Hydrogenation of Carbon Dioxide to Methane by Ruthenium Nanoparticles in Ionic Liquid.

The efficient transformation of carbon dioxide into fuels can be an excellent alternative to sequestration. In this work, we describe CO2 hydrogenation to methane in imidazolium-based ionic liquid media, using ruthenium nanoparticles prepared in situ as catalyst. The best yield of methane (69 %) was achieved using 0.24 mol % ruthenium catalyst (in [omim][NTf2 ], 1-octyl-3-methylimidazolium bistrifluoromethanesulfonylimide, at 40 bar of hydrogen pressure plus 40 bar of CO2 pressure, and at 150 °C.

Pretreatment and fractionation of wheat straw using various ionic liquids.

Pretreatment of lignocellulosic biomass with ionic liquids (ILs) is a promising and challenging process for an alternative method of biomass processing. The present work emphasizes the examination of wheat straw pretreatment using ILs, namely, 1-butyl-3-methylimidazolium hydrogensulfate ([bmim][HSO4]), 1-butyl-3-methylimidazolium thiocyanate ([bmim][SCN]), and 1-butyl-3-methylimidazolium dicyanamide ([bmim][N(CN)2]). Only [bmim][HSO4] was found to achieve a macroscopic complete dissolution of wheat straw during pretreatment. The fractionation process demonstrated to be dependent on the IL used. Using [bmim][SCN], a high-purity lignin-rich material was obtained. In contrast, [bmim][N(CN)2] was a good solvent to produce high-purity carbohydrate-rich fractions. When [bmim][HSO4] was used, a different behavior was observed, exhibiting similarities to an acid hydrolysis pretreatment, and no hemicellulose-rich material was recovered during fractionation. A capillary electrophoresis (CE) technique allowed for a better understanding of this phenomenon. Hydrolysis of carbohydrates was confirmed, although an extended degradation of monosaccharides to furfural and hydroxymethylfurfural (HMF) was observed.

Pre-treatment of lignocellulosic biomass using ionic liquids: wheat straw fractionation.

This work is devoted to study pre-treatment methodologies of wheat straw with 1-ethyl-3-methylimidazolium acetate ([emim][CH3COO]) and subsequent fractionation to cellulose, hemicellulose and lignin. The method developed and described here allows the separation into high purity carbohydrate and lignin fractions and permits an efficient IL recovery. A versatility of the established method was confirmed by the IL reuse. The fractionation of completely dissolved biomass led to cellulose-rich and hemicellulose-rich fractions. A high purity lignin was also achieved. To verify the potential further applicability of the obtained carbohydrate-rich fractions, and to evaluate the pre-treatment efficiency, the cellulose fraction resulting from the treatment with [emim][CH3COO] was subjected to enzymatic hydrolysis. Results showed a very high digestibility of the cellulose samples and confirmed a high glucose yield for the optimized pre-treatment methodology.

Outlook on the phase equilibria of the innovative system of "protected glycerol": 1,4-dioxaspiro[4.5]decane-2-methanol and alternative solvents.

Fundamental data on 1,4-dioxaspiro[4.5]decane-2-methanol are scarce. This work presents the foremost systematic data on the solubility of 1,4-dioxaspiro[4.5]decane-2-methanol in sustainable solvents such as water and ionic liquids accompanied by the interpretation of interactions occurring in such binary systems. 1,4-Dioxaspiro[4.5]decane-2-methanol, here called protected glycerol, has been synthesized in order to protect the two hydroxyl groups of glycerol, thus avoiding the formation of side products in a specific process. A series of imidazolium salts accompanied by pyridinium, phosphonium, and ammonium ones with various types of counterions were used in this study. The liquid-liquid and solid-liquid equilibrium measurements in binary systems were carried out by using a dynamic method at atmospheric pressure over the temperature range from 273.00 to 378.30 K or below the boiling point of the solvent. Among all tested sustainable solvents, protected glycerol exhibited limited solubility, with only a few of them in the temperature range studied. The majority of the examined ionic liquids, either hydrophilic or hydrophobic, showed complete miscibility with this monohydroxyol. The Fourier-transform infrared (FTIR) spectroscopy studies of solute and solvents showing a miscibility gap and of their mixtures were performed to obtain insight into major inter- and intramolecular interactions in the investigated systems. Furthermore, the differential scanning calorimetry was used for the first time to determine the melting point, the enthalpy of melting, and the temperature and enthalpy of the solid-solid phase transition of 1-allyl-3-methylimidazolium chloride [Amim][Cl]. The results for the solubility of protected glycerol in sustainable solvents can be used to design future alternative reactions, such as telomerization with protected glycerol in ionic liquids for more specific building blocks and extraction/or separation that involves these mixtures.

Insight into the phase equilibrium phenomena of systems containing dienes and dicyanamide ionic liquids as a new potential application.

This work presents a systematic investigation into liquid-liquid phase equilibria for systems containing three various ionic liquids and four dienes as they have not been reported yet. The systems employed in this study containing dicyanamide based ionic liquids and dienes reveal the phase envelopes that have a similar shape to binodal curves with the upper critical solution temperature. Generally, 1-methyl-3-octylimidazolium dicyanamide ([C(8)mim][DCA]) was found to be a better solvent for nonpolar dienes. The 1-butyl-3-methylimidazolium dicyanamide ([C(4)mim][DCA]) ionic liquid is a much worse solvent for 1,5-cyclooctadiene, 1,3-cyclooctadiene, 1,5-hexadiene, and 1,7-octadiene compared to other ionic liquids studied. The miscibility gaps shrink for a less polar [C(8)mim][DCA] or even more for 1-dodecyl-3-methylimidazolium dicyanamide ([C(12)mim][DCA]). In the range of the studied temperatures, the solubility of dienes is significantly higher compared to the solubility of the ionic liquids containing the shorter alkyl chain in the cation. The solubility of the presented dienes in ([C(4)mim][DCA]) ionic liquid is also relatively high and may reach up to 0.19 mol fraction of the diene. The attained results demonstrate that nonpolar compounds can be dissolved to some extent in highly charged and polar solvents such as ionic liquids.