Use of ESR and Xe-129 NMR spectroscopy to characterize CuZSM-5 zeolite synthesized in the presence of a copper-phthalocyanine complex

In the presence of a copper phthalocyanine complex (CuPc) it is possible to synthesize ZSM-5 zeolite containing the complex, and the crystallinity is good provided the amount of CuPc trapped is much lower than the number of c hannel intersections where it can be located without too much distortion. T he crystallinity is retained after decomposition of the CuPc in a stream of air at 500 degrees C. The copper-ZSM-5 system is characterized by the comb ined application of xenon adsorption, ESR and Xe-129 NMR spectroscopy. Thes e techniques allow the location and the oxidation states of the copper ions after various thermal treatments to be studied. Xe-129 NMR gives evidence about the partial self-reduction of the Cu2+ ions during the dehydration pr ocess. The ESR spectra taken after adsorption of ammonia or xylene confirm that the Cu2+ ions are located in the channels. However, the NMR spectrosco py of adsorbed xenon shows that when there is no chemisorbed phase the Cu2 are stabilized in the crystallites but outside the channels. They return t o the channels upon chemisorption of ammonia. (C) 1999 Elsevier Science B.V . All rights reserved.