Industrial-Scale Organic Solvent Nanofiltration for Dimer Impurity Removal: Enhancing Vitamin D₃ Production

This work details the removal of an azine-dimer (AD) impurity from 7-dehydrocholesterol (DHC), a precursor of vitamin D3, using a newly developed, sustainable hybrid membrane process, from the idea to implementation. Developed by an international team collaborating under tight time frame and COVID restrictions, this innovative method exemplifies a versatile, energy-saving, and cost-effective separation technology by organic solvent nanofiltration (OSN). Traditional purification methods proved to be unsuccessful, costly, or unsustainable, but this process achieved DHC purification with a minimal yield loss of 0.1%. This separation challenge goes beyond typical OSN applications (solute concentration or solvent exchange) by separating two similar solutes in a solvent mixture. In a three-stage OSN process, the impurity level was reduced from approximately 2600 ppm to below 50 ppm in the final permeate. After developing and scaling up the process, the OSN, precipitation, and filtration units were engineered and constructed. These units were installed in the dsm-firmenich vitamin D3 plant, and the purification process was successfully commissioned.