Surprisingly high solubility of the ionic liquid trihexyltetradecylphosphonium chloride in dense carbon dioxide

For the first time an ionic liquid is observed to be appreciably miscible in dense CO₂, up to about 7 mass%. The solubility in CO₂ is more than one order of magnitude higher than for alkanes of similar carbon number. The investigated P–T phase behavior of four isopleths for the ionic liquid trihexyltetradecylphosphonium chloride in CO₂ shows a concentration independence of the isopleths for the investigated compositions similar to the known phase behavior of organic compounds such as adamantane, octacosane and squalane in supercritical CO₂ at high pressures. Overall, the results demonstrate that a single-phased ionic liquid–CO₂ solvent system for chemical synthesis is conceivable.