Isothermal High-pressure Flow Calorimeter Research Articles

Excess molar enthalpies for mixtures of supercritical CO2 and ethyl acetate and their role in supercritical fluid applications

Mixtures of supercritical CO2 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 (HmE) for (CO2+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 CO2-rich region. The effects of pressure and temperature on the excess molar enthalpy of (CO2+EA) are large. The most exothermic HmE values were observed for a coincident CO2 mole fraction value of 0.737 at T/K=(323.15 and 333.15) and P/MPa=9.00: (−4489 and −4407)J·mol−1, respectively. Two-phase splitting was observed in the CO2-rich region at T/K=333.15 and P/MPa=9.00; in this region HmE varies linearly with CO2 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 (CO2+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 (CO2+EA) mixtures formed in supercritical antisolvent precipitation experiments was discussed.

Role of excess molar enthalpies in supercritical antisolvent micronizations using dimethylsulfoxide as the polar solvent

The role of excess molar enthalpies ( H m E ) in the supercritical antisolvent (SAS) micronizations using dimethylsulfoxide (DMSO) as the polar solvent was investigated. Excess molar enthalpies for CO 2 + DMSO mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in SAS micronizations. In most cases, mixtures showed very exothermic mixing. A local temperature increase can be expected in the precipitation chamber as a consequence of the heat evolved when CO 2 dissolves in DMSO. Based on the H m E measurements, local temperature increases were calculated and shown to explain immiscibility of CO 2 and DMSO and agglomerated or irregular particles for average temperature and pressure conditions where complete miscibility and uniform particles could have been expected. H m E data were also discussed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO 2 + DMSO.

Measurements and modeling of high-pressure excess molar enthalpies and isothermal vapor–liquid equilibria of the carbon dioxide + N, N-dimethylformamide system

Mixtures of supercritical CO 2 and N, N-dimethylformamide (DMF) 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 + DMF mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in supercritical processes: 313.15 and 323.15 K at 9.00, 12.00, 15.00 and 18.00 MPa and 333.15 K at 9.00 and 15.00 MPa. The Peng–Robinson and the Soave–Redlich–Kwong equations of state were used in conjunction with the classical mixing rules to model the literature vapor–liquid equilibrium and critical data and the excess enthalpy data. In most cases, CO 2 + DMF mixtures showed very exothermic mixing and excess molar enthalpies exhibited a minimum in the CO 2-rich region. The lowest H m E value (−4526 J mol −1) was observed for a CO 2 mole fraction value of 0.713 at 9.00 MPa and 333.15 K. On the other hand, H m E at 9.00 MPa and 323.15 and 333.15 K 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. The effects of pressure and temperature on the excess molar enthalpy are large. For a given mole fraction, mixtures become less exothermic as pressure increases or temperature decreases. These excess enthalpy data were analyzed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO 2 + DMF. All throughout this paper, the key concepts and modeling tools originate from the work of van der Waals: the paper is intended as a small piece of recognition of van der Waals overwhelming contributions to thermodynamics.

Enthalpies of Absorption of Carbon Dioxide in Aqueous Sodium Glycinate Solutions at Temperatures of (313.15 and 323.15) K

The enthalpies of absorption (ΔrH) of carbon dioxide in aqueous sodium glycinate (SG) solutions of 0.10 in mass fraction were determined at temperatures of (313.15 and 323.15) K and a pressure of 12.00 MPa using an isothermal high-pressure flow calorimeter. Very exothermic absorption enthalpies are obtained at the two temperatures studied. ΔrH values expressed in kJ·mol−1 of SG decrease very quickly as CO2 loading increases until saturation is reached; from this point, a slowly decreasing value is obtained for the absorption enthalpy. CO2 loading is expressed as mol CO2/mol amine (α). The calorimetric data provide a means to determine the saturated loading point of CO2 in the solution; values of (0.90 and 0.86) mol CO2/mol SG were estimated for this magnitude at temperatures of (313.15 and 323.15) K, respectively. Enthalpies of solution of CO2 were also calculated. These enthalpies become more exothermic as α decreases until a limit value characteristic of each amine is observed for low CO2 loading. This ...

Excess molar enthalpies for mixtures of supercritical CO 2 and linalool

Excess molar enthalpies ( H m E ) for mixtures of supercritical CO 2 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 CO 2-rich region. The lowest H m E 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, H m E at 7.64 MPa and 313.15 and 323.15 K varies linearly with CO 2 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 CO 2–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 H m E with temperature and pressure in the design of supercritical fluid deterpenation processes is discussed.

Excess molar enthalpies for binary mixtures related to supercritical antisolvent precipitation: Carbon dioxide + N-methyl-2-pyrrolidone

An isothermal high-pressure flow calorimeter has been used to measure excess molar enthalpies ( H m E ) 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 m E values (≈−4500 J mol −1) were observed for mixtures at 338.15 K and 9.48 MPa. On the other hand, H m E 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.

