Copper-manganese-zinc spinels in zeolites: study of EMR spectra

The aim of this study is the application of electron magnetic resonance (EMR) spectroscopy to determine the interactions between NaY and HY zeolites and Cu-Mn-Zn spinels loaded onto the zeolite surfaces. The materials were characterized using XRD and IR spectroscopies. Four types of EMR lines were observed for Cu-Mn-Zn/NaY, Cu-Mn-Zn/HY samples. The difference between the EMR spectra recorded at 77 and 293 K has been shown. The spectra recorded at 77 K allowed us to distinguish between the species formed on NaY and HY zeolites. The EMR spectrum of Cu-Mn-Zn/NaY recorded at 77 K showed only one line attributed to antiferromagnetic spinels Cu_1.4Mn_1.6O₄ and ZnMn₂O₄ or/and Cu_0.5Zn_0.5Mn₂O₄. The spinels appeared to be more stable (more strongly attached) on HY zeolite than on NaY one. It was proved that different strength of interactions between the zeolites and Cu-Mn-Zn spinels was caused by differences in the acidity of NaY and HY zeolites.