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Papers by Albertina Cabañas

Research paper thumbnail of Excess enthalpies, and vapor-liquid equilibrium and surface properties of the highly non-ideal associated mixtures formed by an alcohol and propanal

Fluid Phase Equilibria, 1996

Excess enthalpies, vapor-liquid equilibrium data and surface tensions of the highly non-ideal ass... more Excess enthalpies, vapor-liquid equilibrium data and surface tensions of the highly non-ideal associated mixtures formed by methanol or ethanol and propanal have been measured in the temperature range of 288.15-318.15 K. These mixtures show negative deviations from ideality, including a negative azeotrope for the methanol-propanal system in the methanol-rich region. The values for the excess enthalpies are very exothermic and become less negative as temperature increases. Methanol-propanal mixtures exhibit minima of approximately-8.6 and-8.0 kJ mol-~, at a mole fraction close to 0.5 and 298.15 and 318.15 K, respectively. The ethanol-propanal system exhibits minima of approximately-7.2 and-5.0 kJ mol-l at 298.15 and 318.15 K, respectively. The surface tension has been measured at 298.15 K. Values for the relative surface adsorption calculated from the surface tension and the chemical potentials indicate that the surface is significantly enriched in propanal for mixtures rich in methanol. The calculated values for the concentration-concentration correlation function are lower than those corresponding to an ideal mixture and exhibit a minimum in the middle of the concentration range. A complex composition dependence of the concentration profiles can be inferred. The Lattice-Fluid Associated Solution, the UNIQUAC Associated Solution and the Extended Real Associated Solution models have been used to describe the bulk properties of the alcohol-propanal mixtures.

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

Journal of Supercritical Fluids, 2000

The role of excess molar enthalpies (HmE) in the supercritical antisolvent (SAS) micronizations u... more The role of excess molar enthalpies (HmE) in the supercritical antisolvent (SAS) micronizations using dimethylsulfoxide (DMSO) as the polar solvent was investigated. Excess molar enthalpies for CO2 + 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 CO2 dissolves in DMSO. Based on the HmE measurements, local temperature increases were calculated and shown to explain immiscibility of CO2 and DMSO and agglomerated or irregular particles for average temperature and pressure conditions where complete miscibility and uniform particles could have been expected. HmE data were also discussed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO2 + DMSO.► We discuss the excess enthalpy role in SAS micronizations using dimethylsulfoxide. ► CO2 + DMSO mixtures are studied under conditions of T and P used in SAS. ► CO2-rich mixtures exhibit very exothermic mixing. ► As a consequence, a local T increase can be expected in the precipitation chamber. ► T increase is estimated and shown to affect phase equilibria and particle morphology.

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

The Journal of Supercritical Fluids, 2010

Mixtures of supercritical CO 2 and N,N-dimethylformamide (DMF) are very often involved in supercr... more 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 E m ) 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 E m 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 E m 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.

Research paper thumbnail of Excess molar enthalpies for mixtures of supercritical CO2 and linalool

The Journal of Supercritical Fluids, 2008

Excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and ethanol aqueous solutions... more 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

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

The Journal of Supercritical Fluids, 2007

An isothermal high-pressure flow calorimeter has been used to measure excess molar enthalpies (H ... more 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.

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

The Journal of Supercritical Fluids, 2007

Excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and ethanol aqueous solutions... more 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

Research paper thumbnail of Synthesis of nanoparticulate yttrium aluminum garnet in supercritical water–ethanol mixtures

The Journal of Supercritical Fluids, 2007

Single-phase YAG nanoparticles have been produced by the rapid hydrolysis and dehydration of Al 3... more Single-phase YAG nanoparticles have been produced by the rapid hydrolysis and dehydration of Al 3+ and Y 3+ salts in EtOH-H 2 O mixtures using continuous supercritical water hydrothermal synthesis. The effects of the nature of the starting solution, the metal concentration, the EtOH content, the flow rate and the temperature on the particle size were studied. EtOH promotes crystallization and highly crystalline materials are obtained at relatively low temperatures. Furthermore the critical temperature of EtOH-H 2 O mixtures is lower than that of pure H 2 O, reducing the operating temperature. From the variables studied, the most important parameter seems to be the temperature and much smaller particles have been obtained when experiments are conducted under supercritical conditions (average 50 nm), in comparison to near critical or subcritical conditions (average 150 nm). The method is simple and clean and requires neither addition of a base to the system nor the use of very high reaction temperatures and potentially allows the continuous production of large quantities of material.

