Thermodynamic properties of {glycerol (1) + tert-butanol (2)} mixtures at temperatures from 278 K to 323 K and pressures up to 100 MPa

Abstract

In the present study the densities at atmospheric pressure and the compression coefficients of a binary liquid mixture {glycerol (1) + tert-butanol (2)} were measured within the temperature range from 278.15 K to 323.15 K (278.15, 288.15, 288.15, 308.15 and 323.15) and pressures up to 100 MPa (10, 25, 50, 75 and 100). Due to the limited solubility of tert-butanol in glycerol and the transition of the mixture to the solid phase the measurements at 278.15 K and 100 MPa were carried out up tox2 = 0.45 (x2 is the mole fraction of tert–butanol). The excess molar volumes, molar isothermal compression, molar isobaric thermal expansion, isochoric coefficient of thermal pressure mixtures, as well as the partial molar volumes of the mixture components, including their limit values, were calculated. The excess molar volume values at 323.15 K (the only temperature at which the compression was measured over the entire composition range) were found to be negative. The partial molar volume of glycerol (GL) at 323.15 K was characterized by the presence of a baric inversion region. The limiting partial molar volume of GL was shown to decrease in its own environment as the pressure rose and to increase in the TBA environment. The molar isothermal compression of the mixture varied depending on the composition without extremes, and the partial molar isothermal compression of GL had negative values. The molar isobaric thermal expansion of the mixture in the area of small tert-butanol (TBA) additives changed slightly at low temperatures and pressures and the increase in both the pressure and the temperature led to dispersion of their concentration dependences. The isochoric coefficient of thermal pressure decreased with an increase in x2, forming a small plateau at small TBA additions. The results obtained were discussed from the perspective of solute–solvent and solute–solute interactions.