Excess molar enthalpies for mixtures of supercritical carbon dioxide and 1,8-cineole

Excess molar enthalpies ( H m E ) for mixtures of supercritical CO 2 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 [CO 2 ( 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 H m E values (≈−4900 J mol −1) are observed for CO 2-rich mixtures at 313.15 K and 7.64 MPa. These data are examined together with phase equilibria and critical parameters previously reported for [CO 2 + 1,8-cineole]. The large negative values of H m E are related to the carbon dioxide change of state from that of a low-density fluid to that of a liquid-mixture component in CO 2-rich mixtures.

Excess molar enthalpies for mixtures of supercritical carbon dioxide and limonene

Excess molar enthalpies (HmE) for mixtures of supercritical CO2 and limonene were measured at 308.15, 313.15 and 323.15K and 7.64 and 10.00MPa using an isothermal high-pressure flow calorimeter. The effects of pressure and temperature on the excess molar enthalpy of [CO2(x)+limonene(1−x)] are large. Mixtures at 308.15K and 10.00MPa show slightly endothermic mixing in the limonene-rich region and moderately exothermic mixing for x>0.5. Mixtures at the other conditions of temperature and pressure studied show exothermic mixing, excess molar enthalpies exhibit a minimum in the CO2-rich region. The lowest HmE values (≈−4500Jmol−1) are observed for mixtures at 313.15K and 7.64MPa. On the other hand, HmE at 7.64MPa and 308.15, 313.15 and 323.15K varies linearly with CO2 mole fraction in the two-phase region where a gaseous and a liquid mixture of fixed composition, for a given condition of temperature and pressure, are in equilibrium. These data are examined together with phase equilibria and critical parameters previously reported for CO2+limonene. Excess molar enthalpies are simultaneously correlated using the Peng–Robinson equation of state and the classical mixing rule with one binary interaction parameter.

Excess molar enthalpies for mixtures of carbon dioxide + a modifier (5 mol% methanol or 1-octanol) and hexane at 308.15 K and 12.40 MPa

The effect of adding a 5 mol% alcohol modifier to carbon dioxide being mixed with hexane at 308.15 K and 12.40 MPa is investigated using an isothermal high-pressure flow calorimeter. Excess molar enthalpies ( H m E ) are determined for the ternary mixtures [CO 2( x 1) + methanol( x 2) + hexane( x 3)] and [CO 2( x 1) + octanol( x 2) + hexane( x 3)] where x 1/ x 2 = 95/5 at 308.15 K and 12.40 MPa. The ternary excess enthalpy data are then compared to excess enthalpy data for CO 2 + hexane mixtures. Mixing becomes more endothermic for both alcohols; the H m E maximum value increases ca. 200 J mol −1. Excess enthalpy data for the methanol + hexane and octanol + hexane mixtures at 308.15 K and 12.40 MPa are also reported. For both alcohols, mixtures show endothermic mixing: H m E maximum values are ca. 500 J mol −1. H m E values are discussed in terms of the critical locus and phase equilibria of the systems involved. Binary excess enthalpy data for the five binary systems involved in this study were correlated using both a Padé function and the Peng–Robinson equation of state. These correlations are used to predict ternary data. Predictions obtained using the Peng–Robinson EOS in combination with the classical mixing rule are much more accurate than those obtained using the Padé function.

Excess molar enthalpies for mixtures of supercritical carbon dioxide and water + ethanol solutions

Excess molar enthalpies ( H m E ) 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 m E values obtained at the lower pressure are very exothermic while those obtained at the higher pressure are moderately endothermic. H m E for CO 2 + H 2O mixtures at 308.15 K and 7.64 MPa and 323.15 K and 15.00 MPa were also measured. These data are examined together with H m E data previously reported for mixtures of supercritical CO 2 and ethanol aqueous solutions, vapor–liquid equilibrium data for the ternary system CO 2 + H 2O + ethanol and the excess enthalpy data for the three related binary systems. CO 2–ethanol interactions are shown to be the main contribution to excess enthalpies when supercritical CO 2 and ethanol aqueous solutions are mixed. Ternary excess enthalpies for CO 2 + H 2O + ethanol are also obtained. Kohler's method is used for estimating these ternary data from the excess enthalpy data of the three related binary systems.

Thermodynamic Study of the N2O + CO2 and N2O + CO2 + Cyclohexane Systems in the Near-Critical and Supercritical Regions

Carbon dioxide, CO2, and nitrous oxide, N2O, are fluids used in supercritical extraction. Mixtures of N2O and CO2 are excellent candidates to be used as supercritical fluids. In this work, excess enthalpies, , are reported for the N2O + CO2 and N2O + CO2 + cyclohexane systems at 308.15 K and 7.64 MPa. This temperature lies between the N2O and CO2 critical temperatures, and the pressure is higher than the N2O and CO2 critical pressures. Measurements have been carried out using an isothermal high-pressure flow calorimeter. Results for the N2O + CO2 system are analyzed simultaneously with excess enthalpy data and excess volume data, , 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 t...