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

Journal of Supercritical Fluids - J SUPERCRIT FLUID, 2007

Excess molar enthalpies (HmE) for mixtures of supercritical CO2 and 1,8-cineole were measured at ... more 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.

Research paper thumbnail of The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

Journal of Materials Chemistry, 2001

Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe ... more Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe 2 O 4 (M~Co, Ni, Zn) and the mixed nickel and cobalt ferrite, Ni x Co 12x Fe 2 O 4 have been synthesised continuously by the hydrolysis and simultaneous oxidation of mixtures of Fe(II) acetate and different M(II) acetates in near-critical and supercritical water using a flow reactor. The materials have been characterised by powder X-ray diffraction (PXD) and, in selected cases, by transmission electron microscopy (TEM). The bulk composition of the samples was determined by Atomic Absorption analysis (AA). Additionally, Energy-dispersive Detection X-ray analysis (EDX) was carried out on some of the samples. TEM pictures showed a ''bimodal'' particle size distribution: small particles of ca. 10 nm and larger particles of up to 100 nm, both of which are highly crystalline. Possible reaction mechanisms are discussed, which may be responsible for the observed morphology. The effects of temperature and residence time on the reaction have been studied.

Research paper thumbnail of Continuous hydrothermal synthesis of inorganic materials in a near-critical water flow reactor; the one-step synthesis of nano-particulate Ce1 − xZrxO2 (x = 0–1) solid solutions

Journal of Materials Chemistry, 2001

A hydrothermal synthesis process working in supercritical conditions (T N 374°C, P N 22 MPa) and ... more A hydrothermal synthesis process working in supercritical conditions (T N 374°C, P N 22 MPa) and in a continuous mode has been developed for inorganic nanopowder synthesis. This paper presents a review of the past 5 years of research conducted on this process. Numerous materials (oxides: ZrO 2 , TiO 2 , Fe 2 O 3 …, ferrites: Fe 2 CoO 4 …, or BaZrO 3 ) were obtained with specific features. Some technical issues have been solved, that are presented here. Heat transfer was studied, leading to a more efficient design of the reactor. Future developments have been examined through process engineering, in which our group is engaged, especially through CFD modelling.

Research paper thumbnail of Excess Enthalpies of Binary Mixtures of Methanol with Heptanone Isomers at 298.15 and 323.15 K

Journal of Chemical & Engineering Data, 1997

The excess molar enthalpies, H m E , for methanol + 2-heptanone, 3-heptanone, and 4-heptanone hav... more The excess molar enthalpies, H m E , for methanol + 2-heptanone, 3-heptanone, and 4-heptanone have been measured as a function of mole fraction at 298.15 and 323.15 K by means of an isothermal flow calorimeter. Values for H m E are endothermic with a maximum value occurring at a mole fraction close to 0.5. The temperature effect on the excess enthalpy values is important. Maximum values at 298.15 K range from 725 to 744 J‚mol -1 . Maximum values at 323.15 K range from 908 to 955 J‚mol -1 . The position of the ketone group has little effect on the measured H m E .

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

Journal of Chemical and Engineering Data, 2010

... Ver nica Salazar, Yolanda S nchez-Vicente, Concepci n ... Values for δ range from less than 1... more ... Ver nica Salazar, Yolanda S nchez-Vicente, Concepci n ... Values for δ range from less than 1 % for the measurements of Carson et al.(8) made by isothermal displacement calorimetry to 5 % for some flow calorimetry measurements.(4, 5) It may be observed that both SG solution ...

Research paper thumbnail of 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 ... more 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.

Research paper thumbnail of 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 con... more 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.

Research paper thumbnail of Thermodynamic Study of the N 2 O + CO 2 and N 2 O + CO 2 + Cyclohexane Systems in the Near-Critical and Supercritical Regions

Industrial & Engineering Chemistry Research, 2000

Carbon dioxide, CO 2 , and nitrous oxide, N 2 O, are fluids used in supercritical extraction. Mix... more 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.

