Disproportionation of polynuclear chloroethylaluminate anions in acidic 1-butyl-3-methylimidazolium chloride–AlEtCl2 molten salts in the presence of a hydrocarbon phase

Abstract

Various 1-butyl-3-methylimidazolium chloride–AlEtCl₂ molten salt mixtures have been equilibrated in the presence of cyclopentane, and the resulting products monitored by Raman spectroscopy in the hydrocarbon and molten salt phases. The experiments were conducted either statically by equilibration of a given volume of cyclopentane with an equal volume of molten salt or dynamically by using a continuous-extraction apparatus. The results show for the first time that polynuclear anions disproportionate and/or dissociate. When a full extraction is performed from a melt based on AlEtCl₂ with any mole fraction higher than 0.667 the resulting molten phase is comprised of [AlCl₄]^–. The nature of the extracted alkylaluminium chloride compound depends on the initial composition. For a melt containing an AlEtCl₂ mole fraction of 0.5–0.75 a mixture of AlEt₂Cl and Al₂Et₃Cl₃ is extracted by the hydrocarbon phase. When this mole fraction is 0.75 the only product extracted is Al₂Et₃Cl₃. The compound AlEtCl₂ is extracted from a mixed acidic salt based on AlCl₃ and AlEtCl₂.