2021 年 24 巻 2-4 号 p. 47-54
The intercalation behavior of vanillin (VL), one of the most famous flavoring components having aldehyde structure, and its related compounds, m-anise aldehyde (MA) and 2-methoxyphenol (MP), into Mg–Al layered double hydroxide (LDH) has been examined by the calcination-rehydration (reconstruction) method using LDH oxide precursor at 25°C for 24 h. The molar ratio of the organic guest in aqueous solution to Al3+ ion in LDH oxide was set at 1.00 in all the experiments. The solid product was found to incorporate the guest depend on its structure together with hydroxide ion and to show the restorable LDH structure. The amounts of the organic guest intercalated (the guest/Al molar ratio of the solid product) were as follows: VL (0.81)>MP (0.41)>MA (0.18), and the effect of each substituent group of the guests was also discussed. In the case of vanillin isomers, the intercalated amounts were differently in the order; VL (0.81)>ortho-vanillin (0.58)>iso-vanillin (0.35), whereas the intercalated amounts of anise isomers were, on the whole, lower than VL isomers as MA (0.18)>ortho-anise (0.034)>para-anise (0.012). The XRD patterns of the solid products showed that VL was intercalated as a monovalent anion to make bilayer and to keep horizontal orientation for the LDH basal layer, and the others were intercalated to keep parallel orientation in the interlayer. Moreover, the results of the guest deintercalation (release) experiments from the solid products by ion exchange with chloride or carbonate ion revealed that the easier intercalated guest, the more difficult released one from the solid products.
