Standard Enthalpies Of Vaporization Research Articles

Measurement and Correlation Studies of the Saturated Vapor Pressure, Density, Refractive Indices, and Viscosity of Methyl 4-tert-Butylbenzoate

The saturated vapor pressure of methyl 4-tert-butylbenzoate was measured from (1.21 to 34.66) kPa in the temperature range from (398.3 to 492.4) K using a Swietoslawski-type ebulliometer. The experimental data were fitted with the Antoine and Clarke–Glew equations, which yielded Antoine parameters (A = 18.031, B = 7261.445, C = 8.857 K) and standard vaporization enthalpy (ΔlgHmθ (298.15 K) = 57.49 kJ mol–1), respectively. The critical properties were estimated on the basis of group contribution method. The acentric factor was calculated using these critical parameters and the saturated vapor pressures with the Antione equation. Furthermore, density, refractive indices, and viscosity of methyl 4-tert-butylbenzoate were also measured in the temperature range of 293.15 to 353.15 K. Temperature-dependence correlation equations for the density (second-order polynomial equation) and viscosity (Vogel–Tamman–Fulcher) were proposed. Modified Rackett equation was used with group contribution methods to predict the ...

Thermochemical properties of different 1-(R-phenyl)-1H-imidazoles

Phenyl substituted imidazoles exhibit versatile biological activity. 1-(R-phenyl)-1H-imidazoles with different functional groups R provide a convenient suitcase of molecules with tunable physicochemical properties adjustable for many practical applications. In this work, the absolute vapor pressures of 1-(R-phenyl)-1H-imidazoles (with R = H, 2-methyl, 4-methyl, 2-methoxy, 4-methoxy, 2-fluoro, 4-fluoro, 2-bromo and 4-bromo) at different temperatures have been measured by the transpiration method for the first time. The standard enthalpies of vaporization of these compounds were derived from the temperature dependencies of the vapor pressures. An internal consistency of the standard vaporization enthalpies has been proven by comparison with vaporization enthalpies of parent species, as well as by a group contribution method. A system of group-additivity values is suggested for a quick assessment of vaporization enthalpies of different 1-(R-phenyl)-1H-imidazoles. Gas-phase standard molar enthalpies of formation of 1-(R-phenyl)-1H-imidazoles have been calculated using the high-level quantum-chemical method G3MP2. The combination of experimentally determined standard vaporization enthalpies with the G3MP2 results allows for the prediction of the liquid-phase standard enthalpies of formation for the studied compounds.

Measurement and Correlation of Saturated Vapor Pressure of Ethylphenyldimethoxysilane and Ethylphenyldiethoxysilane

The saturated temperatures of ethylphenyldimethoxysilane (EPDMOS) and ethylphenyldiethoxysilane (EPDEOS) were determined using an inclined ebulliometer from 2.035 to 64.0 kPa. The experimental data were fitted with the Antoine and Clarke–Glew equations by a weighted least-squares regression method, which yielded Antoine parameters (A = 9.1280, B = 1590.18, C = −100.39 K and A = 9.1049, B = 1678.64, C = −102.84 K) and standard vaporization enthalpies (ΔlgHm0(298.15 K) = 62.52 kJ·mol–1 and ΔlgHm0(298.15 K) = 65.19 kJ·mol–1) for EPDMOS and EPDEOS, respectively. The critical properties of EPDMOS and EPDEOS, such as critical temperature, pressure, and volume, were estimated by the group contribution method introduced by Nannoolal et al. The acentric factors of EPDMOS and EPDEOS were estimated from these critical parameters and the reduced saturated vapor pressures calculated from either the Clarke–Glew equation or the Antoine equation.

Thermodynamic analysis of synthesis of cyclopentanol from cyclopentene and comparison with experimental data

Cyclopentanol is a very important chemical intermediate, which has been widely used in the chemical industry, and could be prepared from cyclopentene by two steps: an initial addition-esterification reaction of cyclopentene with acetic acid and the subsequent transesterification reaction with methanol. However, so far, no direct theoretical or experimental work has been reported on this process. In this work, we have carried out the thermodynamic calculation of the indirect process and also validated the thermodynamic prediction through experimental work. The liquid heat capacities of cyclopentanol and cyclopentyl acetate were estimated using the Ruzicka–Domalski group contribution method, the standard enthalpy of formation and standard entropy of gaseous cyclopentyl acetate by the Yoneda group contribution method, the standard vaporization enthalpy of cyclopentyl acetate by the Ducros group contribution method. The enthalpy changes, free energy changes, equilibrium constant and equilibrium conversion of the addition-esterification and transesterification reactions were calculated according to the principles of chemical thermodynamics in the temperature range from 273.15 to 373.15 K. The results showed that both the addition-esterification reaction and transesterification reaction were exothermic, the free energy changes increased with a rise on temperature, which indicated that low temperature was favorable for the reactions in the temperature range from 273.15 to 373.15 K. The optimal addition-esterification reaction conditions were a temperature range from 333.15 to 353.15 K, molar ratios of acetic acid to cyclopentene in the range from 2:1 to 3:1. For the transesterification reaction, the ideal temperature ranges from 323.15 to 343.15 K, with a molar ratio of methanol to cyclopentyl acetate in the range from 3:1 to 4:1. These thermodynamic calculation results for the addition-esterification reaction of cyclopentene and acetic acid experiments results are in good agreement with the experimental results.

