Jérôme Pauly

Extraction of Biomolecules Using Phosphonium-Based Ionic Liquids + K3PO4 Aqueous Biphasic Systems

Aqueous biphasic systems (ABS) provide an alternative and efficient approach for the extraction, recovery and purification of biomolecules through their partitioning between two liquid aqueous phases. In this work, the ability of hydrophilic phosphonium-based ionic liquids (ILs) to form ABS with aqueous K3PO4 solutions was evaluated for the first time. Ternary phase diagrams, and respective tie-lines and tie-lines length, formed by distinct phosphonium-based ILs, water, and K3PO4 at 298 K, were measured and are reported. The studied phosphonium-based ILs have shown to be more effective in promoting ABS compared to the imidazolium-based counterparts with similar anions. Moreover, the extractive capability of such systems was assessed for distinct biomolecules (including amino acids, food colourants and alkaloids). Densities and viscosities of both aqueous phases, at the mass fraction compositions used for the biomolecules extraction, were also determined. The evaluated IL-based ABS have been shown to be prospective extraction media, particularly for hydrophobic biomolecules, with several advantages over conventional polymer-inorganic salt ABS.

Prediction of solid–fluid phase diagrams of light gases–heavy paraffin systems up to 200 MPa using an equation of state–GE model

Abstract This paper presents a procedure for the simultaneous prediction of fluid–fluid and solid–fluid equilibria of light gases–heavy hydrocarbons systems under pressure. The fluid phases behaviour is described by the modified LCVM, an equation of state–G E model and the solid phase non-ideality is represented by the Wilson equation using the predictive local composition concept. This procedure was tested for several binary and ternary systems as well as multi-component systems leading to a good representation of both fluid–fluid and solid–fluid equilibria with a typical average absolute deviation of 1.5 K for the solid–fluid phase boundary of binary and ternary mixtures and of 0.5 K for multi-component systems. The AAD% in the fluid–fluid phase boundary of multi-component systems is of 3.2%.

Measurement and prediction of temperature and pressure effect on wax content in a partially frozen paraffinic system

Liquid–solid phase equilibrium measurements were carried out at various pressures and temperatures below the onset of crystallization in a mixture made up of a distribution of paraffins with composition exponentially decreasing from n-C6 to n-C36. Liquid and solid phases in partially frozen mixtures were separated by isobaric and isothermal filtration and analyzed by gas chromatography. Waxy solid content and wax composition were then deduced from a mass balance after correction for the entrapped liquid in the solid residue. The results were then compared to the prediction of a model which was previously developed for the representation of the wax appearance temperature of synthetic light gas–heavy paraffins systems.

The pressure effect on the wax formation in diesel fuel

The prevention of wax formation under high pressure on new diesel engine requires a good understanding of the behaviour of the paraffin molecules crystallization. In this work a diesel from a Petrogal refinery was investigated under pressure. In particular the melting curve was measured from atmospheric pressure to 100 MPa by an optical technique. The behaviour of the solid phase with the pressure was also investigated up to 50 MPa by filtration. The results obtained show an increase in the diesel cloud point of about 25 8C at the operating pressure of a common rail engine. It is clear from our results that the increase of the diesel cloud point must be taken into account in the development of new diesel engines where the diesel is injected under high pressure. All the results obtained were successfully predicted with a thermodynamic model able to describe multiphase equilibrium. q 2002 Elsevier Science Ltd. All rights reserved.

Reference Correlation of the Viscosity of Squalane from 273 to 373 K at 0.1 MPa

The paper presents a new reference correlation for the viscosity of squalane at 0.1 MPa. The correlation should be valuable as it is the first to cover a moderately high viscosity range, from 3 to 118 mPa s. It is based on new viscosity measurements carried out for this work, as well as other critically evaluated experimental viscosity data from the literature. The correlation is valid from 273 to 373 K at 0.1 MPa. The average absolute percentage deviation of the fit is 0.67, and the expanded uncertainty, with a coverage factor k = 2, is 1.5%.

