Hydrogenation of catmint oil

Abstract

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.

What is claimed is: 
     
         1 . A process for preparing hydrogenated catmint oil comprising:
 (a) distilling a beginning amount of crude catmint oil to produce (i) a distillate fraction comprising volatile components driven off from the crude catmint oil, wherein the weight of the distillate fraction comprises about 2% to about 20% of the weight of the beginning amount of crude catmint oil, and (ii) a pot fraction;   (b) contacting the pot fraction produced in step (a) with hydrogen and a hydrogenation catalyst to produce hydrogenated catmint oil; and   (c) optionally, recovering the hydrogenated catmint oil of step (b).   
     
     
         2 . 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 crude catmint oil. 
     
     
         3 . The process of  claim 1  wherein the step of distilling (a) comprises a step of (i) vacuum distilling, (ii) steam distilling, (iii) solvent distilling, or (iv) steam distilling followed by solvent distilling. 
     
     
         4 . The process of  claim 3  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. 
     
     
         5 . The process of  claim 4  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. 
     
     
         6 . The process of  claim 3  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. 
     
     
         7 . The process of  claim 6  wherein the alcohol is selected from the group consisting of methanol, ethanol, isopropanol and n-propanol. 
     
     
         8 . The process of  claim 3  wherein steam distilling, solvent distilling, or steam distilling followed by solvent distilling, is performed under vacuum. 
     
     
         9 . The process of  claim 1  which further comprises a step, before distillation, of contacting the beginning amount of crude catmint oil with an oxidizing agent selected from Na 2 B 4 O 7 .10H 2 O, hydrogen peroxide and mixtures thereof. 
     
     
         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 . A process for preparing hydrogenated catmint oil comprising:
 (a) distilling a beginning amount of crude catmint oil that has at least about 150 ppm of sulfur-containing compounds to produce (i) a distillate fraction that comprises at least about 8 wt % of the amount of sulfur-containing compounds in the beginning amount of crude catmint oil, and (ii) a pot fraction;   (b) contacting the pot fraction produced in step (a) with hydrogen and a hydrogenation catalyst to produce hydrogenated catmint oil; and   (c) optionally, recovering the hydrogenated catmint oil of step (b).   
     
     
         12 . The process of  claim 11  wherein the step of distilling (a) comprises a step of (i) vacuum distilling, (ii) steam distilling, (iii) solvent distilling, or (iv) steam distilling followed by solvent distilling. 
     
     
         13 . The process of  claim 12  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. 
     
     
         14 . The process of  claim 13  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. 
     
     
         15 . The process of  claim 12  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. 
     
     
         16 . The process of  claim 12  wherein steam distilling, solvent distilling, or steam distilling followed by solvent distilling, is performed under vacuum. 
     
     
         17 . 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. 
     
     
         18 . 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.