Calculation Of Vle Data For System Containing α-Pinene By Unifac Model

a-Pinene is one of the main components in turpentine and as a renewable green organic compound. It has a special bicyclo and-C=C-structure with high reactivity, so it is widely used as the raw material of spices, medicine, paint and other chemical products. Because of the close boiling points of turpentine compositions and high requirements of low energy separation equipment, it is necessary to use an accurate model for vapor liquid equilibrium (VLE) calculation, while designing or making chemical production equipment.According to the principle of UNIFAC model group division, α-pinene was divided into one bicyclo [3.1.1] hept-2-ene (set as group G) and three-CH3. Set the minimum sum of pressure deviation squares as the objective function OF, then calculate the new group’s interaction parameters amn, volume parameter Rk and surface area parameter Qk. The group interaction parameters amn and anm of G and-CH3are0.98210and4.6584; that of G and-C=C-are156.64and-86.670; that of G and ACH are-33.810and-40.797; and that of G and ACCH3are-11.656and52.456respectively. Volume parameter Rk and surface area parameter Qk are3.2756and1.9840.This paper uses UNIFAC model with new groups and the original groups to estimate VLE data of a-pinene with alkanes, alkenes and aromatic hydrocarbon system respectively, which is compared with the experimental data in the literature. In the binary systems, what is calculated with the new groups is the average absolute deviations of vapor composition and temperature in a-pinene and aromatic hydrocarbons isobaric system under three pressure, which are0.0038,0.0024,0.0016and0.12K,0.29K,0.10K, less than the calculated deviations from the UNIFAC model with original groups, which are0.0078,0.0064,0.0054and0.95R,1.01K,0.82K. Also in a-pinene and alkane, olefin binary system, compared with literature values, the VLE data which are estimated from the new groups are slightly better than that from the original groups. In the binary system of a-pinene and n-octene, with their similar structures and according to the similar dissolve mutually principle, the interaction of molecules is larger than other binary system, so its vapor composition deviation is greater than that of other binary systems whether using new groups or original groups.According to the estimation the VLE data of a-pinene ternary systems including a:a-pinene (1)+p-cymene (2)+(S)-(-)-limonene (3) at100.7kPa, b:α-pinene (1)+β-pinene (2)+p-cymene (3)at100.7kPa, c:a-pinene (1)+β-pinene (2)+(S)-(-)-limonene (3) at80.0kPa, d:a-pinene (1)+β-pinene (2)+(S)-(-)-limonene (3) at101.3kPa and e:α-pinene (1)+p-cymens (2)+longifolene (3) at atmosphere, it is less difference between new groups and original groups from which vapor compositions deviation is calculated. But compared with the original groups, the positive and negative deviation of temperature which is calculated from new groups are more uniform, and the average absolute deviation of temperature is lesser. Vapor compositions and temperature deviations of system b and e are larger than other systems because of the induced force.By comparison, the VLE data which are calculated from the new group is generally better than that of the original groups in the system containing a-pinene. Because UNIFAC model has its defects, one of which is that it cannot distinguish the results while estimate the isomeric system, and the other is that the results are not satisfactory while estimate the strong polarity and high temperature systems. The deviation is slightly large while it is calculated by the model in part of the system. Therefore the model has further room for improvement and can continue to introduce new groups and expand the parameter matrix and parameter correction.