In the present work, we report the development of models for the prediction of two fuel properties: flash points (FPs) and cetane numbers (CNs), using quantitative structure property relationship (QSPR) approaches. Compounds inside the scope of the QSPR models are those likely to be found in alternative jet and diesel fuels, i.e., hydrocarbons, alcohols, and esters. A database containing FPs and CNs for these types of molecules has been built using experimental data available in the literature. Various approaches have been used, ranging from those leading to linear models, such as genetic function approximation and partial least squares, to those leading to nonlinear models, such as feed-forward artificial neural networks, general regression neural networks, support vector machines, and graph machines. Except for the case of the graph machine method, for which the only inputs are the simplified molecular input line entry specification (SMILES) formulas, previously listed approaches working on molecular de...

Flash Point and Cetane Number Predictions for Fuel Compounds Using Quantitative Structure Property Relationship (QSPR) Methods

Property data for tetraalkylammonium cations, [H(CH2)n]4N+, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series.

Tetraalkylammonium Ions in Aqueous and Non-aqueous Solutions

Molecular properties and intermolecular forces—factors balancing the effect of carbon surface chemistry in adsorption of organics from dilute aqueous solutions

A molecular dynamics simulation study of structural and dynamical properties in liquid mixtures of formamide and water is presented. Site-site radial pair distribution functions, local mole fractions, pair energy distributions, and tetrahedral orientational order are the quantities analyzed to investigate the local structure in the simulated mixtures, along with a review of the intermolecular structure in terms of the distribution of hydrogen bonds. Our results indicate that there is a substitution of formamide molecules by water in the hydrogen bonds and a formation of a common hydrogen bond network. By analyzing the extent of tetrahedral order in the liquid as a function of composition, it is observed that whereas the tetrahedral network of liquid water is progressively lost by increasing the formamide concentration, the water structure within the first coordination shell is preserved and somewhat enhanced. The hydrogen-bond mean lifetimes were estimated by performing a time integration of the autocorrelation functions of bond occupation numbers. The lifetimes associated with hydrogen bonds between water, formamide, and interspecies pairs are found to increase with increasing formamide concentration. The lifetimes of the water hydrogen bonds show the largest variations, supporting the picture of an enhancement of the water structure among the nearest neighbors within the first coordination shell. We have used two different force field models for water, SPC/E [J. C. Berendsen et al., J. Phys. Chem. 91, 6269 (1987)] and TIP4P/2005 [J. L. F. Abascal and C. Vega, J. Chem. Phys. 123, 234505 (2005)]. Our results for structural and dynamical properties yield very small differences between those models, the TIP4P/2005 predicting a slightly more structured liquid and, consequently, exhibiting a slightly slower translational and librational dynamics.

Computational study of structural and dynamical properties of formamide-water mixtures

Calorimetric determination of hydrogen-bonding enthalpy for neat aliphatic alcohols

Thermochemistry of solvation of non-electrolytes in mono- and polyatomic alcohols and their mixtures with water

Enthalpy-related interaction parameters in H/D isotopically distinguishable aqueous solutions of tetramethylurea cyclic derivatives at 298.15 K

The heats of dissolution of tetramethyl-bis-carbamide (the pharmaceutical Mebicarum) in H2O and D2O were measured at 288.15, 298.15, and 318.15 K using a sealed microcalorimeter with an isothermal shell. The error of measurements did not exceed 0.2%. The limiting molar enthalpies of dissolution Δsol
 H
 n
 ∞ and the H/D-isotope enthalpy effects of hydration δΔhydr
 H
 n
 ∞(H2O → D2O) were determined. Different effects of temperature on the pattern of variation of δΔ hydr
 H
 n
 ∞ were found: when T ≤ 315 K, this value is positive and decreases with T, while for T ≥ 315 K, hydration of tetramethyl-bis-carbamide upon replacement of H2O by D2O progressively becomes less endothermic.

Effect of temperature on the H/D-isotope effects in the enthalpy of hydration of tetramethyl-bis-carbamide

D2O-H2O solvent isotope effects on the enthalpy of 1,1,3,3-tetramethylurea hydration between 278.15 and 318.15 K

The problem of the introduction of the term internal pressure from the standpoint of intermolecular forces is solved. It is shown that internal pressure is created by the macrosystem average force field of the structural units of a liquid. Internal pressure is shown to be not an energy characteristic, but a macrosystem average force parameter of the interaction between the structural units of a liquid phase system, although it has the energy density dimension, [J/m3].

Dmitriy V. Batov

Papers

Thermochemistry of solvation of non-electrolytes in mono- and polyatomic alcohols and their mixtures with water

Enthalpy-related interaction parameters in H/D isotopically distinguishable aqueous solutions of tetramethylurea cyclic derivatives at 298.15 K

Effect of temperature on the H/D-isotope effects in the enthalpy of hydration of tetramethyl-bis-carbamide

D2O-H2O solvent isotope effects on the enthalpy of 1,1,3,3-tetramethylurea hydration between 278.15 and 318.15 K

Intermolecular forces and the internal pressure of liquids