Vapor Pressure Measurements Research Articles

Measurements of PvT Properties, Vapor Pressures, Saturated Densities, and Critical Parameters for trans-1,1,1,4,4,4-Hexafluoro-2-butene (R1336mzz(E))

Measurements of PvT properties, vapor pressures, saturated densities, and critical parameters were carried out for trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E); CF3CH═CHCF3). Thirty-nine PvT ...

Weaving a Network of Reliable Thermochemistry around Lignin Building Blocks: Methoxy-Phenols and Methoxy-Benzaldehydes

The methoxy-, hydroxy-, and carbonyl-substituted benzenes are the simplest fragments from the lignin separation feedstocks. Extensive experimental thermochemical studies of these compounds were carried out, including combustion calorimetry, vapor pressure measurements, and differential scanning calorimetry. We have collected available primary experimental results on enthalpies of formation and vapor pressures as well as on phase transitions, liquid–gas, liquid–solid, and crystal–liquid. These data were evaluated using empirical, semiempirical, and quantum chemical methods. The consistent sets of evaluated thermodynamic data were used to design the method for predicting enthalpies of vaporization and enthalpies of formation of di- and trisubstituted benzenes. It is expected that parameters and pairwise interactions will be transferable to predict the thermochemical properties of poly methoxy-substituted and poly hydroxy-substituted benzenes that appear in reaction products of lignin transformations in the value-adding chemicals and materials.

Composições de Solventes de Baixa Toxicidade para Formulação de Vernizes de Uso em Restauro

Varnishes consist basically of a resin and solvent. Aromatic solvents are widely used for varnish formulations, but they present considerable toxicity which requires their replacement. Two binary solvent systems with an oxygenated solvent (ethyl acetate or isoamyl acetate) and cyclohexane were studied as possible substitutes for xylene in varnish formulations. The toxicity of solvents was analyzed using data from the Globally Harmonized System of Classification and Labeling of Chemicals and the National Institute for Occupational Safety and Health. The solubility of Damar, Paraloid B72, Regalrez 1094, and Laropal K80 resins in these solvents was evaluated by Hansen and Teas Solubility Parameters, sigma profiles, and experimental method. Vapor pressure measurements were obtained from solvents and viscosity and gloss measurements from varnish formulations. The results indicated the potential of binary solvent systems as substitutes for xylene, but require further studies on their effects on pictorial materials on which they are applied.

From volatility to solubility: Thermodynamics of imidazolium-based ionic liquids containing chloride and bromide anions

Ionic liquids (ILs) are effectively used for tuning the composition and the morphology of nanoparticles or stabilizing agents for nanoparticles for catalytic dehydrogenation. Thermodynamic properties of ionic liquids, e.g. vapor pressures and vaporization enthalpies help optimise these processes. Vapor pressures and vaporization enthalpies of the series of 1-alkyl-3-methylimidazolium ionic liquids with chloride and bromide anions have been measured by using quartz-crystal microbalance (QCM). Possible thermal decomposition pathways of [C2C1Im][Br] during vaporization were analyzed by using high-level quantum-chemical methods. These theoretical results explained and supported the absence of decomposition in QCM experimental conditions. According to the measured vapor pressures the [CnC1Im][Cl] and [CnC1Im][Br] series are very suitable for catalytic applications, taking also into account their sufficient thermal stability at the level of 523–543 K. Solubility parameters of ILs and practically relevant solutes were assessed with help of experimental vaporization enthalpies.

Vapor-liquid equilibrium, liquid density and excess enthalpy of the carbon dioxide+acetone mixture: Experimental measurements and correlations

ABSTRACT New vapor-liquid equilibrium data of the CO2+acetone mixture were determined from vapor pressure measurements using a static and synthetic method from (283.15 to 383.15) K and a composition range from (4 to 85) % in CO2 mole fraction. The fugacity coefficients approach with the Soave-Redlich-Kwong equation of state was used to calculate the composition of the phases and the binary interaction parameter. The average relative deviation between the experimental and calculated pressure values was 0.14 % and the maximum deviation was 5.0 %. Carbon dioxide shows total miscibility and good solubility in acetone in the conditions studied. The liquid density of the mixture was measured with a vibrating-tube densimeter from (283.15 to 353.15) K, at sufficient pressure to guarantee the liquid state, and a composition range from (6 to 82) % in CO2 mole fraction. The liquid density values calculated by the equation of state with the Peneloux correction were compared with the experimental values and agreement was good with a maximum deviation of 7 % and an average deviation of 0.7 %. The excess molar enthalpies were measured by a flow-calorimetric technique at (283.30 and 298.30) K and pressures from (9.00 to 14.00) MPa. Finally, the experimental data on vapor pressure, density, and excess molar enthalpy were fitted using empirical equations, and the first two were compared with data reported in the literature. Average deviations were between (0.07 and 30) % in the vapor-liquid equilibrium, and between (0.51 and 8.8) % in the density.

