Liquid–liquid equilibria and thermo physical properties for 1-methyl-2-pyrrolidinone + heterocyclic nitrogen compounds + hexadecane systems at 298.15 K

Liquid–liquid equilibrium data for {1-methyl-2-pyrrolidinone (NMP) + heterocyclic nitrogen compounds + hexadecane} systems were analytically determined at 298.15 K and atmospheric pressure using stirred and thermo-regulated cell. The experimental data were modeled with the NRTL and UNIQUAC equations. Besides, the Bachman–Brown correlation was used to ascertain the reliability of the experimental data. Additionally, excess molar volumes (V^E) and deviations in the molar refractivity (ΔR) data at 298.15 K were determined for the {NMP + heterocyclic nitrogen compounds} binary systems using a digital vibrating-tube densimeter and a precision digital refractometer. The V^E and ΔR data were modeled with the Redlich–Kister equation.     

Diffusion coefficients and electrical conductivities for calcium chloride aqueous solutions at 298.15 K and 310.15 K

Experimental values for mutual diffusion coefficients (interdiffusion coefficients) for CaCl₂ aqueous solutions at 298.15 K and 310.15 K, not available in the literature, were experimentally determined between 0.005 mol dm^?3 and 0.1 mol dm^?3. The measurements were performed by using a conductimetric open-ended capillary cell. Values at infinitesimal concentration, D⁰, were also obtained. These data were analysed using the Onsager–Fuoss and Gordon models. In addition, molar conductance data were measured at 310.15 K for CaCl₂ aqueous solutions at the same concentration range and the value at infinitesimal concentration determined. Afterwards, it was split into the ionic limiting values. By replacing them into the Nernst equation, diffusion coefficients at infinitesimal concentration were derived (1.335 × 10^?9 m² s^?1 and 1.659 × 10^?9 m² s^?1) at both temperatures (298.15 K and 310.15 K, respectively). They agree well with the extrapolated experimental ones (1.312 × 10^?9 m² s^?1 and 1.613 × 10^?9 m² s^?1).     

Phase equilibria of (CO2 + H2O + NaCl) and (CO2 + H2O + KCl): Measurements and modeling

We report experimental measurements of the phase behavior of (CO₂ + H₂O + NaCl) and (CO₂ + H₂O + KCl) at temperatures from 323.15 K to 423.15 K, pressure up to 18.0 MPa, and molalities of 2.5 and 4.0 mol kg⁻¹. The present study was made using an analytical apparatus and is the first in which coexisting vapor- and liquid-phase composition data are provided. The new measurements are compared with the available literature data for the solubility of CO₂ in brines, many of which were measured with the synthetic method. Some literature data show large deviations from our results.The asymmetric (γ–φ) approach is used to model the phase behavior of the two systems, with the Peng–Robinson equation of state to describe the vapor phase, and the electrolyte NRTL solution model to describe the liquid phase. The model describes the mixtures in a way that preserves from our previous work on (CO₂ + H₂O) the values of the Henry's law constant and the partial molar volume of CO₂ at infinite dilution Hou et al. [22]. The activity coefficients of CO₂ in the aqueous phase are provided. Additionally, the correlation of Duan et al. [14] for the solubility of CO₂ in brines is tested against our liquid-phase data.     

Catalytic removal of diesel soot particulates over K and Mg substituted La1 − xKxCo1 − yMgyO3 perovskite oxides

K and Mg substituted perovskite catalysts La_1 − xK_xCo_1 − yMg_yO₃ (x = 0–0.4, y = 0–0.2) for soot combustion were prepared by citric acid complexation and characterized by XRD, FT-IR, SEM, TEM, EDS, H₂-TPR, XPS and TG. Soot combustion was remarkably accelerated when K was introduced into LaCoO₃. Then Mg was doped into the K substituted LaCoO₃, soot combustion was further improved for the restrained growth of Co₃O₄ phase. K/Mg substitutions were responsible for enhancing activity of catalysts by improving reducibility as suggested by H₂-TPR studies. Among all the catalysts, La_0.6K_0.4Co_0.9Mg_0.1O₃ exhibited the highest activity.     

