In situ FT-IR, in situ HT-XRD and TPDE study of thermal decomposition of sulfated β-cyclodextrin intercalated in layered double hydroxides

The thermal decomposition behavior of an intercalate derived from magnesium-aluminum layered double hydroxide (Mg/Al LDH) and hexa-sulfated β-cyclodextrin [NaSO3-β-CD(6)] has been studied by in situ Fourier transform infrared (FT-IR) spectroscopy, in situ high temperature X-ray diffraction (HT-XRD), temperature-programmed decomposition (TPDE), thermogravimetry (TG), and differential thermal analysis (DTA). In situ FT-IR shows that the decomposition of glucose groups of β-CD is complete at 230, 170 and 270 °C in NaSO3-β-CD(6), HSO3-β-CD(6) and SO3-β-CD(6)/LDH, respectively, indicating that intercalation of the SO3-β-CD(6) anion into an LDH host can increase its thermal stability. In the hybrid compound SO3-β-CD(6)/LDH the -SO3- groups are gradually converted to SO42- which are grafted to the LDH layers. In situ XRD shows that there are two decreases in d0 0 3 basal spacing of SO3-β-CD(6)/LDH observed in the temperature range 20-150 °C and 200-350 °C. The first corresponds to the destruction of the interlayer hydrogen bonding area and the second is attributed to the decomposition of SO3-β-CD(6) and dehydroxylation of the LDH layers. TPDE combined with GC-MS is used for the first time to study the thermal decomposition of LDHs, and the results are in accordance with those from in situ FT-IR, in situ XRD and TG-DTA.