Deresh Ramjugernath

Activity coefficients of hydrocarbon solutes at infinite dilution in the ionic liquid, 1-methyl-3-octyl-imidazolium chloride from gas-liquid chromatography

Activity coefficients for hydrocarbon solutes at infinite dilution in 1-methyl-3-octyl-imidazolium chloride have been measured using the medium pressure gas–liquid chromatography method. The hydrocarbon solutes used were n-pentane, n-hexane, n-heptane, n-octane, 1-hexene, 1-heptene, 1-octene, 1-hexyne, 1-heptyne, 1-octyne, cyclopentane, cyclohexane, cycloheptane, benzene, and toluene. Activity coefficients at infinite dilution were determined at the following three temperatures (298.15, 308.15, and 318.15) K. Selectivities for benzene and the hydrocarbons are presented and the results indicate that 1-methyl-3-octyl-imidazolium chloride is a reasonable solvent for the separation of an alkane or an alkene from benzene.

Solubilities of Carbon Dioxide and Oxygen in the Ionic Liquids Methyl Trioctyl Ammonium Bis(trifluoromethylsulfonyl)imide, 1-Butyl-3-Methyl Imidazolium Bis(trifluoromethylsulfonyl)imide, and 1-Butyl-3-Methyl Imidazolium Methyl Sulfate

Ionic liquids (ILs) are being considered as solvents for gas absorption processes as they have the potential, in general, for improved efficiency of gas separations, as well as lower capital and operating costs compared to current commercial processes. In this study the solvent properties of ILs are investigated for use in the absorption of carbon dioxide (CO2) and oxygen (O2). The absorption of these gases in ILs was measured in the temperature range 303.15-333.15 K and at pressures up to 1.5 MPa by gravimetric analysis. The ILs used were methyl trioctyl ammonium bis (trifluoromethylsulfonyl) imide ([MOA][Tf2N]), 1-butyl-3-methyl imidazolium bis (trifluoromethylsulfonyl) imide ([BMIM][Tf2N]), and 1-butyl-3-methyl imidazolium methyl sulfate ([BMIM][MeSO4]). The measurement technique employed in this study is fast and accurate, and requires small quantities of solvent. The results indicated that absorption of both gases increased with a decrease in operating temperature and an increase in pressure. [MOA][Tf2N] had the highest CO2 and O2 solubility. [BMIM][Tf2N] was determined to have the highest selectivity for CO2 absorption. [BMIM][MeSO4] achieved the lowest CO2 absorption with a moderate O2 absorption, revealing this IL to be the least desirable for CO2 and O2 absorption. Calculation of Henrys law constants for all systems confirmed the deductions made from absorption data analysis. Calculation of enthalpy and entropy of absorption for each system revealed CO2 absorption in [MOA][Tf2N] to be the least sensitive to temperature increases. The absorption data was modeled using the generic Redlich-Kwong cubic equation of state (RK-EOS) coupled with a group contribution method.

Phase equilibria study of {N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide + aromatic hydrocarbons or an alcohol} binary systems.

Isoquinolinium ionic liquid (IL) has been synthesized from N-hexylisoquinolinium bromide as a substrate. Specific basic characterization of the synthesized compound is included, which includes NMR spectra, elementary analysis, and water content. The basic thermal properties of the pure IL, that is, melting and solid-solid transition temperatures, as well as the enthalpy of fusion, or solid-solid transition have been measured using a differential scanning microcalorimetry technique. The density and viscosity as a function of temperature have been measured for the pure IL at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The temperature-composition phase diagrams of 8 binary mixtures composed of the IL N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([HiQuin][NTf(2)]) and an aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, n-propylbenzene) or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol) have been determined from ambient temperature to the boiling-point temperature of the solvent at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 270 to 330 K. For the binary systems, the eutectic diagrams were observed with immiscibility in the liquid phase with an upper critical solution temperature (UCST). In the case of the mixture {IL + benzene, or alkylbenzene} the eutectic systems with mutual immiscibility in the liquid phase with very high UCSTs were observed. These points were not detectable with our method and were observed at low IL mole fraction. For mixtures with alcohols, it was observed that with an increasing chain length of an alcohol, the solubility decreases and the UCST increases. The coexistence curves corresponding to liquid-liquid phase equilibrium boundaries and the solid-liquid phase equilibrium has been correlated using the well-known nonrandom two-liquid (NRTL) model.

