Applicability of UNIFAC to predict liquid-liquid equilibria.

摘要

UNIFAC is a BASIC language program used to calculate activity coefficients of compounds based on their functional groups, system temperature, and individual mole fractions. Using these activity coefficients and the mole fractions of the compounds found from the tie-line data in the literature (convert weight fractions to mole fractions for UNIFAC), the applicability of UNIFAC to predict liquid-liquid equilibria is examined.;From this evaluation, it can be concluded that UNIFAC is a potentially viable technique for analyzing liquid-liquid data. UNIFAC, tested against literature data, predicted accurately in selected binary and ternary systems. UNIFAC predicted excellently for water in all systems it was analyzed in. UNIFAC also predicted well for propionic and acetic acids. However, UNIFAC predicted poorly for alcohols and nitro groups. Further investigations need to be performed on certain types of chemicals (i.e. alcohols, nitro groups, aromatic rings) before concrete conclusions can be made.;Six ternary systems were analyzed for this evaluation of UNIFAC. A deviation was calculated to compare the equilibria points for the two liquid phases. An acceptable deviation was considered to be less than or equal to ten relative percent (≤10%). Of the six systems analyzed, UNIFAC predicted accurately for three of them. Two of the systems had deviations less than 15 relative percent while the final system had a deviation over 15 relative percent.