%0 Journal Article
%T Infrared Spectroscopic Characterization of CIT-6 and a Family of *BEA Zeolites
%A Sean R. Tomlinson
%A Tyler McGown
%A John R. Schlup
%A Jennifer L. Anthony
%J International Journal of Spectroscopy
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/961404
%X Infrared spectroscopy is known to be a useful tool for identifying local structure changes in zeolites. Infrared spectroscopy is often employed to complement X-ray diffraction data. Local structure changes in zeolite CIT-6 and its zeolite beta (*BEA) analogs caused by calcination, altering framework composition, and ion exchange have been identified with mid- and far-infrared spectroscopy. Differences in the local structures of the samples were observed in mid- and far-infrared spectra, including changes in the intratetrahedral asymmetric stretch, the double-ring mode, and the intratetrahedral bending mode regions. The infrared spectra indicate that calcination or acetic acid extraction changed the structure of CIT-6 to that of zeolite beta (*BEA). Zinc ion exchange or the substitution of aluminum into the framework structure of acetic acid extracted samples retained the CIT-6 structure. 1. Introduction Microporous molecular sieves are employed in catalytic, ion exchange and adsorption/separation processes and are, therefore, of scientific and commercial interest [1]. While ¡°zeolite¡± specifically refers to aluminosilicate microporous molecular sieves, the term is often applied to compounds with similar crystalline structures. Zeolites are remarkable because of their uniform pores (which are less than 2£¿nm), their channel configuration, and their void space organization. Because of zeolites¡¯ vast application potential, the characterization of chemical composition, structure, and bonding are important, leading to the use of various analytical techniques to obtain such data. Chemical composition of zeolites can be obtained with atomic absorption spectroscopy (AAS), atomic emission spectrometry (ICP-AES), and X-ray fluorescence spectrometry (XRF) [2]. Both 29Si and 27Al nuclear magnetic resonance (NMR) spectroscopies have proven to be valuable tools in understanding local environments surrounding atoms in the lattice. When NMR data are coupled with density functional theory (DFT) calculations, valuable insights into the crystalline structure of zeolites result [3]. X-ray diffraction (XRD) is also widely used to determine crystalline structure of zeolitic materials, and these data permit identification of samples by comparison with XRD results of known samples [4¨C6]. Vibrational spectroscopy, including both Raman and infrared (IR), is often employed to investigate the chemistry (with probe molecules) and short-range order in zeolites [7¨C15]. In the 1970s, Flanigen et al. proposed zeolite functional group assignments for the absorption bands between 1250 and
%U http://www.hindawi.com/journals/ijs/2013/961404/