A new method for the prediction of flash points for ternary miscible mixtures

The flash point is one of the most important physicochemical parameters used to characterize the fire and explosion hazard for flammable liquids. The flash points of ternary miscible mixtures with different components and compositions were measured in this study. Four model input parameters, being normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms and the stoichiometric concentration of the gas phase for mixtures, were employed and calculated based on the theory of vapor–liquid equilibrium. Both multiple linear regression (MLR) and multiple nonlinear regression (MNR) methods were applied to develop prediction models for the flash points of ternary miscible mixtures. The developed predictive models were validated using data measured experimentally as well as taking data on flash points of ternairy mixtures from the literature. Results showed that the obtained average absolute error of both the MLR and the MNR model for all the datasets were within the range of experimental error of flash point measurements. It is shown that the presented models can be effectively used to predict the flash points of ternary mixtures with only some common physicochemical parameters.

Thermodynamics of vaporization of 3-isopropylbiphenyl

Enthalpies of vaporization, $$ \Delta_{\text{l}}^{\text{g}} H_{\text{m}}^{\circ}, $$ were determined for 3-isopropylbiphenyl in the temperature range from 323 to 373 K. Measurements were performed on an isothermal heat conducting Calvet microcalorimeter according to the standard procedure with an estimated accuracy of 0.7 per cent. The average values of the standard enthalpies of vaporization were adjusted to 298.15 K. The latter has been used to calculate the standard formation enthalpy for 3-isopropylbiphenyl in the gaseous state. A second-order group additivity method has been applied to predict the vaporization enthalpies of some cyclic compounds. The contributions of tert-butyl, methyl, and isopropyl group to the vaporization enthalpies of the aromatic hydrocarbon derivatives are estimated.

Flash points measurements and prediction for binary miscible mixtures

Flash point is one of the most important parameters used to characterize the potential fire and explosion hazards for flammable liquids. In this study, flash points of twenty eight binary miscible mixtures comprised eighteen flammable pure components with different compositions were measured by using the closed cup apparatus. The obtained experimental data are further employed to develop simple and accurate models for predicting the flash points of binary miscible mixtures. Based on the vapor–liquid equilibrium theory, the normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms, and the stoichiometric concentration of the gas phase were selected as the dominant physicochemical parameters that were relevant to the overall flash point property of liquids. With these parameters for pure components as well as the compositions of mixtures, the new form of characteristic physicochemical parameters for mixtures were developed and used as the input parameters for the flash point prediction of mixtures. Both the modeling methods of multiple linear regression (MLR) and multiple nonlinear regression (MNR) were employed to model the possible quantitative relationships between the parameters for mixtures and the flash points of binary miscible mixtures. The resulted models showed satisfactory prediction ability, with the average absolute error for the external test set being 2.506 K for the MLR model and 2.537 K for the MNR model, respectively, both of which were within the range of the experimental error of FP measurements. Model validation was also performed to check the stability and predictivity of the presented models, and the results showed that both models were valid and predictive. The models were further compared to other previously published models. The results indicated the superiority of the presented models and revealed which can be effectively used to predict the FP of binary miscible mixtures, requiring only some common physicochemical parameters for the pure components other than any experimental flash point or flammability limit data as well as the use of the Le Chatelier law. This study can provide a simple, yet accurate way for engineering to predict the flash points of binary miscible mixtures as applied in the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes.

Characterization and Evaluation of Standard Enthalpy of Vaporization and Kinetic Studies of Volatile bis(<i>N</i>-ethyl-5-methyl-salicylaldimine)nickel(II) Complex

The bis(N-ethyl-5-methylsalicylaldimine)nickel(II) [Ni(5-me-saletN)2] complex was synthesized and characterized by elemental analyses, FT-IR, TG-DTA, mass spectrometry and vapour pressure measurement studies. The TG curve of the complex showed a single-step weight loss commencing from 490 K to nil residue at 600 K, without competing fragmentation step. The non-isothermal vaporization activation energy value determined by Coats-Redfern method yielded the value of 93.5 ± 7 kJmol–1. The dynamic TG run proved the complex to be completely volatile. And the equilibrium vapour pressure of the complex over the temperature range of 421 - 524 K, determined by the TG-based transpiration technique yielded the value of 94.2 ± 1.2 kJmol–1 for its standard enthalpy of vaporization . The entropy of vaporization was calculated from the intercept and found to be 249.4 ± 2.6 Jmol–1•K–1.

