Selectivity and solvency of mixed solvents

Abstract

1. A comparison has been made of the solvency of extradants on the basis of calculated values of solubility parameter. 2. A study has been made of the conditions of phase equilibrium in ternary systems consisting of benzene, n-hexane, and mixed solvent. It has been shown that the band-type binodal curve [for DEG] is converted to a closed-type curve by the addition of 30% DMSO, 30% N-MP, or 50% DMFA. 3. The use of DMSO, DMFA, or N-MP in the extraction of aromatic hydrocarbons from a feedstock of a given composition gives approximately the same effect in increasing the solvency of the DEG. However, the addition of DMFA or N-MP causes a sharper drop in selectivity coefficient than does the addition of DMSO. 4. The use of mixed solvents, in addition to decreasing the solvent ratio, makes it possible to reduce the viscosity of commercial extractants of the DEG type and hence to lower the process temperature; this is of great significance in the extraction of low-boiling feedstocks. 5. The conditions of mixed-solvent regeneration have been investigated.