Xylene isomer purification is an important separation in the chemistry industry as it is critical to the production of polyethylene terephthalate (PET). Commercially available technologies for this separation are complex and are often energy-intensive. Recently, membrane materials capable of separating this isomeric mixture without a phase change have been developed and potentially provide a low-energy footprint technology with simpler operation. While there has been no large-scale application of membrane-based xylene isomer separation, this study conducts a techno-economic analysis (TEA) to evaluate the commercial attractiveness of a p-xylene selective carbon molecular sieve (CMS) membrane. First, single-stage organic solvent reverse osmosis (OSRO) and pervaporation (PV) processes were used to evaluate the influence of membrane properties and process parameters on separation performance. At low p-xylene recovery, pervaporation system outmatches OSRO with a reduction of ~23 kJ energy required per kg of p-xylene product. However, PV module heating compared to constant feed pressurization in OSRO resulted in a 5 – 6 times energy requirement at high recovery for PV systems. Finally, two membrane cascade systems–a single PV stage followed by two OSRO stages and a three-stage OSRO, were benchmarked against the commercial Parex process. Results show a cost savings of 52- 85% for the optimal PV/OSRO cascade system compared to the commercial Parex process, demonstrating the commercial attractiveness of membrane systems in small molecule solvent separations.