Phase equilibria and modeling of pyridinium-based ionic liquid solutions.

The phase diagrams of the ionic liquid (IL) N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide ([BM(4)Py][NTf(2)]) with water, an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol), an aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), an alkane (n-hexane, n-heptane, n-octane), or cyclohexane have been measured at atmospheric pressure using a dynamic method. This work includes the characterization of the synthesized compound by water content and also by differential scanning calorimetry. Phase diagrams for the binary systems of [BM(4)Py][NTf(2)] with all solvents reveal eutectic systems with regards to (solid-liquid) phase equilibria and show immiscibility in the liquid phase region with an upper critical solution temperature (UCST) in most of the mixtures. The phase equilibria (solid, or liquid-liquid) for the binary systems containing aliphatic hydrocarbons reported here exhibit the lowest solubility and the highest immiscibility gap, a trend which has been observed for all ILs. The reduction of experimental data has been carried out using the nonrandom two-liquid (NRTL) correlation equation. The phase diagrams reported here have been compared with analogous phase diagrams reported previously for systems containing the IL N-butyl-4-methylpyridinium tosylate and other pyridinium-based ILs. The influence of the anion of the IL on the phase behavior has been discussed.

Assessment of certain ionic liquids for separation of binary mixtures based on gamma infinity data measurements

The effect of interactions between organic solvents or water on the interfacial and bulk properties of 1-benzyl-3-methylimidazolium dicyanamide, [BzMIM][DCA] and 1-benzyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [BzMIM][NTf2] were determined via measurement of activity coefficients γ∞13 at infinite dilution for 64 solutes. The data were obtained using the gas–liquid chromatography technique. Measurements were undertaken at six temperatures, in 10 K intervals, in the range of 318.15 to 368.15 K. The solutes studied included both non-polar and polar compounds, such as alkanes, alkenes, and alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters. Density, ρ, and viscosity η, measurements for a range of temperatures, T for the chosen ionic liquids (ILs), [BzMIM][DCA] and [BzMIM][NTf2] were also undertaken at pressure, p = 101 kPa. The gas–liquid partition coefficients, KL at infinite dilution, and the fundamental thermodynamic functions, partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements. The values of selectivity and capacity for three separation cases, viz. hexane/hex-1-ene, cyclohexane/cyclohexene, and ethylbenzene/styrene were calculated from γ∞13 values and compared to literature for imidazolium-based or dicyanamide-based, or bis{(trifluoromethyl)sulfonyl}imide-based ionic liquids (ILs). The results from the study indicate that [BzMIM][DCA] has large selectivity values for all three of the separation cases studied.

Application of the bio-inspired Krill Herd optimization technique to phase equilibrium calculations

Abstract The Krill Herd optimization technique, which is based on the simulated herding behaviour of the krill crustacean, is applied to calculations involving phase equilibrium and phase stability, as the application of this emerging technique is extremely limited in the literature. In this work, the Krill Herd algorithm (KH) 1 and the modified Levy-flight Krill Herd algorithm (LKH) 2 has been applied to phase stability (PS) 3 and phase equilibrium calculations in non-reactive (PE) 4 and reactive (rPE) 5 systems, where global minimization of the total Gibbs energy is necessary. Several phase stability and phase equilibrium systems were considered for the analysis of the performance of the technique that includes both vapour and liquid phase conditions. The Krill Herd algorithm was found to reliably determine the desired global optima in PS, PE and rPE problems with generally higher success rates and lower computing time requirements than previously applied metaheuristic techniques such as those involving swarm intelligence and genetic and evolutionary algorithms.