Fracture characteristics of Al2O3/YAG composite at room temperature to 2023 K

The fracture behavior of the notched unidirectionally solidified eutectic Al₂O₃/YAG composite was investigated by tensile test at room temperature to 2023 K, and the results were analyzed by the finite element method. The stress–strain behavior, notched strength and the fracture toughness were strongly dependent on temperature and displacement speed. The specimens fractured in a brittle manner at low temperatures and at high displacement speeds but in a ductile manner accompanying plastic deformation at high temperatures and at low displacement speeds. The notched strength for a given displacement speed of 10⁻⁷ m/s increased with increasing temperature from 132 MPa at 1873 K to 153 MPa at 1923 K, and then decreased to 133 and 110 MPa at 1973 and 2023 K, respectively. Also the notched strength for a given temperature of 2023 K increased with decreasing displacement speed from 67 MPa at the displacement speed of 10⁻⁵ m/s to 124 MPa at 10⁻⁶ m/s, and then decreased to 110 and 72 MPa at 10⁻⁷ and 10⁻⁸ m/s, respectively. The stress distribution and the plastic zone size ahead of the notch were calculated by a finite element method using the dependence of flow stress on temperature and displacement speed. Based on the calculation result, the experimentally observed increase in the notched strength with increasing temperature and decreasing displacement speed up to the maximum value could be accounted for by the increase in plastic zone size ahead of the notch. Also, the observed decrease in notched strength with further increasing temperature and decreasing displacement speed could be accounted for by the decrease in the stress carrying capacity of the yielded ligament.     

Vapor–liquid phase equilibrium of carbon dioxide with mixed solvents of DMSO + ethanol and chloroform + methanol including near critical regions

A visual and volume-variable high-pressure phase equilibrium analyzer was used for measuring the vapor–liquid phase boundaries of the ternary systems containing carbon dioxide and mixed solvents of dimethyl sulfoxide (DMSO) + ethanol or chloroform + methanol at temperatures from 298.15 K to 348.15 K over wide composition ranges including near critical points. Four pseudo-binary systems of carbon dioxide plus mixed solvents with constant molar ratios of DMSO/ethanol = 3/7, 5/5, 7/3, and chloroform/methanol = 1/2, were studied in this work. The critical conditions at each investigated temperature were estimated from the experimental isothermal phase boundaries by interpolation. The Peng–Robinson equation of state with the two-parameter van der Waals mixing rules was applied to calculate the phase boundaries. The experimental values were compared with the predicted results from the Peng–Robinson equation using the binary interaction parameters determined from the vapor–liquid equilibrium data of the constituent binaries. The agreement is reasonably well for carbon dioxide + chloroform + methanol, but obvious overestimations are found near the critical regions of carbon dioxide + DMSO + ethanol, especially at higher temperatures.     

Phase equilibrium data of guaçatonga (Casearia sylvestris) extract + ethanol + CO2 system and encapsulation using a supercritical anti-solvent process

The aim of this research was to investigate the phase equilibrium behavior of a system containing guaçatonga extract + ethanol + CO₂ in order to help define the adequate conditions of temperature and pressure for the co-precipitation process, performed by means of supercritical anti-solvent (SAS) technique. Guaçatonga (Casearia sylvestris) is a native medicinal plant from Brazil, rich in valuable components such as β-caryophyllene, α-humulene and bicyclogermacrene. Phase equilibrium data were obtained by the static method using guaçatonga extract dissolved in ethanol (1:100, wt/wt), at temperatures ranging from 35 to 75 °C and CO₂ mass content from 60 to 90 wt%. It was noticed that the system exhibited solid–vapor–liquid, solid–liquid–liquid and solid–vapor–liquid–liquid transition types and a lower critical solution temperature behavior. Phase behavior study was considered for the definition of the SAS conditions applied for the encapsulation of guaçatonga extract in the biopolymer Pluronic F127. The conditions tested ranged from 80 to 140 bar at 45 °C. At 80 bar only segregated particles of extract and the biopolymer were detected, while at 110 and 140 bar an extract encapsulation was achieved.     

