SOLID-STATE DEFECTS IN CALCINED CAA ZEOLITE

Ca ion-exchanged zeolites have been characterized by electron spin res onance (e.s.r.), Al-27 magic-angle spinning nuclear magnetic resonance (MAS n.m.r.), Si-29 NIAS n.m.r., and diffuse reflectance Fourier tran sform infrared spectroscopy (i.r.). The presence of the radical specie s that are assigned to solid-state defects was confirmed in CaA zeolit es, and the amount of the radical was dependent on the thermal treatme nt temperature in air. The present experimental results suggest that t he formation of extralattice aluminum in the CaA sodalite cage and the change of calcium species by thermal treatment relate to the formatio n and disappearance of radical species. (C) Elsevier Science Inc. 1997 .