Conversion process of lanolin to 7-Dehydrocholestrol
The conversion of lanolin to 7-dehydrocholestrol is an important procedure in the production of vitamin D.
Lanolin is converted to cholesterol by a method which comprises of following steps:

dissociating cholesterol from lanolin by transesterification
reaction;

performing short-path distillation to obtain cholesterol crude
product

purifying by silica gel column chromatography

crystallizing to obtain refined cholesterol with purity higher than
95% and yield higher than 70%.


The extracted cholesterol is converted to 7-dehydrocholesterol and then treated with UV light to produce vitamin D3. The method has such advantages as high product consumption, little pollution, simple process and easy operation, thus is suitable for mass production.
References

https://patents.google.com/patent/CN1958596A/en
https://patents.google.com/patent/CN1263769C/en
https://www.sigmaaldrich.com/technical-documents/articles/biofiles/nutrition-research.html