Benzene Cyclohexane Research Articles

Nanoconfinement-Induced Phase Segregation of Binary Benzene–Cyclohexane Solutions within a Chemically Inert Matrix

Binary solutions provide a fertile arena to probe intermolecular and molecular/surface interactions under nanoconfinement. Here, the phase segregation of a solution comprising 0.80 mol fraction benzene and 0.20 mol fraction cyclohexane confined within SiO2 nanopores was evaluated using small-angle neutron scattering with hydrogen–deuterium contrast matching. It is demonstrated that benzene and cyclohexane are fully miscible at 303 K (30 °C), yet they unambiguously phase segregate by 153 K (−120 °C), which is below their respective freezing points and below the cubic-to-monoclinic phase transition of cyclohexane. Specifically, the cyclohexane and benzene separate into a core|shell morphology with cyclohexane concentrated toward the nanopore centers. Additionally, pure benzene is shown to form a frozen core of bulk density with a thin shell of slightly reduced density immediately adjacent to the SiO2 nanopore wall at 153 K. Because the SiO2 matrix is chemically inert to cyclohexane and benzene, the observed...

Dimerization Constants from Acoustic Measurements: Solutions of Benzene, Cyclohexylamine and Aniline in Cyclohexane

A model assuming that the formation of dimers determines the acoustic properties of liquid mixtures, in the inert solvent cyclohexane, was applied to describe the observed dependences of sound speed on composition. The dimerization constants were estimated. The results allow one to propose that the solutes tend to form associates larger than dimers in concentrated solutions, while in dilute systems solute–solvent interactions play an important role.

Benzyl- and Vinyl-Functionalized Imidazoium Ionic Liquids for Selective Separating Aromatic Hydrocarbons from Alkanes

The separation of aromatics and aliphatic hydrocarbons is one of the most challenging and energy consuming operations in the petrochemical industry. In this study, two ionic liquids (ILs), N-benzyl-N-methylimidazoium bis(trifluoromethylsulfonyl)imide (IL-a) and N-benzyl-N-vinylimidazolium bis(trifluoromethylsulfonyl)imide (IL-b), were synthesized. Six ternary systems, i.e., toluene–heptane–IL (IL-a or IL-b), benzene–hexane–IL (IL-a or IL-b), and benzene–cyclohexane–IL (IL-a or IL-b), were studied in terms of both quantum chemical calculation and liquid–liquid extraction (LLE). The quantum calculation results showed that both ILs had stronger interaction with aromatics than that with alkanes. For both ILs, stronger binding energy was obtained with toluene than that with benzene. The liquid–liquid extraction experiments were conducted at 298.2 K and atmospheric pressure. The distribution coefficients of aromatic compounds (benzene and toluene) were over 0.72 when IL-a was used as extractant and above 0.75 w...

Aliphatic-aromatic stacking interactions in cyclohexane-benzene are stronger than aromatic-aromatic interaction in the benzene dimer.

Stacking interactions between cyclohexane and benzene were studied in crystal structures from the Cambridge Structural Database and by ab initio calculations. Calculated at the very accurate CCSD(T)/CBS level of theory, the cyclohexane-benzene interaction energy is -3.27 kcal mol-1, which is significantly stronger than the interaction in the benzene dimer (-2.84 kcal mol-1) indicating the importance of aliphatic-aromatic interactions.

Synthesis, Photo-sensitive and Electrochemical Properties of Rod-like Aromatic Aldehyde with Azo Bridge

Abstract Eight new rod-like liquid crystal molecules composed by a long rigid core of three six-member rings (cyclohexane ring or benzene ring), azo, ester and terminal aldehyde groups have been prepared. These rod-like liquid crystalline molecules were designed to construct new structures to further study photo-isomerization in their mesophases. All the compounds have been characterized based on their basic spectral data, differential scanning calorimeter (DSC) and hot stage polarizing optical microscope (HS-POM). The result showed that all the molecules, even those with the shortest terminal methyl group, have liquid crystalline properties. Their mesophases are nematic within the temperature ranges from 85 to 145°C. They exhibit photo-sensitivities not only in methanol solutions but also in a mesophase when exposed to UV light. The highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO) and the differences between the frontier molecular orbitals (Eg) of these compounds were determined by cyclic voltammetry. The effect of even-odd carbon number of the terminal straight alkyl chain on the UV spectral data and the Eg were observed. The difference between the Eg of these compounds are in excellent agreement with the difference of their maximum absorption wavelength in UV spectra.

