Benzene In N-hexane Research Articles

Pervaporation and Gas Separation Properties of High-Molecular Ladder-like Polyphenylsilsesquioxanes.

This paper presents the results of studies on the pervaporation properties (for benzene/hexane mixtures) and gas permeability (for He, H2, N2, O2, CO2, CH4, C2H6, and C4H10) of ladder-like polyphenylsesquioxanes (L-PPSQ) with improved physical and chemical properties. These polymers were obtained by condensation of cis-tetraphenylcyclotetrasiloxanetetraol in ammonia medium. The structure of L-PPSQ was fully confirmed by a combination of physicochemical analysis methods: 1H, 29Si NMR, IR spectroscopy, HPLC, powder XRD, and viscometry in solution. For the first time, a high molecular weight of the polymer (Mn = 238 kDa, Mw = 540 kDa) was achieved, which determines its improved mechanical properties and high potential for use in membrane separation. Using TGA and mechanical analysis methods, it was found that this polymer has high thermal (Td5% = 537 °C) and thermal-oxidative stability (Td5% = 587 °C) and good mechanical properties (Young's module (E) = 1700 MPa, ultimate tensile stress (σ) = 44 MPa, elongation at break (ε) = 6%), which is important for making membranes workable under various conditions. The polymer showed a high separation factor for a mixture of 10% wt. benzene in n-hexane (126) at a benzene flow of 33 g/(m2h).

Statistical mechanical theory of fluid mixtures

A general statistical mechanical theory of fluid mixtures (liquid mixtures and gas mixtures) is developed based on the statistical mechanical expression of chemical potential of components in the grand canonical ensemble, which gives some new relationships between thermodynamic quantities (equilibrium ratio Ki, separation factor αij and activity coefficient γi) and ensemble average potential energy ūi for one molecule. The statistical mechanical expressions of separation factor αij and activity coefficient γi derived in this work make the fluid phase equilibrium calculations can be performed by molecular simulation simply and efficiently, or by the statistical thermodynamic approach (based on the saturated-vapor pressure of pure substance) that does not need microscopic intermolecular pair potential functions. The physical meaning of activity coefficient γi in the liquid phase is discussed in detail from a viewpoint of molecular thermodynamics. The calculated Vapor–Liquid Equilibrium (VLE) properties of argon–methane, methanol–water and n-hexane–benzene systems by this model fit well with experimental data in references, which indicates that this model is accurate and reliable in the prediction of VLE properties for small, large and strongly associating molecules; furthermore the statistical mechanical expressions of separation factor αij and activity coefficient γi have good compatibility with classical thermodynamic equations and quantum mechanical COSMO–SAC approach.

Coadsorption of n-Hexane and Benzene Vapors onto the Chromium Terephthalate-Based Porous Material MIL-101(Cr) An Experimental and Computational Study

The adsorption of n-hexane–benzene mixture onto a chromium terephtalate-based porous material (MIL-101(Cr)) has been studied experimentally and theoretically. The adsorption isotherms of the single components show that MIL-101(Cr) has a better affinity for benzene than for n-hexane. This is in good agreement with the enthalpies of adsorption determined at low coverage. Values of −68 kJ·mol–1 and −61 kJ·mol–1 were found for benzene and n-hexane, respectively. These are consistent with the simulated enthalpies of adsorption and also with the benzene/n-hexane selectivities which range between 2 and 3 depending on the equilibrium pressure. The saturation plateau obtained with n-hexane is 30% lower than that obtained with the adsorption of benzene onto MIL-101(Cr). In the case of the mixture of n-hexane–benzene, the saturation plateau is located between those obtained after adsorption of the single components. This is an indication that the coadsorption of n-hexane and benzene does not occur at the expense of one component of the mixture. However, the kinetics of adsorption of the mixture shows that benzene is adsorbed preferentially at low coverage. This is consistent with the chromatographic separation of n-hexane–benzene mixture by MIL-101(Cr).

