Excess molar enthalpies for mixtures of supercritical carbon dioxide and limonene (original) (raw)
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Excess molar enthalpies for mixtures of supercritical carbon dioxide and water+ethanol solutions
The Journal of Supercritical Fluids, 2005
Excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and ethanol aqueous solutions were measured at 323.15 K and 7.64 and 15.00 MPa using an isothermal high-pressure flow calorimeter. H E m values obtained at the lower pressure are very exothermic while those obtained at the higher pressure are moderately endothermic. H E m for CO 2 + H 2 O mixtures at 308.15 K and 7.64 MPa and 323.15 K and 15
The Journal of Chemical Thermodynamics, 2012
Mixtures of supercritical CO 2 and ethyl acetate (EA) are very often involved in supercritical fluid applications and their thermodynamic properties are required to understand and design these processes. Excess molar enthalpies (H E m ) for (CO 2 + EA) mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in supercritical processes: pressures from (9.00 to 18.00) MPa and temperatures from (313.15 to 333.15) K. Mixtures showed exothermic mixing; excess molar enthalpies exhibited a minimum in the CO 2 -rich region. The effects of pressure and temperature on the excess molar enthalpy of (CO 2 + EA) are large. The most exothermic H E m values were observed for a coincident CO 2 mole fraction value of 0.737 at T/K = (323.15 and 333.15) and P/MPa = 9.00: (À4489 and À4407) J Á mol À1 , respectively. Two-phase splitting was observed in the CO 2rich region at T/K = 333.15 and P/MPa = 9.00; in this region H E m varies linearly with CO 2 mole fraction. For a given mole fraction and temperature, mixtures become more exothermic as pressure decreases. These trends were analyzed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for (CO 2 + EA). Excess molar enthalpies here reported were correlated using the Soave-Redlich-Kwong and Peng-Robinson equations of state, and the classical mixing rule with two binary interaction parameters. The influence of the thermal effects on the phase behavior of (CO 2 + EA) mixtures formed in supercritical antisolvent precipitation experiments was discussed.
Excess molar enthalpies for mixtures of supercritical CO 2 and linalool
Journal of Supercritical Fluids, 2008
Excess molar enthalpies (HmE) for mixtures of supercritical CO2 and linalool were measured at conditions of temperature and pressure typical of supercritical extraction processes: 313.15 and 323.15 K and 7.64, 10.00 and 12.00 MPa. The measurements were carried out using an isothermal high-pressure flow calorimeter. The effects of pressure and temperature on the excess molar enthalpy are large. Mixtures formed by low-density carbon dioxide and linalool show very exothermic mixing and excess molar enthalpies exhibit a minimum in the CO2-rich region. The lowest HmE values (≈−4000 J mol−1) are observed for mixtures at 313.15 K and 7.64 MPa. Mixtures formed by high-density carbon dioxide and linalool show considerably endothermic mixing (≈400–600 J mol−1) in the linalool-rich region and moderately exothermic mixing for the other compositions. On the other hand, HmE at 7.64 MPa and 313.15 and 323.15 K varies linearly with CO2 mole fraction in the two-phase region where a gaseous mixture and a liquid mixture of fixed composition, for a given condition of temperature and pressure, are in equilibrium. Results are analyzed in terms of phase equilibria, pure carbon dioxide density and CO2–terpene molecular interactions. Excess molar enthalpies are simultaneously correlated using the Soave–Redlich–Kwong and Peng–Robinson equations of state and the classical mixing rule. The significance of these large variations of HmE with temperature and pressure in the design of supercritical fluid deterpenation processes is discussed.
Excess molar enthalpies for mixtures of supercritical carbon dioxide and 1,8-cineole
Journal of Supercritical Fluids, 2007
Excess molar enthalpies (HmE) for mixtures of supercritical CO2 and 1,8-cineole were measured at 308.15, 313.15 and 323.15 K and 7.64 MPa and at 308.15 and 323.15 K and 10.00 MPa using an isothermal high-pressure flow calorimeter. The effects of pressure and temperature on the excess molar enthalpy of [CO2 (x) + 1,8-cineole (1 − x)] are large. Mixtures at 308.15 K and 10.00 MPa show slightly endothermic mixing in the 1,8-cineole-rich region and moderately exothermic mixing for x > 0.2. Excess molar enthalpies become very exothermic at the other conditions of temperature and pressure studied. The lowest HmE values (≈−4900 J mol−1) are observed for CO2-rich mixtures at 313.15 K and 7.64 MPa. These data are examined together with phase equilibria and critical parameters previously reported for [CO2 + 1,8-cineole]. The large negative values of HmE are related to the carbon dioxide change of state from that of a low-density fluid to that of a liquid-mixture component in CO2-rich mixtures.
