Polymeric Membrane Nanofiltration and Its Application to Separations in the Chemical Industries

AbstractThe application of membrane technology, particularly water‐based nanofiltration, as a separation process in the chemical industries has increased tremendously in recent years. However, the use of membranes capable of molecular separation in non‐aqueous systems (e.g. nanofiltration) is a relatively new and growing application of membrane technology. The main challenge in applying polymeric nanofiltration membranes to non‐aqueous systems is that the polymers developed for water‐based applications are not suitable. Polyimide is a particularly interesting polymer as it has excellent chemical resistance, and membranes produced from it provide desirable separation properties – i.e. economically viable flux and good separation of nanoscale molecules. Various research works have shown that commercial polyimide organic solvent nanofiltration (OSN) membranes, trademark STARMEM™,1are robust and suitable for performing molecular separations. This work will discuss in detail the use of STARMEM™ in a pharmaceutical application. The EIC‐OSN process was developed for separating the enantiomers of chiral compounds in pharmaceutical applications. High optical purity (94.9%) of (S)‐phenylethanol fromrac‐phenylethanol was achieved through the use of STARMEM™122. Process simulation of the ideal eutomer‐distomer system predicted that the highest theoretical resolvability from this process would be 99.2%. Other application areas of OSN are varied, including purification and fractionation in the natural products industry, homogeneous catalyst recovery, monomer separation from oligomers, etc. Currently, OSN is used in a small number of processes including a very large petrochemical application, but it has the potential to be applied to a wide range of separations across the full spectrum of the chemical industries.