An investigation of the conformational behavior of n-hexane adsorbed in zeolites by FT-Raman spectroscopy

In the present work, we have examined the conformational behavior of n-hexane adsorbed in several representative zeolites such as silicalite (MFI) and two faujasite zeolites with FAU structure including siliceous Y (Si-Y) and Na-Y by using the FT-Raman technique. The results indicate that, upon loading n-hexane into silicalite at room temperature, the population of the all-trans (TTT) conformer increases and the concentrations of the isomers with one gauche bond, such as TTG and TGT, decrease concomitantly. Lowering the temperature further shifts the conformational equilibra toward the TTT configuration. At room temperature, the distribution of different conformers of n-hexane in both Si-Y and Na-Y is similar to that of pure n-hexane liquid. However, at 153 Ka significant difference in conformation between n-hexane in Si-Y and in Na-Y was observed. In particular, the population of the TTT conformer in Na-Y increases markedly compared to that in Si-Y at 153 K.