Fluorescence quenching and laser photolysis of dipyrrolylbenzenes in the presence of chloromethanes

Fluorescence quenching of 1,4-bis(1H-pyrrol-1-yl)benzene, 1-(1H-pyrrol-2-yl)-1-(1-vinyl-1H-pyrrol-1-yl)benzene, and 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene with chloromethanes (methylene chloride, chloroform, and carbon tetrachloride) in solvents with different polarities follows electron-transfer mechanism. The occurrence of an electron-transfer step is confirmed by formation of short-lived pyrrolylbenzene radical cations. An exception is quenching of fluorescence of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene in n-hexane in the presence of CCl4 and CHCl3 and in pure CCl4. In this case, neutral 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene·-Cl radical is formed via recombination of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene radical cation and chloride anion. A relation was found between the nature of the short-lived species detected by laser photolysis and stable product obtained by stationary photolysis.

Second-derivative variance minimization method for automated spectral subtraction.

A new second-derivative variance minimization (SDVM) procedure is used to automatically extract spectra of a dilute component (solute) from a mixture whose spectrum is dominated by a major component (solvent). This procedure involves the subtraction of Savitzky-Golay second-derivative preprocessed pure solvent and mixture spectra by minimizing the variance of the difference spectrum. The resulting undifferentiated output spectra contain primarily features associated with the solute and/or solute-induced perturbations of the solvent. The SDVM method is found to outperform several related methods, including a previously proposed derivative minimization method, as demonstrated using 1000 randomly generated solute/solvent synthetic spectral pairs and experimental Raman spectra of dilute solutions of benzene in n-hexane and water in acetone. The former experimental solution produced SDVM difference spectra containing benzene bands with virtually no n-hexane interference, while the latter revealed water-induced shifts in acetone spectral features. Several other types of SDVM applications, such as the spectroscopic analysis of layered composites, are discussed.

Preliminary characterization of anhydrous ethanol used in Brazil as automotive fuel

This work reports preliminary studies on the characterisation of anhydrous ethanol (AEA) used as an automotive fuel mixed with gasoline in Porto Alegre (South Brazil). Pre-concentration of the impurities contained in 1000 ml of AEA was carried on through solid-phase extraction using XAD-4™ resin. The main compounds in the extract were identified by means of spectral data from the library of the equipment. The concentrate was then fractionated using a preparative liquid chromatographic column filled with activated silica gel and the elution procedure was carried out with, n-hexane, n-hexane–benzene (1:1, v/v) and dichloromethane. Prior to analysis by GC–MS, each fraction was reduced to 1 ml with a gentle stream of nitrogen. Saturated linear hydrocarbons and aromatic hydrocarbons eluted in the first fraction and oxygenated compounds such as aldehydes, ketones and alcohols, eluted in the second one, were the main compounds detected in the sample.

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy

The reaction of aluminum bromide with benzene in n-hexane was studied by 27Al NMR spectroscopy in the temperature range from –80 to +20 °C. The formation of C6H6·Al2Br6 (1 : 2) complexes is accompanied by broadening of the resonance line with δ 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the line width passed through a maximum near –60 °C. A procedure for determination of the constant K for the formation of 1 : 2 complexes at –20, 0, and +20 °C based on the line broadening with an increase in the C6H6 : Al2Br6 molar ratio was proposed. The thermodynamic parameters of complex formation, ΔG, ΔH, and ΔS, were calculated.

