Study on Segregation Process and Equilibrium Distribution Coefficients of Impurities during Zone Refining of Bibenzyl

The purification of commercial Bibenzyl by zone refining has been investigated with a view to establishing operational parameters and optimum processing conditions. Three factors are inspected, which are zone passing number, translation rate, and zone length. The axial profiles of product purity are determined. Meanwhile, the axial concentration profiles of four main impurities, which are Cyclohexylbenzene, Diphenylmethane, 1,1-Diphenylethane, and 1,2-Diphenylpropane have been also determined. The equilibrium distribution coefficients of the four impurities in Bibenzyl are calculated by measuring their effective distribution coefficients at zone travel rate of 4.97, 8.80, 11.89, and 17.43 mm/h. The results indicate that zone refining of Bibenzyl is very successful. The product purity can increase from 98.3466% to 99.8353% after 8 zone passes. The each additional zone pass and slower translation rate are helpful to purification of Bibenzyl. For 1 pass, longer zone length is better for purification of Bibenzyl. The equilibrium distribution coefficients of Cyclohexylbenzene, Diphenyhnethane, 1,1-Diphenylethane, and 1,2-Diphenylpropane are 0.3917, 0.3677, 0.1687, and 3.8148, respectively.