Vapor–Liquid Equilibrium of α-Pinene, Longifolene, and Abietic Acid of Pine Oleoresin: HS-GC Measurements and Model Correlation

Investigating phase equilibrium on the terpenoid of the pine oleoresin system is of great importance for the usage relevant to the oleoresin. Herein, the binary and ternary isothermal vapor–liquid equilibrium (VLE) of α-pinene, longifolene, and abietic acid (three main components of oleoresin) at 313.15, 323.15, and 333.15 K were measured by headspace gas chromatography (HS-GC). There was no azeotropic behavior observed of α-pinene and longifolene. Abietic acid’s influence on separating α-pinene and longifolene was discussed. The relative volatilities of α-pinene and longifolene decrease in the presence of abietic acid, indicating a negative impact of abietic acid on their separation. The experimental data were correlated well with the nonrandom two-liquid, universal quasichemical, and Wilson models. The binary interaction parameters for each equation were also obtained, and the largest mean relative deviation of vapor-phase mole fraction and the largest absolute average deviation of pressure are 0.1975% and 0.0856 kPa, respectively.