ACS Catal., 2015, 5 (1), pp 16–19.
Soran Shwan, Magnus Skoglundh, Lars F. Lundegaard, Ramchandra R. Tiruvalam, Ton V.W. Janssens, Anna Carlsson, and Peter N.R. Vennestrøm
The effect of the gas phase during solid-state ion-exchange of copper into zeolites was studied by exposing physical mixtures of copper oxides (CuI2O and CuIIO) and zeolites (MFI, *BEA and CHA) to various combinations of NO, NH3, O2 and H2O. It is shown that heating these mixtures to 250oC results in active catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR), indicating that the Cu has become mobile at that temperature. Such treatment allows for a fast (<5-10 h) preparation of copper exchanged zeolites. Scanning transmission electron microscopy analysis of Cu-CHA prepared using this method shows homogenous distribution of the Cu in the primary particles of the zeolite. In-situ XRD reveals that the Cu ion-exchange is related to the for-mation of CuI2O. When the zeolite is mixed with CuIIO, addition of NO to the NH3-containing gas phase enhances the formation of CuI2O, and the Cu ion-exchange. The mobility of Cu at low temperatures is proposed to be related to the formation of [CuI(NH3)x]+ (x=2) complexes.