Tuesday, November 6, 2007
335ah

Vapor–Liquid Equilibria For The CO2 + Heptane Mixture At 314.86 K, 373.15 K, 418.11 K And Compressed Liquid Densities From 313 To 363 K Up To 25 Mpa

Mariana Medina-Bermúdez, Luis A. Saavedra-Molina, and Luis A. Galicia-Luna. Laboratorio deTermodinámica-SEPI, INSTITUTO POLITECNICO NACIONAL-ESIQIE, Lab. Termodinamica, UPALM, Edif. Z, 1er Piso, Sec. 6, Mexico, 07738, Mexico

In this work, the vapor-liquid equilibrium (VLE) for the CO2+heptane system was measured at temperatures of 314.86, 373.003 and 418.105 K, having maximum operating pressure of 13.02 MPa. The VLE measurements were carried out in an apparatus based on the static-analytic method [1], it consists of an equilibrium cell made of titanium alloy to measure at pressures up to 60 MPa and temperatures up to 637 K, a sampler-injector ROLSITM which takes a sample of a phase from the cell and sends it to the gas chromatograph connected by a thermo regulated line. VLE data were correlated with the Peng-Robinson equation of state using the Van der Waals and Wong Sandler mixture rules. The Wong Sandler mixture rules gave a better representation of vapor-liquid equilibrium for CO2+Heptane mixture. The absolute average deviation (%AAD) using the Peng Robinson equation and the Wong Sandler mixing rule was less than 0.7198 and 0.0011 for pressure and y1, respectively. On the other hand, the compressed liquid densities for heptane and mixtures containing CO2(1)+heptane(2) at compositions of x1=0.0218, 0.3148, 0.5085, 0.7513 and 0.9496 were measured at temperatures from 313.15 to 362.36 K and pressures up to 25MPa. Densities measurements were performed in an apparatus based on the static-synthetic method [2], it consists of a sapphire visual cell and a vibrating tube densimeter. Also excess volumes were calculated for each composition. The compressed liquid densities were correlated with the BWRS EoS (Benedict-Webb-Rubin-Starling equation of state) and with the five and six parameter equations. The experimental densities data of heptane were compared with those from literature, the deviations between experimental and literature data were 0.066%. [3]

Keywords: vapor–liquid equilibria, density, alkanes, Heptane, carbon dioxide.

[1] Luis A. Galicia Luna and A. Ortega Rodriguez (2000); New Apparatus for the Fast Determination of High-Pressure Vapor Liquid Equilibria of Mixtures and of Accurate Critical Pressures; J.Chem. Eng. Data 45, 265-271.

[2] Abel Zuñiga Moreno and Luis A. Galicia Luna (2002); Densities of 1-Propanol and 2-propanol via a Vibrating Tube Densimeter from 313 to 363K and up to 25 MPa; J.Chem. Eng. Data 47, 155-160.

[3] Abel Zuñiga Moreno (2006); Desarrollo de un método experimental para determinar solubilidades de sólidos en solventes supercriticos; Tesis doctorado ESIQIE-IPN, México D.F, p 166.



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