Research paper thumbnail of Excess Molar Enthalpies of Nitrous Oxide/Hexane Mixtures in the Liquid and Supercritical Regions

Industrial & Engineering Chemistry Research, 1998

The excess molar enthalpies H m E of nitrous oxide (N 2 O)/hexane mixtures were measured in the l... more The excess molar enthalpies H m E of nitrous oxide (N 2 O)/hexane mixtures were measured in the liquid and supercritical region covering the whole concentration range. The H m E values at 308.15 K and 7.64 and 9.48 MPa and at 318.15 K and 12.27 and 15.00 MPa are moderately positive in the hexane-rich region and moderately negative in the N 2 O-rich region. The H m E values at 308.15 K and 12.27 and 15.00 MPa are moderately positive over the entire composition range. Large negative H m E values are obtained at 318.15 K and 7.64 and 9.48 MPa. The changes observed in H m E with temperature and pressure are discussed in terms of liquid-vapor equilibrium and critical constants for N 2 O/hexane. The H m E values for N 2 O/hexane mixtures are also calculated using cubic equations of state (EOS) and the classical and Wong-Sandler mixing rules.

Research paper thumbnail of The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

Journal of Materials Chemistry, 2001

Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe ... more Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe 2 O 4 (M~Co, Ni, Zn) and the mixed nickel and cobalt ferrite, Ni x Co 12x Fe 2 O 4 have been synthesised continuously by the hydrolysis and simultaneous oxidation of mixtures of Fe(II) acetate and different M(II) acetates in near-critical and supercritical water using a flow reactor. The materials have been characterised by powder X-ray diffraction (PXD) and, in selected cases, by transmission electron microscopy (TEM). The bulk composition of the samples was determined by Atomic Absorption analysis (AA). Additionally, Energy-dispersive Detection X-ray analysis (EDX) was carried out on some of the samples. TEM pictures showed a ''bimodal'' particle size distribution: small particles of ca. 10 nm and larger particles of up to 100 nm, both of which are highly crystalline. Possible reaction mechanisms are discussed, which may be responsible for the observed morphology. The effects of temperature and residence time on the reaction have been studied.

Research paper thumbnail of 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... more 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

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

Fluid Phase Equilibria, 2006

... T showing the critical points of the pure components (■) [8], the (P, T) coordinate where exp... more ... T showing the critical points of the pure components (■) [8], the (P, T) coordinate where experimental data were taken (●) and binary critical loci: (—) experimental, references are given in Section 1; (– –) calculated using the procedure of Heidemann and Khalil [9] and the Peng ...

Research paper thumbnail of Alcohol-Assisted Deposition of Copper Films from Supercritical Carbon Dioxide

Chemistry of Materials, 2003

Device quality Cu films were deposited from solutions of bis(2,2,6,6-tetramethyl-3,5heptanedionat... more Device quality Cu films were deposited from solutions of bis(2,2,6,6-tetramethyl-3,5heptanedionate) copper(II) [Cu(tmhd) 2 ] in supercritical CO 2 (scCO 2 ) using alcohols as reducing agents in a cold wall, high-pressure reactor. At 270°C and pressures between 200 and 230 bar, deposition of copper by the reduction of Cu(tmhd) 2 with ethanol was selective for catalytic surfaces such as Co and Ni over the native oxide of Si wafers or TiN. At 300°C and above, depositions proceeded readily on all surfaces studied. Secondary ion mass spectroscopy indicated that Cu films are remarkably pure; carbon and oxygen contamination were on the order of 0.1% or less. Resistivities of the films were approximately 2 µΩ-cm. Reduction of Cu(thmd) 2 with primary alcohols including methanol, 1-propanol, and 1-butanol proceeded readily to yield copper films on Co substrates at 270°C. Sterically hindered alcohols were less effective at the same conditions. Deposition with 2-butanol required higher alcohol concentrations while attempted depositions with 2-propanol were not successful. Reaction mechanisms consistent with these observations are discussed. 10.