Journal of Chemical and Engineering Data, 2010
Mixtures of supercritical CO 2 and acetone are very often involved in supercritical fluid applications, and their thermodynamic properties are required to understand and design these processes. Excess molar enthalpies (H m E ) for CO 2 + acetone mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in supercritical processes: pressures from (9.00 to 18.00) MPa and temperatures from (313.15 to 333.15) K. Mixtures showed exothermic mixing; excess molar enthalpies exhibited a minimum in the CO 2 -rich region. The effects of pressure and temperature on the excess molar enthalpy of CO 2 + acetone are large. The most exothermic H m E values were observed for a coincident CO 2 mole fraction value of 0.771 at (323.15 and 333.15) K and 9.00 MPa: (-4176 and -4366) J · mol -1 , respectively. Two-phase vapor-liquid CO 2 -rich regions are observed at (323.15 and 333.15) K and 9.00 MPa where H m E linearly varies with CO 2 mole fraction. For a given mole fraction and temperature, mixtures become more exothermic as pressure decreases. These trends were analyzed in terms of molecular interactions, phase equilibria, density, and critical parameters previously reported for CO 2 + acetone. Excess molar enthalpies here reported were correlated using the Peng-Robinson equation of state and the classical mixing rule with two binary interaction parameters. The influence of the thermal effects on the phase behavior of CO 2 + acetone mixtures formed in supercritical antisolvent precipitation experiments was discussed.
Excess enthalpies of mixtures of olive oil and supercritical carbon dioxide
The Journal of Supercritical Fluids, 1999
The excess enthalpies HE of CO 2 +olive oil mixtures were measured under the conditions of temperature and pressure typically used in supercritical fluid extraction by means of an isothermal flow calorimeter. Values of HE at 35°C and 17 MPa are moderately endothermic. Values of HE at 35°C and 15 MPa are moderately endothermic in the olive oil-rich region and exothermic in the carbon dioxide-rich region. Values of HE at 35°C and 9 MPa and at 80°C and 9, 15 and 17 MPa are considerably exothermic. The HE versus composition plots show trends corresponding to a two-phase region. The changes observed in the excess enthalpy with temperature and pressure are discussed in terms of densities and critical constants of carbon dioxide, triolein and olive oil and liquid-vapor equilibrium data for CO 2 +triolein, CO 2 +oleic acid+triolein and CO 2 +rapeseed oil.
Industrial & Engineering Chemistry Research, 2000
Carbon dioxide, CO 2 , and nitrous oxide, N 2 O, are fluids used in supercritical extraction. Mixtures of N 2 O and CO 2 are excellent candidates to be used as supercritical fluids. In this work, excess enthalpies, H m E , are reported for the N 2 O + CO 2 and N 2 O + CO 2 + cyclohexane systems at 308.15 K and 7.64 MPa. This temperature lies between the N 2 O and CO 2 critical temperatures, and the pressure is higher than the N 2 O and CO 2 critical pressures. Measurements have been carried out using an isothermal high-pressure flow calorimeter. Results for the N 2 O + CO 2 system are analyzed simultaneously with excess enthalpy data and excess volume data, V m E , taken from the literature, using different equations of state and mixing rules. The magnitude of the heat involved is large because of the proximity of experimental conditions to the mixture's critical locus. Experimental data for the ternary system are analyzed using different equations of state and mixing rules, and several empirical and semiempirical prediction methods are tested.
The Journal of Supercritical Fluids, 2007
An isothermal high-pressure flow calorimeter has been used to measure excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and N-methyl-2-pyrrolidone (NMP) under conditions of temperature and pressure typically used in supercritical CO 2 antisolvent precipitation (SAS): 313.15 and 338.15 K and 9.48, 15.00 and 20.00 MPa. Mixtures showed exothermic mixing; excess molar enthalpies exhibited a minimum in the CO 2 -rich region. The effects of pressure and temperature on the excess molar enthalpy of CO 2 + NMP are large. The lowest H E m values (≈−4500 J mol −1 ) were observed for mixtures at 338.15 K and 9.48 MPa. On the other hand, H E m at this condition of temperature and pressure varies linearly with CO 2 mole fraction in the two-phase region where a gaseous and a liquid mixture of fixed composition are in equilibrium. These data were analyzed in terms of phase equilibria data and critical locus for CO 2 + NMP and the related SAS experiments. Very exothermic excess molar enthalpies were obtained for conditions of temperature and pressure with marked coalescence phenomena for micro and submicro particles of tetracycline, amoxicillin and ampicillin produced by SAS. Excess molar enthalpies here reported and those previously measured at 298.15 K and 7.50, 10.60 and 12.60 MPa were correlated using the Soave-Redlich-Kwong and Peng-Robinson equations of state and the classical mixing rule with two binary interaction parameters.