Methods and apparatus for production of natural l-menthol

Abstract

Embodiments are provided that provide for efficient production of highly pure natural I-menthol. In some embodiments, a method for preparing natural I-menthol involves providing crude mentha oil in a crystallizer and gradually reducing the temperature of the crystallizer in a step-wise manner, thereby producing highly pure crystals in less than two weeks. The methods disclosed herein are suitable for pharmaceutical GMP.

What is claimed is: 
     
         1 . A system for purifying I-menthol, comprising:
 a crystallizer containing crude mentha oil of plant origin;   a stripping system adapted to pass a gas through the crystallizer;   an automated process control system comprising a processor programmed to:
 initiate reduction of a temperature in the crystallizer in order to reduce the temperature of the crude mentha oil from a temperature at which the crude mentha oil is a liquid to a temperature below 30° C. in a gradual manner over a period of at least 8 hours to cause I-menthol crystals to form in the crystallizer; 
 activate the stripping system in order to pass the gas over the crystals in the crystallizer to remove liquid from the crystals; and 
 initiate heating of the crystallizer in order to melt the crystals; and 
   a conduit configured to receive melted I-menthol from the crystallizer, wherein the crystallizer and the conduit together comprise a closed system that prevents contact between the content of the closed system and outside contaminants.   
     
     
         2 . The system of  claim 1 , wherein the crystallizer comprises a plurality of cooling plates and/or cooling coils. 
     
     
         3 . The system of  claim 2 , wherein the automated process control system independently controls the temperature for each of said plurality of cooling plates and/or cooling coils. 
     
     
         4 . The system of  claim 1 , wherein the system is automated. 
     
     
         5 . The system of  claim 1 , further comprising a crystal formation detector. 
     
     
         6 . The system of  claim 1 , wherein the conduit is in fluid communication with a storage tank, wherein the storage tank is part of the closed system. 
     
     
         7 . The system of  claim 1 , wherein the conduit is in fluid communication with a pelletizer, wherein the pelletizer is part of the closed system.