Supercritical CO2–ionic liquid mixtures for modification of organoclays

The use of supercritical CO2 as solvent in the modification of montmorillonite by imidazolium and phosphonium ionic liquids bearing long alkyl chains (C18) known for their excellent thermal stability is described. The objective is to combine the environmentally friendly character of ionic liquids and supercritical carbon dioxide for the organophilic treatment of lamellar silicates. Dialkyl imidazolium and alkyl phosphonium salts were synthesized to be used as new surfactants for cationic exchange of layered silicates. Then, the synthesized phosphonium (MMT-P) or imidazolium (MMT-I) modified montmorillonites, cationically exchanged under supercritical carbon dioxide with or without co-solvent, have been analyzed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and compared to montmorillonites treated by conventional cationic exchange.

An environmentally benign and efficient cationic exchange process..Figure optionsDownload high-quality image (84 K)Download as PowerPoint slideResearch highlights
► A new clean cationic exchange process.
► Combination of both elements of green chemistry: supercritical carbon dioxide and ionic liquids.
► Optimized intercalation of modifier agents.
► Excellent thermal stability of modified layered silicates.