction over Co(en)2(NO2)3 complex (en=ethylenediamine), ion exchanged into Na-Y zeolite, was studied extensively and compared with that by the same complex in an aqueous solution, which has been reported previously.At room temperature, the catalytically active species are similar in both media, exhibiting similar reaction mechanisms.Ammonia treatment of the catalyst at 363 K caused the reduction of cobalt cation to Co^II with the removal of NO2 groups.The catalytic behavior of this Co^II(en)-Y zeolite was compared to that of Co^II(NH3)-Y zeolite, prepared by a conventional cation-exchange method.During the No-NH3 reaction, mononitrosyl and dinitrosyl intermediate species were much more stable in Co(NH3) zeolite than Co(en)-Y zeolite, resulting in different reaction orders and kinetic isotope effects.It is demonstrated that a zeolite cavity can be a microreactor, where residual water acts as a solvent to assist the stabilization of the catalytically active species.