Weaving a web of reliable thermochemistry around lignin building blocks: Vanillin and its isomers

Vanillin and its isomers are a promising biobased building blocks for monomer synthesis. Extensive experimental thermochemical studies of these compounds have been carried out, including combustion calorimetry, vapor pressure measurements, and differential scanning calorimetry. We have collected available primary experimental results on enthalpies of formation and vapour pressures as well as on phase transitions liquid–gas, liquid–solid, crystal-liquid. These data were evaluated using empirical, semi-empirical and quantum chemical methods. The consistent sets of evaluated thermodynamic data were used to design the method for predicting enthalpies of vaporization and enthalpies of formation of di- and tri-substituted benzenes. It is expected that parameters and pairwise interactions will be transferable to predict the thermochemical properties of poly-methoxy-substituted and poly-hydroxy-substituted benzenes that appear in reaction products of lignin transformations in the value-adding chemicals and materials.

Rapid Vapor-Collection Method for Vapor Pressure Measurements of Low-Volatility Compounds.

Dynamic vapor microextraction (DVME) is a new method that enables rapid vapor pressure measurements on large molecules with state-of-the-art measurement uncertainty for vapor pressures near 1 Pa. Four key features of DVME that allow for the rapid collection of vapor samples under thermodynamic conditions are (1) the use of a miniature vapor-equilibration vessel (the "saturator") to minimize the temperature gradients and internal volume, (2) the use of a capillary vapor trap to minimize the internal volume, (3) the use of helium carrier gas to minimize nonideal mixture behavior, and (4) the direct measurement of pressure inside the saturator to accurately account for overpressure caused by viscous flow. The performance of DVME was validated with vapor pressure measurements of n-eicosane (C20H42) at temperatures from 344 to 374 K. A thorough uncertainty analysis indicated a relative standard uncertainty of 2.03-2.82% for measurements in this temperature range. The measurements were compared to a reference correlation for the vapor pressures of n-alkanes; the deviation of the measurements from the correlation was ≤2.85%. The enthalpy of vaporization of n-eicosane at 359.0 K was calculated to be ΔvapH = 91.27 ± 0.28 kJ/mol compared to ΔvapH(corr) = 91.44 kJ/mol for the reference correlation. Total measurement periods as short as 15 min (3 min of thermal equilibration plus 12 min of carrier gas flow) were shown to be sufficient for high-quality vapor pressure measurements at 364 K.

Vapor-Pressure Measurement of Ternary System CaCl2 + [Emim]Br + H2O, CaCl2 + [Emim]Cl + H2O, CaCl2 + [Emim]Ac + H2O, and CaCl2 + [Emim]NO3 + H2O

Calcium chloride (CaCl2) aqueous solution as a liquid desiccant has the disadvantage of low vapor pressure and easy crystallization. Ionic liquids (ILs) such as [Emim]Cl, [Emim]Ac, and [Emim]Br have been verified to have a good ability to reduce the vapor pressure. In this paper, the vapor pressures of four kinds of CaCl2 + ILs + H2O were measured, which were CaCl2 + [Emim]Br + H2O (mass ratio CaCl2/[Emim]Br = 2:1) at temperatures of between 311.10 and 394.45 K, CaCl2 + [Emim]Cl + H2O (mass ratio CaCl2/[Emim]Cl = 2:1) at temperatures of between 306.58 and 393.89 K, CaCl2 + [Emim]Ac + H2O (mass ratio CaCl2/[Emim]Ac = 2:1) at temperatures of between 304.93 and 382.71 K, and CaCl2 + [Emim]NO3 + H2O (mass ratio CaCl2/[Emim]NO3 = 2:1) at temperatures of between 312.46 and 391.80 K, with the mass fraction of solute ranging from 0.2 to 0.5. The Antonie-type equation was used to fit the measured results. The average absolute relative deviation (AARD %) values of the measured vapor pressures and calculated vapor pressures were 0.52, 0.40, 0.33, and 0.27%, which showed good consistency and accuracy. Comparing the vapor pressures of the different solutions at the same concentration, the following order of the four anions with the ability to reduce the vapor pressure of CaCl2 + H2O can be drawn at a mass fraction of 0.4: Br– > Cl– > NO3– > Ac–.

