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RESEARCH PRODUCT

Densities and viscosities of imidazolium and pyridinium chloroaluminate ionic liquids

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Abstract The chloroaluminate ionic liquids are used in various types of reactions. However, due to their particular vulnerability on water, their physical properties have not been previously investigated very extensively. The densities and viscosities of series imidazolium and pyridinium chloroaluminate ionic liquids having alkyl (butyl, hexyl, octyl) or aralkyl (benzyl, ethylphenyl) chain at the cation, various effective molar fraction of AlCl 3 (χ AlCl3  = 0.5, 0.65, 0.7), as well as they mixture and mixture with common organic solvents (hexane, toluene) were measured at the temperature range 293.15–343.15 K (20–70 °C). Densities, and particularly viscosities decrease with the increase of temperature. The density decreases with the increase of the length of the alkyl chain. The type of cation also influences the density, however, the order is different than for non-haloaluminate ionic liquids and depends on the alkyl chain length. Viscosity increases with increasing alkyl chain length, but it is not a linear trend. The ionic liquid with meta position of the alkyl chain is considerably more dense and more viscous than para isomer. The presence of aromatic phenyl ring at the side chain of the cation increases both density and viscosity. Higher effective molar fraction of AlCl 3 increases density and decreases viscosity, however, for the imidazolium ionic liquid the change of viscosity diminishes at higher temperatures. Organic solvents decrease both density and viscosity of the ionic liquids, but aliphatic hexane imposes much smaller effect than aromatic toluene. The mixture of two ionic liquids has density and viscosity between those for constituents. This extends the application of the aralkyl ionic liquids over temperatures, in which they are in solid state.