Ethylene glycol intercalation in MgAlCO3 hydrotalcite and its low-temperature intermediate phases

Abstract Three series of hydrotalcites (Mg : Al = 2 : 1, 3 : 1, and 4 : 1) and their low-temperature intermediate phases were treated with ethylene glycol. The hydrotalcites with 3 : 1 and 4 : 1 Mg : Al ratios intercalated ethylene glycol, but the sample with the 2 : 1 ratio did not. However, a hydrotalcite intermediate phase with carbonate anions grafted into the hydroxide layers (HT-B), and its hydrated form (HT-B-r), did intercalate ethylene glycol, even in samples with 2 : 1 Mg : Al ratios, owing to the low charge density of this intermediate phase. In all treated samples, intercalation resulted in the formation of an ethylene glycol monolayer or bilayer between the hydroxide layers. The quantity of intercalated ethylene glycol in all samples increased as the Mg : Al ratio increased and when interlayer water was present. Low-temperature intermediate phases HT-B and HT-B-r incorporated with 20–40% more ethylene glycol than did samples with hydrotalcite structure. Moderate heat treatment (225 °C) of intercalates caused grafting of approximately one ethylene glycol molecule per Al cation. The grafting of ethylene glycol molecules and carbonate anions proceeded independently, resulting in the formation of samples with both organic and inorganic components.