Ratio Of Distribution Coefficients Research Articles

Areas of energy advantage for flowsheets of separation modes for mixtures containing components with similar volatilities

Objectives. The conditions for the effective application of the sharp distillation technique (without a component distributed between the distillate and bottom flows) for the separation of quaternary zeotropic mixtures containing components with similar volatilities were determined. The area of energy advantage for the flowsheet based on the preliminary fractionation of the mixture, compared with the flowsheet, the first distillation column of which works based on the indirect separation mode, was identified for an ethyl acetate–benzene–toluene–butyl acetate system. Energy savings of up to 20% were achieved. The direct and indirect distillation modes can become competitive when the point of the original composition is located near single K-surfaces or in a region with a different ratio of distribution coefficients. Sharp distillation is not suitable for the separation of a mixture containing a pair of components exhibiting relative unity volatility with medium boiling points.Methods. The mathematical modeling in the Aspen Plus V.10.0 software package was chosen as the research method. The simulation was based on the Wilson local composition equation. The relative errors in the description of the phase equilibrium did not exceed 3%.Results. The structure of the vapor–liquid equilibrium diagram and diagram of surfaces of the unit component distribution coefficients were studied for the ethyl acetate–benzene–toluenebutyl acetate and acetone–toluene–butyl acetate–o-xylene systems. Flowsheets based on the sharp, indirect (both systems), or direct (second system) distillation modes were proposed. The distillation process was simulated, and the parameters of the column work were determined (the quality of the substances meets the State Standard requirements of the Russian Federation for minimal energy consumption).Conclusions. Recommendations regarding the use of sharp distillation for the separation of quaternary mixtures containing components with similar volatilities were devised.

Measurement and correlation of liquid–liquid equilibria for ternary systems {cyclooctane + aromatic hydrocarbon + 1-ethyl-3-methylpyridinium ethylsulfate} at T = 298.15 K and atmospheric pressure

This work reports liquid–liquid equilibrium (LLE) results for the ternary systems {cyclooctane + benzene + 1-ethyl-3-methylpyridinium ethylsulfate}, {cyclooctane + toluene + 1-ethyl-3-methylpyridinium ethylsulfate}, and {cyclooctane + ethylbenzene + 1-ethyl-3-methylpyridinium ethylsulfate} at T = 298.15 K and under atmospheric pressure. The selectivity, percent removal of aromatic, and distribution coefficient ratio, derived from the tie-line data, were calculated to determine if this ionic liquid is a good solvent for the extraction of aromatics from cyclooctane. The phase diagrams for the ternary systems are shown, and the tie-lines correlated with the NRTL model have been compared with the experimental data. The consistency of the experimental LLE data was ascertained using the Othmer–Tobias and Hand equations. No data for mixtures presented here have been found in the literature.

Selective Solid-Phase Extraction of α-Tocopherol by Functionalized Ionic Liquid-modified Mesoporous SBA-15 Adsorbent

Ordered mesoporous adsorbents were prepared by physically grafting functionalized ionic liquids onto SBA-15 (a mesoporous siliceous substrate) using incipient wetness immersion method. These adsorbents were successfully applied to the selective extraction and separation of alpha-tocopherol (an isomer of vitamin E) from a model mixture of soybean oil deodorizer distillate. Various parameters affecting adsorption process such as adsorption time, the structures and loadings of ionic liquids, the adsorption isotherm, and the reusability of adsorbent were investigated using liquid-solid extraction. As high as 211 mg/g adsorbent of the adsorption capacity for alpha-tocopherol was obtained through the adsorption isotherm tests using [emim][Gly]/SBA-15 (functionalized ionic liquid 1-ethyl-3-methylimidazolium glycine which was physically coated on SBA-15) as the adsorbent, in which the functionalized ionic liquids contained the amino acid glycine as the anion. The adsorbent [emim][Gly]/SBA-15 also exhibited a very high adsorption selectivity for alpha-tocopherol. The extraction selectivity or the ratio of distribution coefficients between alpha-tocopherol and the major interference component glyceryl triundecanoate (K(d(alpha-tocopherol))/K(d(triglyceride))) was 10.5. The concentration of alpha-tocopherol was significantly increased from 15.6% in original feedstock solution that contained fatty acid methyl ester, triglyceride and alpha-tocopherol to 73.0% after stripping by diethyl ether. Five adsorbent recycle tests showed good reusability of the functionalized ionic liquid-modified mesoporous adsorbent.