Research paper thumbnail of Excess enthalpies, and vapor-liquid equilibrium and surface properties of the highly non-ideal associated mixtures formed by an alcohol and propanal

Fluid Phase Equilibria, 1996

Excess enthalpies, vapor-liquid equilibrium data and surface tensions of the highly non-ideal ass... more Excess enthalpies, vapor-liquid equilibrium data and surface tensions of the highly non-ideal associated mixtures formed by methanol or ethanol and propanal have been measured in the temperature range of 288.15-318.15 K. These mixtures show negative deviations from ideality, including a negative azeotrope for the methanol-propanal system in the methanol-rich region. The values for the excess enthalpies are very exothermic and become less negative as temperature increases. Methanol-propanal mixtures exhibit minima of approximately-8.6 and-8.0 kJ mol-~, at a mole fraction close to 0.5 and 298.15 and 318.15 K, respectively. The ethanol-propanal system exhibits minima of approximately-7.2 and-5.0 kJ mol-l at 298.15 and 318.15 K, respectively. The surface tension has been measured at 298.15 K. Values for the relative surface adsorption calculated from the surface tension and the chemical potentials indicate that the surface is significantly enriched in propanal for mixtures rich in methanol. The calculated values for the concentration-concentration correlation function are lower than those corresponding to an ideal mixture and exhibit a minimum in the middle of the concentration range. A complex composition dependence of the concentration profiles can be inferred. The Lattice-Fluid Associated Solution, the UNIQUAC Associated Solution and the Extended Real Associated Solution models have been used to describe the bulk properties of the alcohol-propanal mixtures.

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

Journal of Supercritical Fluids, 2000

The role of excess molar enthalpies (HmE) in the supercritical antisolvent (SAS) micronizations u... more The role of excess molar enthalpies (HmE) in the supercritical antisolvent (SAS) micronizations using dimethylsulfoxide (DMSO) as the polar solvent was investigated. Excess molar enthalpies for CO2 + 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 CO2 dissolves in DMSO. Based on the HmE measurements, local temperature increases were calculated and shown to explain immiscibility of CO2 and DMSO and agglomerated or irregular particles for average temperature and pressure conditions where complete miscibility and uniform particles could have been expected. HmE data were also discussed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO2 + DMSO.► We discuss the excess enthalpy role in SAS micronizations using dimethylsulfoxide. ► CO2 + DMSO mixtures are studied under conditions of T and P used in SAS. ► CO2-rich mixtures exhibit very exothermic mixing. ► As a consequence, a local T increase can be expected in the precipitation chamber. ► T increase is estimated and shown to affect phase equilibria and particle morphology.

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

The Journal of Supercritical Fluids, 2010

Mixtures of supercritical CO 2 and N,N-dimethylformamide (DMF) are very often involved in supercr... more 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 E m ) 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 E m 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 E m 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.

Research paper thumbnail of Excess molar enthalpies for mixtures of supercritical CO2 and linalool

The Journal of Supercritical Fluids, 2008

Excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and ethanol aqueous solutions... more 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

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

The Journal of Supercritical Fluids, 2007

An isothermal high-pressure flow calorimeter has been used to measure excess molar enthalpies (H ... more 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.

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

The Journal of Supercritical Fluids, 2007

Excess molar enthalpies (H E m ) for mixtures of supercritical CO 2 and ethanol aqueous solutions... more 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

Research paper thumbnail of Synthesis of nanoparticulate yttrium aluminum garnet in supercritical water–ethanol mixtures

The Journal of Supercritical Fluids, 2007

Single-phase YAG nanoparticles have been produced by the rapid hydrolysis and dehydration of Al 3... more Single-phase YAG nanoparticles have been produced by the rapid hydrolysis and dehydration of Al 3+ and Y 3+ salts in EtOH-H 2 O mixtures using continuous supercritical water hydrothermal synthesis. The effects of the nature of the starting solution, the metal concentration, the EtOH content, the flow rate and the temperature on the particle size were studied. EtOH promotes crystallization and highly crystalline materials are obtained at relatively low temperatures. Furthermore the critical temperature of EtOH-H 2 O mixtures is lower than that of pure H 2 O, reducing the operating temperature. From the variables studied, the most important parameter seems to be the temperature and much smaller particles have been obtained when experiments are conducted under supercritical conditions (average 50 nm), in comparison to near critical or subcritical conditions (average 150 nm). The method is simple and clean and requires neither addition of a base to the system nor the use of very high reaction temperatures and potentially allows the continuous production of large quantities of material.