Measurement and Correlation of the Saturated Vapor Pressure of Vinyltriethoxysilane

The temperature of vapor saturation of vinyltriethoxysilane was determined in the range 331.30–420.15 K using an inclined ebulliometer at pressures ranging from 2.035 to 71.035 kPa. The experimental data were fitted with the Antoine equation and the Clarke–Glew equation and gave the Antoine parameters (A = 10.00572, B = 1983.331, C = −35.143 K) and standard vaporization enthalpy (\( \Delta_{l}^{g} H_{m}^{0} \) (298.15 K) = 48.29 kJ·mol−1). The critical properties of vinyltriethoxysilane, including the critical temperature, critical pressure and critical volume were estimated using the group contribution method introduced by Nannoolal et al. The acentric factor of vinyltriethoxysilane was estimated using these critical parameters and the saturated vapor pressure calculated using the Antoine equation.

Vaporization enthalpies of a series of the halogen-substituted fluorobenzenes

Vapor pressures of 2-, 3-, and 4-halogen-substituted fluorobenzenes (halogen=Cl, Br, and I) were measured by the transpiration method. Molar standard enthalpies of vaporization were calculated from temperature dependences of vapor pressures. New enthalpies of vaporization at 298K and those available from literature were tested for consistency by correlation gas-chromatography and evaluated by group-additivity method. Contributions to vaporization due to mutual interactions of halogens on the benzene ring were derived and recommended for prediction vaporization enthalpies of halogen-substituted aromatics.

Vapor pressures and vaporization enthalpies of 5-nonanone, linalool and 6-methyl-5-hepten-2-one. Data evaluation

Vapor pressures and vaporization enthalpies for 5-nonanone, linalool and 6-methyl-5-hepten-2-one seem to be in disarray. Temperature dependences of vapor pressures for these pure compounds were measured by using the static and the transpiration techniques. Molar standard enthalpies of vaporization at the reference temperature were derived. Available literature data on vapor pressures and vaporization enthalpies were collected and analyzed. The consistent data set for each compound was evaluated. Reliable thermodynamic parameters of vaporization were derived and used to test some commonly used predicting procedures.

Thermodynamic properties of furan-2-carboxylic and 3-(2-furyl)-2-propenoic acids

The standard enthalpies of combustion, formation, fusion, and sublimation of crystalline furan-2-carboxylic and 3-(2-furyl)-2-propenoic acids are determined by experimental methods and recalculated to 298 K. The possibility of using additive calculation schemes based on the principle of group contributions to calculate the standard enthalpies of vaporization and formation of substances with similar combinations of functional fragments in the gas phase is analyzed.

Vapor Pressure, Vaporization Enthalpy, Standard Enthalpy of Formation and Standard Entropy of n-Butyl Carbamate

The vapor pressures of n-butyl carbamate were measured in the temperature range from 372.37K to 479.27K and fitted with Antoine equation. The compressibility factor of the vapor was calculated with the Virial equation and the second virial coefficient was determined by the Vetere model. Then the standard enthalpy of vaporization for n-butyl carbamate was estimated. The heat capacity was measured for the solid state (299.39–324.2K) and liquid state (336.65–453.21K) by means of adiabatic calorimeter. The standard enthalpy of formation ΔfHθ[crystal (cr),298.15K] and standard entropy Sθ(crystal,298.15K) of the substance were calculated on the basis of the gas-phase standard enthalpy of formation ΔfHθ(g,298.15K) and gas-phase standard entropy Sθ(g,298.15K), which were estimated by the Benson method. The results are acceptable, validated by a thermochemical cycle.

Vaporization enthalpies of a series of the fluoro- and chloro-substituted methylbenzenes

Vapor pressures of fluorobenzene, chlorobenzene, 2-chloro-, 3-chloro-, and 4-chloro-methylbenzenes, 2-chloro-1,3-dimethylbenzene, 2,6-dichloro-1-methylbenzene were measured by the transpiration method. Molar standard enthalpies of vaporization at the reference temperature were calculated from temperature dependences of vapor pressures. Available literature data on halogenobenzenes were collected and evaluated by using correlation gas-chromatographic method. Simple group-additivity procedure was developed for estimation vaporization enthalpies of mono- and di-halogen-substituted benzenes.

