Fluid phase topology of ethanol+benzene+cyclohexane at 101.3 kPa

In this article, isobaric vapor–liquid equilibria for the ternary mixture of ethanol?+?benzene?+?cyclohexane was experimentally investigated at atmospheric pressure. Vapor–liquid equilibria data for ethanol?+?benzene?+?cyclohexane at 101.3?kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits three binary homogeneous azeotropes and a ternary minimum azeotrope at the studied conditions. Satisfactory results were obtained for correlation of equilibrium compositions with UNIQUAC activity coefficients model and also for prediction with UNIFAC method. In both cases, low root mean square deviations of vapor mole fraction and temperature were calculated. The capability of ethanol as modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. However, owing to the complex topology of the ternary mixture it leads to a distillation scheme with three columns and difficult operation and thus, ethanol is not recommended as a separating agent for benzene?+?cyclohexane azeotrope.     

Excess enthalpies of 2-propanol + cyclohexane and 2-propanol + benzene + cyclohexane at 298.15 K

With an isothermal dilution calorimeter excess enthalpies have been determined at 298.15 K for 2-propanol + cyclohexane and 2-propanol + benzene + cyclohexane mixtures. The results are fitted with an associated-solution model. Predicted excess enthalpies for the ternary mixture agree well with the experimental results.     

Application of the Prigogine-Flory-Patterson theory part III. Mixtures of a bicyclic compound,benzene, cyclohexane,n-hexane with a cycloalkane,cyclohexene, a cycloalkadiene and benzene

The Prigogine-Flory-Patterson theory of liquid mixtures has been qpplied to the H _m ^E and V _m ^E for binary mixtures of a bicyclic compound, benzene, cyclohexane and n-hexane with a cycloalkane, cyclohexene, a cycloalkadiene and benzene. Furthermore the Prigogine-Flory theory has been used to predict activity coefficients at infinite dilution from the experimentally determined H _m ^E at 25°C for the mixtures cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene and benzene with a bicyclic compound. The predictions are compared to experimental results.     

60Co-v Radiolysis of a Mixture of Benzene and Cyclohexane in Presence of Diphenyl Mercury

In the radiolysis of cyclohexane in presence of 4×10^?3M diphenylmercury (Hg φ₃) three isomers of hexane, methylcyclopentane (G=0.018), benzene (G=0.42) and cyclohexene (G=0.047) were detected. Addition of benzene in the mixture of cyclohexane and Hg φ₃ formed two isomers of pentane, hexene and one isomer of hexane as additional products, while cyclohexene was eliminated completely. Normally, eight products were detected in presence of 10 to 50% benzene. Total radiolytic yield of products increased in presence of 15 to 25% benzene but in presence of 35 to 50% benzene G values became very low. Considerable amount of hexene is formed in a mixture of benzene and cyclohexane but neither benzene nor cyclohexane in presence of Hg φ₂ formed this compound. In the presence o. benzene and φ₂Hg hexane yield is very much reduced. Protection is observed in presence of 10% as well as 35 to 50% benzene in this system. The plot of benzene concentration in moles/litre versus methylcyclopentane is linear and from the slope of the straight line, the values of rate constants were found to be 2.65×10^?2 litre/mole sec., 5.25×10^?3 litre mole sec., 9×10^?7 litre/mole sec. for methylcyclopentane, cyclohexane and benzene respectively. A plot of G(–c-C₆H₁₂) versus 1/[C₆H₆] also gave a straight line which confirms the sponge type protection in this multicomponent system.     