Application of the partially thermally coupled distillation flowsheets for the extractive distillation of ternary azeotropic mixtures

An application is considered of the extractive distillation flowsheets with partially thermally coupled columns for the separation of ternary azeotropic mixtures with the different type of vapor–liquid equilibrium diagrams. The feasible extractive distillation flowsheets with such columns are identified for all types of the ternary azeotropic mixture vapor–liquid equilibrium diagrams. The manifold of flowsheets is the search space to identify the optimal arrangement for the separation of the individual mixture. An applicability analysis of all possible extractive distillation flowsheets for all types of vapor–liquid equilibrium diagram decreases the number of feasible configurations for the selection of the optimal extractive distillation sequence for the mixture with unique vapor–liquid equilibrium diagram separation. For example, in the case of benzene–cyclohexane–toluene mixture distillation with N-methylpyrrolidone as an entrainer, only 10 extractive distillation flowsheets instead of 22 potential ones must be analyzed, calculated and optimized for the identification of the best extractive distillation arrangement.

Selective Separation of Aromatics from Paraffins and Cycloalkanes Using Morpholinium-Based Ionic Liquid

Morpholinium-based ionic liquids (MILs) have attracted increasing interest because of their good extraction performance and low toxicity. In this study, two MILs, N-benzyl-N-methylmorpholinium bis(trifluoromethylsulfonyl)imide (MIL-a) and N-allyl-N-methylmorpholinium bis(trifluoromethylsulfonyl)imide (MIL-b), were synthesized. Six ternary systems, toluene–heptane–IL (MIL-a or MIL-b), benzene–hexane–MIL (IL-a or MIL-b) and benzene–cyclohexane–IL (IL-a or MIL-b), were studied in terms of both quantum chemical calculation and liquid–liquid extraction. The calculation results showed that both MILs had stronger interaction with aromatics than with alkanes. For both cations of MILs, stronger binding energy was obtained with toluene than with benzene. The difference between MIL-a-toluene and MIL-a-cyclohexane was larger than that of MIL-b. As a result, MIL-a showed higher selectivity on toluene than MIL-b. In other ternary systems, the interaction difference was larger than that between MIL-a-benzene and MIL-a-alkanes, which led to a better selectivity of benzene on MIL-b. The liquid–liquid extraction experiment was conducted at 298.2 K and atmospheric pressure. The distribution coefficients of aromatic compounds (benzene and toluene) were over 0.60 when MIL-a was used as extractant, and above 0.50 when MIL-b was used. The selectivity was more than 80, and the distribution coefficient of toluene was over 1.4, when MIL-b was used in the ternary system with benzene and hexane. Both MILs could be reused without significant loss of selectivity and distribution coefficients.

Separation of Benzene and Cyclohexane with Mixed Solvent Using Extractive Distillation

Isothermal Vapour-liquid equilibrium for cyclohexane (1) + benzene (2) binary system, cyclohexane (1) + benzene (2) dimethylformamide (3) ternary system and cyclohexane (1) + benzene (2) dimethylformamide (3) + cosolvent (4) quaternary systems were obtained. The effects of cosolvents (diethyl glycol, dimethylsulfoxide, N-methylformamide) on the performance of dimethylformamide in benzene-cyclohexane separation were studied. The result shows the selected cosolvents suppress the effectiveness of dimethylformamide. The result also shows that the ratio of cosolvents to dimethylformamide affects the separation factor.

Effect of solvent on diffusion: probing with nonpolar solutes.

