Industrial-Scale\nOrganic Solvent Nanofiltration for\nDimer Impurity Removal: Enhancing Vitamin D<sub>3</sub> Production

This work details the removal of an azine-dimer (AD)\nimpurity from\n7-dehydrocholesterol (DHC), a precursor of vitamin D<sub>3</sub>,\nusing a newly developed, sustainable hybrid membrane process, from\nthe idea to implementation. Developed by an international team collaborating\nunder tight time frame and COVID restrictions, this innovative method\nexemplifies a versatile, energy-saving, and cost-effective separation\ntechnology by organic solvent nanofiltration (OSN). Traditional purification\nmethods proved to be unsuccessful, costly, or unsustainable, but this\nprocess achieved DHC purification with a minimal yield loss of 0.1%.\nThis separation challenge goes beyond typical OSN applications (solute\nconcentration or solvent exchange) by separating two similar solutes\nin a solvent mixture. In a three-stage OSN process, the impurity level\nwas reduced from approximately 2600 ppm to below 50 ppm in the final\npermeate. After developing and scaling up the process, the OSN, precipitation,\nand filtration units were engineered and constructed. These units\nwere installed in the dsm-firmenich vitamin D<sub>3</sub> plant, and\nthe purification process was successfully commissioned.