Vapour pressures and enthalpies of vaporization of a series of the alkylbiphenyls

Vapour pressure of 2-methyl-biphenyl, 3-methyl-biphenyl, 4,4′-di-methyl-biphenyl, 3-iso-propyl-biphenyl, 3-tert-butyl-biphenyl and 4,4′-di-tert-butyl-biphenyl were measured by the transpiration method. Vapour pressure of 3-iso-propyl-biphenyl, 3-tert-butyl-biphenyl and 4-tert-butyl-biphenyl measured by ebulliometry. Equations for temperature dependences of the saturated vapour pressures were derived. Molar standard enthalpies of vaporization at the reference temperature were calculated from temperature dependences of vapour pressures. Additionally, enthalpies of vaporization of 3-iso-propyl-biphenyl were directly measured in the temperature range from 323 to 373K using an isothermal heat conducting Calvet microcalorimeter. The enthalpy of vaporization at the reference temperature 298K of 3-iso-propyl-biphenyl was calculated from the experimental temperature dependence of vaporization enthalpy. The Ambrose–Walton equation was applied for correlation and prediction of vapour pressures and vaporization enthalpies of alkyl-substituted biphenyls.

Measurements and correlation of saturated vapor pressures of diethoxy(methyl)(o-tolyl)silane, diethoxy(methyl)(m-tolyl)silane and diethoxy(methyl)(p-tolyl)silane

Vapor pressures, vaporization enthalpies and acentric factors for new compounds, diethoxy(methyl)(o-tolyl)silane, diethoxy(methyl)(m-tolyl)silane and diethoxy(methyl)(p-tolyl)silane were reported. The saturated temperature was measured using the inclined ebulliometer in the pressure range from 2000 to 61,000Pa and the normal boiling point was measured according to the Siwoloboff method. The standard vaporization enthalpy was derived from the temperature dependence of vapor pressure data. The critical parameters were estimated by an improved group contribution method and the acentric factors have been estimated from the Antoine equation and the experimental normal boiling points.

Vapor–Liquid Equilibria of Glycerol, 1,3-Propanediol, Glycerol + Water, and Glycerol + 1,3-Propanediol

Vapor–liquid equilibria of two compounds, glycerol (or 1,2,3-propanetriol) and 1,3-propanediol, and two mixtures, glycerol + water and glycerol + 1,3-propanediol, were determined using a static apparatus. The obtained pressure values range from 6 Pa to 45 kPa for the compounds and from (32 to 163) kPa for the mixtures. From the temperature dependence of the vapor pressures, the molar enthalpies of vaporization at the mean temperature of the experimental range were derived from the Clausius–Clapeyron equation. From these results the standard enthalpies of vaporization at T = 298.15 K were calculated. The experimental data of the mixtures were correlated using the nonrandom two-liquid (NRTL) model.

Experimental Vapor Pressures of Five Saturated Fatty Acid Ethyl Ester (FAEE) Components of Biodiesel

Vapor pressures of five saturated fatty acid ethyl esters (FAEEs), ethyl hexanoate (or ethyl caproate), ethyl octanoate (or ethyl caprylate), ethyl decanoate (or ethyl caprate), ethyl dodecanoate (or ethyl laurate), and ethyl tetradecanoate (or ethyl myristate), were measured at pressures from 1 Pa to 180 kPa and temperatures from (253.15 to 463.15) K using a static apparatus. These esters are a light fraction present in biodiesel derived from palmist oil and copra oil (Ballerini and Alazard-Toux, Les biocarburants; IFP Publications: Paris, 2006). The experimental data (P–T) were smoothed using the Antoine equation and compared with the available literature values. The molar enthalpies of vaporization at the mean temperature of the experimental range were derived from the Clausius–Clapeyron equation. From these results the standard enthalpies of vaporization at T = 298.15 K were calculated.

Vapor pressure, heat capacities, and phase transitions of tetrakis(tert-butoxy)hafnium

Vapor pressure, liquid heat capacities, and phase change enthalpies and temperatures for technologically important organometallic precursor tetrakis(tert-butoxy)hafnium are reported. The vapor pressure was measured using the static method in the temperature range from 280 to 308 K. The standard vaporization enthalpy was derived from the temperature dependence of vapor pressure data. The liquid heat capacities were determined by Calvet calorimetry in the temperature range from 294 to 350 K. The enthalpy and temperature of fusion were measured by differential scanning calorimetry. The present study significantly extends and updates the information on physico-chemical properties for this material.

Determination of standard enthalpy of vaporization and thermal decomposition reactions from derivative thermogravimetric (DTG) curves

The paper proposes the use of the derivative thermogravimetric (DTG) curve for the acquisition of equilibrium vapor pressure and dissociation pressure for the materials and derivation of their standard enthalpy of formation from single DTG curve recorded under optimum experimental conditions, such as heating rate and the sweep rate of the carrier gas passed over the sample. The vapor pressure and the standard enthalpy of sublimation (Δ subH ° 298.15) of CdI 2 and the dissociation pressure and the standard enthalpy of formation of CaCO 3 derived from their DTG curves are found to be in good agreement with the best assessed values reported in the literature.