High-pressure phase equilibrium data for the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems

Biodegradable polymers have received increased attention due to their potential applications in the medicine and food industries; in particular, poly(l-lactic acid) (PLA) is of primary importance because of its biocompatibility and resorbable features. Recently, the synthesis of this biopolymer through the enzyme-catalyzed ring-opening polymerization of l-lactic acid in a compressed fluid has been considered promising. The aim of this work was to report the phase equilibrium data (cloud points) of the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems. The phase equilibrium experiments were conducted in a variable-volume view cell employing the static synthetic method. These experiments were conducted in the temperature range of 323.15–353.15 K and at pressures up to 25 MPa; the mass ratio of ethanol to either CO₂ or propane was maintained at 1:9. The l-lactic acid + (propane + ethanol) system exhibited vapor–liquid, liquid–liquid and vapor–liquid–liquid transitions, whereas the l-lactic acid + (carbon dioxide + ethanol) system only exhibited liquid–liquid type transitions.     

High-pressure phase equilibria for the binary system carbon dioxide + dibenzofuran

The experimental solubility of dibenzofuran in near-critical and supercritical carbon dioxide and the solid–liquid–vapor (SLV) equilibrium line for the CO₂ + dibenzofuran system are reported. The built in-house static view cell apparatus used in these measurements is described. The solubility of naphthalene in supercritical CO₂ and the CO₂ + naphthalene SLV line are also determined in order to assess the reliability and accuracy of the measurement technique. The solubility of dibenzofuran in carbon dioxide is determined at 301.3, 309.0, 319.2, 328.7 and 338.2 K in the 6–30 MPa pressure range. Solubility data are correlated using the Chrastil model and the Peng–Robinson equation of state. This equation is also used to predict the CO₂ + dibenzofuran SLV line. Results show the feasibility of using supercritical CO₂ to extract dibenzofuran.     

Synthesis and characterization of S2O82 −/ZnFexAl2 − xO4 solid acid catalysts for the esterification of acetic acid with n-butanol

New spinel-types of S₂O₈^2 −/ZnFe_xAl_2 − xO₄ solid acid catalysts were prepared by sol–gel method. Their catalytic performances for the synthesis of n-butyl acetate were investigated. The catalysts were characterized by means of XRD, IR, XPS, FT-IR of adsorbed pyridine and NH₃-TPD. The experimental results showed that S₂O₈^2 −/ZnFe_xAl_2 − xO₄ solid acid catalysts maintained the spinel structure as well as the support of ZnFe_xAl_2 − xO₄. Fe^3 + ions were well incorporated and highly dispersed into the spinel lattice. S₂O₈^2 −/ZnFe_0.15Al_1.85O₄ exhibited the maximum conversion of acetic acid with 98.2%. Moreover, S₂O₈^2 −/ZnFe_0.15Al_1.85O₄ showed better reusability, which remained above 72.7% conversion of acetic acid even after being used five times.     

Methane steam reforming in the absence and presence of H2S over Ce0.8Pr0.2O2 − δ, Ce0.85Sm0.15O2 − δ and Ce0.9Gd0.1O2 − δ SOFCs anode materials

