Characterization of aluminosilicate zeolites by UV Raman spectroscopy

A series of aluminosilicate zeolites are characterized by UV Raman spectros copy for the first time, and UV Raman spectra of various zeolites give stro ng and clear bands with high resolution, while conventional Raman spectra o f these zeolites are difficult to obtain because of a strong background flu orescence. Additionally, these zeolites show several new bands in UV Raman spectroscopy. A summary of these UV Raman spectra over various zeolites sug gests that the bands at 470-530, 370-430, 290-410, and 220-280 cm(-1) can b e assigned to the bending modes of 4-, 5-, 6-, and 8-membered rings of alum inosilicate zeolites, respectively. Furthermore, it is found that the band intensity of zeolites in UV Raman spectroscopy is dependent on the Si/Al ra tio. Moreover, the UV Raman spectra of crystallization, for zeolite X at va rious times show that, in the initial stage of crystallization, the 4-membe red rings (510 cm(-1)) interconnect each other to form beta -cages with 6-m embered rings (390 cm(-1)), which further crystallize to zeolite X. (C) 200 1 Elsevier Science B.V. All rights reserved.