US3275696A - Process for the production of citronellol - Google Patents

Description

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United States Patent 3,275,696 PROCESS FOR THE PRODUCTION OF CITRONELLOL Emanuel Goldstein, Paramus, N.J., assignor to Universal Oil Products Company, Des Plaines, 111., a corporation of Delaware No Drawing. Filed July 27, 1964, Ser. No. 385,502

1 Claim. (Cl. 260-6315) This application is a continuation-in-part of copending application Serial No. 91,577, filed February 27, 1961, now abandoned. This invention is directed to a process for the production of citronellol and more particularly is directed to the production of citronellol by the hydrogenation of geraniol in the presence of Raney cobalt catalyst.

Citronellol has odor properties which make it valuable as an ingredient of perfumery compositions. It is found in nature as a component of many essential oils but generally it is obtained by reducing geraniol either chemically or by catalytic hydrogenation. One of the most readily available sources of geraniol for conversion to citronellol is a processed naturally occurring oil, described in commerce as geraniol mixture, which frequently contains in addition to geraniol substantial quantities of citronellol as well as minor amounts of non-alcoholic terpenic hydrocarbons. The relative quantities of these materials in the geraniol mixtures of commerce vary considerably and are dependent primarily upon the natural source of the geraniol mixture and upon the chemical treatment employed in processing and purifying it.

In obtaining citronellol commercially, catalytic hydrogenation of geraniol has become the standard procedure, but the obtainment of citronellol by the catalytic hydrogenation of geraniol suffers from a number of disadvan- Principal among these disadvantages is that it is exceedingly difiic-ult to obtain citronellol substantially free from its further reaction product, dimethyloctanol. This production of dimethyloctanol concomitantly with the citronellol severely detracts from the success of the hydrogenation because in addition to obviously lowering the yield of the citronellol product, the presence of dimethyloctanol detracts from the odor of the citronellol which is its principally desired property. Moreover, the disadvantages resulting from the presence of the dimethyloctanol are not readily eliminated by separation of the dimethyloctanol from the citronellol because such separation is not readily effected by usual methods due to the similarity of the physical properties of citronellol and dimethyloctanol.

To obtain the desired citronellol relatively free from the undesired dimethyloctanol, an extremely selective hydrogenation must be effected whereby of the two olefinic double bonds existing in the geraniol molecule in the 2 lol which compete in the hydrogenation and become saturated thereby lowering the net obtainment of citronellol and increasing the net production of dimethyloctanol.

To obtain the desired result of hydrogenating geraniol to citronellol relatively free from dimethyloctanol, various catalysts have been utilized heretofore but none have achieved the selectivity desired whereby large quantities of citronellol are produced without simultaneously producing substantial quantities of the undesired dimethyl- 'ice octanol. Moreover, prior to the advent of modern analytical methods such as gas-liquid chromatography, it was exceedingly difiicult to ascertain the composition of the hydrogenation product and thus the selectivity of the catalysts utilized. However, it is now observed by using such analytical methods that hydrogenating commercial geraniol mixture in the presence of catalysts containing nickel or platinum results in an increase in the dimethyloctantol content of from an initial level of from about 0 to 4 percent by weight to a final level of from about 46 to 51 percent by weight, respectively. Obviously, citronello products containing such high concentrations of dimethyloctanol are greatly lowered in commercial value for the reasons set forth above. Nevertheless, catalysts containing nickel or platinum were used heretofore in the hydrogenation of geraniol because it was generally accepted that no catalyst could be found which could substantially improve upon the results obtained with such catalysts.

It has now been discovered, however, that the conversion of geraniol to citronellol by catalytic hydrogenation can be effected without the aforementioned disadvantages and with almost negligible production of dimethyloctanol of the order of only from about 1 to 5 percent by weight net increase by conducting the hydrogenation in the presence of Raney cobalt catalyst. This discovery becomes even more significant when it is considered that such a low production of dimethyloctanol is achieved when hydrogenating commercial geraniol mixtures which initially contain almost as much citronellol as geraniol.

