LOCAL-STRUCTURE DETERMINATION OF ALUMINUM IN Y-ZEOLITE - APPLICATION OF LOW-ENERGY X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY

The local Al structure and electronic properties in Na-Y, NH4-Y and H-Y zeolites have been determined by low energy Al XAFS. The Al-O bond distance of 1.700 angstrom in H-Y is longer than that in NH4-Y and Na-Y, 1.636 and 1.620 angstrom, respectively. In addition, the white line intensity of the Al ion in H-Y is higher than in NH4-Y and Na-Y, indicating the electron density on the Al ion is lower in H-Y than in the other two catalysts. The results of experimental Al-O bond distance and white line intensities are qualitatively in agreement with theoretically calculated Al-O bond distances in aluminosilicate clusters. However, further work is required in order to quantitatively evaluate the near edge structure of the X-ray absorption data.