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US 8,785,698 B2Granted
Methods and apparatus for production of natural L-menthol
AssigneeNagaoka & Co., Ltd.
InventorsRyosuke Nagaoka, Hideaki Izukura, Susumu Tokita, Yuri Shibata, Yoshiyuki Nagaoka
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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.
Claims8
A method for purifying 1-menthol, comprising:
- providing crude mentha oil in a crystallizer, wherein the crude mentha oil is from a mint plant and comprises 1-menthol in the range of about 50% to about 95% by weight, and wherein the crude mentha oil is free of organic solvents;
- crystallizing 1-menthol from the crude mentha oil by gradually reducing temperature in the crystallizer from a starting temperature at which the 1-menthol is a liquid to a cooled temperature in the range of −30° C. to 25° C. at a cooling rate in the range of 0.1° C./day to 10° C./day to form 1-menthol crystals;
- passing a gas over the 1-menthol crystals to remove residual oil and impurities while gradually elevating the temperature in the crystallizer to a temperature in the range of 30° C. to 40° C., wherein purified 1-menthol crystals of at least 98% purity by weight are obtained;
- melting the purified 1-menthol crystals to remove 1-menthol from the crystallizer as a melt;
- and
- cooling the melt into a dried, solid 1-menthol product, wherein the method is performed in a closed system without human contact with the crude mentha oil or the 1-menthol.
3 more elements
Dependencies are inferred from the claim text.