Vapor Pressure Correlation Research Articles

Vapor pressure and thermal properties of heavy oil distillation cuts

The vapor pressure, liquid heat capacity, and heat of combustion were measured for distillation cuts obtained from several heavy oils using a deep vacuum fractionation apparatus. Derivatives of fitted vapor pressure equations were used to determine heats of vaporization based on the Clausius–Clapeyron equation. Existing correlations were evaluated against these data and new correlations were proposed including a generalized Cox vapor pressure correlation (as a function of molecular weight and boiling point temperature) and a correlation for the heat of vaporization based on the generalized Cox equation. Two versions of Tsonopoulos correlations were developed for liquid heat capacity: one using the Watson Factor and another using the H/C ratio. In general, the new correlations improved the prediction of heavy cut properties compared with correlations from the literature and performed similarly for light cuts (both for the development dataset and for independent test datasets). In addition, the heats of combustion of some cuts were measured and used to validate the elemental analysis based correlations from the literature.

Vapor pressure and Flory-Huggins interaction parameters in binary polymeric solutions

This communication reports two unique relationships for (1) Flory-Huggins interaction parameter (χ) and (2) vapor pressure of solvent (P), which explicitly show their composition dependency. There is no empirical constant in the proposed relationships, and no trial and error and/or data-fitting optimization is required for determination and/or correlation of vapor pressure and Flory-Huggins interaction parameter. A straightforward computational technique for implementation of models is provided. For a number of systems, the calculated data have been compared and evaluated against experimental ones and the reliability and accuracy of proposed relationships was assured. IARD (%) values on the order of 0.05 demonstrate the accuracy of the proposed method.

An Efficient Method for Correlation of Vapor Pressure of Gaseous Compounds Containing C-H-O

Prediction of available vapor pressure data in the case of compounds containing C-H-O led to derivations and recommendations of standard equations for this property. The accuracy of vapor pressure estimations is essential to use as a basis to calculate acentric factor, thermal and equilibrium properties. In this study, according to the previous work, an accurate equation to estimate vapor pressure is developed to 130 pure C-H-O compounds as a function of reduced temperature and critical pressure. With new proposed equation, vapor pressures have been calculated in comparison with experimental data reported in literature for 2019 data points of 130 pure C-H-O compounds and the overall average absolute relative deviation is only 0.333%. The accuracy of the developed equation has been compared to that of Antoine and other mostly used equations. Our comparisons show that new equation leads to more accurate results than those of literature methods.

Recommended vapor pressures for aniline, nitromethane, 2-aminoethanol, and 1-methyl-2-pyrrolidone

Recommended vapor pressure data for important industrial solvents, aniline (CAS RN: 62-53-3), nitromethane (CAS RN: 75-52-5), 1-methyl-2-pyrrolidone (CAS RN: 872-50-4), and 2-aminoethanol (CAS RN: 141-43-5), were developed by the simultaneous correlation of vapor pressure and related thermal data (heat capacities of condensed phases, ideal-gas heat capacities and calorimetrically determined enthalpies of vaporization). For 1-methyl-2-pyrrolidone and 2-aminoethanol, new vapor pressure data were obtained using the static method and new liquid phase heat capacities were determined by Tian–Calvet calorimetry while for remaining compounds relevant thermodynamic data were taken from the literature. The thermodynamic properties in the ideal gaseous state were calculated using the methods of statistical thermodynamics based on experimental as well as calculated fundamental vibrational frequencies and molecular structure data. Comparisons with literature values are shown for all measured and derived properties.

Removal efficiencies for 136 tetra- through octa-chlorinated dibenzo-p-dioxins and dibenzofuran congeners with activated carbons.

In this study, the removal efficiency of 136 tetra- to octa-chlorinated dibenzo-p-dioxin (CDD)/furan (F) congeners from a nitrogen + oxygen carrier gas was studied using a laboratory-scale, fixed bed adsorption system. Two kinds of activated carbon with dissimilar pore structures were used as adsorbents. The total concentration of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in the source gas was 541 ng/Nm(3) and that of the 17 toxic 2,3,7,8-substituted PCDD/Fs 96.35 ng/Nm(3), accounting for 17.8% of the total original weight amount. Their toxic equivalent quantity (TEQ) was 8.31 ng I-TEQ/Nm(3). For both activated carbons, the removal efficiencies of the ten PCDD/F homologue groups rise with chlorine substitution number. The removal efficiencies vary approximately as a power function of vapor pressure (correlation coefficients r(2) = 0.93 and 0.81, respectively). Competitive adsorption and desorption occur as adsorption time went on, causing elution of the lower chlorinated homologues, i.e. tetra-CDD/F and Penta-CDD/F congeners. In addition, there are significantly different concentration distributions for isomers in the same homologue groups. However, their removal efficiencies have weak correlation with their initial concentrations. The correlation coefficients are from -0.47 to 0.32 and from -0.57 to 0.46 respectively for the two kinds of activated carbons.