液相法苯选择加氢制环己烯催化反应动力学方程

 测定了Ru－M－B／ZrO2催化剂上选择加氢制环己烯反应过程中苯、环己烯及环己烷浓度随时间变化的c～t曲线，获得了苯选择加氢制环己烯反应中各步反应的级数和速率常数等动力学参数．结果给出，苯转化的反应级数对苯为1，对氢低压下为2，高压下为0；环己烯继续加氢生成环己烷的反应级数对环己烯为0，对氢低压下为2，高压下为0．在此基础上建立了苯选择加氢制环己烯各步反应的动力学方程，并对动力学方程进行了验证．     

Thermodynamic Properties of Multicomponent Liquid Mixtures

Considering a ternary liquid mixture to be made up of three binary mixtures, by means of cell model using Sutherland type potential function for pair interaction between molecules, a statistical theory for binary liquid mixtures has been extended for ternary systems. In the light of above extension, excess volume ( V E ), excess energy ( E E ) and excess entropy ( TS E ) have been computed for three binary (benzene + cyclohexane, benzene + chlorobenzene and cyclohexane + chlorobenzene) and the resultant ternary system (benzene + cyclohexane + chlorobenzene) at 298.15 K. All the above mentioned excess properties have been computed from the data of ultrasonic velocity and density only.     

Separation of Benzene and Cyclohexane Using Eutectic Solvents with Aromatic Structure

The separation of benzene and cyclohexane is a challenging process in the petrochemical industry, mainly because of their close boiling points. Extractive separation of the benzene-cyclohexane mixture has been shown to be feasible, but it is important to find solvents with good extractive performance. In this work, 23 eutectic solvents (ESs) containing aromatic components were screened using the predictive COSMO-RS and their respective performance was compared with other solvents. The screening results were validated with experimental work in which the liquid–liquid equilibria of the three preselected ESs were studied with benzene and cyclohexane at 298.5 K and 101.325 kPa, with benzene concentrations in the feed ranging from 10 to 60 wt%. The performance of the ESs studied was compared with organic solvents, ionic liquids, and other ESs reported in the literature. This work demonstrates the potential for improved extractive separation of the benzene-cyclohexane mixture by using ESs with aromatic moieties.     

红外光谱法考察苯加氢过程中的氢溢流效应

以点状Pt/η-Al_2O_3催化剂作为产生溢流氢的“源”, 用原位红外光谱观察η-Al_2O_3上苯的加氢过程, 发现溢流氢在η-Al_2O_3表面上可以迁移相当长的距离, 它的迁移速度是苯加氢反应的控制步骤。结合TPSR-MS数据, 认为苯的加氢是分步进行的, 它先被加氢成环已二烯, 再转化成环已烯, 最终形成环已烷脱附。这些反应都是快速反应。     

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, [C_nmim][PF₆] (n = 4, 5, 6), with benzene and cyclohexane was studied at T = 298.15 K 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 [C_nmim][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.     

Pervaporation for separating benzene/cyclohexane mixture by P(AA-MA) copolymer membranes

P(AA-MA)copolymers composed of acrylic acid and methyl acrylate with different molecular weights and sequence structures were synthesized by combination of ATRP and selective hydrolysis.These copolymers were used as membrane materials to separate benzene/cyclohexane mixture by pervaporation.The effects of molecular weight and sequence structure of the copolymers on the pervaporation performance were investigated in detail.For the random copolymers,the permeate flux decreased rapidly with the increasing of molecular weight.The separation factor was also influenced by the molecular weight,which was changed from no selectivity to cyclohexane selectivity with increasing the molecular weight.Contrarily,the block copolymer membrane showed good benzene selectivity with separation factor of 4.3 and permeate flux of 157 g/(m~2h)to 50 wt%benzene/cyclohexane mixture.     

Growth of a faujasite-type zeolite membrane and its application in the separation of saturated/unsaturated hydrocarbon mixtures

