Characterization of Cu + ions in CuHZSM-5 zeolites and CuSAPO-34 molecular sieve Cu + laser-induced luminescence and 129Xe-NMR diagnosis

Abstract

We report on an attempt to characterize by laser-induced phosphorescence spectroscopy Cu + sites at low concentration in CuHZSM-5 and CuSAPO-34 samples which have been heated to 623 K in vacuum. Evidence is given that atleast two different sites for the copper ion location are available in the ZSM-5 structure. The laser-induced luminescence diagnosis of Cu + ions allows a determination of the relative concentration of these sites in the samples. It provides evidence that the concentration of sites with square pyramidal symmetry varies linearly with the total number of Cu + ions per unit cell. The signal intensity of Cu + is highly dependent on the site environment and especially on the Al position. 129Xe-NMR confirms the presence of Cu + and that there is no Cu 2+ interacting with Xe in the zeolite pores.