Reactivity of kaolinite in ionic liquids: preparation and characterization of a 1-ethyl pyridinium chloride–kaolinite intercalate

Abstract

A novel class of organic–inorganic nanohybrid material was prepared by the intercalation in kaolinite of a molten organic salt (1-ethyl pyridinium chloride, EP) above its melting temperature. The intercalation proceeded at 170 °C under N₂. It did not succeed when kaolinite was used as the starting material, whereas the melt intercalation process was possible when DMSO–kaolinite (DMSO-K) was used as the starting material. The amount of EP loaded in the galleries of kaolinite is 24.3% (0.574 mol of EP per unit-cell) which produces an increase of the basal spacing d₀₀₁ from 1.10 nm in the case of DMSO-K to 1.35 nm. The melt intercalation process could be dramatically improved by the choice of the temperature of reaction as well as of the atmosphere. At lower temperatures (less than 140 °C), even if the reaction medium is the ionic liquid, the intercalation is not observed. This results from the non-release of DMSO from the interlamellar space of DMSO-K, a step essential for the intercalation of EP to proceed. This work indicates that the intercalation of EP and the displacement of DMSO from the interlamellar spaces of kaolinite take place concurrently, not in a sequential manner. However, the process is initially driven by the thermal removal of DMSO.