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

Journal of Supercritical Fluids - J SUPERCRIT FLUID, 2007

Excess molar enthalpies (HmE) for mixtures of supercritical CO2 and 1,8-cineole were measured at ... more 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.

Research paper thumbnail of The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

Journal of Materials Chemistry, 2001

Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe ... more Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe 2 O 4 (M~Co, Ni, Zn) and the mixed nickel and cobalt ferrite, Ni x Co 12x Fe 2 O 4 have been synthesised continuously by the hydrolysis and simultaneous oxidation of mixtures of Fe(II) acetate and different M(II) acetates in near-critical and supercritical water using a flow reactor. The materials have been characterised by powder X-ray diffraction (PXD) and, in selected cases, by transmission electron microscopy (TEM). The bulk composition of the samples was determined by Atomic Absorption analysis (AA). Additionally, Energy-dispersive Detection X-ray analysis (EDX) was carried out on some of the samples. TEM pictures showed a ''bimodal'' particle size distribution: small particles of ca. 10 nm and larger particles of up to 100 nm, both of which are highly crystalline. Possible reaction mechanisms are discussed, which may be responsible for the observed morphology. The effects of temperature and residence time on the reaction have been studied.

Research paper thumbnail of Continuous hydrothermal synthesis of inorganic materials in a near-critical water flow reactor; the one-step synthesis of nano-particulate Ce1 − xZrxO2 (x = 0–1) solid solutions

Journal of Materials Chemistry, 2001

A hydrothermal synthesis process working in supercritical conditions (T N 374°C, P N 22 MPa) and ... more A hydrothermal synthesis process working in supercritical conditions (T N 374°C, P N 22 MPa) and in a continuous mode has been developed for inorganic nanopowder synthesis. This paper presents a review of the past 5 years of research conducted on this process. Numerous materials (oxides: ZrO 2 , TiO 2 , Fe 2 O 3 …, ferrites: Fe 2 CoO 4 …, or BaZrO 3 ) were obtained with specific features. Some technical issues have been solved, that are presented here. Heat transfer was studied, leading to a more efficient design of the reactor. Future developments have been examined through process engineering, in which our group is engaged, especially through CFD modelling.

Research paper thumbnail of Excess Enthalpies of Binary Mixtures of Methanol with Heptanone Isomers at 298.15 and 323.15 K

Journal of Chemical & Engineering Data, 1997

The excess molar enthalpies, H m E , for methanol + 2-heptanone, 3-heptanone, and 4-heptanone hav... more The excess molar enthalpies, H m E , for methanol + 2-heptanone, 3-heptanone, and 4-heptanone have been measured as a function of mole fraction at 298.15 and 323.15 K by means of an isothermal flow calorimeter. Values for H m E are endothermic with a maximum value occurring at a mole fraction close to 0.5. The temperature effect on the excess enthalpy values is important. Maximum values at 298.15 K range from 725 to 744 J‚mol -1 . Maximum values at 323.15 K range from 908 to 955 J‚mol -1 . The position of the ketone group has little effect on the measured H m E .

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

Journal of Chemical and Engineering Data, 2010

... Ver nica Salazar, Yolanda S nchez-Vicente, Concepci n ... Values for δ range from less than 1... more ... Ver nica Salazar, Yolanda S nchez-Vicente, Concepci n ... Values for δ range from less than 1 % for the measurements of Carson et al.(8) made by isothermal displacement calorimetry to 5 % for some flow calorimetry measurements.(4, 5) It may be observed that both SG solution ...

Research paper thumbnail of 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 ... more 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.

Research paper thumbnail of 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 con... more 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.

Research paper thumbnail of Thermodynamic Study of the N 2 O + CO 2 and N 2 O + CO 2 + Cyclohexane Systems in the Near-Critical and Supercritical Regions

Industrial & Engineering Chemistry Research, 2000

Carbon dioxide, CO 2 , and nitrous oxide, N 2 O, are fluids used in supercritical extraction. Mix... more 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.