EXTRACTION OF CESIUM NITRATE FROM CONCENTRATED SODIUM NITRATE SOLUTIONS WITH 21-CROWN-7 ETHERS: SELECnVITY AND EQUILIBRIUM MODELING

ABSTRACT The extraction of cesium nitrate from a high concentration of sodium nitrate by a family of 21-crown-7 ethers in 1,2-dichloroethane has been investigated. Dibenzo-21-crown-7 (DB21C7) and bis[4(5),4′(5′)-rm-butylbenzo]-21-crown-7 (BtBB21C7) ethers have higher selectivity for cesium but lower extraction efficiency than dicyclohexano-21-crown-7 (DC21C7) ether. As measured by the distribution coefficient ratio Dcs/DNa, the cesium selectivity averaged 78 and 93 for DB21C7 and BtBB21C7, respectively. However, in the case of DC21C7, the cesium selectivity was lower and decreased approximately three-fold from 10 to 3 as cesiüm loading increased. Alkyl substitution on the benzo group has only a small effect on the extraction behavior. It was shown by use of the equilibrium modeling program SXLSQI that the extraction of sodium and cesium could be adequately modeled by augmenting the previously determined cesium nitrate equilibrium model with a 1:1 Na+:crown organic-phase complex. No evidence for a mixed-metal species was found. In accord with our previous study, cesium nitrate extraction entails formation of a 1:1 Cs+:crown complex, but a minor 1:2 complex also forms in the case of DC21C7. Although the sodium and cesium made possible by the U. S. Department of Energy Postgraduate Research Program administered by the Oak Ridge Associated Universities.

Solvent extraction of some base and precious metals using 1,3,4-thiadiazole-2-nonylmercapto-5-thiol

This investigation is one of a series of studies in which the fundamental chemistry which underlies the extraction and separation of precious metals is considered. The title compound (TNSTH) was used as a solvent extraction reagent and shows some promise for extracting and separating the chloro-anions of Au(III) and Pd(II) from strong hydrochloric acid solutions (ca. 5 M). The distribution coefficients from such media were in the order of 10 4. The title reagent may be used to separate the precious metals from each other. For example, the separation coefficients (i.e., ratios of distribution coefficients) for mixed solutions are 10 6 for Au(III)/Rh(III) and Pd(II)/Rh(III); 145 for Au(III)/Pd(II); 180 for Pd(II)/Cu(I or II); 10 6 for Pd(II)/Pt(IV). The time for half of the Pd(II) to be extracted is approximately 6 min, which is acceptable for a commercial process. The title reagent provides a means of separating precious metals from base metals as the latter, with the exception of copper, are not extracted. In the case of copper, the extraction is as Cu(I) rather than Cu(II). The stoichiometry of the Pd(II) extraction is Pd:TNSTH is 1:1.5. Some additional information concerning the nature of the complexes formed by the title compound and chloro-anions in alcoholic solution indicates that Cu(TNST), Ag(TNST), Pd(TNST) 2, and RhCl 3(TNST) 2 are formed. Most of the metals, with the notable exception of rhodium(III) and iridium(IV), can be stripped using a thiourea/HCl solution. The reagent TNSTH appears to be a chelating agent with donor N and S atoms.

SEPARATION OF RARE EARTHS ON ANION EXCHANGE RESINS. IV. INFLUENCE OF TEMPERATURE ON ANION EXCHANGE BEHAVIOUR OF THE RARE EARTH ETHYLENEDIAMINETETRAACETATES.

The influence of temperature on the anion exchange behaviour of the rare earth elements in the system: Amberlite IRA-400 [H2Y2−]—aq. solution of disodium ethylenediaminetetraacetate (Na2H2Y) has been investigated. In the system examined the change of temperature has a double effect: (1) the height equivalent to a theoretical plate decreases with a rise of temperature; (2) the distribution coefficients of the individual ions undergo changes according to the enthalpy values of the ion exchange reactions. As the enthalpies of the ion exchange reactions differ in magnitude and sign for different rare earths, the separation factors (ratio of distribution coefficients) may undergo considerable changes with a change of temperature. Both effects contribute to the final resolution value; for some elements the order of elution is even reversed. New possibilities in qualitative analysis, resulting from the determination of the selectivity coefficient of an exchange reaction for a given ion at different temperatures, have been pointed out.