Ascención Romero-Martínez

Solubilities of carbon dioxide and hydrogen sulfide in propylene carbonate, N-methylpyrrolidone and sulfolane

Abstract Gas solubilities of carbon dioxide and hydrogen sulfide have been measured in propylene carbonate, N -methylpyrrolidone and sulfolane at several temperatures ranging from 298 to 373 K and in the pressure range 51–2330 kPa. Values of the Henrys law constant and of heat of solution were derived from the solubility data. The experimental results have been correlated with the Soave-Redlich-Kwong equation of state using a binary interaction parameter.

Solubility of CO2 in aqueous mixtures of diethanolamine with methyldiethanolamine and 2-amino-2-methyl-1-propanol

Abstract Using the static method with recirculation of the vapor phase, experimental data for the solubility of CO 2 in aqueous mixtures of known composition of diethanolamine (DEA) with methyldiethanolamine (MDEA) and DEA with 2-amino-2-methyl-1-propanol (AMP) have been obtained in the CO 2 partial pressure range 3–3000 kPa. The data for DEA–MDEA solutions were obtained at 313.15 K and are reported at four different compositions: 10 wt.% DEA–15 wt.% MDEA, 10 wt.% DEA–20 wt.% MDEA, 20 wt.% DEA–10 wt.% MDEA and 10 wt.% DEA–35 wt.% MDEA, data for the solution of 10 wt.% DEA–20 wt.% MDEA were also obtained at 393.15 K. The data for DEA–AMP solutions were obtained at 313.15 and 373.15 K and are reported at two different compositions: 25 wt.% DEA–5 wt.% AMP and 20 wt.% DEA–10 wt.% AMP. The results are given as the partial pressure ( p ) of CO 2 against its mole ratio α (mol CO 2 /mol alkanolamine), in the range of temperature studied. The solubility of CO 2 in all the studied systems decreases with an increase in temperature and increases with an increase in the partial pressure of CO 2 , at a given temperature, and it is a strong function of the composition of the blend of alkanolamines in solution. The aqueous mixture with 10 wt.% AMP, at 313.15 K, shows higher capacity to absorb CO 2 than any of the other mixtures studied here. From the experimental solubility results, exothermic values of the enthalpy of solution, Δ H s , were derived.

Liquid—liquid coexistence curves for binary systems

Abstract The liquid—liquid coexistence curves of polar+non-polar binary systems have been determined experimentally. The polar compounds studied were ethanenitrile, methanol and N-methylpyrrolidone, whereas the non-polar compounds were chosen from the n-alkane series. The upper critical solution temperature for each set of mixtures increases with increasing n-alkane chain length, and the critical composition of the polar component also increases in this fashion.

Liquid—liquid equilibria for ternary systems. I. C6-isomers + sulfolane + toluene at 298.15 K

Experimental binodal curved and tie line data have been obtained at 298.15 K for the ternary liquid—liquid equilibria of four C6-isomer+sulfolane+toluene systems, where the isomers studied are n-hexane, cyclohexane, 2-methylpentane and 1-hexene. The tie line data were correlated with the well-known NRTL model. Values of selectivity, distribution coefficient and capacity or solvent power for sulfolane were derived from the equilibrium data.

Experimental liquid-liquid miscibility curves for binary systems: ethanenitrile and butanenitrile with n-alkanes

Liquid-liquid miscibility temperatures, as a function of composition, have been determined experimentally for the binary systems formed by ethanenitrile (acetonitrile) with octane, nonane, decane, undecane and dodecane and butanenitrile with octane, decane, dodecane, tetradecane and pentadecane. This study was also extended to include binary systems of pentanenitrile with long-chain alkanes, however, no liquid-liquid phase separation was observed from room temperature down to 270 K. All the measured systems present solubility curves characterized by asymmetry with respect to equimolar composition and the presence of an upper critical solution temperature (UCST). The experimental results show that for a given set of binary mixtures with a common nitrile the solubility diminishes with increasing alkane chain length, which is a clear manifestation of increasing non-ideality, and for mixtures with a common alkane the solubility increases with increasing nitrile chain length, which in turn is evidence of the decreasing effective polarity of the nitriles as their chain length increases. The Weimer-Prausnitz modification for polar components of Hildebrands Regular Solution Theory incorporating a Flory-Huggins entropy of mixing has been used to calculate the UCST for the ten systems measured and these values compare very well with those obtained experimentally considering that no adjustable parameter is included in the theory. The theory was also used to calculate the critical composition and qualitative agreement is observed with experimental data.