Faujasite type zeolite membranes were synthesized on porous ceramic alumina supports by using direct (in situ) and secondary (seeded) growth methods. In the secondary growth method a seed layer of ZSM-2 nanocrystals (prepared according to a report by Schoeman et al. J. Colloid Interface Sci. 1995, 170, 449–456) was deposited on the surface of the support before the hydrothermal growth. For both in situ and secondary growth, the mixture composition was 4.17 Na₂O:1.0 Al₂O₃:10 TEA (triethanol ammonium):1.87 SiO₂:460 H₂O. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron microprobe analysis (EPMA), indicate well intergrown 5–30 μm thick FAU films with Si/Al ∼1–1.5. The separation of saturated/unsaturated hydrocarbon mixtures is demonstrated over a range of temperatures (40–160°C). The mixtures examined (and the corresponding equimolar mixture separation factors) are benzene/cyclohexane (160), benzene/n-hexane (144), toluene/n-heptane (45), propylene/propane (6.2), and ethylene/methane (8.4). In all cases, the membranes are unsaturated hydrocarbon permselective. With equimolar feed mixtures (5 kPa/5 kPa benzene/cyclohexane) and in the temperature range 65–160°C, the membranes exhibit separation factor of 20–160 with the benzene flux in the range 10⁻⁴–10⁻³ mol m⁻² s⁻¹. Decreasing the total feed partial pressure (0.31/0.31 kPa benzene/cyclohexane) reduces both separation factor (12) and benzene flux. Similar trend is observed when the benzene/cyclohexane ratio in the feed mixture (0.5/9.5 kPa benzene/cyclohexane) is reduced. A sorption diffusion model based on the Stefan–Maxwell formulation has also been employed to show that the benzene/cyclohexane separation can mainly be attributed to differences of their adsorption properties.     

Adsorption and reaction of cyclohexene on a Ni(111) surface

We studied the adsorption and reaction of cyclohexene (C6H10) on Ni(111) at different temperatures with high-resolution in-situ X-ray photoelectron spectroscopy (HR-XPS). For exposure at 125 K, we find intact cyclohexene with two distinct C 1s signals at 283.3 and 284.2 eV, due to the nonequivalent carbon atoms in the molecule. The energetic separation is significantly increased relative to the gas-phase value, due to the interaction with the substrate. Upon exposure at 210 K, complete dehydrogenation of cyclohexene to benzene (C6H6) and hydrogen is observed; coverage-dependent changes of the benzene adsorption site occur in a way similar to those for pure benzene layers, which indicates a phase separation in benzene and hydrogen islands. The thermal evolution of the adsorbed layers was studied by temperature-programmed (TP-) XPS and temperature-programmed desorption spectroscopy (TPD). Upon heating, the benzene + hydrogen layer formed at 210 K shows a coverage-dependent reorientation of the benzene molecules during partial desorption. The cyclohexene layer adsorbed at 125 K only shows partial conversion of cyclohexene to benzene and hydrogen upon heating to 185 or 210 K, with the remaining cyclohexene being stable up to approximately 300 K. We propose that upon heating these molecules are stabilized by coadsorbed benzene and hydrogen; furthermore, the mobility of benzene and hydrogen in this coadsorbed layer is reduced, so that no phase separation can occur.     

Selective adsorptive separation of cyclohexane over benzene using thienothiophene cages

The selective separation of benzene (Bz) and cyclohexane (Cy) is one of the most challenging chemical separations in the petrochemical and oil industries. In this work, we report an environmentally friendly and energy saving approach to separate Cy over Bz using thienothiophene cages (ThT-cages) with adaptive porosity. Interestingly, cyclohexane was readily captured selectively from an equimolar benzene/cyclohexane mixture with a purity of 94%. This high selectivity arises from the C–H⋯S, C–H⋯π and C–H⋯N interactions between Cy and the thienothiophene ligand. Reversible transformation between the nonporous guest-free structure and the host–guest assembly, endows this system with excellent recyclability with minimal energy requirements.

Selective adsorptive separation of cyclohexane was realized from an equimolar benzene and cyclohexane mixture via crystalline thienothiophene cages with a selectivity of 94%.     

Thermodynamic properties of the mixture benzene+cyclohexane+2-methyl-2-butanol at the temperature 298.15 K: excess molar volumes prediction by application of cubic equations of state

Excess molar volumes, changes of refractive indices, and changes of isentropic compressibilities of the ternary mixture benzene (1)+cyclohexane (2)+2-methyl-2-butanol (3), and the corresponding binary mixtures benzene (1)+2-methyl-2-butanol (3), and cyclohexane (2)+2-methyl-2-butanol (3) have been evaluated from density, refractive index, and speed of sound measurements at 298.15 K, and atmosphere. These derived properties of binary, and ternary mixtures were fitted to Redlich–Kister, and Nagata equations, respectively, the correlation parameters being gathered. In spite of the high non-ideality observed, the excess molar volumes were satisfactorily predicted by means of cubic equations of state with simple mixing rules.     