Measurement, correlation, and prediction of vapor pressure for binary and ternary systems containing an alkylsulfate-based ionic liquid

Vapor pressure data for water, 1-propanol, 2-propanol, as well as the mixtures of {water+1-propanol} and {water+2-propanol}, were measured by a quasi-static ebulliometric method, in the presence of an alkylsulfate-based IL, namely, 1-ethyl-3-methylimidazolium methylsulfate ([EMIM][MS]) or 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ES]). The experimental vapor pressure data for binary systems containing IL were correlated by NRTL model with an overall relative root mean square deviation (rRMSD) of 0.0053, and the obtained binary NRTL parameters were employed to predict the vapor pressure for two ternary systems with an overall rRMSD of 0.0196. In addition, isobaric vapor–liquid equilibria were predicted for the ternary systems containing [EMIM][MS], [EMIM][ES], 1,3-dimethylimidazolium methylsulfate ([MMIM][MS]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][OTf], respectively, with IL mole fraction of 0.05, 0.15, and 0.25 at 101.325kPa. It was found that the addition of IL can enhance the relative volatility of propanol to water, and the separation ability follows the order of [MMIM][MS]>[EMIM][MS]>[EMIM][ES]>[EMIM][BF4]>[EMIM][OTf], which was further explained at electronic level with quantum chemical calculation. Therefore, the azeotropic mixtures of {water+1-propanol}, and {water+2-propanol} might be separated effectively by the addition of the alkylsulfate-based ILs in extractive distillation.

Measurements of PρT properties, vapor pressures, saturated densities, and critical parameters for R 1234ze(Z) and R 245fa

Pressure-density-temperature (PρT) properties, vapor pressures, and saturated liquid and vapor densities for refrigerants R 1234ze(Z) (cis-1,3,3,3-tetrafluoroprop-1-ene; CF3CHCHF) and R 245fa (1,1,1,3,3-pentafluoropropane; C3H3F5) were measured with two types of isochoric methods. Pressure was measured with a digital quartz pressure transducer. Temperature was measured with 25 Ω standard platinum resistance thermometer on the ITS-90 temperature scale. Density was calculated from the mass of sample and the inner volume of pressure vessel. By using the present vapor pressure data, new vapor pressure correlations for R 1234ze(Z) and R 245fa have been formulated. In addition, the critical temperature Tc, critical density ρc, and critical pressure Pc were directly determined on the basis of direct observation of the meniscus disappearance.

Measurement, correlation, and prediction of vapor pressure for binary and ternary systems containing an ionic liquid 1,3-dimethylimidazolium methylsulfate

Vapor pressure data for water, ethanol, 1-propanol, and 2-propanol, as well as the mixtures of {water+1-propanol} and {water+2-propanol}, were experimentally measured in the presence of an ionic liquid (IL) 1,3-dimethylimidazolium methylsulfate ([MMIM][MS]) at varying IL-contents and temperatures using a quasi-static ebulliometric method. The experimental vapor pressure data for binary systems containing IL were correlated using NRTL model with an overall relative root mean square deviation (rRMSD) of 0.0055, and the obtained binary NRTL parameters were employed to predict the vapor pressure for two ternary systems with an overall rRMSD less than 0.0234. Moreover, the inter-molecular interaction between [MMIM][MS] and volatile solvent was assessed theoretically in terms of the predicted activity coefficients of solvents for binary systems and quantum chemical calculations with polarizable continuum model. Finally, isobaric VLE data were predicted for three ternary systems containing [MMIM][MS] with IL mole fraction of 0.05, 0.15, and 0.25 at 101.325kPa, respectively. The results indicate that [MMIM][MS] might be applied as a promising entrainer to separate the azeotropic mixtures of {water+ethanol}, {water+1-propanol}, and {water+2-propanol} by extractive distillation.

