Urs Welz-Biermann

Desulfurization by oxidation combined with extraction using acidic room-temperature ionic liquids

Room-temperature ionic liquids (ILs) are commonly used for desulfurization by extraction for their unique solvent characteristics. In this study, 1-ethyl-3-(4-sulfobutyl)imidazolium bis(trifluoromethanesulfonyl)imide ([EimC4SO3H]NTf2) was used as catalyst and extractant for desulfurization of DBT in n-octane. The results show that dibenzothiophene (DBT) could be removed from the oil phase effectively by this process, and that the sulfur content in a model oil could be decreased from 1600 ppm to less than 20 ppm. The extraction efficiency of the IL was greatly influenced by the structure of the anions and cations. The order of extraction capability of ILs was [EimC4SO3H]NTf2 > [EimC4SO3H]HSO4 > [C4Py]NTf2 > [Bmim]NTf2 > [Bmim]PF6. Experiments on the recycling and reuse of the room-temperature IL were also performed, and we found that [EimC4SO3H]NTf2 could be recycled 5 times without significant decrease in the desulfurization activity. The extraction mechanism was also probed in detail, and we found that DBT was oxidized to its corresponding sulfone by H2O2 and NaClO, which was then extracted by the IL phase. However, different extraction mechanisms are at work with different oxidants.

Esterification of glycerol with acetic acid using double SO3H-functionalized ionic liquids as recoverable catalysts

Esterification of glycerol with acetic acid was studied using a series of Bronsted acidic ionic liquids as catalysts. The results indicate that double SO3H-functionalized ionic liquids show high catalytic activity and fair reusability even at very low catalyst loadings, while the conventional non-functionalized ionic liquids show poor activity. The Bronsted acidity–catalytic activity relationships were also investigated and the results showed that the sequence of the catalytic activity observed in the transformation was in good agreement with the Bronsted acidity order determined by the Hammett method.

Microwave-assisted extraction of lactones from Ligusticum chuanxiong Hort. using protic ionic liquids

Traditional Chinese medicine is still the main source for medical treatment in China. Extraction processes are usually adopted to separate bioactive ingredients from local plants. However, volatile traditional organic solvents are commonly used in the extraction process, which would lead to solvent loss and environment pollution. In this work, in order to improve the extraction process and develop a greener process, a microwave-assisted extraction (MAE) method was investigated to extract senkyunolide I, senkyunolide H and Z-ligustilide from Ligusticum chuanxiong Hort. Two ionic liquids, N,N-dimethyl-N-(2-hydroxyethoxyethyl)ammonium propionate (DMHEEAP) and N,N-dimethyl(cyanoethyl)ammonium propionate (DMCEAP), were employed as extractants. Important factors such as system temperature, extraction time, solid-to-solvent ratio and particle size were studied. The results show the system temperature was main factor which affects the microwave assisted extraction process. The extraction equilibrium could be reached in a short period of time. The extraction efficiency was not affected by the phase ratio within a certain solid/solvent ratio range. The particle size of Ligusticum chuanxiong powder had no remarkable effect on extraction efficiency. The back-extraction of protic ionic liquids using n-hexane was realized, and the concentration of senkyunolide I and senkyunolide H hardly decreased, but the concentration of Z-ligustilide decreased by 39.7%. The extraction mechanism of the investigated microwave assisted ionic liquid extraction was the same as traditional organic solvent extraction.

Thermochemistry of alkyl pyridinium bromide ionic liquids: calorimetric measurements and calculations.

Two ionic liquids, 1-ethylpyridinium bromide (EPBr) and 1-propylpyridinium bromide (PPBr), were prepared and the structures were characterized by 1H NMR. The thermodynamic properties of EPBr and PPBr were studied with adiabatic calorimetry (AC) and thermogravimatric analysis (TG-DTG). The heat capacity was precisely measured in the temperature range from 78 to 410 K by means of a fully automated adiabatic calorimeter. For EPBr, the melting temperature, enthalpy, and entropy of solid-liquid phase transition were determined to be 391.31 +/- 0.28 K, 12.77 +/- 0.09 kJ x mol(-1), and 32.63 +/- 0.22 J x K(-1) x mol(-1), respectively, and for PPBr they were 342.83 +/- 0.69 K, 10.97 +/- 0.05 kJ x mol(-1), and 32.00 +/- 0.10 J x K(-1) x mol(-1), respectively. The thermodynamic functions (H(T)(0) - H(298.15)(0)) and (S(T)(0) - S(298.15)(0)) were derived from the heat capacity data in the experimental temperature range with an interval of 5 K. The thermostablility of the compounds was further studied by TGA measurements. The phase change behavior and thermodynamic properties were compared and estimated in a series of alkyl pyridinium bromide ionic liquids. Results indicate that EPBr has higher melting and decomposition temperature, as well as phase transition enthalpy and entropy but lower heat capacity than PPBr due to their different molecular structures.

