(47d) Membrane Extraction (pertraction) as a Tool for Process Intensification

Classical extraction is a well known technique used in the separation of components within the industry. Pertraction was developed as an extraction process which reduces the effect of emulsion formation resulting from mixing two solvent phases. In pertraction, a membrane is used to separate the two phases. Typically, the solute of interest is present in the aqueous phase and is transported into an organic phase across a hydrophobic membrane. Considering the independent mobility of the two phases, there is better control over optimization. With the use of fibers, the contact area for these pertraction processes can be significantly increased.

In terms of process intensification, there is presently a drive from batch to continuous processing in fine-chemicals industries. This drive offers advantages with respect to volumetric productivity, yield and selectivity, footprint and safety. Pilot studies of micro-structured reactors in a production environment are in progress. It makes, however, little sense to shift only the reactor to continuous operation and not the work up which would result in accumulation of the reaction mixture in storage vessels. The next logical step is the introduction of continuous intensified separation equipment that has a similar performance with respect to separation efficiency as continuous reactors regarding productivity.  

This study is focused on the use of a flat sheet membrane contactor for pertraction with two different chemical applications tested. In the first part, an aqueous work up of a synthetic organic reaction mixture was carried out. This work up was aimed at the removal of spent organic acids and bases from the reaction mixture using pertraction. The work up was successfully carried out without emulsion formation and potentially with a smaller volume of washing water. The second application studied was the dehydration of a reaction mixture, with the objective of removing both dissolved and dispersed water formed. In the latter case the test system was an esterification reaction and dehydration into a hygroscopic solution. For both applications the mass transfer coefficient was determined in order to calculate the surface area of membrane required for an industrial module.