High pressure phase equilibrium studies.

Thesis (Ph.D. Eng.)-University of Natal, Durban, 2000.This project involved the design, construction and commissioning of a new isothermal multipmpose high-pressure vapour-liquid equilibrium (HPVLE) apparatus of the static type. The equilibrium cell was approximately 200 cm3 in volume, and by use of a stepper motor and piston, was also variable in volume. The equipment had a combined pressure and temperature operating limit of 175 bar and 175 °C respectively. The equilibrium cell contents could be viewed through two pairs of illuminated sapphire windows. The equilibrium cell was mounted in an air-bath, which provided the isothermal environment. The air-bath was constructed of mild steel and was copper-lined with a Fibrefrax sandwich that provided more than adequate insulation to ensure that there were no temperature gradients induced by conduction and heat element radiation. The sampling method and procedures utilized in this project caused no disturbance to the equilibrium .condition. The liquid and vapour phases were sampled by a novel means of circulating representative equilibrium samples through the sample loop of a V ALCO six-port two-position sampling valve. The sample loop contained approximately 300 μl of sample, which was homogenized in jet-mixers. Analysis of the equilibrium sample was by gas chromatography. Experimental measurements of isothermal HPVLE were undertaken for the systems, carbon dioxide + toluene, carbon dioxide + methanol and propane + 1-propanol. In addition, to show the versatility of the apparatus, P-V-T measurements were undertaken for the nitrogen, propane and the propane + nitrogen binary system. Isothermal measurements were undertaken for carbon dioxide + toluene at 38 °C, 80 °C and 118.3 °C. There was excellent agreement between literature and the data measured. For the carbon dioxide + methanol system, measurements were undertaken at 40 °C, 90 °C and 100 °C. The 90 °C isotherm had not previously been measured. The propane+ 1-propanol system was measured at 105.1 °C and 120 °C. It was compared to the experimental data of Muhlbauer [1990]. There was a slight difference in the vapour compositions between literature and the data measured in this project. Experimental data of Muhlbauer [1990] showed a higher mole fraction of the volatile component (propane). Modeling of all the systems for the various isotherms measured were undertaken using both the direct and combined methods. The direct method involved the use of the Soave and PengRobinson equations of state with various mixing rules e.g. van der Waals, Wong and Sandler, Huron-Vidal and modifications thereof. The combined method, based on a liquid phase model and an equation of state model for the corresponding activity and fugacity coefficients was used as discussed in Prausnitz et al. [1980]. A new combined method model was proposed that incorporated the Peng-Robinson-StryjekVera equation of state with the Wong-Sandler mixing rule together with the NRTL activity coefficient model. The model modeled all systems measured as well or at times better than current models in literature. P-V-T measurements undertaken for propane, nitrogen and the propane + nitrogen binary system illustrated the versatility of the experimental apparatus. From the measured P-V-T data, second virial coefficients were computed for propane and nitrogen. Second virial cross coefficients for the binary system, propane + nitrogen, were also calculated. Critical property computations were undertaken for the three binary systems measured using the method citied by Deiters and Schneider [1976]. The critical properties were computed by the Soave, Peng-Robinson and Peng-Robinson-Stryjek-Vera equations of state. Vapour-liquid equilibrium data measured were tested for thermodynamic consistency using the test suggested by Chueh et al. [1965] and residual plots. The consistency tests indicated that the data measured were not inconsistent. This was the findings for the carbon dioxide + toluene, carbon dioxide + methanol and propane + 1-propanol systems for all the isotherms measured

Phase Diagrams in Chemical Engineering: Application to Distillation and Solvent Extraction

Chapter 19Published under CC BY 3.0 licenseAvailable from: http://www.intechopen.com/books/advances-in-chemical-engineering/phase-diagrams-in-chemical-engineering-example-of-distillationInternational audienceA phase diagram in physical chemistry and chemical engineering is a graphical representation showing distinct phases which are in thermodynamic equilibrium. Since these equilibrium relationships are dependent on the pressure, temperature, and composition of the system, a phase diagram provides a graphical visualization of the effects of these system variables on the equilbrium behavior between the phases. Phase diagrams are essential in the understanding and development of separation processes, especially in the choice and design of separation unit operations, e.g. knowledge about high pressure phase equilibria is essential not just in chemical processes and separation operations, but is also important for the simulation of petroleum reservoirs, the transportation of petroleum fluids, as well as in the refrigeration industry. In order to utilize the knowledge of phase behavior it is important to represent or correlate the phase information via the most accurate thermodynamic models. Thermodynamic models enable a mathematical representation of the phase diagram which ensures comprehensive and reproducible production of phase diagrams. The measurement of phase equilibrium data is necessary to develop and refine thermodynamic models, as well as to adjust them by fitting or correlating their parameters to experimental data. Generally the measurement of phase equilibria is undertaken using two categories of experimental techniques, viz. synthetic and analytic methods. The choice of the technique depends on the type of data to be determined, the range of temperatures and pressures, the precision required, and also the order of magnitude of the phase concentrations expected

CO 2 Solubility in Hybrid Solvents Containing 1- Butyl-3-methylimidazolium tetrafluoroborate and Mixtures of Alkanolamines