High pressure solid–liquid phase equilibria in synthetic waxes

A high pressure apparatus which rests on a polarizing microscope has been designed to determine visually the liquid–solid phase transitions in complex waxy systems. The apparatus was used to measure the wax disappearance temperature under pressures up to 100 MPa in several synthetic mixtures made up of regular distributions of n-paraffins ranging from n-C13 to n-C24 with various numbers of components.

Reference Correlations for the Density and Viscosity of Squalane from 273 to 473 K at Pressures to 200 MPa

This paper presents new reference correlations for both the density and viscosity of squalane at high pressure. These correlations are based on critically evaluated experimental data taken from the literature. In the case of the density, the correlation, based on the Tait equation, is valid from 273 to 473 K at pressures to 200 MPa. At 0.1 MPa, it has an average absolute deviation of 0.03%, a bias of −0.01%, and an expanded uncertainty (at the 95% confidence level) of 0.06%. Over the whole range of pressures, the density correlation has an average absolute deviation of 0.05%, a bias of −0.004%, and an expanded uncertainty (at the 95% confidence level) of 0.18%. In the case of the viscosity, two correlations are presented, one a function of density and temperature, based on the Assael-Dymond model, and the other a function of temperature and pressure, based on a modified Vogel-Fulcher-Tammann equation. The former is slightly superior to the latter at high temperatures (above 410 K), whereas the reverse is ...

A THERMODYNAMIC MODEL TO PREDICT WAX FORMATION IN PETROLEUM FLUIDS

Some years ago the authors proposed a model for the non-ideality of the solid phase, based on the Predictive Local Composition concept. This was first applied to the Wilson equation and latter extended to NRTL and UNIQUAC models. Predictive UNIQUAC proved to be extraordinarily successful in predicting the behaviour of both model and real hydrocarbon fluids at low temperatures. This work illustrates the ability of Predictive UNIQUAC in the description of the low temperature behaviour of petroleum fluids. It will be shown that using Predictive UNIQUAC in the description of the solid phase non-ideality a complete prediction of the low temperature behaviour of synthetic paraffin solutions, fuels and crude oils is achieved. The composition of both liquid and solid phases, the amount of crystals formed and the cloud points are predicted within the accuracy of the experimental data. The extension of Predictive UNIQUAC to high pressures, by coupling it with an EOS/GE model based on the SRK EOS used with the LCVM mixing rule, is proposed and predictions of phase envelopes for live oils are compared with experimental data.

Impedance analysis for characterizing the influence of hydrostatic pressure on piezoelectric quartz crystal sensors

The effect of hydrostatic pressure on the electrical behavior of quartz crystal resonators vibrating in the megahertz range is investigated by impedance analysis. The responses in frequency and dissipation of five AT-cut polished quartz crystals immersed in helium gas are analyzed and compared from conductance spectra around the resonance on several overtones. A model is then proposed to correlate the variations in frequency and dissipation with pressure and to explain the particular behavior observed on the fundamental harmonic mode.

Viscosity measurements of liquids under pressure by using the quartz crystal resonators.

A quartz crystal viscometer has been developed for measuring viscosity in liquids under pressure. It employs an AT-cut quartz crystal resonator of fundamental frequency 3 MHz inserted in a variable-volume vessel designed for working up to 80 MPa. Viscosity is determined by two methods from resonance frequency and bandwidth measurements along up to eight different overtones. The resonance frequency allows an absolute measurement of the viscosity but leads to an accuracy limited to 5% whereas the bandwidth technique which works in a relative way provides an accuracy of 2%. The techniques were tested by carrying out measurements in two pure compounds: heptane and toluene. Measurement results demonstrate the feasibility of the technique in this viscosity range. The apparatus was also used to determine the viscosity of n-decane with dissolved methane. The results obtained with these mixtures reveal the applicability of the apparatus for reservoir fluids study.