Liquid-liquid miscibility curves for binary systems: N-methylpyrrolidone with several hydrocarbon isomers

Abstract Eustaquio-Rincon, R., Romero-Martinez, A. and Trejo, A., 1993. Liquid-liquid miscibility curves for binary systems: N-methylpyrrolidone with several hydrocarbon isomers. Fluid Phase Equilibria, 91: 187-201. Experimental liquid-liquid miscibility data have been obtained for 14 binary systems formed by N-methylpyrrolidone with isobutane, cis-butene-2, trans-butene-2, 2,2-dimethylbutane, 2,3-dimethylbutane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, 1-hexene, 1-heptene and 1-octene. The temperatures studied range from 240 K for 1-hexene up to 374 K for isobutane. All the systems present miscibility curves with upper critical solution temperatures (UCSTs). The system with 1,3-butadiene presents complete miscibility. The values of UCST are correlated using pure component property data.

Surface tension of isomers of pure hydrocarbons: a method for estimation and prediction

Abstract A new method to estimate and predict surface tension in the full liquid-state temperature range for isomers of pure hydrocarbons has been developed. The method requires as input parameters the surface tension value corresponding to the linear or normal member of a given hydrocarbon homologous series, modified by an empirical parameter here proposed for each isomer under study. This in turn is calculated using molar volume and solubility parameter values for both the normal and the isomer hydrocarbon. This new method was used to calculate surface tension values for 56 isomers of n -alkane and four isomers of the 1-alkene homologous series in the range 253–373 K. The average error obtained from a comparison between experimental and calculated surface tension values for 497 points of the 60 isomers considered was only 1.5%. The developed method may also be used to obtain surface tension data with high reliability above and below the temperature range for which experimental data are available for both normal and isomer hydrocarbons.

Vapour pressure, critical temperature, and critical pressure of dichloromethane

Abstract Experimental vapour pressures of dichloromethane are reported. The critical temperature and critical pressure were determined by direct observation of the disappearance of the gas-to-liquid meniscus. Coefficients are given of Cragoe and of Wagner equations which fit the complete set of measured vapour pressures up to the critical point.

Electronic Structure, Molecular Interaction, and Stability of the CH4-nH2O Complex, for n = 1-21

Molecular calculations were carried out with four different methodologies to study the CH 4- nH 2O complex, for n = 1-21. The HF and MP2 methods used considered the O atom with pseudopotential to freeze the 1s shell. The other methodologies applied the Bhandhlyp and B3lyp exchange and correlation functionals. The optimized CH 4- nH 2O structures are reported, specifying the number and type of H 2O subunits (triangle, square, pentagon, etc.) that comprised the nH 2O counterpart cluster or cage, that interacted with the CH 4 molecule, and, in the latter case, that provided its confinement. Results are focused to understand the stability of the CH 4- nH 2O complex. The quality of the electron correlation effect, as well as the size of the nH 2O cage to confine the guest molecule, and the number and type of H 2O subunits comprising the nH 2O cluster or cage are the most important factors to provide the stability of the complex and also dictate the particular n value at which the CH 4 molecule confinement occurs. This number was 14 for the HF, Bhandhlyp, and B3Lyp methods and 16 for the MP2 method. The reported hydrate structures for n < 20 could be predictive for future experiments.

Isothermal Multiphase Flash Calculations with the PC-SAFT Equation of State

A computational approach for isothermal multiphase flash calculations with the PC‐SAFT (Perturbed‐Chain Statistical Associating Fluid Theory) equation of state is presented. In the framework of the study of fluid phase equilibria of multicomponent systems, the general multiphase problem is the single most important calculation which consists of finding the correct number and types of phases and their corresponding equilibrium compositions such that the Gibbs energy of the system is a minimum. For solving this problem, the system Gibbs energy was minimized using a rigorous method for thermodynamic stability analysis to find the most stable state of the system. The efficiency and reliability of the approach to predict and calculate complex phase equilibria are illustrated by solving three typical problems encountered in the petroleum industry.