Influence of Solvent and Acid Properties on the Relative Volatility and Separation Selectivity for Extractive Distillation of Close-Boiling Acids

The increasing need for sustainable processes stimulates the production and recovery of renewable organic acids. purification these acids is often difficult because similar acid volatilities but can be improved through extractive distillation. Generic insights into solvent effects on separation efficiency close-boiling are however lacking. This study provides effect acidity, acidity difference between acids, hydrogen-bonding strength solvent, solvent-to-feed ratio efficiency. For an acetic acid–formic (AA–FA) mixture, addition high-boiling increases relative volatility FA over AA significantly. a Lewis base reverses volatility, which depends applied BF3 affinity. several binary mixtures (such as AA–FA monochloroacetic acid–dichloroacetic acid), where have relatively big in (?pKa ? 1), selectivity appears practically independent individual with affinity base. lower ?pKa, obtained, observed pivalic acid–butyric valeric acid–2-methyl butyric mixtures. When one mixture contains secondary ketone group (i.e., levulinic acid–octanoic mixture), strongest based pKa not necessarily attracted most by added This, at first sight, unexpected behavior likely result complex intra- intermolecular interactions quantitatively line COSMO-RS-based predictions.