Thermodynamic Properties of Ionic Liquids - Measurements and Predictions -

Research of ionic liquids (ILs) is one of the most rapidly growing fields in the past years, focusing on the ultimate aim of large scale industrial applications. Due to their unique tunable properties, such as negligible vapor pressure at room temperature, stable liquid phase over a wide temperature range and thermal stability at high temperatures, ionic liquids are creating an continuously growing interest to use them in synthesis and catalysis as well as extraction processes for the reduction of the amount of volatile organic solvents (VOSs) used in industry. For the general understanding of these materials it is of importance to develop characterization techniques to determine their thermodynamic and physicochemical properties as well as predict properties of unknown Ionic Liquids to optimize their performance and to increase their potential future application areas. Our laboratory in cooperation with several national and international academic and industrial partners is contributing to these efforts by the establishment of various dedicated characterization techniques (like activity coefficient measurements using GC technology) as well as determination of thermodynamic and physicochemical properties from a continuously growing portfolio of (functionalized) ionic liquids. Based on the received property data we published several papers related to the adjacent prediction of properties (like molar enthalpy of vaporization, parachor, interstice volume, interstice fractions, thermal expansion coefficient, standard entropy etc.). Additionally our laboratory created and launched a new most comprehensive Ionic Liquid property data base--delphIL.(www.delphil.net). This fast growing collections of IL data will support researchers in the field to find and evaluate potential materials for their applications and hence decrease the time for new developments. In this chapter we introduce the following techniques, summarize recent published results completed by our own investigations: 1. Activity coefficient measurements using GC technique, 2. Thermodynamic properties determined by adiabatic calorimetry and thermal analysis (DSC, TG-DTG). 3. Estimation and prediction of physicochemical properties of ILs based on experimental density and surface tension data.

Estimation and Prediction of the Physicochemical Properties of Imidazolium-Based Ionic Liquids

The physicochemical properties of ionic liquids (ILs) at 298.15 K could be estimated and predicted in terms of empirical and semi-empirical equations as well as by interstice model theory. In this paper, the molecular volume, density, standard molar entropy, lattice energy, surface tension, parachor, molar enthalpy of vaporization, interstice volume, interstice fraction, and thermal expansion coefficient are discussed. These properties were first estimated by experimentally determining the density and surface tension for 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][EtSO4]), 1-butyl-3-methylimidazolium octylsulfate ([C4mim][OcSO4]), and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([C2mim][NTf2]). The molecular volume and parachor of the three homologues of the imidazolium-based ILs [C(subscript n)mim][EtSO4], [C(subscript n)mim][OcSO4], and [C(subscript n)mim][NTf2] (n=1-6) were predicted and their densities and surface tensions were obtained. Other properties were also calculated using the obtained density and surface tension values. The predicted density was compared to the experimental values for [C4mim] [NTf2] and [C2mim] [OcSO4], which shows that the deviation between experimental and predicted data are within experimental error. Finally, we compared the values for the molar enthalpy of vaporization estimated by Kabos empirical equation with those predicted by Verevkins simple rule for [C2mim] [EtSO4], [C4mim][OcSO4], [C2mim] [NTf2], [C4mim][NTf2], N-butyltrimethylammonium bis (trifluoromethylsulfonyl)imide [N4111][NTf2], N-methyltrioctylammonium bis (trifluoromethylsulfonyl)imide ([N8881][NTf2]), and N-octyl-3-methylpyridinium tetrafluoroborate ([m3opy][BF4]) and found that the values obtained by these two equations were in good agreement with each other. Therefore, we suggest that the molar enthalpy of vaporization of ILs can be predicted by Verevkins simple rule when experimental data for density and surface tension are not available.

N,N′-[1,4-Phenyl­enebis(methyl­ene)]bis­(N,N-diethyl­ethanaminium) dibromide

In the crystal structure of the title compound, C20H38N2 2+·2Br−, the centroid of the aromatic ring is located on an inversion center, so that the asymmetric unit consists of one-half molecule of the dication and one bromide anion. C—H⋯Br interactions connect the two components into a three-dimensional network. An intramolecular C—H⋯π interaction is also observed.