English

This work presents two developments in Antoine vapor pressure correlation: (1) Generalization of the correlation using the principle of corresponding state; (2) Prediction of the Antoine coefficients form molecular weight. The coefficients of the generalized correlation are correlated to molecular weight (r2=0.99) for the group of normal alkanes (C1 to C20). The method is validated using experimental data obtained from reliable literature covering 169 vapor pressure data points covering 11 fluids. The method reproduced the experimental data with a grand absolute average percent deviation (AAPD) of 2.93 while the original Antoine correlation reproduced the same data with 1.90. The method provides a simple procedure for the prediction of Antoine coefficients. On the other hand, the developments, significantly reduces the number of coefficients of C1 to C20 from (3×20=) 60 to (3×3=) 9. This saves the labor work needed for storage and processing of the large number of coefficients values. Key words: Antoine coefficients, normal alkanes, vapor pressure.

Deep-Vacuum Fractionation of Heavy Oil and Bitumen, Part II: Interconversion Method

In Part I of this two-part series, a recently developed deep-vacuum fractionation apparatus (DVFA-II) was standardized and used to fractionate heavy oil samples by boiling point at a pressure below 1 Pa. Up to 50 wt % of a Western Canadian bitumen was distilled, compared with 26 wt % distilled with conventional spinning band distillation (SBD), and eight cuts were recovered. Here, an interconversion technique is developed to determine the normal boiling point (NBP) curve from the low-pressure boiling point data collected using DVFA-II. A simultaneous correlation of vapor pressure and heat capacity data based on the Clapeyron equation was used to determine the NBP of each cut. Of the vapor pressure correlations considered, the three-parameter Cox equation best fit the data, with average absolute relative deviations within 7% and 1% for the vapor pressure and heat capacity data (ΔC′exp), respectively. The estimated maximum and minimum errors in the calculated NBPs were 2.2% and −2.5% (8 and 9 K), respective...

Measurement and correlation of vapour pressures of pyridine and thiophene with [EMIM][SCN] ionic liquid

In this work (vapour+liquid) equilibrium (VLE) measurements were performed on binary systems of the ionic liquid 1-ethyl-3-methylimidazolium thiocynate [EMIM][SCN] with thiophene or pyridine at pressures close to the atmospheric pressure using a static device at temperatures between 273K and 363K. Experimental data were correlated by the PC-SAFT EoS. The binary interaction parameters kij were optimised on experimental VLE data. The results obtained for the two binary mixtures studied in this paper indicate that the PC-SAFT EoS can be used to represent systems containing ionic liquids.

Measurements and Correlations of cis-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze(Z)) Saturation Pressure

cis-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze(Z)) is being investigated as a working fluid possessing a low global warming potential (GWP) for high-temperature heat pumping applications, organic Rankine cycles, and air-conditioning and refrigeration applications, and as a potential solvent, propellant, and foam blowing agent. Its GWP is less than one. The open literature contains a total of 79 vapor–pressure data from three sources and the critical state properties from a single source. The current paper provides 64 vapor–pressure data from two different laboratories over the temperature range from 238.13 K to 372.61 K. These data are regressed using Wagner and extended Antoine vapor–pressure correlations and then compared to the existing open literature data and correlations. The normal-boiling-point temperature and acentric factor for R1234ze(Z) are estimated to be 282.73 K and 0.3257, respectively.

High‐accuracy measurements of the vapor pressure of ice referenced to the triple point

AbstractThe vapor pressure of hexagonal (Ih) water ice was measured over the temperature range 175 K to 253.4 K and referenced to the value at the triple point of water. This experiment combined a highly accurate humidity generation system containing an ice‐coated saturator (millikelvin‐level temperature control) to provide humidified streams of nitrogen to a cavity‐enhanced laser absorption spectrometer. The measured ice vapor pressures had relative standard uncertainties ranging from 0.4% to 0.7% over the entire temperature range. We demonstrate that these measurements validate thermodynamic correlations for ice vapor pressure based on integration of the Clapeyron equation. Moreover, they also indicate that some commonly used vapor pressure correlations are inaccurate and should be avoided.

Recommended sublimation pressure and enthalpy of benzene

Recommended vapor pressures of solid benzene (CAS Registry Number: 71-43-2) which are consistent with thermodynamically related crystalline and ideal-gas heat capacities as well as with properties of the liquid phase at the triple point temperature (vapor pressure, enthalpy of vaporization) were established. The recommended data were developed by a multi-property simultaneous correlation of vapor pressures and related thermal data. Vapor pressures measured in this work using the static method in the temperature range from 233K to 260K, covering pressure range from 99Pa to 1230Pa, were included in the simultaneous correlation. The enthalpy of sublimation was established with uncertainty significantly lower than the previously recommended values.