Accordingly, therefore, it is an object of this invention to provide a process for the production of citronellol by the catalytic hydrogenation of geraniol which avoids the problems heretofore inherent in such a procedure. Another object of this invention is to provide a process for the production of citronellol substantially free from dimethyloctanol by hydrogenerating geraniol in the presence of Raney cobalt catalyst. A further object of this invention is to provide a process for the production of citronellol substantially free from dimethyloctanol by hydrogenating geraniol in a mixture containing citronellol in the presence of Raney cobalt catalyst.

While the properties and characteristics of catalysts can not always be predicted with certainty nor their operation in any particular reaction readily explained, the high selectivity of Raney cobalt catalyst in the hydrogenation of geraniol is most surprising in view of the fact that it has long been believed that a selective hydrogenation of geraniol could not be achieved due to the existence of two comparable double bonds in geraniol, only one of which must be saturated to form the desired citronellol product prior to saturation of the second bond to form the undesired dimethyloctanol. Moreover, this remarkable selectivity of Raney cobalt is quite unexpected because other cobalt containing catalysts such as cobalt oxide do not exhibit a comparable level of selectivity.

In conducting the process of this invention, the geraniol to be converted to citronellol is charged with the Raney cobalt catalyst to a suitable pressure vessel equipped with stirring and heating means and therein treated with hydrogen under hydrogenation conditions of elevated pressure and temperature for a time sufiicient to convert substantially all of the geraniol to citronellol. The citronnellol may then be recovered from the hyrogenation product and purified by conventional treating steps to obtain a citronellol product having desirable odor properties, and particularly suitable for perfumery use.

In conducting the process, a batch-type operation is preferred in which the reactants and catalyst are charged to the reaction vessel only at the start of the hydrogenation and the product is recovered only at the termination of the hydrogenation. However, if desired, a continuoustype operation may be utilized wherein the reactants and product, and if there is no fixed bed of catalyst, also the catalyst are continuously charged into and withdrawn 'from the pressure vessel during the hydrogenation.

The hydrogenation conditions of temperature and pressure under which the hydrogenation is effected may be varied with temperatures of from about 100 to 150 C. and pressures of from about 100 to 500 pounds per square inch being preferred, although temperatures of from about 25 to 200 C. and pressures from about 50 to 550 pounds per square inch gage may also be used when desired.

The Raney cobalt catalyst utilized in the process of this invention is the Raney cobalt catalyst of commerce which is generally prepared by the alkali digestion of an aluminum cobalt alloy. The Raney cobalt is preferably used in a finely divided form, but may, if desired, also be used as a composite of the catalyst supported on an inert carrier. The Raney cobalt catalyst may be used in varying amounts depending upon the particular rate of hydrogenation desired with amounts of from about 1 to 25 percent by weight of the geraniol charge being satisfactory in most instances and with amounts of from about 2 to 20 percent by weight being preferable to avoid any possible excessive hydrogenation rates with possible formation of the undesired dimethyloctanol.

In conducting the process it is desirable to terminate 'the hydrogenation when the amount of hydrogen remixed with the geraniol which also adsorb the hydrogen this making estimation of hydrogen adsorption requirements difiicult. However, certain indicators of this point in the hydrogenation have been observed whereby an approximation can be made of the point in the hydrogenation when substantially all of the geraniol has been converted. One indicator of this point is the decrease in the hydrogen adsorption rate when the reduction of geraniol has been substantially completed. This, of course, is due to the extreme selectively of the Raney cobalt catalyst to preferentially saturated only one of the double bonds. Another indicator of this point is the refractive index of the hydrogenation mixture which decreases in value as the geraniol is converted during the hydrogenation.

Utilizing either or both of these indicators to follow the progress of the hydrogenation, it is generally advisable to stop the hydrogenation when there is a small proportion of the geraniol remaining of the order of about 5 percent by weight of the mixture. By terminating the hydrogenation at this point, the likelihood of converting the citronellol in the hydrogenation mixture to dimethyloctan-ol is substantially lessened, and moveover, this small quantity of geraniol remaining in admixture with the citronellol is not significantly detrimental to its commercial value.

