Dominique Richon

New apparatus to perform fast determinations of mixture vapor–liquid equilibria up to 10 MPa and 423 K

A new apparatus to measure vapor–liquid equilibria of mixture has been designed to work up to 10 MPa and 423 K. This apparatus makes it possible to take reproducible and representative samples and inject them directly into a chromatographic circuit {the same requirements were already satisfied by another apparatus described in a previous paper [P. Figuiere, J. F. Hom, S. Laugier, H. Renon, D. Richon, and H. Szwarc, AIChE J. 26, 872 (1980)]}. The use of the new apparatus is very simple. Comparisons with data from Kay and Albert [Ind. Eng. Chem. 48, 422 (1956)] reveal a strong similarity in the whole pressure range. Measurements in the critical region do not involve significant experimental difficulty.

An enhanced method to calibrate vibrating tube densimeters

Abstract The conversion of vibrating periods to densities through the calibration of the Anton Paar DMA 512 vibrating tube densimeter (VTD) to perform P–ρ–T measurements on fluids is examined. After reviewing various calibration models with their detailed internal characteristics, a new one is proposed that accurately extends the use of the densimeter over a wide range of densities, including vapors under low pressures, compressed liquids and near critical fluids. A good accuracy is obtained by fitting only two mechanically defined parameters on liquid reference density data. Detailed considerations on the mechanical model and on the calibration procedure are exposed and illustrated through sample results.

Vapor-liquid equilibrium data for the propane-methanol and propane-methanol-carbon dioxide system

Abstract Experimental measurements have been performed using three different apparatuses, making it possible to check the consistency of the data. The results with the propane-methanol system were obtained at 313.1, 343.1 and 373.1 K and between 0.35 and 4.3 MPa, those with the ternary system at 313.1 and 343.1 K and between 0.51 and 3.20 MPa.

Partial vapor pressure of CO2 and H2S over aqueous methyldiethanolamine solutions

Abstract A new apparatus is presented to measure low partial vapor pressures of acid gas. New measurements are given for carbon dioxide and hydrogen sulfide into aqueous solutions of methyldiethanolamine (MDEA). Large discrepancies among the measured VLE data and the slopes of their solubility curves are found between the authors due to systematic experimental errors, and particularly in the low acid loading regions. Different modeling approaches are proposed herein.

Enhanced density-based models for solid compound solubilities in supercritical carbon dioxide with cosolvents

The ability to correlate and predict the solubility of solids in supercritical fluids is of the utmost importance for the design and the evaluation of supercritical processes. Previously, we have investigated the solubility of a pharmaceutically interesting solid compound in supercritical carbon dioxide, alone or mixed with cosolvents. In this work, these solubility data are correlated through several density-based semi-empirical models. These models have been either modified or extended to be applied to mixtures including a cosolvent. The validity of the resulting correlations is checked by using the solubility data of another pharmaceutical solid, naproxen.

Simultaneous determination of vapor–liquid equilibria and saturated densities up to 45 MPa and 433 K

A new apparatus to simultaneously measure vapor–liquid equilibria and volumetric properties of coexisting phases is presented. It was especially designed to study hydrocarbon–carbon dioxide mixtures up to 45 MPa and 433 K. Tests have been performed on isopentane–carbon dioxide mixtures. Comparison of the new results to those from literature shows that the just developed apparatus gives reliable data. Reproducibility tests have displayed very small data dispersion.

Bubble pressures and saturated liquid molar volumes of difluoromonochloromethane—fluorochloroethane binary mixtures: experimental data and modelling

Abstract A previously described apparatus (variable volume cell method) was used to obtain bubble pressures and saturated liquid molar volumes at four temperatures for systems involving difluoromonochloromethane with tetrafluorodichloroethane, trifluorotrichloroethane and difluoromonochloroethane. The experimental bubble pressures are well represented by the Peng-Robinson equation of state with one adjusted interaction parameter. Adjusting a second interaction parameter does not significantly improve the representation. Soave and Mathias equations give a quite similar representation. Saturated liquid molar volumes calculated from the different equations of state, with binary interaction parameters adjusted on bubble pressure data, do not agree well with experimental results: the standard deviation between calculated and experimental densities is ≈ 8% with the Peng-Robinson equation of state and ≈ 18% with that of Soave and Mathias.

Simultaneous determination of vapor—liquid equilibria and volumetric properties of ternary systems with a new experimental apparatus

Abstract A new apparatus based on a static method using a variable volume cell, for measurements up to 20 MPa and 353 K, is presented. The cylindrical part of the cell, made of transparent sapphire, allows direct optical measurements of phase volumes. The phase volumes, along with total numbers of moles of each component at given pressure and temperature, are measured for three loadings (differing only by total composition); their values are introduced in mass balance equations to calculate mole fractions in each phase and the three saturated molar volumes. Comparisons are made between present results, those published by Hottovy et al. (1981) on the carbon dioxide—tetradecane system, and those published by Briones et al. (1987) on the carbon dioxide—acetic acid and carbon dioxide—water—acetic acid systems.

A static method for determination of vapour—liquid equilibria and saturated liquid molar volumes at high pressures and temperatures using a new variable-volume cell

Abstract A new static apparatus is described which uses a variable-volume cell, as in the work of Meskel-Lesavre et al. (1981), for the simultaneous determination of vapour—liquid equilibria and saturated liquid molar volumes; the ranges of pressure and temperature are extended up to 60 MPa and 573 K. Variation of volume in the equilibrium cell is obtained by deformation of a bellows strained by a pressurizing liquid. The pressure P is recorded at a given temperature as a function of the volume of a mixture, the composition of which is known accurately by weighing each component. Not too close to the critical point, the P versus V diagram displays a well-defined break point indicating the bubble point, the coordinates of which are the bubble pressure and the saturated molar volume of the liquid phase multiplied by the total number of moles. Several tests have been performed to check the reproducibility and reliability of the experimental determinations. The experimental results at 323.1, 348.1 and 423.1 K for methane— n -nonane are in good agreement with those of Shipman and Kohn (1966). The isotherm at 423.1 K is extended to higher pressures.

Vapor–liquid equilibrium data and critical points for the system H2S+COS. Extension of the PSRK group contribution equation of state

Abstract Isothermal vapor–liquid equilibrium data for the binary system hydrogen sulfide+carbonyl sulfide were measured in the temperature range from 232 to 293 K using the static-synthetic technique. From the isothermal P − x data, the azeotropic conditions were derived. The critical line of this system was visually detected in a flow apparatus. Interaction parameters for this binary system were fitted simultaneously to all the experimental VLE and critical data for the Predictive Soave–Redlich–Kwong group contribution equation of state.