Hydrogenation of catmint oil
Disclosed are methods for treating catmint oil. The treated catmint oil can be used for the production of hydrogenated catmint oil, which is enriched in the insect repellent, dihydronepetalactone.
1. A process for preparing hydrogenated catmint oil comprising:
(a) contracting crude catmint oil with an oxidizing agent comprising ozone to produce a first treated catmint oil;
(b) separating the first treated catmint oil from the oxidizing agent to produce a second treated catmint oil;
(c) contacting the second treated catmint oil with hydrogen and a hydrogenation catalyst to produce hydrogenated catmint oil; and
(d) optionally recovering the hydrogenated catmint oil.
2. The process of claim 1 further comprising:
(a-1) distilling a beginning amount of the second treated catmint oil to produce (i) a distillate fraction comprising volatile components driven off from the second treated catmint oil, wherein the weight of the distillate fraction comprises about 2% to about 20% of the weight of the beginning amount of the second treated catmint oil, and (ii) a pot fraction;
(b-1) contacting the pot fraction produced in step (a-1) with hydrogen and a hydrogenation catalyst to produce hydrogenated catmint oil; and
(c-1) optionally, recovering the hydrogenated catmint oil of step (b-1).
3. The process of claim 1 wherein the weight of the distillate fraction comprises about 5% to about 10% of the weight of the beginning amount of the second treated catmint oil.
4. The process of claim 1 wherein the step of distilling (a-1) comprises a step of (i) vacuum distilling, (ii) steam distilling, (iii) solvent distilling, or (iv) steam distilling followed by solvent distilling.
5. The process of claim 4 which comprises a step of solvent distilling, or of steam distilling followed by solvent distilling, and wherein, at the beginning of solvent distilling, the weight of the solvent comprises about 5% to about 60% of the combined weight of catmint oil plus solvent.
6. The process of claim 5 wherein, at the beginning of solvent distilling, the weight of the solvent comprises about 10% to about 25% of the combined weight of catmint oil plus solvent.
7. The process of claim 4 which comprises a step of solvent distilling, or of steam distilling followed by solvent distilling, and wherein a solvent comprises a C 1 to C 5 straight-chain or branched alcohol.
8. The process of claim 7 wherein the alcohol is selected from the group consisting of methanol, ethanol, isopropanol and n-propanol.
9. The process of claim 4 wherein steam distilling, solvent distilling, or steam distilling followed by solvent distilling, is performed under vacuum.
10. The process of claim 1 wherein the pot fraction is contacted with hydrogen and a hydrogenation catalyst at a temperature of about −10° C. to about 200° C.
11. The process of claim 1 wherein the second treated catmint oil is contacted with hydrogen and a hydrogenation catalyst at a temperature of about −10° C. to about 200° C.
12. The process of claim 1 wherein distillation is conducted at a temperature of lower than about 200° C.
13. The process of claim 1 wherein distillation is conducted at a pressure of less than about 68.9 KPa.