The excess enthalpy of (trichloroethene + carbon disulphide), (trichloroethene + trichloromethane), and (trichloroethene + tetrachloromethane) at various temperatures and pressures

The excess molar enthalpies of (trichloroethene + carbon disulphide) at 293.15 K (0.1, 15.0, and 30.0 MPa) and 303.15 K (0.1 and 15.0 MPa), of (trichloroethene + trichloromethane) at 293.15 K (0.1, 15.0, and 30.0 MPa) and 303.15 K (0.1 MPa), and of (trichloroethene + tetrachloromethane) at 293.15 K (0.1, 15.0, and 30.0 MPa) have been measured over the entire composition range using an isothermal high-pressure flow calorimeter. The excess enthalpies are positive and follow the normal pressure and temperature dependence for non-electrolyte mixtures.

The excess enthalpy of methyliodide + carbon disulphide, methyliodide + dichloromethane and dichloromethane + carbon disulphide over a range of temperatures and pressures

Excess molar enthalpies of the systems methyliodide + carbon disulphide, methyliodide + dichloromethane and dichloromethane + carbon disulphide have been measured over the entire concentration range at 283.15 and 303.15 K using an isothermal high-pressure flow calorimeter. The method consists of combining the streams of two fluids under isothermal-isobaric conditions and, after establishing the equilibrium state, measuring the energy absorbed or released with the help of an electronically controlled cooling-heating combination. With the present arragement both exothermic and endothermic energy effects from 0.005 to 0.5 Js −1 can be measured with a precision of ±1 per cent even under high pressures. The effect of pressure was also studied by measuring excess molar enthalpies for the above systems at 15 and 30 MPa along the 293.15 isotherm. All the measured excess enthalpies were found to be positive. The temperature and pressure dependence of the excess molar enthalpies is discussed. The results for such systems composed of small and rigid but anisotropic molecules should prove useful for the development of molecular theory which today can successfully be applied only to small, rigid molecules of less anisotropic shape.

Excess enthalpy of the system chloroform + carbon tetrachloride and a thermodynamic evaluation of its state dependence

Siddiq, M.A. and Lucas, K., 1984. Excess enthalpy of the system chloroform + carbon tetrachloride and a thermodynamic evaluation of its state dependence. Fluid Phase Equilibria, 16: 87–98. Excess molar enthalpies of the system chloroform + carbon tetrachloride have been measured over the entire concentration range at 283.15, 293.15, 303.15, 313.15 and 323.15 K using an isothermal high-pressure flow calorimeter. The effect of pressure was also studied by measuring excess enthalpies at 15 and 30 MPa along the 293.15, 313.15 and 323.15 K isotherms. The temperature dependence of the excess enthalpies was used to calculate vapour-liquid equilibria as a function of temperature. The results are excellent. Further evaluation of the temperature and pressure dependences of the excess enthalpy is discussed.

The excess enthalpy of (tetrachloromethane + carbon disulphide) and (tetrachloromethane + dichloromethane) over a range of temperatures and pressures

Measurements of the excess molar enthalpy of (tetrachloromethane + carbon disulphide) and (tetrachloromethane + dichloromethane) have been made using an isothermal high-pressure flow calorimeter. The measurements for (tetrachloromethane + carbon disulphide) cover the range 283.15 to 323.15 K at pressures between 0.1 and 30 MPa. The excess molar enthalpies for (tetrachloromethane + dichloromethane) are reported at 298.15 K at 0.1, 15, and 30 MPa, and at 323.15 K at 0.2 MPa. The thermodynamic consistency of the results is shown by deriving the temperature dependence of the excess molar Gibbs free energy from them and comparing with published experimental values.

ChemInform Abstract: AN ISOTHERMAL HIGH‐PRESSURE FLOW CALORIMETER. THE EXCESS ENTHALPY OF (CYCLOHEXANE + N‐HEXANE) AT DIFFERENT PRESSURES AT 288.15, 298.15, AND 313.15 K

Chemischer InformationsdienstVolume 14, Issue 12 Article ChemInform Abstract: AN ISOTHERMAL HIGH-PRESSURE FLOW CALORIMETER. THE EXCESS ENTHALPY OF (CYCLOHEXANE + N-HEXANE) AT DIFFERENT PRESSURES AT 288.15, 298.15, AND 313.15 K M. A. SIDDIQI, M. A. SIDDIQISearch for more papers by this authorK. LUCAS, K. LUCASSearch for more papers by this author M. A. SIDDIQI, M. A. SIDDIQISearch for more papers by this authorK. LUCAS, K. LUCASSearch for more papers by this author First published: March 22, 1983 https://doi.org/10.1002/chin.198312075AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue12March 22, 1983 RelatedInformation

An isothermal high-pressure flow calorimeter the excess enthalpy of (cyclohexane + n-hexane) at different pressures at 288.15, 298.15, and 313.15 K

An isothermal high-pressure flow calorimeter suitable for measuring enthalpy of mixing for endothermic and exothermic processes is described. The enthalpy of mixing can be measured from 263 K to 343 K and up to 40 MPa. With the present arrangement, energy effects from 0.005 to 0.5 J · s −1 can be measured with a precision of ± 1 per cent or better. Excess molar enthalpies H m E have been obtained for (cyclohexane + n-hexane) at 0.1, 15, and 30 MPa at different temperatures.