Selective solvation of polystyrene in tetralin/cyclohexane mixtures

Refractive index increments and density increments have been measured at 307.6K for polystyrene in binary solvents of 1,2,3,4-tetrahydronaphthalene (tetralin, TET) and cyclohexane over the whole range of solvent composition. Comparison of these increments with the corresponding values obtained at dialysis equilibrium (i.e. at constant chemical potential of low molecular weight species) yielded the coefficients of selective adsorption (γ₁) of TET by the polymer. Positive values of γ₁ were exhibited at solvent compositions up to 78% (v/v) of the thermodynamically better solvent, TET. Theoretical curves of γ₁ vs. composition were calculated on the basis of, firstly, relevant interaction parameters and, secondly, interaction parameters in conjunction with solubility parameters. Both procedures afforded self-consistent results, which were, however, uniformly lower than the experimental values of γ₁.     

Lattice coordination number in polystyrene solutions

Intrinsic viscosities of five polystyrene samples of molar masses ca. 10⁵–10⁶ have been measured at 34.5°C in cyclohexane (θ-solvent), 1,2,3,4-tetrahydronaphthalene (good solvent) and in binary mixtures of these two liquids. Experimental values of ⁵−³ (where is the expansion factor) were compared with values calculated on the basis of two theories which assume the lattice coordination number Z to be infinite and finite respectively. Z=∞ greatly overestimates ⁵−³, whilst good accord is obtained if Z=3 or 4 according to molar mass and solvent power.     

Unperturbed dimensions and the g factor of a star-shaped polystyrene

Unperturbed dimensions of a star-shaped polystyrene near the θ temperatures, 25°C, 35°C and 45°C were determined by the measurement of intrinsic viscosity of the polymer in poor solvents. It was found that the inferred mean square radius of gyration of the star-shaped polystyrene, while much smaller than that of the linear polystyrene, as expected, changes much faster with the increase of temperature. The geometric factor g of the star-shaped polystyrene was found to be temperature-dependent.     

High temperature swelling of coal/tetralin mixtures in a high pressure microdilatometer

High pressure microdilatometer experiments were performed on a subbituminous (Wyodak) and a bituminous (Illinois no. 6) coal in helium and hydrogen atmospheres with and without added tetralin. Wyodak coal samples showed no swelling but contractions ranging between 24 and 40 vol% upon heating at 20 and 100 °C min^{− 1} under helium or hydrogen pressures between 150 and 1000 psig (˜1.0–6.9 MPa). Under the same conditions, Illinois no. 6 coals displayed contractions (25–60 vol%) prior to swelling up to 117 vol%. Upon tetralin addition (at 35–190 wt% of the coal), Wyodak coal samples did not swell but showed an increasing contraction with increasing helium or hydrogen pressure due to a slight softening and fusion of the coal particles. In contrast, addition of tetralin at much lower concentrations (5–35 wt%) had a marked effect on the contraction and swelling behaviour of Illinois no. 6. A maximum swelling of 200 vol% was obtained at a tetralin addition of 30 wt%. The increased swelling results from more extensive softening and fusion of coal particles in the presence of tetralin. Both coals showed a decreasing char yield with increasing tetralin concentration. The substantially lower extent of interaction observed between Wyodak coal samples and tetralin compared to Illinois no. 6 coal can be attributed to the differences in pore structure and/or chemical constitution of the two coal samples. Examination of the resultant solids by optical microscopy revealed the microstructural changes produced by thermal treatment in dilatometer experiments.     

