EPR Study of Cr + and Cu + in Some Zeolites Introduced by Solid- and Liquid-State Reactions

This study reports on the EPR of C r 5 + and C u 2 + ions, introduced by solidand liquid-state reactions with the synthetic zeolites 3A, 4A and 5A, and the natural zeolite clinoptilolite. C r 3 + was oxidized to Cr 5 + in the samples, the coordination around Cr 5 + being square pyramidal. Superhyperfine (shf) interaction of Cr with A1 nucleus was observed in both solidand liquid-stateintroduced 5A zeolite, whereas this shf could not be observed for the solid-state introduced 4A zeolite. The liquid-state Cr-introduced 4A zeolite needed a heat treatment at 473 K for Vi h for the appearance of shfs. Furthermore, it has been found that the coordinat ion structure around the C u 2 + is square pyramidal in solid-state introduced samples, whereas it is octahedral in the liquid-state introduced ones.