Membranes Target Organic Solvents

Separation technology promises energy savings and other benefits.

By Seán Ottewell, Editor at Large

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Combining OSN with existing conventional molecular separation techniques may lead to wider acceptance, he believes. "Seeing OSN as a process efficiency tool rather than a standalone technology is what we actively support for future prospects as we see the best use of the technology in optimizing production costs and increasing yield."

Such optimizations could include: product stream polishing pre-chromatography/pre-crystallization; product concentration post-chromatography; product concentration pre-distillation; and solvent recycling post-chromatography.

Meanwhile, research work continues. Livingston's group at Imperial College is probing several areas that may give clues as to where the future of OSN could lie — and how mainstream the techology could become.

For example, one key area covers materials synthesis, membrane formation and membrane characterization. Here, the focus is on developing new OSN membranes — both polymeric and ceramic — and comparing their performance with commercially available materials. The researchers also are looking at the design and fabrication of membrane modules.

Another area of research is to identify applications where OSN can replace energy-intensive distillation processes and complex solvent workups. In particular, this involves catalyst recycling, integration of reaction and separation in membrane reactors, and improved solvent operations such as solvent exchanges and fractionation. Researchers are creating novel separation flowsheets and developing continuous membrane processes as alternatives to traditional distillation and chromatography separations.

A third area focuses on improving the understanding of how high-performance aromatic-heterocyclic-polymer-based membranes could serve in OSN applications. Such membranes potentially could be used in harsh environments such as those posed by strong acids and strong bases; research on extending their application to a range of solvents is underway.

Another strand of work is looking at next-generation drugs based on biomolecules such as peptides and oligonucleotides. Today, their manufacture is based on solid-phase synthesis and involves cumbersome separations. This project focuses on developing new manufacturing routes to improve the separation processes central to their synthesis — and integrating them with reaction processes.

Finally, there's OSN crystallization, which uses solvent-resistant nanofiltration membrane technology to enhance crystallization of organic compounds. OSN crystallization has the potential to reduce energy or chemical inputs and allow tighter control of process conditions, improving crystal parameters. Investigations into OSN crystallization so far have explored using membranes to control crystal size, shape and polymorphism.

Meanwhile, Sulzer Chemtech, Allschwil, Switzerland, is active in developing applications for OSN, which it also calls solvent-resistant nanofiltration, notes Corrie Korink-Zoetekouw, manager business development, process technology. The company says the technology can be applied as a standalone solution or combined with conventional separation technologies such as distillation, evaporation, chromatography and crystallization in a hybrid solution. Benefits include a reduction in the energy needed for separation processes, plus improved product quality and yield. Sulzer foresees applications in any processing situation where gentle product conditions can improve product quality.

ottewell.jpgSeán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at

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