Vapor Pressures and Thermophysical Properties of 1-Heptanol, 1-Octanol, 1-Nonanol, and 1-Decanol: Data Reconciliation and PC-SAFT Modeling

Abstract

were measured by a static method near ambient temperatures over an operating pressure range from 0.5 to 1270 Pa, thus complementing literature vapor pressure data obtained by ebulliometry at higher temperatures. Liquid heat capacities of 1-octanol, 1-nonanol, and 1decanol were determined by Tian−Calvet calorimetry. Ideal-gas thermodynamic properties of 1-alkanols up to 1-heptanol were obtained by a combination of quantum chemistry and statistical mechanics and validated against available experimental data. Ideal-gas heat capacities and entropies for longer homologues were obtained by deriving a methylene increment due to having a too complex conformational shape for analogical treatment. The thermodynamic consistency of available data was validated by simultaneous correlation of selected vapor pressures, literature enthalpies of vaporization, and heat capacity differences between the ideal gaseous and the liquid phase. The results are represented by the Cox equation and compared with available literature data. Moreover, the results were used to examine the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state for its performance in describing vapor pressures, enthalpies of vaporization, residual liquid heat capacities, and liquid densities of neat 1-alkanols from 1-hexanol to 1-decanol. A new PC-SAFT parameter set for each of them was also regressed that improves the PC-SAFT performance for the studied properties in comparison to existing parameters published in the literature.

Quantum Chemical Calculation and Evaluation of Partition Coefficients for Classical and Emerging Environmentally Relevant Organic Compounds

“…1-Octanol (CAS 111-987-5; M = 0.13023 kg/mol; ρ­(298 K) = 830 kg/m 3 ) has a vapor pressure of 11.18 Pa at 298 K . The solubility of water in 1-octanol at 298 K is 48.79 mg/g (mole fraction 0.2701) (see Table S1).…”

Vapor Pressures and Thermophysical Properties of Dimethoxymethane, 1,2-Dimethoxyethane, 2-Methoxyethanol, and 2-Ethoxyethanol: Data Reconciliation and Perturbed-Chain Statistical Associating Fluid Theory Modeling

“…A modification of the approach denoted R1TM was introduced, where all terminal tops (thus letter “T” in the acronym) are treated using the 1-D HR model instead of only symmetrical tops as in the original R1SM approach. Use of the R1TM approach significantly improved the agreement with experimental ideal-gas data for n -alkanols …”

“…It combines carefully selected quantum chemistry calculations and three statistical mechanics models: (i) the rigid rotor–harmonic oscillator (RRHO) approximation; (ii) corrections for symmetric top rotations using the one-dimensional hindered rotor approximation (1-DHR); (iii) mixing model using the population of conformers based on the Boltzmann distribution. We recently revealed that treating the hydroxyl groups with their low rotational barriers by combination of HO and mixing model, as suggested in the R1SM approach, is inadequate . A modification of the approach denoted R1TM was introduced, where all terminal tops (thus letter “T” in the acronym) are treated using the 1-D HR model instead of only symmetrical tops as in the original R1SM approach.…”

“…We recently revealed that treating the hydroxyl groups with their low rotational barriers by combination of HO and mixing model, as suggested in the R1SM approach, is inadequate. 79 A modification of the approach denoted R1TM was introduced, where all terminal tops (thus letter "T" in the acronym) are treated using the 1-D HR model instead of only symmetrical tops as in the original R1SM approach. Use of the R1TM approach significantly improved the agreement with experimental ideal-gas data for n-alkanols.…”

“…Use of the R1TM approach significantly improved the agreement with experimental ideal-gas data for n-alkanols. 79 However, rotation of the hydroxyl top (unlike that of symmetrical methyl top) typically gives rise to three energetically distinct minima and a doubt arises in the R1TM approach, how to decouple this degree of freedom and exclude it from the mixing model. Thus, only the most stable conformer of each set of conformers that significantly differ only by rotation of the hydroxyl group was considered in the mixing model reducing the number of conformers treated in The data from references written in bold were used in the SimCor method.…”