四氢萘/甲苯混合溶剂中硫璜的溶解特性

为解决硫磺溶解过程中溶剂种类选择少、溶解度低的问题,从溶剂分子结构出发选用四氢萘和甲苯混合溶剂在60~99℃、5~30 min、四氢萘与甲苯质量比(MROTTT)1~15参数范围内进行硫磺溶解实验。通过对四氢萘、甲苯单体及二者复合溶剂对硫磺的溶解性对比分析,结果表明,在温度83℃、时间7 min、MROTTT为15时,混合溶剂对硫磺的溶解度最大,达到14.17 g/100 g混合溶剂。     

Dynamic light scattering and viscoelasticity of semidilute polystyrene/cyclohexane solutions

In the present work, dynamic light scattering (DLS) measurements from polystyrene in cyclohexane semidilute solutions were carried out at 60 °C with scattering angles varied from 30° to 120°. The correlation functions were analyzed with the double KWW function and the CONTIN program. The amplitude of the fast mode A_f of the field correlation function g¹(t) was used to calculate the longitudinal stress modulus M_o using Wang’s theory. A comparison between M_o calculated from DLS data and the shear stress modulus G obtained from mechanical measurement was made.     

Interaction parameters in ternary polystyrene solutions at high temperature

A combination of dilute solution viscometry and Rayleigh light scattering has been used to evaluate experimentally the interaction parameters χ_ij in solutions comprising tetralin (1), polystyrene (2) and 3-methyl cyclohexanol (3). The measurements were carried out at 371.5 K, where binary solutions of the polymer in 3-methyl cyclohexanol are under θ-conditions and tetralin is a thermodynamically good solvent for polystyrene. For polymer-solvent interaction, values of χ₁₂ = 0.40 ± 0.01 and χ₂₃ = 0.50 were obtained. The solvent-solvent interaction parameter χ₁₃ was composition dependent, having limiting values of 0.52 and 0.73 at X₁ = 0 and X₁ = 1, respectively, where X₁ is the mol fraction of liquid 1 in binary mixtures of liquids (1) and (3).     

The unperturbed molecular dimensions of poly(ethylene oxide) in aqueous solutions from intrinsic viscosity measurements and the evaluation of the theta temperature

Intrinsic viscosity measurements were carried out on five well characterized fractions of poly(ethylene oxide) in aqueous solutions at 24.9°, 34.9°, and 45.5°C. The Stockmayer-Fixman extrapolation was applied to the data: it yields the unperturbed dimensions K₀ of the chain. The unperturbed root-mean-square end-to-end distance $\text{〈}\text{R}\text{?}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_0$ calculated for the polymer fractions in water indicate that the polymer molecules are expanded in this solvent as the temperature is raised. The temperature coefficient of unperturbed dimension, $\text{d In}\text{〈}\text{R}\text{?}{}^2\text{〉}{}_0\text{d}\text{t}\text{= 0.024}\text{K}{}^{\mathrm{?1}}$, calculated for poly(ethylene oxide) in water using the present data is about 100 times higher than the literature values of 0.23 (±0.02) × 10^?3 K^?1 and 0.2 (±0.2) × 10^?3 K^?1, respectively, obtained from force-temperature (‘thermoelastic’) measurements on elongated networks of the polymer in the amorphouse state and form viscosity measurements on this polymer in benzene. A value of θ=108.3°C was obtained from the temperature dependence of the interaction parameter B in the Stockmayer-Fixman equation.     

Pervaporation performance of polydimethylsiloxane membranes for separation of benzene/cyclohexane mixtures

Crosslinked polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat‐plate composite membrane. The different function composition of the PDMS/PEI composite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PEI composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this work were employed in pervaporation separation of benzene/cyclohexane mixtures. Effects of feed temperature, feed composition, concentration of crosslinking agent on the separation efficiency of benzene/cyclohexane mixtures were investigated experimentally. In addition, the swelling rate and stableness of composite membrane during long time operation were studied, which should be significant for practical application. The results demonstrated that the pervaporation method could be very effective for separation of the benzene/cyclohexane mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Temperature dependence of unperturbed dimension and interaction parameters of polyester resin in solvents

The flow behaviour of a polyester in various solvents was studied at temperatures ranging from 10 to 80°C. The practical data obtained from the temperature dependence of limiting viscosity number [η] were used to calculate unperturbed dimensions and interaction parameters of the polyester resin in poor, moderate and good solvents. The data provided information regarding conformational transitions in the polymer chains in terms of exothermic or endothermic local ordering of solvents on resin segments and their fixation on polymer coils. The temperature dependence of unperturbed dimensions K_e, Flory–Huggins interaction parameter χ₁₂, the second virial coefficient A₂, entropy parameter U₁, enthalpy parameter K₁, and viscosity expansion factor α_n, has been used to estimate the solvent quality for the resin.     

