A novel forward osmosis approach for organic solvent dehydration in pharmaceutical manufacturing
Organic solvents are widely used in the pharmaceutical industry for various purposes, such as dissolving active ingredients, performing reactions, purifying synthesis products, and enhancing the bioavailability of orally administered drugs. However, these solvents often need to be dehydrated to achieve the desired results, especially for processes such as crystallization. The conventional methods for dehydration, such as vacuum distillation, require the application of heat and pressure, which are not only time- and energy-consuming, but may also have negative effects on the quality and stability of the pharmaceutical intermediates, especially those that are sensitive to heat.
To overcome these challenges, researchers at Asahi Kasei Corp. (Düsseldorf, Germany and Tokyo, Japan; www.asahi-kasei.com) have developed a novel membrane-based system that dehydrates organic solvents without heat or pressure. The system is based on the phenomenon of forward osmosis, in which a liquid moves through a semipermeable membrane due to concentration differences. The system consists of a hollow-fiber membrane module and a draw solution that are suitable for organic solvents used in pharmaceutical manufacturing.
The membrane module contains polymer membranes that are selectively permeable to water, but not to the organic solvents or the pharmaceutical intermediates. The draw solution is a concentrated solution that creates a high osmotic pressure across the membrane, driving the water from the organic solvent to the draw solution side. The draw solution is then regenerated by removing the water and recycled back to the system.
The advantages of this membrane system are manifold. First, it can dehydrate organic solvents below 1,000 ppm without applying heat or pressure, thereby minimizing the impact on heat-sensitive pharmaceutical intermediates. Second, it can handle a variety of organic solvents, including alcohols, ethers, esters, and hydrocarbons, as well as highly soluble liquids, such as tetrahydrofuran (THF), toluene, or methanol. Third, it can shorten the process time and reduce the energy consumption compared to vacuum distillation. Fourth, it can prevent the loss of pharmaceutical intermediates, as they are retained on the organic solvent side of the membrane.
The following table summarizes the main features and benefits of the membrane system compared to vacuum distillation:
| Feature | Vacuum distillation | Membrane system |
|---|---|---|
| Dehydration method | Heat and pressure | Forward osmosis |
| Water content in organic solvent | < 1,000 ppm | < 1,000 ppm |
| Impact on heat-sensitive intermediates | High | Low |
| Solvent compatibility | Limited | Wide |
| Process time | Long | Short |
| Energy consumption | High | Low |
| Loss of intermediates | Possible | None |
The membrane system is currently undergoing practical verification in collaboration with Ono Pharmaceutical Co., Ltd., one of the largest pharmaceutical companies in Japan. The commercialization of the system is targeted for 2027. The system is expected to contribute to the optimization of manufacturing processes and the improvement of product quality in the pharmaceutical industry.
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