Limiting mutual diffusion coefficients of carbon tetrachloride in methanol and of benzene, toluene, naphthalene, and biphenyl in cyclohexane as well as in ethanol at different temperatures are reported. These new data, together with literature diffusivities for the same probe solutes and for solute mesitylene in various solvents, are utilized to elucidate the effect of solvent on diffusion. Here, the data are consistent with our recent findings [J. Chem. Phys. 2013, 138, 224503] on the effects of free volume fraction, molar density, molecular mass, and fractional viscosity of solvent on diffusion. The results in this study show that the relation developed previously for solvent dependence of diffusion of disc-shaped solutes is also valid for spherical carbon tetrachloride. It is further found in this investigation that diffusivities are weakly dependent on a solvent's dielectric constant. A relation that includes the dielectric effect of solvent is demonstrated to be capable of describing the solvent dependence of diffusion of the nonpolar solutes of different shapes and sizes in this work to within an average deviation of ±2.7%. Comparisons with other diffusion models reveal that the newly developed relation is more accurate for representing the effect of solvent on diffusion. An expression for Zwanzig's "effective hydrodynamic radius" is also presented.

Reprint of: Simulation based ionic liquid screening for benzene–cyclohexane extractive separation

In order to screen ionic liquids (IL) as suitable solvents for the separation of benzene and cyclohexane, the extraction efficiency of ILs (12 cations and 22 anions) was estimated based on COSMO-RS predictions of infinite dilution activity coefficients of benzene and cyclohexane in different ILs..[C4mim][AlCl4] was found to be the most promising solvent. To provide deep insight on how the IL structure influences the extraction efficiency, molecular interactions between IL ions and benzene were determined from DFT calculations. Moreover, liquid–liquid equilibrium data of the ternary system benzene–cyclohexane—[C4mim][AlCl4] were experimentally determined and used to fit parameters of the NRTL activity coefficient model. Based on the NRTL model the continuous extraction process was simulated and compared with a reference process using sulfolane as solvent. For the extraction process using [C4mim][AlCl4], high cyclohexane product purity (99.65wt%) and high benzene recovery efficiency (98.03%) can be reached with at much lower energy consumption and higher product yield compared to conventional extraction solvents. In conclusion, the ionic liquid [C4mim][AlCl4] is a promising solvent for the extractive separation of benzene and cyclohexane.

Simulation based ionic liquid screening for benzene–cyclohexane extractive separation

In order to screen ionic liquids (IL) as suitable solvents for the separation of benzene and cyclohexane, the extraction efficiency of ILs (12 cations and 22 anions) was estimated based on COSMO-RS predictions of infinite dilution activity coefficients of benzene and cyclohexane in different ILs..[C4mim][AlCl4] was found to be the most promising solvent. To provide deep insight on how the IL structure influences the extraction efficiency, molecular interactions between IL ions and benzene were determined from DFT calculations. Moreover, liquid–liquid equilibrium data of the ternary system benzene–cyclohexane—[C4mim][AlCl4] were experimentally determined and used to fit parameters of the NRTL activity coefficient model. Based on the NRTL model the continuous extraction process was simulated and compared with a reference process using sulfolane as solvent. For the extraction process using [C4mim][AlCl4], high cyclohexane product purity (99.65wt%) and high benzene recovery efficiency (98.03%) can be reached with at much lower energy consumption and higher product yield compared to conventional extraction solvents. In conclusion, the ionic liquid [C4mim][AlCl4] is a promising solvent for the extractive separation of benzene and cyclohexane.

Description and approximation of mass-transfer in pervaporation process on the base of nonequilibrium thermodynamics approach

Pervaporation is a nonequilibrium membrane process. The pressure or chemical potential gradients are the factors that determine the irreversibility of membrane transfer in pervaporation. In this work, we consider the opportunity of describing and approximating pervaporation data using a nonequilibrium thermodynamic approach. Pervaporation curves for a wide range of feed solution concentrations have been built based on data on a few binary systems. The thermodynamic properties of feed solutions were calculated using vapor–liquid equilibrium data. The sigmoidal Boltzmann function, Gauss function and Praal equation were used to approximate vapor–liquid equilibrium data. Approbation of proposed variants in the construction of pervaporation curves was carried out for five binary systems: ethanol–water at 50°С and 60°С, acetone–water at 30°С, benzene–cyclohexane at 25°С, methanol–methyl-tert-butyl ether at 25°С, and ethanol–butanone at 55°С. The agreement between calculation results and experimental data is in the limits which are sufficient for applied estimations.

