Recovery of Formic Acid and Acetic Acid from Waste Water Using Reactive Distillation

Abstract

Processing of biobased feedstock materials may lead to formation of multicomponent azeotropic mixtures. Reactive separations provide an opportunity to circumvent azeotropes by changing the substance properties through chemical reactions. Exemplarily several effluents from black liquor processing contain aqueous mixtures of low molecular weight fatty acids such as formic acid and acetic acid. These mixtures form inseparable azeotropes. Separation of the system formic acid–acetic acid–water by esterification with methanol was investigated. Reactive distillation experiments in batch and continuous mode confirmed complete removal of formic acid in a first step. Acetic acid may then be isolated by distillation or by reactive distillation.

Keywords:

• reactive distillation
• azeotrope
• esterification
• acetic acid
• formic acid
• fatty acid

ACKNOWLEDGEMENTS

The authors acknowledge support from Candela Campos Dominguez and Raphael Neubauer during their project work at TU Graz. The authors also appreciate the support of Herta Luttenberger and Peter Letonja.