No abstract

Ionic liquids (IL) are receiving increasing attention due to their potential as "green" solvents, especially when used in combination with SC-CO2. In this work liquid-vapor equilibria of binary mixtures of CO2 with two imidazolium-based ionic liquids (IL) with a nitrate anion have been experimentally determined: butylmethylimidazolium nitrate (BMImNO3) and hydroxypropylmethylimidazolium nitrate (HOPMImNO3), using a Cailletet apparatus that operates according to the synthetic method. CO2 concentrations from 5 up to 30 mol % were investigated. It was found that CO2 is substantially less soluble in HOPMImNO3 than in BMImNO3. Since these ILs are very hygroscopic, water easily can be a major contaminant, causing changes in the phase behavior. In case these Ils are to be used in practical applications, for instance, together with CO2 as a medium in supercritical enzymatic reactions, it is very important to have quantitative information on how the water content will affect the phase behavior. This work presents the first systematic study on the influence of water on the solubility of carbon dioxide in hygroscopic ILs. It was observed that the presence of water reduces the absolute solubility of CO2. However, at fixed ratios of CO2/IL, the bubble point pressure remains almost unchanged with increasing water content. In order to explain the experimental results, the densities of aqueous mixtures of both ILs were determined experimentally and the excess molar volumes calculated.

A homogeneous enzymatic reaction in an ionic liquid (IL)-CO 2 medium integrated with the separation of the product is proposed. It takes advantage of the miscibility switch phenomenon using CO 2 , which is able to force two immiscible phases to form one homogeneous phase to perform the reaction. After completion of the reaction the homogeneous fluid phase is split in two or three phases upon pressure decrease in order to facilitate the product recovery. For this purpose the enzyme Candida antarctica lipase B (CaL B) and the IL 1-hydroxy-1-propyl-3-methyl imidazolium nitrate (HOPMImNO 3 ) are used. In this study the solubility of CO 2 in solutions of CaL B in HOPMImNO 3 was experimentally determined using the Cailletet apparatus, which operates according to the synthetic method. Concentrations of the enzyme vary from 3 to 12% by weight, and concentrations of CO 2 from 5 to 20 mol% were investigated in a temperature range from 30 to 75 • C and pressures up to 12 MPa were applied. No precipitation of the enzyme was observed when dissolving CO 2 in the IL. At constant CO 2 /IL ratios the pressure of the bubble points remained almost unchanged with the enzyme concentration. Triacetin tests showed that the reduction of the activity of the enzyme after storage for three months in liquid HOPMImNO 3 was only of the order of 20%. Recovery and purification of the IL was possible by precipitation of the enzyme using isopropanol (IPA) as an anti-solvent.

Liquids. -Hydrogen-bond donating ionic liquids are found to be excellent solvents for the lipase-mediated epoxidation of alkenes as well as the Baeyer-Villiger oxidation of ketones and aldehydes. The enzyme catalyst forms a stable solution in the ionic liquid, which implies the possibility for an easy recycling of the reaction system. -(KOTLEWSKA, A. J.; VAN RANTWIJK, F.; SHELDON, R. A.; ARENDS*, I. W. C. E.; Green Chem. 13 (2011) 8, 2154-2160, http://dx.doi.org/10.1039/c1gc15255f ; Biocatal. Org. Chem., Delft Univ. Technol., NL-2628 BL Delft, Neth.; Eng.) -K. Wilckens 49-038

The paper reports infinite dilution activity coefficients of a series of polar and nonpolar solutes (alkanes, alcohols, ketones, ethers, aromatic hydrocarbons, halogenated compounds) in 1-butyl-3-methylimidazolium nitrate and 1,1-hydroxypropyl-3-methylimidazolium nitrate ionic liquids at (323, 333, and 343) K. The data were measured by gas−liquid chromatography using the ionic liquid as a stationary phase.