Racemic leucine separation by hollow‐fiber extraction

Racemic leucine can be separated into d‐ and l‐isomers by fractional extraction across microporous hollow fibers. In this extraction, an aqueous solution of the racemate is fed to the lumen of the fibers, and an octanol solution of dodecyl‐l‐hydroxyproline flows countercurrently outside of the fibers. The interface between feed and extractant is stabilized by filling the pores in the hollow‐fiber walls with a cross‐linked polyvinylalcohol gel which offers negligible resistance to mass transfer. The extraction with dodecyl‐l‐hydroxyproline deliberately imitates earlier studies, facilitating comparisons of hollow‐fiber extraction with other techniques. The results show that the isomer yield per equipment volume of racemic separation is 100 times greater than that in a continuously rotating extractor, and 1,000 times greater than that in a conventional packed tower.