We report here on the activity and stability of low-content praseodymium–, samarium– and gadolinium–cerium oxide catalysts for the steam reforming of methane under water deficient conditions. These materials display different methane reforming activities, and remain free of praseodymium, samarium and gadolinium oxide phases respectively after use in a reaction gas stream composed of 50% CH₄–5% H₂O – (in the absence and presence of 50 or 200 ppm H₂S) – balance He at 740 °C. The results show that Ce_0.8Pr_0.2O_2 − δ, Ce_0.85Sm_0.15O_2 − δ and Ce_0.9Gd_0.1O_2 − δ are effective catalysts for reforming of methane and H₂S in the feed promotes the catalytic activity. Ce_0.8Pr_0.2O_2 − δ appeared to attain the highest activity for methane reforming, a feature that is associated with the ability of praseodymium to undergo a red–ox (Pr^4 +/Pr^3 +) and spreading action in the cerium oxide host structure, possibly resulting in a red–ox relationship between the components.     

Solid-state synthesis and spark plasma sintering of submicron BaYxZr1 − xO3 − x/2 (x = 0, 0.08 and 0.16) ceramics

Fine powders (particle size of 100–200 nm) of BaY_xZr_1 − xO_3 − x/2 (x = 0, 0.08, 0.16) were produced by solid-state reaction at 1000–1050 °C using nanocrystalline ZrO₂ and BaCO₃ raw materials. The powders were densified by means of the spark plasma sintering process resulting in dense and homogeneous submicron microstructures. Near full density ceramics with grain size < 300 nm were obtained by sintering at 1600 °C for 1–5 min.     

Phase behavior of catalytic deactivated compounds and water with 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] ionic liquid at T = 298.15–323.15 K and p = 1 bar

Density, surface tension and refractive index of the binary mixture of catalytic deactivated compounds with 1-ethyl-3-methylimidazolium acetate {[EMIM][OAc]} ionic liquid were measured at temperature of 298.15–323.15 K from which the derived thermodynamic properties including excess molar volume and deviation of surface tension and refractive index were calculated. The derived thermodynamic properties could be explained well by the interaction between similar and dissimilar aromatic structure of the molecules over the entire mole fraction of ILs. It was observed that all the catalytic deactivated compounds and water molecules have significant structural interaction with [EMIM][OAc] via CH?π bond interaction, π?π stacking and n?π interaction over the entire mole fraction of IL at T = 298.15 K. Further the composition of ionic liquid have significant influence on the interaction between dissimilar aromatic structure of molecules like pyridine, indoline and quinoline in liquid phase as compared to temperature. The surface tension increases in the order of: hiophene > pyridine > quinoline > pyrrole > indoline > water; while the refractive index increases in the order: pyridine < water < pyrrole < thiophene < indoline < quinoline. The deviation of surface tension was found to be inversely proportional to the deviation of refractive index at T = 298.15 K. From these results it was concluded that the structure of the ionic liquids is very important for extraction processes on catalytic deactivated compounds, especially for pyridine, indoline and quinoline as compared to water molecules.     

Liquid–liquid equilibria for ternary systems of dimethyl carbonate + C1–C4 alcohols + water at 298.15 K and atmospheric pressure

The ternary liquid–liquid equilibria (LLE) of the following systems were analytically determined at 298.15 K and atmospheric pressure using stirred and thermo-regulated cells: {dimethyl carbonate (DMC) + methanol + water}, {DMC + ethanol + water}, {DMC + 1-propanol + water}, {DMC + 2-propanol + water}, {DMC + 1-butanol + water} and {DMC + 2-butanol + water}. The experimental ternary LLE data were correlated with the non-random two liquid (NRTL) and UNIversal QUAsiChemical (UNIQUAC) activity coefficient models. In addition, the Bachman–Brown correlation was used to ascertain the reliability of the experimental data for each system.     

