A review of requirements for equations to calculate the conductivity of a mixture of ions in low dielectric constant solvents (i.e., water at high temperatures) shows that there are conceptual difficulties with all current equations. To explore whether these difficulties limit our ability to predict mixtures, four models for the activity coefficients, two models for the conductivity of a single strong electrolyte, and an equation for the change in equivalent conductivity on mixing single strong electrolytes were chosen. These equations were then tested on the theoretical equation of Turq et al. (J. Phys. Chem. 1995, 99, 822−827) for three ion mixtures. Next the equations were tested on a single 1−1 electrolyte, NaCl (aq) at 652.6 K and 22.75 MPa measured by Gruskiewicz and Wood (J. Phys. Chem. B 1997, 101, 61549−6559) and new measurements at 623.9 K and 19.79 MPa. Then it was tested with new measurements on Na2SO4 (aq) from 300 to 574 K because, in water at high temperatures, this salt produces a solution containing six different ions (Na+, SO4 2-, NaSO4 -, HSO4 -, H+, OH-). The equations were able to reproduce the experimental data. Values of equilibrium constants, K, for the dissociation of NaCl and NaSO4 - and equivalent conductances Λo derived by a least-squares fit agreed with reported data determined by other methods, showing that conductivity measurements can yield accurate equilibrium constants in complex mixtures of ions. The values of K and Λo were not very sensitive to changes in (1) the single electrolyte conductance equation, (2) assumed values of Λo for minor species, or (3) equilibrium constants for minor reactions. Uncertainty in the activity coefficient model was the largest contributor to uncertainty in K and Λo. This method should allow rapid and accurate measurements of the equilibrium constant for any reaction, which changes the number of ions in solution. The equilibrium constants for many reactions of this type are unknown in water at high temperatures.

The organic acids present in petroleum, commonly called “naphthenic acids” (NA), are identified as carboxylic acids of the general formula “RCOOH”, where R represents a hydrocarbon chain that does not necessarily show cycloaliphatic structure. The presence of stable oil-in-water emulsions in the crude oils hinders the dehydration process, which is required during the production step. Some compounds, such as the organic acids (NA) present in the crude oils, are involved in the stabilization of the emulsions, because of their amphiphilic structure. The emulsion-breaking process is improved if the organic acids are determined qualitatively and quantitatively. We proposed the study of a quantitative extraction procedure of NA contained in crude oils. First of all, we performed the liquid−liquid extraction of the organic acids, using alcoholic solutions. Because this method did not allow the quantitative recovery of the acids, we developed a separation process based on an ion-exchange resin (QAE Sephadex A25). The isolated acid fraction was then derivatized as methyl esters and quantified by gas chromatography experiments, using the internal standard method allowing the determination of the NA composition. The extraction yield was checked via the total acid number (TAN) measurement, using the standard ASTM D664-95 (IP 177/96), which is the standard method commonly used in the oil industry. The extraction of NA on ion-exchange resins required the preliminary study of a model molecule mixture of carboxylic acids, to ensure the complete control of the procedure. Four crude oil samples that were provided by Total (France) (Y1, Y2, Y3, Y4) were then analyzed. The results confirmed the presence of such acids in the crude oils.

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The reaction of the OH radicals with 4-hydroxy-2-butanone was investigated in the gas phase using an absolute rate method at room temperature and over the pressure range 10-330 Torr in He and air as diluent gases. The rate coefficients were measured using pulsed laser photolysis (PLP) of H(2)O(2) to produce OH and laser induced fluorescence (LIF) to measure the OH temporal profile. An average value of (4.8 ± 1.2) × 10(-12) cm(3) molecule(-1) s(-1) was obtained. The OH quantum yield following the 266 nm pulsed laser photolysis of 4-hydroxy-2-butanone was measured for the first time and found to be about 0.3%. The investigated kinetic study required accurate measurements of the vapor pressure of 4-hydroxy-2-butanone, which was measured using a static apparatus. The vapor pressure was found to range from 0.056 to 7.11 Torr between 254 and 323 K. This work provides the first absolute rate coefficients for the reaction of 4-hydroxy-2-butanone with OH and the first experimental saturated vapor pressures of the studied compound below 311 K. The obtained results are compared to those of the literature and the effects of the experimental conditions on the reactivity are examined. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H2B may contribute to the photochemical pollution in a local or regional scale.

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