Adsorption and separation of organic six-membered ring analogues on neutral Cd(II)-MOF generated from asymmetric schiff-base ligand

A new CdL(2)-MOF was synthesized based on an asymmetric Schiff-base ligand LH, which is obtained by condensation of 5-formyl-8-hydroxyquinoline and 3-pyridinecarboxylic acid hydrazide. A series of organic six-membered ring analogues, namely, 1,4-dioxane, cyclohexane, cyclohexene, benzene, cyclohexanone, and cyclohexanol, can be absorbed by the CdL(2) porous framework in liquid-phase to generate G(n)?CdL(2) (n = 1 and 2) host-guest complexes. In addition, the CdL(2) host framework displays different affinity for these six-membered ring substrates and can effectively separate them under mild conditions (i.e., 1, 4-dioxane > cyclohexane > cyclohexene and benzene > cyclohexanone > cyclohexanol). The empty CdL(2) displays strong green-yellow emission. Furthermore, these host-guest systems show an interesting guest-driven luminescent emission, and the emission intensities of these guest-loaded complexes are effectively reduced.     

Hydrogenation of benzene in the presence of ruthenium on a modified montmorillonite support

Liquid-state hydrogenation of benzene on a supported ruthenium catalyst is studied. The degree of utilization of the inner surface of the porous system is determined. In the presence of water, hydrogenation occurs with the formation of cyclohexene along with cyclohexane.     

Densities,speeds of sound and isentropic compressibilities of binary and ternary mixtures containing benzene,cyclohexane and hexane at 298.15 K

Densities, ϱ, and speeds of sound, u, have been measured for the ternary mixture {benzene + cyclohexane + hexane} and the corresponding binary mixtures {benzene + cyclohexane}, {benzene + hexane} and {cyclohexane + hexane}, at the temperature 298.15 K. Using these results, the isentropic compressibilities, κ_s, the excess isentropic compressibilities, κ_s^E, and the speeds of sound deviations, Δu, have been calculated for both the binary mixtures and the ternary system. Excess isentropic compressibilities, κ_s^E, and the speeds of sound deviations, Δu, have been fitted to the Redlich-Kister equation in the case of binary mixtures, while the equation of Cibulka was used to fit the values relating to the ternary system. The empiric equations of Redlich-Kister, Tsao-Smith, Kohler and Colinet have been applied in order to predict the κ_s^E and Δu of ternary mixtures from the binary contributions.     

Measurement of (liquid + liquid) equilibria for ternary systems of (N-formylmorpholine + benzene + cyclohexane) at temperatures (303.15, 308.15, and 313.15) K

This work demonstrates the ability of N-formylmorpholine (NFM) to act as an extraction solvent for the removal of benzene from its mixture with cyclohexane. The (liquid + liquid) equilibria (LLE) were measured for a ternary system of {N-formylmorpholine (NFM) + benzene + cyclohexane} under atmospheric pressure and at temperatures (303.15, 308.15, and 313.15) K. The experimental distribution coefficients (K) and selectivity factors (S) were obtained to reveal the extractive effectiveness of the solvent for separation of benzene from cyclohexane. The LLE results for the system studied indicate that increasing temperature decreases selectivity of the solvent. The reliability of the experimental results was tested by applying the Othmer–Tobias correlation. In addition, the universal quasichemical activity coefficient (UNIQUAC) and the non-random two liquids equation (NRTL) were used to correlate the LLE data using the interaction parameters determined from the experimental data. The root mean square deviations (RMSDs) obtained comparing calculated and experimental two-phase compositions are 0.0367 for the NRTL model and 0.0539 for the UNIQUAC model.     

The partial hydrogenation of benzene to cyclohexene by nanoscale ruthenium catalysts in imidazolium ionic liquids

The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.     

Novel applications of ziegler-type catalysts,aromatization of tetralin and disproportionation of cyclic olefins

Ziegler catalysts based on Co and Ni efficiently promote the aromatization of tetralin as well as the disproportionation of cyclohexadiene and cyclohexene into benzene and cyclohexane.