Testing a Paul trap through determining the evaporation rate of levitated single semi-volatile organic droplets.

Rigorous knowledge of the optical fingerprint of droplets is imperative for the understanding of complex aerosol processes. Here, a Paul trap is operated to store single semi-volatile organic droplets in air. The droplets are illuminated with a green laser and the elastic scattering is collected on a CMOS camera. The setup provides excellent performance in terms of confinement and stability, allowing us to detect size changes of the order of few nanometres. The stability also allows us to measure vapour pressures with remarkable reproducibility. This approach supplies a robust method for the optical interrogation in the sub-micron range.

Dynamic and reversible shape response of red blood cells in synthetic liquid crystals

Mammalian cells are soft, and correct functioning requires that cells undergo dynamic shape changes in vivo. Although a range of diseases are associated with stiffening of red blood cells (RBCs; e.g., sickle cell anemia or malaria), the mechanical properties and thus shape responses of cells to complex viscoelastic environments are poorly understood. We use vapor pressure measurements to identify aqueous liquid crystals (LCs) that are in osmotic equilibrium with RBCs and explore mechanical coupling between RBCs and LCs. When transferred from an isotropic aqueous phase into a LC, RBCs exhibit complex yet reversible shape transformations, from initially biconcave disks to elongated and folded geometries with noncircular cross-sections. Importantly, whereas the shapes of RBCs are similar in isotropic fluids, when strained by LC, a large variance in shape response is measured, thus unmasking cell-to-cell variation in mechanical properties. Numerical modeling of LC and cell mechanics reveals that RBC shape responses occur at constant cell membrane area but with membrane shear moduli that vary between cells from 2 to 16 × 10-6 N/m. Temperature-dependent LC elasticity permits continuous tuning of RBC strains, and chemical cross-linking of RBCs, a model for diseased cells, leads to striking changes in shape responses of the RBCs. Overall, these results provide insight into the coupling of strain between soft mammalian cells and synthetic LCs, and hint at new methods for rapidly characterizing mechanical properties of single mammalian cells in a population and thus cell-to-cell variance.

Reply to “Comment on ‘Measurements of Vapor Pressures of Aqueous Solutions in the NaCl–KCl–H2O System from 493.15 to 693.25 K in a Fused Silica Capillary High-Pressure Optical Cell’”

Reply to “Comment on ‘Measurements of Vapor Pressures of Aqueous Solutions in the NaCl–KCl–H₂O System from 493.15 to 693.25 K in a Fused Silica Capillary High-Pressure Optical Cell’”

Comment on “Measurements of Vapor Pressures of Aqueous Solutions in the NaCl–KCl–H2O System from 493.15 to 693.25 K in a Fused Silica Capillary High-Pressure Optical Cell”

Comment on “Measurements of Vapor Pressures of Aqueous Solutions in the NaCl–KCl–H₂O System from 493.15 to 693.25 K in a Fused Silica Capillary High-Pressure Optical Cell”

Temperature and concentration dependencies of the saturated vapor pressure for the solutions of nanoparticles AL2O3 in isopropanol and fullerenes C60 in o-xylene

An investigation of the saturated vapor pressure for the solutions of Al2O3 nanoparticles in the isopropanol and fullerenes C60 in o-xylene is presented in this paper. An average size of Al2O3 nanoparticles was measured by transmission electron microscopy (TEM) and found to be equal 27.3 nm whereas a hydrodynamic diameter for the same nanoparticles in isopropanol does not exceed 50 nm. The measurement of the saturated vapor pressure is conducted using a static method in a temperature range from 300 K to 350 K for the nanofluids with the mass concentrations 0–9.55% of the nanoparticles Al2O3 in isopropanol and the mass concentration 0–0.55% of fullerenes C60 in o-xylene.An analysis revealed that the total uncertainty of the measured saturated vapor pressure for the nanofluids does not exceed 242 Pa and 559 Pa for the solutions of the isopropanol/Al2O3 and o-xylene/C60 respectively. The temperature and concentration dependences of the saturated vapor pressure for the nanofluids have been discussed. The latent heat of evaporation was calculated and examined using experimental information on the saturated vapor pressure of the nanofluids. It was proven that additives of the nanoparticles Al2O3 and fullerenes C60 could both increase and decrease the saturated vapor pressure and the latent heat of evaporation of the isopropanol and o-xylene. We also discussed a hypothesis that explains changes in the saturated vapor pressure and the latent heat of evaporation of the nanofluids not only by the temperature and concentration of the nanoparticles in the nanofluids but also through structural changes in the base fluids due to a presence of Al2O3 and C60 additives.

