On the improved absorption of carbon monoxide in the ionic liquid 1-hexyl-3-methylimidazolium chlorocuprate

Abstract

This study is focused on the design of a liquid phase system to be used in facilitated transport-supported ionic liquid membranes (SILMs) for the recovery of carbon monoxide from gaseous streams based on the ability of CO molecules to form "pi" complexation bounds with Cu+ ion. As liquid phase we propose the use of the ionic liquid 1-hexyl-3-methyl-imidazolium chlorocuprate prepared by the direct mixture of copper(I) chloride (CuCl) with 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]). A comprehensive look at the reaction mechanism and the equilibrium parameters obtained from the experimental characterization of the physical and chemical solubility of carbon monoxide in pure [hmim][Cl], and in mixtures CuCl/[hmim][Cl] is presented. The gas equilibrium solubility experimental work was carried out in the CuCl/[hmim][Cl] molar ratio range from 0 to 0.75, temperature from 273.15 to 303.15 K and pressures up to 20 bar. The values of the Henry's law constant for the physical solubility of CO in [hmim][Cl] changed from 15.3 × 10-3 to 2.7 × 10-3 mol kg-1 bar-1 as the temperature increased from 273.15 to 293.15 K. The chemical solubility of CO in the reactive ionic liquid media increased with the increase of the concentration of CuCl, with the increase of pressure and as temperature decreases. In the operation range of variables the maximum absorption of CO was of 2.26 mol kg-1 that was reached working at 20 bar, at CuCl/[hmim][Cl] molar ratio of 0.75 and 273.15 K.