Separation of benzene–cyclohexane mixtures by filled blend membranes of carboxymethyl cellulose and sodium alginate

Blend membranes were prepared by solution blending of sodium alginate (SA) and sodium carboxymethyl cellulose (CMC) in water with varied compositions. One of the blend membranes containing 25% SA and 75% CMC was found to show optimum flux and benzene selectivity for 19.6wt% benzene in cyclohexane. This unfilled blend membrane designated as F0 was further filled with 2, 4, 6 and 8wt% organophilic bentonite filler to obtained four filled membranes designated as F2, F4, F6 and F8, respectively. These five (one unfilled and four filled) membranes were characterized by various conventional methods like FTIR, XRD, DTA (for unfilled blend membranes) and SEM (for filled membranes). These membranes were used for pervaporative separation of benzene from its mixtures with cyclohexane over the concentration range of 0.5–20wt% benzene. The filled F8 membrane showed lower flux (35.65kgμm/m2h) than the unfilled F0 membrane (77kgμm/m2h) but separation factor for benzene of the F8 membrane (212) was much higher than the F0 membrane (88.7).

Control of Benzene–Cyclohexane Separation System via Extractive Distillation Using Sulfolane as Entrainer

Benzene and cyclohexane (CYH) can be separated via extractive distillation using sulfolane (SULF) as entrainer. In this Article, the steady state of an extractive distillation system has been simulated using the RadFrac model in Aspen plus, and the controllability of this system with feed flow rate and feed composition disturbances has been studied in Aspen Dynamics. Sensitivity analysis is used to obtain optimal operation conditions. The common control scheme for extractive distillation is infeasible. Two control structures are demonstrated in this Article. Each control structure has three main temperature controllers, two in the extractive distillation column and one in entrainer recovery column. Although both control structures can solve all disturbance issues and maintain the product purities very close to the set points, the dynamic responses of initial control structure have large transient deviation when +20% feed flow rate disturbance is introduced, while the improved control structure can overcome this obstacle.

Bimetallic Ru–Cu Nanoparticles Synthesized in Ionic Liquids: Kinetically Controlled Size and Structure

We report a new synthesis of size-controlled bimetallic Ru–Cu nanoparticles (NPs) in ionic liquids using two organometallic precursors. Interestingly enough, upon mixing ruthenium and copper precursors, smaller bimetallic NPs (1.9–2.8 nm) are formed as compared to single metals (Cu: 5 nm; Ru: 4 nm) in a large range of copper molar fractions (χCu = 0.005–0.91). Surface and microscopy techniques evidence that NPs have metallic copper on the surface and crystalline hexagonal close-packed metallic ruthenium core. This structure is further assessed by the catalytic activity of the bimetallic NPs, showing that conversion of benzene in cyclohexane is reduced with increasing χCu. A new and versatile synthesis of size-controlled bimetallic NPs under 10 nm using different decomposition rates of organometallic precursors in ionic liquids is described.

Benzene hydroisomerization over Pt/MOR/Al2O3 catalysts

Benzene hydroisomerization is among the promising processes converting benzene into methylcyclopentane (MCP), which is an environmentally friendlier, octane boosting component of motor fuels. Benzene hydroisomerization into MCP over the Pt/MOR/Al2O3 (MOR = mordenite) catalytic system is reported here. The dependence of the yield of the target product on the acidic properties of the support and platinum precursor ([Pt(NH3)4]Cl2 or H2PtCl6) have been investigated in order to optimize the catalyst composition. The acidic properties of the surface have been altered by introducing 30–95 wt % alumina into the support. Catalytic activity has been measured in the hydroisomerization of cyclohexane and a benzene (20 wt %) + n-heptane (80 wt %) mixture in a flow reactor at 250–350°C, 1.5 MPa, H2: CH = 3: 1, a cyclohexane LHSV of 6 h−1, a mixed feedstock LHSV of 2 h−1, a catalyst bed volume of 2 cm3, and catalyst pellet sizes of 0.25–0.75 mm. The most efficient catalyst for cyclohexane and n-heptane isomerization and benzene hydroisomerization is the platinum-containing catalyst (0.3 wt % Pt) whose support consists of 30 wt % MOR and 70 wt % Al2O3. The highest yield of the target products of isomerization in the presence of this catalyst is attained in the temperature range from 280 to 310°C, which is thermodynamically favorable for MCP formation from benzene. This indicates that this catalyst is promising for the hydroisomerization of benzene-containing gasoline fractions. Use of H2PtCl6, a readily available chemical, as the platinum precursor is favorable for commercialization of the catalyst and ensures price attractiveness in its industrial-scale manufacturing.