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay is a rapid, cheap, screening test for the in vitro anti-tuberculous activity of chalcones

Rapid and reliable drug susceptibility testing facilitates replenishment of the TB drug pipeline in the fight against drug resistant Mycobacterium tuberculosis. This study compared the performance of the MTT and MABA assays on the anti-tuberculous activity of a set of chalcones. Twenty seven chalcones and chromenochalcones were screened against the laboratory strain M. tuberculosis H37Rv, using a microtitre plate MTT assay at 7 days. The MIC for 20 active compounds was subsequently determined using the MABA, MTT and the Macroscopic broth assays at 7, 14 and 21 days. No significant difference in the MICs, or increase in the MICs was observed over time between the MABA (p=0.209) and the MTT (p=0.207) assays, in contrast to the gold standard, the Macroscopic broth assay (p=0.000). The MICs (16 to >128μg/ml) were much higher than the currently used TB drugs. In conclusion, the MTT assay is a cost effective method (R0.06/well) for the rapid in vitro screening of chalcones against M. tuberculosis, producing reliable results in 8 days. The chalcone with a MIC of 16μg/mL shows promise as a potential lead compound and should be investigated further.

Rigorous characterization of static and dynamic apparatus for measuring limiting activity coefficients

Abstract In differential ebulliometry the true liquid equilibrium composition is related to the charge composition through an equipment characterization parameter E, which is a function of the vaporization ratio φ. Exact computation of γ1∞ requires an iterative solution of a set of three equations. A similar but simpler formulation is possible for differential static apparatus, which accounts exactly for the vapor hold-up. An equipment parameter E is most conveniently resolved in terms of the total equipment volume and involves two new dimensionless groups RT and RG. An iterative procedure involving regula–falsi gave rapid convergence for all systems studied. The flexible one-constant Wilson equation is recommended. For systems of large relative volatility large errors in γ1∞ will result, even at low pressure, if vapor hold-up is not accounted for and if RT⪢1. New values for the self-association constant k are proposed for 2-propanol and ethanol as functions of temperature.

Phase-dependent energy cross-parameters in a monatomic binary fluid system

This paper reports the effects of varying the cross-energy parameter , via a multiplying factor in each phase, on the fluid phase equilibrium compositions of a binary monatomic Lennard-Jones-based mixture (methane/xenon) using constant pressure Gibbs ensemble Monte Carlo simulations. Homogeneous ( ) increases in within the two-phase region resulted in monotonic enrichment of methane in the liquid phase; decreasing had the opposite effect. This was valid only within a certain interval (the two-phase region) at each simulation state point because below the lower bound a single vapour phase was observed and above the upper bound a single liquid phase was observed. Homogeneous were effective at several state points for satisfactory predictions of experimental compositions. At other states, such predictions were not possible with homogeneous but it is demonstrated that perturbing the energy parameter independently in each phase ( ) results in the experimental compositions being predicted satisfactorily. Different combinations of heterogeneous energy cross-parameters do not necessarily result in unique compositions. Variations in revealed that several minima are present on the composition error surface in the – plane and also the existence of a temperature-dependent homogeneous , which has slopes of opposite sign on either side of the critical temperature of pure methane.

Valorisation of chicken feathers: Characterisation of chemical properties

The characterisation of the chemical properties of the whole chicken feather and its fractions (barb and rachis), was undertaken to identify opportunities for valorizing this waste product. The authors have described the physical, morphological, mechanical, electrical and thermal properties of the chicken feathers and related them to potential valorisation routes of the waste. However, identification of their chemical properties is necessary to complete a comprehensive description of chicken feather fractions. Hence, the chicken feathers were thoroughly characterised by proximate and ultimate analyses, elemental composition, spectroscopic analyses, durability in different solvents, burning test, and hydrophobicity. The proximate analysis of chicken feathers revealed the following compositions: crude lipid (0.83%), crude fibre (2.15%), crude protein (82.36%), ash (1.49%), NFE (1.02%) and moisture content (12.33%) whereas the ultimate analyses showed: carbon (64.47%), nitrogen (10.41%), oxygen (22.34%), and sulphur (2.64%). FTIR analysis revealed that the chicken feather fractions contain amide and carboxylic groups indicative of proteinious functional groups; XRD showed a crystallinity index of 22. Durability and burning tests confirmed that feathers behaved similarly to animal fibre. This reveals that chicken feather can be a valuable raw material in textile, plastic, cosmetics, pharmaceuticals, biomedical and bioenergy industries.