Optimization of an automated FI-FT-IR procedure for the determination of o-xylene, toluene and ethyl benzene in n-hexane

Optimization of an automated FI-FT-IR procedure for the determination of o-xylene, toluene and ethyl benzene in n-hexane

Frequency resolved interferometric coherent Raman spectroscopy with incoherent light: Raman frequency shifts, dephasing rate constants, and nonresonant hyperpolarizabilities of mixtures of benzene in hexane

A newly developed frequency and time resolved coherent anti-Stokes Raman scattering (CARS) technique is used to study properties of the A 1 g ring breathing mode of benzene in a dilution series of liquid mixtures with n-hexane. Recent advances in the interferometric use of incoherent light in CARS measurements (I (2)CARS) provide excellent precision in the recovered dephasing rate constants, vibrational frequencies, and the ratios of the resonant to non-resonant contributions to the signal. Using this technique we observe a more than two-fold decrease in the dephasing rate constant of the vibration, accompanied by a 0.54 cm −1 increase in the vibrational frequency in the limit of infinite dilution of benzene in n-hexane. These changes in the vibrational spectrum are discussed in terms of the condensed phase dynamics that are responsible. It is also seen how the non-resonant contributions to the signal manifest themselves quantitatively in these frequency and time resolved I (2)CARS measurements.

Thermodynamics of binary and larger organic-organic and organic-water systems

We have applied our model to the enthalpy and excess Gibbs energy of mixing data of the binary systems Ethanol-Methylcyclohexane, Water-methylacetate, -ethylacetate, -butylacetate and -pentylacetate, and to the ternary systems Acetonitrile-Benzene-Carbon Tetrachloride, Ethanol—Chloroform—1,4-Dioxane, Cyclohexane—2-Propanol—Water, and to the quaternary system Ethyl Alcohol—n-Hexane—Benzene—Methylcyclopentane. In all cases our model uses only maximum two interaction parameters for each binary and no ternary or larger parameters are needed. Our model can describe all above the systems very well.

Prediction of pervaporation separation characteristics for the methanol—pentane—nylon-6—poly (acrylic acid) blended membrane system

The system of methanol—pentane—nylon-6—poly (acrylic acid) blended membranes was used to predict the pervaporation separation characteristics using the modified Fels and Huang model which has previously been used for the system of n-hexane—benzene—polyethyelene films. Since this model requires knowledge of the diffusion coefficient at zero concentration and the solubility data of the pure components in the membrane, these values were measured experimentally. The calculated separation factors and permeabilities of this system were then compared with the experimentally determined values. The predicted permeabilities of each component were in reasonably close agreement with the experimental values.

DETERMINATION OF COMPOUND CLASS COMPOSITION OF OIL FRACTIONS OF SOME COAL LIQUIDS BY ANALYTICAL LIQUID CHROMATOGRAPHY

ABSTRACT A high-performance liquid chromatography method was developed to determine the amount of each of the compound classes (such as saturates, aromatics and polars) in the oil fraction (pentane soluble fraction) of coal liquids. The method utilizes bonded cyanosilane and aminocyanosilane columns and mixtures of benzene in n-hexane and tetrahydrofuran in methyl tert-butyl ether as mobile phases. A Tracor LC-rotating disc flame ionization detector was used to quantify the chromatographic peaks. Oil fractions derived from different rank coals, liquefied at 385° and 445°C. were analyzed for their compound class compositions. The trends in the percentages of saturates, aromatics and polars varied with liquefaction temperature and coal rank.

Rate constants for the reaction of muonium with aromatic compounds

Rate constants for the reaction of muonium with benzene in water, methanol and n-hexane and for the reaction of muonium with p-difluorobenzene, anilin, hexafluorobenzene and styrene are reported. All rate constants are below the calculated diffusion controlled limit. The activation energy for the reaction of muonium with benzene in n-hexane is very small, indicating the possibility of tunnelling by muonium.

Investigation of thermal transformations of propylene and its role in the formation of benzene by pyrolysis of n-hexane

We investigated the thermal transformations of propylene and mixtures of n-hexane and propylene at 800‡C by use of radioactive hydrocarbons labeled with14C. The data obtained lead to the conclusion that on pyrolysis of n-hexane benzene is formed by the interaction of propylene with 1,3-butadiene or by intermediate formation of 1,3-butadiene.

