Thermodynamic Study of the N 2 O + CO 2 and N 2 O + CO 2 + Cyclohexane Systems in the Near-Critical and Supercritical Regions (original) (raw)
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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.
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.
Supercritical pressure–density–temperature measurements on CO2–N2, CO2–O2 and CO2–Ar binary mixtures
The Journal of Supercritical Fluids, 2012
This paper presents new supercritical volumetric measurements on three binary mixtures mainly composed of carbon dioxide. The interest in the tested mixtures derives primarily from carbon capture and storage applications. In particular, CO 2 -rich streams with low amounts of nitrogen, oxygen and argon are representative of the flows that are treated by the compression units and the purification units employed in the oxy-fuel fired power plants. These flows are then transported from power plants to storage sites in supercritical conditions. For each type of binary mixture, two different molar compositions are here considered. Isothermal pressure-density-temperature measurements are performed for all the mixtures in a temperature range from 303 K to 383 K and in a pressure range from 1 MPa to 20 MPa by way of a vibrating tube densimeter-based apparatus. The experimental data are used subsequently for the regression of new binary interaction coefficients for two types of cubic equations of state, the Peng-Robinson and the Redlich-Kwong-Soave-Peneloux, and a multi-parameter equation, the Benedict-Webb-Rubin-Starling. The absolute deviations with respect to experimental data are in the range 2.10-2.56%, 3.05-4.07% and 1.71-1.97% for the three equations respectively. The results confirm the superiority of the multi-parameter equation of state over the cubic models in the supercritical region.
Calorimetry in the near-critical and supercritical regions. Nitrous oxide + hydrocarbon mixtures
Pure and Applied Chemistry, 1999
The high pressure calorimeters developed in the last 20 years are briefly reviewed. Most of them have been used to obtain excess enthalpy data (H E m ) in the critical and supercritical regions. Data are available for many mixtures formed by carbon dioxide and for a few involving other supercritical fluids such as ethane, methane, nitrous oxide, etc. Data for several N 2 O þ hydrocarbon mixtures were recently measured from 308.15 to 323.15 K and from 7.64 to 15.00 MPa. Excess enthalpies for N 2 O þ hydrocarbon mixtures were calculated using several cubic equations of state (EOS). Two noncubic EOS which combine the Carnahan-Starling hard-sphere term with the van der Waals and Redlich-Kwong attractive terms, were also used. The classical van der Waals mixing rules and those proposed by Wong and Sandler were used. The ability of the cubic EOS to correlate the excess enthalpies of the N 2 O þ hydrocarbon mixtures seems to be related to the proximity of conditions of temperature and pressure to the N 2 O critical point.
Excess molar enthalpies for mixtures of supercritical carbon dioxide and limonene
Fluid Phase Equilibria, 2006
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
Supercritical Fluid Extraction (SFE) is the process of separating a soluble material from an insoluble residue using the supercritical fluid as the extracting solvent. This extraction is the most effective and efficient way to extract valuable constituent in botanicals. Supercritical carbon dioxide is a fluid state of carbon dioxide that is held above its critical temperature (Tc=31.1 °C) and critical pressure (Pc=73.8 bar). It is a natural solvent and has been widely used in practical applications because of its non-toxic, non-flammable, plentiful, inexpensive and tunable of solvent properties by just adjusting temperature and pressure. Due to carbon dioxide's relatively low critical temperature, it is especially suitable for processing thermo-labile compounds, such as pharmaceutical and nutraceutical compounds. Nevertheless, the cost of SFE equipment is outside the range of most of our finances. A high-pressure intensifier pump is used to achieve the required pressure. In this research, the supercritical CO2 condition was achieved by other alternative using dry ice. It is a solid phase of CO2 when frozen. At standard temperature and pressure (STP), CO2 usually behaves as a gas. If dry ice is put in an enclosed vessel, it will sublimate to become a gas and the pressure will increase depending on the mass of dry ice until the desired pressure (supercritical pressure) is achieved. By supercritical CO2 from dry ice, the equipment of SFE will be simpler and cheaper. It is also suitable for batch operation to get equilibrium data of supercritical fluid extraction. Exploration of Equation of State, such as Ideal Gas, van der Waals, Redlich Kwong, Soave-Redlich Kwong and Peng Robinson, was done to predict the operating condition (supercritical pressure and temperature). In this research, by comparing the calculated and the experimental data, Peng Robinson is considered as the most appropriate Equation of State.
2018
In supercritical CO2 extraction process , there are two essential steps: the extraction step in the extractor where the SC-CO2 allows the solvent or extract removal from product structure and the separation step which consists of the separation of CO2-solvents or CO2-extract in a cascade of cyclone separators downstream the extractor. Cyclone separators are separation devices that use the centrifugal and gravity forces to remove liquid phase from flue gases. Two supercritical extraction processes are studied here: organogels supercritical drying for aerogels production and supercritical extraction of polar compounds from natural products. Concerning the first process, the organogel is prepared by an aminoacid-type organogelator with aromatic solvents such as tetralin or toluene. The experimental results showed a good solvent recovery rate in the case of tetralin, exceeding 90% but an unsatisfactory separation for toluene with a yield below 65%. In order to understand the experimenta...
The Effect of Fluid Flow Rate and Extraction Time in Supercritical Carbon Dioxide
2019
1 Centre of Lipid Engineering and Applied Research (CLEAR), Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia 2 Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia 3 Department of Chemical Engineering, Universiti Teknologi Petronas, 32610 Bandar Sri Iskandar, Perak, Malaysia
International Journal of Thermodynamics
Mutual solubilities of a mixture containing 80.52% ethanol and 19.48% octane were measured in a carbon dioxide solvent using a high-pressure type phase equilibrium apparatus at pressures up to 100 bar and at a temperature of 75°C. Experimental results showed that a considerable separation was not achieved in the ethanol-octane ratio investigated in this work. The experimental data were then compared with the theoretical data which were obtained from the regular solution equations. Regular solution theory was employed for each phase by applying activity coefficient expressions. The regular solution theory approach has been found to be encouraging for the prediction of solubility data (vapor phase data) and also showed that the interaction parameters were dependent on pressure.