Phase behavior measurement for poly(isobornyl acrylate) + cosolvent systems in supercritical solvents at high pressure

We have conducted experiments to obtain cloud-point data of binary and ternary mixtures for poly(isobornyl acrylate) [P(IBnA)] (Mw = 100,000) + isobornyl acrylate(IBnA) in supercritical carbon dioxide (CO₂), P(IBnA) (Mw = 100,000) + dimethyl ether (DME) in CO₂, P(IBnA) (Mw = 100,000) in propane and butane, and P(IBnA) (Mw = 1,000,000) in propane, propylene, butane and 1-butene at high pressure conditions. Phase behaviors for these systems were measured at a temperature range from 323.4 K to 474.1 K and pressure up to 296.7 MPa. The cloud-point curves of P(IBnA) (Mw = 100,000) + IBnA and DME in CO₂ change from upper critical solution temperature (UCST) behavior to lower critical solution temperature (LCST) behavior as IBnA and DME concentration increases, and liquid–liquid–vapor phase behavior appears for the P(IBnA) (Mw = 100,000) + CO₂ + 80.3 wt.% IBnA system. Phase behaviors of P(IBnA) and 50 wt.% IBnA in CO₂ and P(IBnA) in propane and butane show the pressure difference in accordance with Mw = 1,000,000 and Mw = 100,000 of P(IBnA). Also, the solubility curves for IBnA in supercritical CO₂ were measured at a temperature range of (313.2–393.2) K and pressure up to 22.86 MPa. The experimental results were modeled with the Peng–Robinson equation of state (PR-EOS) using a mixing rule including two adjustable parameters. The critical property of IBnA is estimated with the Joback–Lyderson method.     

Effect of total reaction pressure on electrical properties of boron doped homoepitaxial (100) diamond films formed by microwave plasma-assisted chemical vapor deposition using trimethylboron

Boron was doped into diamond films which were synthesized homoepitaxially on polished (100) diamond substrates by means of microwave plasma-assisted chemical vapor deposition (MPCVD) using trimethylboron as the dopant at a constant substrate temperature of 1073 K. The morphologies and electrical properties of the synthesized diamond films were dependent on the total reaction pressure. A maximum Hall mobility, 760 cm² V⁻¹ s⁻¹, was obtained for the film synthesized at 10.7 kPa. The values of Hall mobility were comparable with those obtained for B₂H₆-doped films at corresponding hole concentrations.     

A study on proton conduction in a layered metal–organic framework,Rb2(adp)[Zn2(ox)3]·3H2O (adp = adipic acid,ox2 − = oxalate)

We newly synthesized a metal–organic framework (MOF) Rb₂(adp)[Zn₂(ox)₃]·3H₂O (adp = adipic acid; ox^2 − = oxalate), where the rubidium ions, carboxylic acid groups, and water molecules are located in an interlayer space of a two-dimensional (2-D) oxalate-bridged network. The structure of this compound was determined using single-crystal X-ray diffraction analysis. Hydrated phases of this compound were examined using thermogravimetry and water vapor adsorption measurements. Proton conductivity in this MOF was investigated by alternating current impedance measurements. Systematic comparison with previously reported isomorphous 2-D compounds A₂(adp)[Zn₂(ox)₃]·3H₂O (A = NH₄ and K) showed that the difference in the ionic radii of the cations leads to a difference in activation energy of proton conductivity and that absence of NH₄⁺ ions causes a significant decrease in proton conductivity, even though the ionic radius of Rb⁺ (1.52 Å) is closer to that of NH₄⁺ (1.61 Å) than that of K⁺ (1.38 Å).     

Photodegradation of tetrahalobisphenol-A (X = Cl,Br) flame retardants and delineation of factors affecting the process

