INTERCALATION BEHAVIOR OF CARBOXYLIC ACIDS AND THEIR SODIUM SALTS WITH LAYERED DOUBLE HYDROXIDE IN METHANOL

Abstract

In order to clarify a specific intercalation behavior of layered double hydroxide (LDH) in methanol, the intercalation reaction of LDH in water and methanol was investigated for carboxylic acids and their sodium salts. The LDHs used are carbonate MgAl-layered double hydroxide (CO₃-LDH) and nitrate MgAl-layered double hydroxide (NO₃-LDH). Carboxylic acids reacted with CO₃-LDH in methanol and with NO₃-LDH in water. In contrast, sodium carboxylates reacted with NO₃-LDH in both solvents. The lack of reaction between sodium carboxylate and CO₃-LDH in methanol indicated that protons from the carboxyl group were largely responsible for decarbonation of CO₃-LDH. Because the intercalation reaction with NO₃-LDH proceeds by ion-exchange, the proportion of anionic guest compound in solvent affected the success of intercalation. Sodium carboxylates with a large number of alkyl carbons, which are insoluble in water, were incorporated into NO₃-LDH through the use of methanol. The basal spacing of the product increased linearly with number of alkyl carbons of carboxylic acid.