Determination And Correlation Of Vapor-liquid Equilibrium Of Terpene System In Turpentine

Turpentine oil is one of the largest natural essential oils,and its main components are monoterpenes and sesquiterpenes.Terpenes in turpentine are important natural flavors.It is widely used in the synthesis of fine chemicals,such as pharmaceuticals,flavors and spices.Distillation is the main method for the separation and purification of terpene components,and the vapor-liquid equilibrium data are the basis of distillation operation.The research work of this paper mainly includes the following contents:(1)The saturated vapor pressure measurements for camphene across a temperature range of 357.01 to 432.16 K were reported.Additionally,the vapor pressure data,obtained also using an improved Ellis equilibrium still,were fitted by Origin 8.0.and the corresponding Antoine parameters of the 2340.8673 Antoine equation were regressed as:log(Ps/kPa)= 7.266-2340.8673/(T/K)+13.4387.The correlation coefficient R2 is 0.9998,and the average relative deviation between the experimental boiling temperature and calculated value was 0.6%.(2)Isobaric vapor-liquid equilibrium(VLE)data have been measured in a modified Ellis still and Gas Chromatography for the following systems:camphene+(±)-limonene,camphene +(+)-3-carene,(+)-3-carene +(±)-limonene,camphene + p-cymene,camphene + a-pinene,(+)-3-carene +a-pinene,a-pinene +(-)-β-caryophyllene,camphene +(-)-β-caryophyllene,and camphene +(+)-3-carene +(±)-limonene,at 101.33 kPa.Furthermore,Isothermal vapor-liquid equilibrium data(VLE)data for camphene +(+)-3-carene system at 313.15 K,373.15 K and 433.15 K were also measured using this modified Ellis still.(3)The thermodynamic consistency of the VLE values was confirmed by the Herington area and van Ness tests.All the D-J values for the binary systems studied are less than 10.All the values of Δy and ΔP for these systems were less than 1.The results demonstrate that all experimental data are considered to be thermodynamically consistent.(4)The VLE data were correlated by NRTL,Wilson and UNIQUAC activity coefficient model in Aspen plus V8.7.The objective function was optimized by the maximum likelihood method and the corresponding binary interaction parameters were returned.The results show that the maximum absolute deviations of vapor phase mole fractions and equilibrium temperature are 0.0013 and 0.09 K for camphene,(+)-3-carene and limonene binary systems,0.0061 and 0.54 K for the camphene,(+)-3-carene,(-)-β-caryophyllene,p-cymene and a-pinene system,respectively.And the maximum absolute deviation between the vapor phase mole fractions and equilibrium pressure of camphene and(+)-3-carene systems at 313.15 K,373.15 K and 433.15 K is 0.0003 and 0.0009 kPa.(5)Taking camphene +(+)-3-carene + limonene as an example,the vapor-liquid equilibrium of ternary system was measured and correlated.Vapor-liquid equilibrium data for camphene +(+)-3-camphene + limonene ternary system was predicted by using the binary interaction parameters obtained by model regression.The maximum absolute deviations between predicted and experimental values of apor phase mole fractions and equilibrium temperature are 0.0067,0.0059 and 0.04 K,respectively.