Detailed Study of Cu Migration in the Course of NH3-Facilitated Solid-State Ion-Exchange into *BEA Zeolites

Cu migration into *BEA zeolite in the course of NH3-faciliated solid-state ion exchange (SSIE) was studied using and as the Cu sources. It was found that and are equally effective when SSIE is carried in the presence of 500 ppm NO and 500 ppm NH3. Removal of NO significantly reduces the efficiency of SSIE for [] since the process becomes limited by -> reduction. When is used as the Cu source the rate of SSIE is no longer limited by the reduction, but becomes limited by the formation and migration of mobile [Cu(NH3)(2)](+) complexes. A time-resolved study of SSIE with NH3 and a mixture at 200 and 250 A degrees C reveals two distinctly different stages during Cu migration, which are tentatively attributed to non-random occupation of different cationic positions that the Cu-species occupy upon consecutive exposure to the atmosphere in the selective catalytic reduction of nitrogen oxides with ammonia.