Authors:P.M. Ghogomu, Elise Provost, M. Bouroukba, M. Dirand, and M. Hoch
The solubility of two n-alkanes in commercial organic liquids, such as diesel fuel and jet fuel represent a problem to industry,
because they precipitate in an unpredictable fashion. First we calculated the metastable enthalpy and entropy of fusion of
the low temperature forms of the n-alkanes. We analyzed the solubility of alkanes n-C22H46, n-C23H48, n-C24H50 and n-C28H58
in ethylbenzene, m-xylene, n-heptane and gas oil. All systems seem to be close ideal, possibly with a slight positive deviation.
We analyzed the solubility at constant temperature of the ternary system solvent C22H46-C24H50, C23H48-C24H50, C13H28-C16H34,
C20H42-C22H46, C20H42-C24H50 and C20H42-C28H58, and looked at cloud points in various ternary systems. When the difference
in the number of carbon atoms in the two alkanes is small, four or less, a metastable solid solution precipitates from the
solvent. If the difference in the number of carbon atoms is six or more, the ‘equilibrium’ phases, or at least phases with
low solubility precipitate.
Authors:J. Rak, P. Skurski, M. Gutowski, and J. Błażejowski
Geometries and energies of isolated CaC2O4H2O, CaC2O4, CaCO3, CaO, H2O, CO and CO2 were determined at the ab initio level using effective core potential valence basis sets of doublezeta quality, supplemented
with polarization functions. The effects of electron correlation were taken into account at the second order Mller-Plesset
level of theory. For CaC2O4H2O, the correlation for the basis set superposition error was also included. Common routines were employed to evaluate entropies,
heat capacities, as well as enthalpies and free enthalpies of formation of all entities. The enthalphies and free enthalpies
of consecutive dehydration of CaC2O4H2O, decarbonylation of CaC2O4 and decomposition of CaCO3 towards CaO and CO2 were determined on the basis of avialable data from the literature or those predicted thoretically. Assuming that upon all
the above mentioned processes the system maintains equilibrium, the fractions reacted, enthalpy changes and differential dependencies
of thesevs. temperature were derived and compared with experimental thermoanalytical data.