Heat capacities of selected chlorohydrocarbons

Isobaric heat capacities in the liquid phase of seven selected halogenated hydrocarbons (1,1,2-trichloroethylene, (Z)- and (E)-1,2-dichloroethylene, 1,1-dichloropropane, 1,2-dichloropropane, 2,2-dichloropropane, and (trichloromethyl)benzene) were measured by using a highly sensitive Tian–Calvet calorimeter in the temperature range from 260K to 340K. Due to high volatility of the studied compounds the correction for sample evaporation was applied. Vapor pressure equations required for applying this correction were iteratively developed by simultaneous correlation of the literature vapor pressures and related thermal data (calorimetrically obtained vaporization enthalpies, heat capacities in the liquid and ideal-gas state). The thermodynamic properties in the ideal gaseous state were calculated using the methods of statistical thermodynamics based on fundamental vibrational frequencies and molecular structure data calculated by DFT at the B3LYP/6-311+G(2df,p) level of theory. Data on liquid heat capacities obtained in this work were merged with available literature data, critically assessed and correlated as a function of temperature.

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.

Spectroscopic measurement of the vapour pressure of ice

We present a laser absorption technique to measure the saturation vapour pressure of hexagonal ice. This method is referenced to the triple-point state of water and uses frequency-stabilized cavity ring-down spectroscopy to probe four rotation-vibration transitions of at wavenumbers near 7180 cm(-1). Laser measurements are made at the output of a temperature-regulated standard humidity generator, which contains ice. The dynamic range of the technique is extended by measuring the relative intensities of three weak/strong transition pairs at fixed ice temperature and humidity concentration. Our results agree with a widely used thermodynamically derived ice vapour pressure correlation over the temperature range 0°C to -70°C to within 0.35 per cent.

Atmospheric polycyclic aromatic hydrocarbons in an industrialized city, Kocaeli, Turkey: study of seasonal variations, influence of meteorological parameters and health risk estimation

Ambient gas and particle phase samples were collected during two sampling periods from a residential area of an industrialized city, Kocaeli, Turkey. The sampling occurred during winter months when structures were being heated, and summer months when structures were not being heated. Σ(13)PAH (gas + particle) concentrations ranged between 6.2 ng m(-3) (DahA) and 98.6 ng m(-3) (Phe) in the heating (winter) period and 3.0 ng m(-3) (BaA) and 35.1 ng m(-3) (Phe) in the non-heating (summer) period. Phe, Flt and Pyr were found to be at high concentrations in both sampling periods. Winter time to summer time concentration ratios for individual ambient PAH concentration ratios ranged between 1.2 (DahA) and 17.5 (Flu), indicating the effect of the emissions from residential heating on measured concentrations of PAHs, but great industrial plants and the only incinerator facility of Turkey are other important pollution sources around the city. Temperature dependence of gas phase PAHs was investigated using the Clausius-Clapeyron equation. A high slope obtained (5069.7) indicated the effect of the local sources on measured gas phase PAHs. Correlation of the supercooled vapor pressure (P) with the gas particle partitioning coefficient (K(p)) and particle phase fraction was also evaluated. The relationship between the meteorological parameters and individual PAH (gas + particle) concentrations was investigated further by multiple linear regression analysis. It was found that the temperature had a significant effect on all of the measured PAH concentrations, while the effects of the wind speed and direction were not significant on the individual PAHs. On the other hand, PAH concentrations showed a strong linear relationship with the ventilation coefficient (VC) which showed the influence of local sources on measured PAHs. Benzo[a]pyrene toxic equivalent (BaP(eq.)) concentrations were used for health risk assessment purposes. The winter period risk level (2.92 × 10(-3)) due to the respiratory exposure to PAHs was found to be almost 3 times higher than in the summer period (1.15 × 10(-3)).

Parametric equation for boiling and sublimation curves

A parametric equation describing correlation of saturated vapor pressure and temperature in gas-liquid and gas-solid single-component systems was deduced.

Influence of Nano-Refrigeration-Oil on Saturated Vapor Pressure of R22

The saturated vapor pressures of R22 uniformly mixed with refrigeration oil and nano- refrigeration-oil were measured experimentally at a temperature range from 263 to 333K and mass fractions from 1 to 5%. The experimental results showed that the saturated vapor pressure of R22/KT56 mixture was lower than that of pure R22; the pressure deviation between them increased with a raising mass fraction of refrigeration oil and temperature. After adding nano-NiFe2O4 and nano-fullerene into KT56, the pressure deviation increased at the same mass fraction and temperature. A saturated vapor pressure correlation for R22 and refrigeration oil/nano-refrigeration-oil mixture was proposed, and the calculated values agreed with the experimental data within the deviation of ± 0.77%.