Ionic liquids alkyl-imidazolium thiocyanates: Comprehensive thermochemical study

Ionic liquids containing imidazolium cation and thiocyanate anion are attracting considerable attention for industrial applications due to low viscosities, low melting points and good conductivity. A comprehensive thermodynamic study of [Cnmim][SCN] series with (n = 2, 4, and 6) was performed in this paper. Vapor pressures were measured by using the quartz-crystal microbalance (QCM). Vaporization enthalpies have been derived by using thermogravimetry and QCM and adjusted to the reference temperature 298.15 K. An absence of possible thermal decomposition during vapor pressure measurements was monitored by the ATR-IR spectroscopy. The liquid phase standard molar enthalpy of formation of [C4mim][SCN] was measured by using combustion calorimetry, combined with the evaluated vaporization enthalpy to get gas-phase standard molar enthalpy of formation. The latter experimental value was in close agreement with theoretical gas-phase molar enthalpy of formation of [C4mim][SCN], calculated by the high-level quantum chemical method G3MP2. These experimental and theoretical results were applied for estimation of aqueous standard molar enthalpies of formation of [Cnmim] cations, as well as for calculation of solubilities of practically relevant solutes in of [Cnmim][SCN] series of ionic liquids.

Experimental measurement and modelling of vapor-liquid equilibrium for 3,3,3- Trifluoropropene (R1243zf) and trans-1,3,3,3-Tetrafluoropropene (R1234ze(E)) binary system

• Experimental measurement of VLE data for R1243zf + R1234ze(E) by a static analytical method. • The R1243zf + R1234ze(E) system is a zeotropic system within 283.15 to 323.14 K. • Experimental data show good agreement with the predicted results of PR-MC-vdW and PR-MC-MHV2 models. The environmental performance becomes the critical factor of the selection of refrigerant. 3,3,3-trifluoropropene (R1243zf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) are environmental friendly candidates to replace R134a. Whereas, in the consideration of environmental factor, safety, and energetic efficiency at the same time, none of the pure refrigerants has been proved to be a suitable solution. Mixed refrigerants provide an approach to this problem because the characteristics of refrigerant blends can be optimized for particular applications in the way pure component refrigerant alone cannot be. The purpose of this work is to explore an R1243zf/R1234ze(E) blend which can be possibly used as a long-term alternative to replace hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). We report the measurements of saturated vapor pressures of R1234ze(E) and R1243zf ranging from 273.17 to 353.13 K, and isothermal vapor-liquid equilibrium of R1243zf + R1234ze(E) systems from 283.15 to 323.14 K. The measurements are performed by static-analytic type apparatus coupled with two electromagnetic capillary samplers (ROLSI®, patent of Armines). The experimental data are correlated by the Peng-Robinson (PR) equation of state (EoS) associated with Mathias-Copeman (MC) alpha function and classical mixing rules. For the comparison of conventional mixing rules and excess free energy ( G E ) mixing rules models, classic van der Waals one fluid mixing rules and modified Huron-Vidal second-order (MHV2) mixing rules are employed respectively to the correlation of experimental VLE data. The modeling results are in good agreement with the measured data, while the PRMC-MHV2 model exhibits better performance in VLE prediction.

