Untersuchungen an oxidischen Katalysatoren. XXIII. Magnetische und Redoxeigenschaften von CrNaY-Zeolithen |
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Authors: | A M Rubintejn A A Slinkin M I Loktev E A Fedorovskaja H Bremer F Vogt |
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Institution: | A. M. Rubinštejn,A. A. Slinkin,M. I. Loktev,E. A. Fedorovskaja,H. Bremer,F. Vogt |
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Abstract: | Studies on Oxide Catalysts. XXIII. Magnetic and Redox Properties of Zeolites CrNaY After pretreatment in vacuo (110–460°C) and in air (45O°C) CrNaY zeolites with different exchange degrees are characterized by EPR and magnetic measurements. The chromium hyperfinc structure in the EPR spectra shows that stable octahedral Cr(H20)]3+ complexes exist up to temperatures of 350–390°C. The decrease of EPR signal intensity with increasing temperature of vacuum pretreatment can be explained by migration of Cr3+ ions into the sodalite cage (SI″, SII″) and hexagonal prism (SI), resp. The high values of μeff. correspond with the tetrahedra1 environment of Cr3+ ions. In the evacuated samples Cr2+ ions are present. The oxidizing pretreatment of samples with high Cr3+ exchange degrees leads to lattice break down. After pretreatment in air all CrNaY zeolites contain chromium with oxidation number +5 and +6. |
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