DETERMINATION OF VAPOR PRESSURE AND ENTHALPY OF VAPORIZATION OF NEOPENTYL GLYCOL ESTERS OF FATTY CARBOXYLIC ACIDS

Chicheva D.S., Krasnykh E.L., Abbyasova A.R.

Samara State Technical University

443100, Samara, Molodogvardeyskaya st, 244

Esters based on fatty acids and neopentyl glycol (NPG) are used as base oils and can also serve as one of the components of synthetic lubricants.

In this work, a series of esters of neopentyl glycol and octanoic, 2-ethylhexanoic, decanoic, and dodecanoic acids was synthesized (see Figure).

Structure of Neopentyl Glycole Diesters

Esters of neopentyl glycol and fatty acids of the C₈-C₁₂ series were obtained by esterification in a self-catalytic mode in the presence of a solvent n-decane. The purity of the samples was determined by gas chromatography. The purity of the samples was more than 98% by weight. The values of sorption enthalpies, vapor pressures, and evaporation enthalpies were determined for the obtained samples.

The value of the change in internal energy Δ_sorpŪ (kJ/mol) and sorption enthalpy Δ_sorpН (kJ/mol) at an experimental temperature was determined from the dependencies:

$$\ln(k/T) = C - \frac{\mathrm{\Delta}_{sorp}Ū}{RT}\ ;\ \mathrm{\Delta}_{sorp}H = \mathrm{\Delta}_{sorp}Ū - RT\ and\ k = \frac{t_{R} - t_{M}}{t_{M}},$$

where t_R– adjusted retention time of the esters, min; t_M - retention time of nonsorbing substance (n-hexane), min.

The vapor pressures of NРG esters were determined by the transpiration method. The obtained p-T-dependences were described by the equation of the form:

$$R\ \ln\left( \frac{P}{P_{aw}} \right) = A_{f} - \frac{B_{f}}{T} + \mathrm{\Delta}_{ж}^{n}{Cp}^{0}\ ln\left( \frac{T}{T_{aw}} \right),$$

where $P$ – is the vapor pressure at T; $P_{aw}$ – is the vapor pressure at the average temperature of the study $T_{aw}$; $A_{f}$ and $B_{f}$ are empirical coefficients obtained by processing p-T data by the least squares method; $\mathrm{\Delta}_{ж}^{n}{Cp}^{0}$ – the difference between the molar heat capacities of the gas and liquid phases [1].

$$\mathrm{\Delta}_{vap}H_{m}^{0}(298,2) = - B_{f} + 298.2\ \mathrm{\Delta}_{ж}^{n}{Cp}^{0}.$$

1. E. L. Krasnykh and S. V. Portnova. Journal of Structural Chemistry. 2017, 58, 4, 706

The research was funded by the Russian Science Foundation (project №. 26-23-20231).