Thermodynamic study of acetamides

An extensive thermodynamic study of acetamide and its derivatives, N-methylacetamide, and N,N-dimethylacetamide, is presented in this work. Phase behavior was investigated by a heat-flux differential scanning calorimetry (DSC) from 183 K confirming the previously reported polymorphism of acetamide and N-methylacetamide. Two different polymorphic forms of N,N-dimethylacetamide were observed for the first time. Two static apparatus were employed for the vapor pressure measurements over a wide temperature range focusing on the ambient temperatures. Vapor pressures of metastable phase of acetamide were determined for the first time. Heat capacities of liquid and crystalline phases were measured by Tian-Calvet calorimetry at temperatures between 265 and 355 K. The ideal-gas thermodynamic properties were calculated using a combination of the density functional theory (DFT) and statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental data for phase behavior, vapor pressures, and condensed phase heat capacities and calculated ideal-gas heat capacities are treated together to ensure overall thermodynamic consistency of the results. The observed trends in the thermodynamic properties of liquid phase were rationalized based on molecular interactions.

On measuring techniques of pore pressure in concrete at elevated temperature

Entrapment of water vapor pressure is a major reason leading to explosive spalling of concrete subjected to elevated temperature. However, the measurement techniques for pore pressure inside concrete specimens were not consistent from different studies. This paper presents an extensive review of pore pressure measurement techniques first. Three main differences (viz., medium to transfer pore pressure, type of pressure gage head, and placement of thermocouples) were found in previous studies. An experimental program comprising twelve pore pressure gages was designed to evaluate effectiveness of all the combinations of factors by conducting one-dimensional heating test of concrete slabs. The test results showed that heat transfer properties and temperature measurements were not influenced by the different measurement techniques. Filling steel tubes with rods or leaving the tubes empty would impair build-up of vapor pressure. On the contrary, filling it with silicon oil will create extra hydraulic pressure due to thermal expansion of the oil itself. The use of sintered metal as a gage head could compensate additional pressure by introducing free volume and collect pore pressure evenly. Placing thermocouples outside the steel tube would not compromise accuracy of temperature measurement and the complexity of the measurement system could be greatly reduced. At last, two requirements are proposed for correctly measuring vapor pressure: (1) expansion of oil must be compensated by free volume; (2) free volume should not interfere with moisture accumulation and vapor pressure build-up.

Mechanistic Understanding of Competitive Destabilization of Carbamazepine Cocrystals under Solvent Free Conditions

Mechanistic understanding of competitive destabilization of carbamazepine:nicotinamide and carbamazepine:saccharin cocrystals under solvent free conditions has been investigated. The crystal phase transformations were monitored using hot stage microscopy, variable-temperature powder X-ray diffraction, and sublimation experiments. The destabilization of the two cocrystals occurs via two distinct mechanisms: vapor and eutectic phase formations. Vapor pressure measurements and thermodynamic calculations using fusion and sublimation enthalpies were in good agreement with experimental findings. The mechanistic understanding is important to maintain the stability of cocrystals during solvent free green manufacturing.

Thermochemistry of the lignin broken bits

The hydroxy- and methoxy substituted benzaldehydes are the simplest broken bits from the lignin valorization technologies. Comprehensive thermochemical study of these compounds was performed including vapour pressure measurements, combustion and differential scanning calorimetry. A large number of primary experimental results on vapour pressures, phase transitions, and enthalpies of formation have been collected from the literature and evaluated with help of empirical and quantum-chemical methods. The consistent sets of thermodynamic data were utilised for developing the simple GA method for prediction of enthalpies of vaporization and enthalpies of formation of di-substituted benzenes in the gas phase. Parameters of GA procedures are expected to be transferable for prediction of thermochemical properties of poly-hydroxy and poly-methoxy substituted benzenes appearing in reaction products during of the lignin valorization.

A combined thermodynamic and crystallographic study of 1,3-diisopropylnaphthalene

The thermodynamic properties and phase behaviour of 1,3-diisopropylnaphthalene were studied for the first time using static vapour pressure measurements, Tian-Calvet calorimetry, and differential scanning calorimetry (DSC). Polymorphic behaviour of the compound was detected and studied in detail by combination of DSC and variable-temperature X-ray powder diffraction. The crystal structure of the disordered metastable phase was obtained using a single-crystal X-ray diffraction for the first time. The experimental study was supplemented by calculating thermodynamic properties in the ideal-gas state using a combination of statistical thermodynamics and quantum-chemical calculations. Recommended vapour pressure equation was derived by simultaneous treatment of vapour pressures, experimental heat capacities of the condensed phases, calculated ideal-gas heat capacities, and temperature and enthalpy of fusion, assuring their mutual thermodynamic consistency.