Pyrolysis of petroleum asphaltene in tetralin

The pyrolysis of a petroleum asphaltene in tetralin donor solvent at 450 °C has been examined, and the products characterized by elemental, molecular weight, n.m.r. and g.c.-m.s. analysis. Degradation to mainly lower molecular weight products takes place, the residual asphaltene having a smaller average cluster size, higher aromaticity and a heteroatom content resistant to further reaction. β-bond scission is important in the early stages of reaction.     

Phase equilibria of binary clathrate hydrates of nitrogen+cyclopentane/cyclohexane/methyl cyclohexane and ethane+cyclopentane/cyclohexane/methyl cyclohexane

In this communication, we first report hydrate dissociation conditions for the nitrogen+cyclopentane, cyclohexane or methyl cyclohexane+water and ethane+cyclopentane, cyclohexane or methyl cyclohexane+water systems at various temperatures. The experimental data were generated using an isochoric pressure-search method. The hydrate dissociation data for the aforementioned systems along with the hydrate dissociation data for the methane, carbon dioxide or hydrogen sulfide+cyclopentane, cyclohexane or methyl cyclohexane+water systems collected from the literature are compared with the corresponding literature data in the absence of the aforementioned heavy hydrocarbons in order to study the hydrate promotion effects of cyclopentane, cyclohexane or methyl cyclohexane. It is shown that these effects on ethane simple hydrate are not considerable unlike the corresponding effects on nitrogen, methane, carbon dioxide and hydrogen sulfide simple hydrates.     

Viscosity behaviour of poly(ethyl methacrylate) in the ethyl acetate/tert-butanol binary mixture: total and preferential adsorption

The behaviour of poly(ethyl methacrylate) (PEMA) in the ethyl acetate (1)/tert-butanol (2) binary mixture is studied by laser light scattering, differential refractometry and viscometry. Ethyl acetate is a solvent for the polymer and tert-butanol is a precipitant. Preferential adsorption of tert-butanol up to 15% alcohol in the binary mixture is observed, ethyl acetate being preferentially adsorbed in the macromolecular coil at higher percentage of alcohol in the solvent mixture. Total adsorption of PEMA is independent of the amount of tert-butanol in the solvent. Various theoretical expressions for the preferential and total adsorption coefficients are used; their agreement or disagreement with the experimental results is explained on the basis of polymer-solvent interactions.     

Investigation of conformational transitions in polyamide-6 macromolecules in mixtures of m-cresol and methanol

The intrinsic viscosity of polyamide-6 (PA-6) solutions in mixtures of m-cresol and methanol decreases with increasing methanol concentration. A conformational transition occurs in the 50–60% methanol concentration range. This phenomenon has been studied by viscometric measurements for various methanol concentrations, a two-fold decrease of intrinsic viscosity having been observed. The results are interpreted by assuming that the observed decrease in intrinsic viscosity is due to a coil-globule conformational change in the polyamide-6 molecules. A decrease of intrinsic viscosity also occurs on increasing the temperature at which the viscometric measurements are carried out. This is explained by the possibility of occurrence of a cis-trans isomerisation, and of a partial helix-coil conformational change.     

Thermolysis of glycol lignin in the presence of tetralin

An organosolv (ethylene glycol) hardwood lignin has been thermally treated in the presence of tetralin, a hydrogen donor solvent. The effects of reaction temperature and time on product distribution were studied as a function of a seventy index, X_c = ?n (R_ω with R_ω = Δt t × exp [(T_r - T_b)/ω] where Δt = time, T_r = reaction temperature, T_b = base temperature, and ω = characteristic parameter. Under the conditions used, up to 60% of the lignin can be converted to liquid and gaseous products. Syringols, guaiacols, aromatic aldehydes and ketones predominate at low treatment severities whilst phenol, catechol and their methyl and ethyl derivatives are the main monomers at high severities. Comparison of our data with parallel works is shown to be effectively done through the severity index, X_c.     