Synthesis and Properties of Cycloparaphenylene-2,5-pyridylidene: A Nitrogen-Containing Carbon Nanoring

The first synthesis of a nitrogen-containing cycloparaphenylene, cyclo[14]paraphenylene[4]2,5-pyridylidene ([14,4]CPPy), has been achieved. A palladium-catalyzed stepwise assembly of 2,2'-bipyridine, benzene, and L-shaped cyclohexane units, followed by NaHSO(4)/o-chloranil-mediated aromatization, successfully provided [14,4]CPPy. While the absorption and fluorescence properties of [14,4]CPPy were somewhat similar to those of cycloparaphenylenes (λ(abs) = 344 nm, ε = 7.3 × 10(4) cm(-1) M(-1), λ(em) = 427 nm, Φ(F) = 0.80), it was found that [14,4]CPPy possesses an interesting halochromic property.

Evaluation of the ionic liquids 1-alkyl-3-methylimidazolium hexafluorophosphate as a solvent for the extraction of benzene from cyclohexane: (Liquid + liquid) equilibria

In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid+liquid) equilibrium of 1-alkyl-3-methylimidazolium hexafluorophosphate, [Cnmim][PF6] (n=4, 5, 6), with benzene and cyclohexane was studied at T=298.15K and atmospheric pressure. The reliability of the experimentally determined tie-line data was confirmed by applying the Othmer–Tobias equation. The solute distribution coefficient and solvent selectivity for the systems studied were calculated and compared with literature data for other ILs and sulfolane. It turns out that the benzene distribution coefficient increases and solvent selectivity decreases as the length of the cation alkyl chain grows, and the ionic liquids [Cnmim][PF6] proved to be promising solvents for benzene–cyclohexane extractive separation. Finally, an NRTL model was applied to correlate and fit the experimental LLE data for the ternary systems studied.

Volumetric behavior of the binary systems benzene–cyclohexane and benzene–2,2,4-trimethyl-pentane at temperatures 293.15–323.15 K

Densities of the binary system benzene–cyclohexane at several temperatures (293.15–323.15K) and at atmospheric pressure were measured using a vibrating-tube densimeter in a static mode. Excess molar volumes were calculated from the densities and correlated using the second-order Redlich–Kister equation. Present data were compared with those determined previously by pycnometric measurements; a fair agreement of the old and new data sets was found. Also comparison with previously presented experimental data of other authors was proved with a good agreement. In order to test ability of the cubic equations and the standard mixing and combining rules to correlate/predict the concentration dependence of the excess volume, Peng–Robinson equation of state was successfully applied to the present data. Close similarity of characteristic parameters of benzene and cyclohexane prevents to discern among mixing rules available in literature and those proposed within this paper. Thus, another binary system, i.e. benzene–2,2,4-trimethylpentane was investigated in the temperature range 293.15–323.15K. Peng–Robinson constants of the components of this system differ in their magnitude and thus allow to study the effect of different combining rules. It was found that the considered two combining rules with slightly different correction constants k12 yielded very similar VmE dependencies on the concentration.

ChemInform Abstract: Preparation and Steric Structure of Condensed-Skeleton Saturated Diphenyl-Substituted Isoindolones.

The Friedel-Crafts reaction of benzene with cis-4-cyclohexene- 1,2-dicarboxylic anhydride (1) yields trans-5-phenyl-cis-2-benzoylcyclohexane- carboxylic acid (2), which gave cyclohexane-condensed pyridazinone (3) with hydrazine, and cis-4,5-tetraethylene-1,2-oxazin-8-one (4) with hydroxyl- amine. From 2 with ethylenediamine, the saturated imidazo[2,3-a]isoindolone (5) was prepared, while the reaction of 2 with 1,3-diaminopropane furnished a mixture of two isomeric pyrimido[2,3-a]isoindolones (6a,b) differing in the relative positions of the benzene ring and cyclohexane annelation hydrogens. From the reaction of 2 with 3-aminopropanol, the oxazino[2,3-a]isoindolone (7) was obtained (...)