The photoassisted degradation (HPLC-UV absorption), dehalogenation (HPLC-IC) and mineralization (TOC decay) of the flame retardants tetrabromobisphenol-A (TBBPA) and tetrachlorobisphenol-A (TCBPA) were examined in UV-irradiated alkaline aqueous TiO₂ dispersions (pH 12), and for comparison the parent bisphenol-A (BPA, an endocrine disruptor) in pH 4–12 aqueous media to assess which factor impact most on the photodegradative process. Complete degradation (2.7–2.8 × 10⁻² min⁻¹) and dehalogenation (1.8 × 10⁻² min⁻¹) of TBBPA and TCBPA occurred within 2 h of UV irradiation, whereas only 45–60% mineralization (2.3–2.7 × 10⁻³ min⁻¹) was complete within 5 h for the flame retardants at pH 12 and ca. 80% for the parent BPA. Factors examined in the pH range 4–12 that impact the degradation of BPA were the point of zero charge of TiO₂ particles (pH_pzc; electrophoretic method), particle or aggregate sizes of TiO₂ (light scattering), and the relative number of OH radicals (as DMPO–OH adducts; ESR spectroscopy) produced in the UV-irradiated dispersion. Dynamics of BPA degradation (2.0–2.4 × 10⁻² min⁻¹) were pH-independent and independent of particle/aggregate size, but did correlate with the number of OH radicals, at least at pHs 4 to 8–9, after which the rates decreased somewhat at pH > 9 with decreasing adsorption owing to Coulombic repulsive forces between the very negative TiO₂ surface and the anionic forms of BPA (pK_as ca. 9.6–11.3), even though the number of OH radicals continued to increase at the higher pHs.     

Preparation of (0 2 0)-oriented BaTi2O5 thick films and their dielectric responses

Barium dititanate (BaTi₂O₅) thick films were prepared on a Pt-coated Si substrate by laser chemical vapor deposition, and ac electric responses of (0 2 0)-oriented BaTi₂O₅ films were investigated using several equivalent electric circuit models. BaTi₂O₅ films in a single phase were obtained at a Ti/Ba molar ratio (m_Ti/Ba) of 1.72–1.74 and deposition temperature (T_dep) of 908–1065 K as well as m_Ti/Ba = 1.95 and T_dep = 914–953 K. (0 2 0)-oriented BaTi₂O₅ films were obtained at m_Ti/Ba = 1.72–1.74 and T_dep = 989–1051 K. BaTi₂O₅ films had columnar grains, and the deposition rate reached 93 μm h^?1. The maximum relative permittivity of the (0 2 0)-oriented BaTi₂O₅ film prepared at T_dep = 989 K was 653 at 759 K. The model of an equivalent circuit involving a parallel combination of a resistor, a capacitor, and a constant phase element well fitted the frequency dependence of the interrelated ac electrical responses of the impedance, electric modulus, and admittance of (0 2 0)-oriented BaTi₂O₅ films.     

Transport properties of sealants for high-temperature electrochemical applications: RO–BaO–SiO2 (R = Mg,Zn) glass–ceramics

The electrical properties and oxygen permeability of glass–ceramics 55SiO₂–27BaO–18MgO, 55SiO₂–27BaO–18ZnO and 50SiO₂–30BaO–20ZnO (%mol), which possess thermal expansion compatible with that of yttria-stabilized zirconia (YSZ) solid electrolytes, were studied between 600 and 950 °C in various atmospheres. The ion transference numbers, determined by the modified electromotive force (e.m.f.) technique under oxygen partial pressure gradients of 21 kPa/(1–8) × 10² Pa and 21 kPa/(1 × 10⁻¹⁸–2 × 10⁻¹²) Pa, are close to unity both under oxidizing and reducing conditions. The electronic contribution to the total conductivity increases slightly on increasing temperature, but is lower than 2% and 7% for the Zn- and Mg-containing compositions, respectively. The conductivity values measured by impedance spectroscopy vary in the range (1.4–7.8) × 10⁻⁶ S/cm at 950 °C under both oxidizing and reducing conditions, with activation energies of 122–154 kJ/mol and a minor increase in H₂-containing atmospheres, indicating possible proton intercalation. In agreement with the electrical measurements which indicate rather insulating properties of the glass–ceramics, the oxygen permeation fluxes through sintered sealants and through sealed YSZ/glass–ceramics/YSZ cells are very low, in spite of an increase of 15–40% during 200–230 h under a gradient of air/H₂–H₂O–N₂ due to slow microstructural changes.