Chromatographie sur couche mince d'agents de protection pour élastoméres (phénols et phosphites organiques)

Thin-layer chromatography of age resisters for elastomers (phenols and organic phosphites) Sixty-three antioxidants for elastomers (phenols and organic phosphites) have been separated on silica gel thin layers with benzene as developing solvent and N-chloro-2,6-dichloro- p-benzoquinone monoimine in buffered alkaline medium as spray reagent. n-Hexane—benzene (8:1) may also be used to verify the identifications if necessary. The active ingredients of several imprecisely defined products have been identified and the relationships between certain mixtures have been established. Some theoretical correlations between the chemical structure and the R F value have been shown.

A Rapid Method for Hydrocarbon-type Analysis of Heavy Oils and Synthetic Fuels by Pyrolysis Thin Layer Chromatography

Abstract Hydrocarbon-type fractions (saturates, aromatics, polynuclear aromatics, and polar compounds) from heavy crude oils and synthetic fuels were separated by thin layer chromatography (TLC) on chromarods, using an Iatroscan TH-10 analyzer. The best results were obtained on a silica gel chromarod when n-hexane, 10 percent benzene in n-hexane, and 5 percent ethyl acetate in benzene were used as developing solvent. A complete analysis of six samples takes 60 min and requires only 60 mg of sample. Separation was applied to pure hydrocarbon mixtures as well as hydrocarbon-type concentrates isolated from Athabasca bitumen by liquid chromatography. The method is applicable to middle distillates, b.p. 200 to 35O°C, as well as to deasphaltened fractions (malthenes) boiling higher than 350°C Seven samples of malthenes (pentane-solubles) were analyzed by this method.

Reversible intermolecular energy transfer between saturated amines and benzene in non-polar solution

Excitation of a mixture of dimethylethylamine (DEMA) and benzene in n-hexane at 222 nm primarily produces excited amine, while at 261 nm excited benzene predominantly results. The fluorescence spectra appreciably overlap. With 222 nm excitation, DEMA fluorescence is quenched by benzene at the diffusion-controlled rate; this quenching results with nearly unit efficiency in sensitized benzene fluorescence. With 261 nm excitation, some sensitized DEMA fluorescence is observed: the rate constant for tins process is ≈ 2.6 × 10 9 M −1 s −1.

Identification of organic compounds : LXXXIX. Paper and thin-layer chromatography of monohydric phenols as antipyrylquinoneimine dyes

The conversion of phenols into coloured derivatives using the reaction with 4-aminoantipyrine and an oxidizing agent has been described. p-Unsubstituted phenols or phenols substituted with halogeno, carboxy or sulpho groups in the p-position react to form red antipyrylquinoneimines. Phenols with p-alkoxy groups react only partially. p-Alkylphenols give yellow products under the same conditions. The red dyes are most effectively separated using the partition system formamide/ n-hexane—benzene (1:1) on paper or thin layers of cellulose, whereas the solvent system dimethylformamide/ n-hexane is suitable for the yellow products. The separation of isomeric m- and p-alkylphenols is carried out on Silufol sheets using benzene—acetone (3:1) as the mobile phase. The separation of m- and p-halogenophenols is achieved by the elimination of the halogen in p-position. The yellow products are relatively less stable both in solution and on chromatograms, and therefore the coloured derivatives should be freshly prepared.

The liquid—liquid equilibrium for activity coefficient determination

A method based on liquid—liquid equilibrium is proposed for the determination of activity coefficients. The reliability of this procedure is tested on the systems cyclohexane—benzene, cyclohexane—toluene, n-hexane—benzene, n-heptane—toluene.

Vapor-Liquid Equilibria for N-Hexane—Benzene Mixtures

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVapor-Liquid Equilibria for N-Hexane—Benzene MixturesC. O. Tongberg and F. JohnstonCite this: Ind. Eng. Chem. 1933, 25, 7, 733–735Publication Date (Print):July 1, 1933Publication History Published online1 May 2002Published inissue 1 July 1933https://doi.org/10.1021/ie50283a006RIGHTS & PERMISSIONSArticle Views265Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (435 KB) Get e-Alerts