Measurement And Calculation Of Vapor-Liquid Equilibrium And Excess Enthalpy Data For Main Constituents In Turpentine Oil System

Turpentine oil, obtained by steam distillation of pine resins, is one of the richest resources of refined oil in the world, its main constituents include a-pinene,β-pinene,p-cymene and (S)-(-)-limonene. Turpentine oil is widely used in the synthesis of fine chemicals, such as synthetic terpenic resins, terpenic surfactants, cosmetic and pharmaceutical.(Vapor+liquid) equilibrium (VLE) and excess enthalpy thermodynamic data had the important significance on the further processing and separation of Turpentine oil components.By comparing different vapor-liquid equilibrium experiment device, the modified Ellis equilibrium still was selected to measure vapor-liquid equilibrium (VLE) data for binary systems of β-pinene+p-cymene and β-pinene+(S)-(-)-limonene and the ternary system of β-pinene+p-cymene+(S)-(-)-limonene at100.7kPa. The experimental data of binary systems were tested for thermodynamic consistency with the method of Herington and point-to-point test of Van Ness. The parameters of four solution models-Wilson, NRTL, UNIQUAC and Liebermann-Fried-were calculated with the aid of the least-squares method to minimize an objective function based on the total pressure. The four models yield similar deviations, but the best fit for the miscible mixtures is obtained with the Wilson model. The thermodynamic consistency of the VLE data of the ternary system was tested with the method of McDermott-Ellis, modified by Wisniak and Tamir. Also, the ternary system data were compared with the predicted values, using the parameters of Wilson model obtained from the binary subsystems. The absolute average deviations for the ternary system was δT=0.17K,δy1=0.0038,δy2=0.0015, and δy3=0.0037, respectively, the predicted bubble-point temperature and the vapor composition for the ternary system were in good agreement with the experimental results.The excess enthalpies data for six binary systems of a-pinene+β-pinene, a-pinene+p-cymene, a-pinene+(S)-(-)-limonene, β-pinene+p-cymene, β-pinene+(S)-(-)-limonene and p-cymene+(S)-(-)-limonene were measured at298.15K,303.15K,313.15K and atmospheric pressure by C80microcalorimeter. The experimental data were correlated by Redlich-Kister equation and the absolute deviation and the relative deviation were quite small. The experimental data of binary systems are in good agreement with that of the reference. The difference of the molecular structure and double bond position for the four components lead to the different of heat needed when mixed and the different of the excess enthalpy numerical. The excess enthalpies Hm,1+23E for three pseudo-binary systems of α-pinene+p-cymene+(S)-(-)-limonene,β-pinene+p-cymene+(S)-(-)-limonene and (S)-(-)-limonene +α-pinene+β-pinene were measured at298.15K,303.15K,313.15K and atmospheric pressure by C80microcalorimeter. The experimental data were compared with the values calculated by the equations of Tsao and Smith recommending and the deviations between the experimental values and the calculated values were quite small. The results show that the excess enthalpy data determined by C80micro calorimeter is accurate and reliable. The results serve to show that all the experimental Hm,1+23E values are positive. Curves show a symmetrical trend and maximum values were observed in the vicinity of x1≈0.5. Using the experimental Hm,1+23E values calculate the excess molar enthalpies Hm,1+23E of the three ternary system at298.15K,303.15K,313.15K and atmospheric pressure. Smooth representations of the tenary system results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams, the general characteristics of each ternary system are similar. Furthermore, at constant x1, the Hm,1+23E values increase monotonically as the mole ratio of x2/x3increases.Using the parameters determined from the HE values for the binary systems of β-pinene+p-cymene and β-pinene+(S)-(-)-limonene, we calculated the bubble-point temperatures and the vapor compositions for the two binary systems. The predicted temperatures and vapor compositions were compared with the experimentally determined values. It can be seen that the bubble-point temperatures predicted by means of the Wilson model agree very well with the experimentally measured values; the average absolute deviation are mostly <0.16K. The predicted vapor compositions are also of reasonable accuracy; the mole fraction average absolute deviations are mostly<0.0032.