Research paper thumbnail of Excess Molar Enthalpies of Nitrous Oxide/Hexane Mixtures in the Liquid and Supercritical Regions

Industrial & Engineering Chemistry Research, 1998

The excess molar enthalpies H m E of nitrous oxide (N 2 O)/hexane mixtures were measured in the l... more The excess molar enthalpies H m E of nitrous oxide (N 2 O)/hexane mixtures were measured in the liquid and supercritical region covering the whole concentration range. The H m E values at 308.15 K and 7.64 and 9.48 MPa and at 318.15 K and 12.27 and 15.00 MPa are moderately positive in the hexane-rich region and moderately negative in the N 2 O-rich region. The H m E values at 308.15 K and 12.27 and 15.00 MPa are moderately positive over the entire composition range. Large negative H m E values are obtained at 318.15 K and 7.64 and 9.48 MPa. The changes observed in H m E with temperature and pressure are discussed in terms of liquid-vapor equilibrium and critical constants for N 2 O/hexane. The H m E values for N 2 O/hexane mixtures are also calculated using cubic equations of state (EOS) and the classical and Wong-Sandler mixing rules.

Research paper thumbnail of The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

Journal of Materials Chemistry, 2001

Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe ... more Magnetic spinel type oxides such as magnetite, Fe 3 O 4 , cobalt, nickel, and zinc ferrites, MFe 2 O 4 (M~Co, Ni, Zn) and the mixed nickel and cobalt ferrite, Ni x Co 12x Fe 2 O 4 have been synthesised continuously by the hydrolysis and simultaneous oxidation of mixtures of Fe(II) acetate and different M(II) acetates in near-critical and supercritical water using a flow reactor. The materials have been characterised by powder X-ray diffraction (PXD) and, in selected cases, by transmission electron microscopy (TEM). The bulk composition of the samples was determined by Atomic Absorption analysis (AA). Additionally, Energy-dispersive Detection X-ray analysis (EDX) was carried out on some of the samples. TEM pictures showed a ''bimodal'' particle size distribution: small particles of ca. 10 nm and larger particles of up to 100 nm, both of which are highly crystalline. Possible reaction mechanisms are discussed, which may be responsible for the observed morphology. The effects of temperature and residence time on the reaction have been studied.

Research paper thumbnail of 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... more 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

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

Fluid Phase Equilibria, 2006

... T showing the critical points of the pure components (■) [8], the (P, T) coordinate where exp... more ... T showing the critical points of the pure components (■) [8], the (P, T) coordinate where experimental data were taken (●) and binary critical loci: (—) experimental, references are given in Section 1; (– –) calculated using the procedure of Heidemann and Khalil [9] and the Peng ...

Research paper thumbnail of Alcohol-Assisted Deposition of Copper Films from Supercritical Carbon Dioxide

Chemistry of Materials, 2003

Device quality Cu films were deposited from solutions of bis(2,2,6,6-tetramethyl-3,5heptanedionat... more Device quality Cu films were deposited from solutions of bis(2,2,6,6-tetramethyl-3,5heptanedionate) copper(II) [Cu(tmhd) 2 ] in supercritical CO 2 (scCO 2 ) using alcohols as reducing agents in a cold wall, high-pressure reactor. At 270°C and pressures between 200 and 230 bar, deposition of copper by the reduction of Cu(tmhd) 2 with ethanol was selective for catalytic surfaces such as Co and Ni over the native oxide of Si wafers or TiN. At 300°C and above, depositions proceeded readily on all surfaces studied. Secondary ion mass spectroscopy indicated that Cu films are remarkably pure; carbon and oxygen contamination were on the order of 0.1% or less. Resistivities of the films were approximately 2 µΩ-cm. Reduction of Cu(thmd) 2 with primary alcohols including methanol, 1-propanol, and 1-butanol proceeded readily to yield copper films on Co substrates at 270°C. Sterically hindered alcohols were less effective at the same conditions. Deposition with 2-butanol required higher alcohol concentrations while attempted depositions with 2-propanol were not successful. Reaction mechanisms consistent with these observations are discussed. 10.