Dehydrogenation of tetralin on Pd/C and Te-Pd/C catalysts in the liquid-film state under distillation conditions

The dehydrogenation of tetralin to naphthalene in the liquid-film state on Pd/C and Te-Pd/C catalysts was investigated under reactive distillation conditions at 493 K. The conversion of tetralin was high, when observed using 0.3 g of Pd/C at a specific volume of tetralin (0.9 mL) was used, while the addition of tellurium into the Pd/C catalyst resulted in a similar high conversion using 0.3 g of Te-Pd/C with a somewhat wider volumetric range (0.8–1.1 mL) of tetralin.     

环己烷/水乳状液的超声破乳

为排除污油等复杂乳化液中的杂质干扰,采用单一组分方法,制备不同体系的环己烷/水乳状液,研究超声在乳状液中的破乳作用,考察超声声强、超声频率、超声辐照时间对乳状液破乳的影响。结果表明:乳状液的初始水含量对超声破乳效果有影响,初始水含量越低,破乳效果越好;超声声强的改变直接影响乳状液分散相液滴的凝聚和发散,超声破乳的声强应在空化临界阈值以下,以0.66 W/cm2最佳;超声辐照时间为6 min,超声频率为20 kHz时破乳效果达到最好。     

Effect of temperature and thermodynamic quality of solvent over unperturbed chain dimensions of nylon 6

A nylon 6 sample having average molecular mass 4.825 × 10⁵ g mol^?1 was fractionated into five different fractions with respect to molecular mass, which ranged from 3691 to 999,000 g mol^?1. The light scattering and intrinsic viscosity measurements were made in m‐cresol and its mixture with 1,4‐dioxane. The second virial coefficient, radius of gyration and Mark Houwink's constant and unperturbed chain dimensions were determined by light scattering and viscosity measurement. It has been observed that all these parameters are composition of solvent and temperature dependent. The solvent having composition of 97% m‐cresol and 3% dioxane, was best and it deteriorated with the increase/decrease in percentage of 1,4‐dioxane in m‐cresol. However, its thermodynamic quality was enhanced with the temperature. Such variation in quality of solvent was reflected in all the estimated parameters and showed maxima at this composition of solvent. The unperturbed dimensions obtained by different methods though, differed in values but showed same trend and NA‐MKB method gave close results to the one obtained through [η_o]. A new expression has also been proposed relating k_o to solvent quality and temperature and the data obtained by us for nylon‐6 and the one obtained from the literature for dextran obeyed this expression up to large extent irrespective of the solvent composition and temperature. The proposed equations have also been applied to dextran/methoxy ethylene and dextran/ethylene glycol systems and worked well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Behaviour of tetralin in coal liquefaction: Examination in long-run batch-autoclave experiments

The decomposition of tetralin in the presence and absence of coal was investigated in batch-autoclave experiments. The effect of temperature, atmosphere and reaction time on tetralin dehydrogenation, isomerization and hydrocracking was studied. At 400 and 450 °C, coal accelerates the formation of 1 - methylindan and n-butylbenzene (as primary products) changing the tetralin into compounds with reduced hydrogen donor capacity. The 1 -methylindan and n-butylbenzene are subsequently (hydro)-cracked to smaller products. At low hydrogen pressure the conversion of tetralin into naphthalene and hydrogen becomes considerable, making uncertain the calculation of hydrogen transfer from the tetralin to the coal on the basis of tetralin/naphthalene ratios.     

环己烷在Au-Co/SBA-15上选择性氧化的研究

以沉积-沉淀法制备了Au-Co/SBA-15催化剂,在没有任何有机溶剂或助剂的条件下,研究了以空气为氧化剂的环己烷选择性氧化。当Au-Co/SBA-15催化剂中金的质量百分含量为1.0%,催化反应在423 K 3.0 MPa下进行120 m in时,催化效果最好,此时环己烷的转化率为22.7%,环己酮和环己醇的总选择性为95.2%,酮醇比为2.9,且催化剂重复使用五次后活性基本不变。