International audienceTo reduce the rate of climate change, feasible and energy-efficient solutions need to be found to capture CO2 at low pressure from flue gas emitted by various industries and energy sectors worldwide. The use of solvents to selectively absorb CO2 is a promising option for CO2 capture. This research investigated the solubility of CO2 in hybrid solvents containing the 1-butyl-3-methyl imidazolium tetrafluoroborate [bmim][BF4] ionic liquid with mixtures of up to three alkanolamine solvents, namely monoethanolamine (MEA), diethanolamine (DEA), and methyl-diethanolamine (MDEA). Gravimetric analysis was used to measure equilibrium CO2 solubility in the hybrid solvents containing various compositions of the above components at CO2 partial pressures of 0.05 MPa to 1.5 MPa and temperatures of 303.15 K to 323.15 K. CO2 solubility in these solvents was benchmarked against pure ionic liquids, as well as conventional alkanolamine solvents, and modeled using the Posey−Tapperson−Rochelle model for the alkanolamines present and the SRK equation of state for the ionic liquid present in the hybrid solvents. It was found that the hybrid solventsachieved significantly higher CO2 solubility at low pressure than pure ionic liquids and conventional alkanolamine solvents. Modeling, however, was found to be less accurate for hybrid systems than data modeled for pure ionic liquid systems

Fluid phase equilibria prediction of fluorocompound-containing binary systems with the predictive E-PPR78 model

International audienceIn order to reduce the overall emissions of greenhouse gases and to be in compliance with the current environmental regulations, a new class of refrigerants, making use of fluorocompounds has appeared. Such refrigerants are often blends of alkanes, CO 2 and fluorocompounds. Consequently an equation of state (EoS) able to predict the properties of both pure compounds and multi-component systems is required to design processes involving fluorocompounds or to implement a product-design approach aimed at identifying new refrigerant mixtures. It is however well-acknowledged that the phase behavior of binary systems like, e.g., an alkane and its corresponding perfluoroalkane, show significant deviations from ideality that need to be accurately accounted for by a thermodynamic model. In this study, in order to get a predictive model applicable to fluorocompound-containing binary systems, six groups were added to the Enhanced-PPR78 model which combines the Peng-Robinson EoS and a group contribution method aimed at estimating the binary interaction parameters, () ij kT, involved in Van der Waals one-fluid mixing rules

(E)-3-(4-Cyclo­hexyl-3-fluoro­benzyl­idene)chroman-4-one

The title compound, C22H21FO2, exhibits substitutional disorder of the F atom and a H atom in the asymmetric unit with different occupancies, the refined F:H ratio being 0.80 (2):0.20 (2). The dihedral angle between the fluorinated benzene ring and the benzene ring of the chromanone system is 37.30°. There are two relatively high residual electron-density peaks associated with the disorder

Equilibrium data and GC-PC SAFT predictions for furanic extraction

International audienceThe present study concerns phase equilibria measurements involving oxygenated components (furan and furfural) and potential solvents of extraction (n-hexane, ethanol and n-octanol) using an ebulli-ometer at atmospheric pressure. New liquid-liquid equilibrium data concerning the ternary system furan þ furfural þ n-hexane are also presented. The experimental technique used for the liquid-liquid equilibrium measurements is based on the static analytic method. The two liquid phases are sampled using a syringe and analyzed using gas chromatograph. Two thermodynamic approaches are considered for the data treatment: the first considers a dissymmetric approach using the NRTL activity coefficient model, and the second considers a group contribution model based on the PC-SAFT EoS (GC-PPC SAFT). The experimentally measured data were successfully correlated with the models proposed

Isothermal phase (vapour + liquid) equilibrium data for binary mixturesof propene (R1270) with either 1,1,2,3,3,3-hexafluoro-1-propene(R1216) or 2,2,3-trifluoro-3-(trifluoromethyl)oxirane in the temperature range of (279 to 318) K range.

International audienceIsothermal (vapour + liquid) equilibrium data (P–x–y) are presented for the 1-propene +1,1,2,3,3,3-hexafluoro-1-propene and the 1-propene + 2,2,3-trifluoro-3-(trifluoromethyl)oxirane binary systems. Both binary systems were studied at five temperatures, ranging from (279.36 to 318.09) K, atpressures up to 2 MPa. The experimental (vapour + liquid) equilibrium data were measured using an apparatus based on the ‘‘(static + analytic)’’ method incorporating a single movable Rapid On-Line Sampler-Injector to sample the liquid and vapour phases at equilibrium. The expanded uncertainties are approximated on average as = 0.07 K, 0.008 MPa, and 0.007 and 0.009 for the temperature, pressure, and the liquid and vapour mole fractions, respectively. A homogenous maximum-pressure azeotrope was observed for both binary systems at all temperatures studied. The experimental data were correlated with the Peng–Robinson equation of state using the Mathias–Copeman alpha function, paired with theWong–Sandler mixing rule and the Non-Random Two Liquid activity coefficient model. The model provided satisfactory representation of the phase equilibrium data measure

6-Hy­droxy-2H-1,3-benzodioxole-5-carbaldehyde

The title compound, C8H6O4, crystallizes with two independent mol­ecules in the asymmetric unit. The benzodioxole ring system is almost planar in each mol­ecule, with maximum deviations of 0.008 (1) and 0.007 (1) Å. The mol­ecular structure is characterized by strong electrostatic intra­molecular O⋯O contacts [2.649 (3) Å] and intra­molecular O—H⋯O hydrogen-bonding inter­actions. Inter­molecular O⋯O inter­actions [3.001 (2) Å] are observed in the crystal structure