As hereto-fore indicated, one of the particular advantages obtained as a result of the extremely high selectivity of Raney cobalt catalyst in the hydrogenation of geraniol to citronellol is that the most readily available source of geraniol, namely the geraniol mixture of commerce which frequently contains initially a substantial quantity of citronellol admixed with the geraniol, may be directly hydrogenated without converting any substantial amount of the citronellol initially present, as well as any of the citronellol produced in the process, to the undesired dimethyloctanol. Moreover, the commercial geraniol mixture may be hydrogenated in a procedure identical to that for substantially pure geraniol without 4 any major departure from the processing procedures and hydrogenating conditions heretofore described.

The process of this invention may be illustrated by the following examples which, however, are not intended to limit the generally broad scope of the present invention in strict accordance therewith. In the following examples, the weight percentages of the compositions indicated were measured by gas-liquid chromatography and were based upon the alcoholic content of the compositions.

Example I A commercial geraniol mixture was hydrogenated according to this invention in the presence of Raney cobalt catalyst by the following procedure.

This geraniol mixture had the following composition:

(1) By analysis for hydroxyl coriterrt, percent by weight C alcohols 87 Terpene hydrocarbons 13 (2) By gas-liquid chromatography analysis, percent by weight Geraniol 55 Citronellol 35 Dimethyloctanol 4 Approximately 1325 grams of this geraniol mixture were charged into a stainless steel stirred autoclave containing about 27 grams of Raney cobalt catalyst. Hydrogen was then charged to the autoclave and the mixture was heated to about 130 C. and hydrogenated at pressures of about 500 to pounds per square inch gage. As the hydrogenation proceeded, the refractive index of the mixture changed as the quantity of the geraniol in the geraniol mixture decreased by conversion. When the refractive index of the mixture had dropped from an initial value of 1.4725 to 1.4585 the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods of indicate the following composition as contrasted with that of the charge:

Upon distillation of the hydrogenated product, to remove the non-alcoholic terpenic materials, about 1052 grams of product were obtained, having an excellent citronellol odor and highly suitable for use in per-fumery. At the termination of the hydrogenation, about 6.76 moles of hydrogen had been adsorbed. This amount of hydrogen represents about a 42 percent excess based upon the moles of geraniol (4.75) present initially in the geraniol mixture. Obviously, the excess of hydrogen has reacted primarily with the small amount of terpenic material initially present in the geraniol mixture because there was only about a 1 percent net increase in the level of the dimethyloctanol.

Example II A commercial geraniol mixture was hydrogenated according to this invention in the presence of Raney cobalt catalyst by the following procedure.

This geraniol mixture had the following composition:

(1) By analysis for hydroxyl content, percent by weight- C alcohols 87 Terpene hydrocarbons 13 present in the geraniol mixture.

5 (2) By gas-liquid chromatography analysis, percent by weight Geraniol 60 Citronellol 36.3 Dimethyloctanol 3 .9

Approximately 1325 grams of this geraniol mixture were changed into a stainless steel, stirred autoclave containing about 27 grams of Raney cobalt catalyst. Hydrogen was then charged to the autoclave and the mixture was heated to about 130 C. and hydrogenated at pressures of about 500 to 125 pounds per square inch gage. As the hydrogenation proceeded, the refractive index of the geraniol mixture decreased and when a value of 1.4580 was reached, which was assumed to indicate almost complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge:

At the termination of the hydrogenation, about 7.13 moles of hydrogen had been adsorbed. This amount of hydrogen represents about a 38 percent excess based upon the moles of geraniol (5.17) percent initially in the geraniol mixture. This excess of hydrogen has obviously primarily reacted with the terpenic materials originally present in the geraniol mixture because there was only a 5.1 .percent net increase in the dimethyloctanol.

The progress of the hydrogenation and the extreme selectivity of the Raney cobalt catalyst to effect hydrogenation of only the double bond in the 2 position is demonstrated by the following data which represents the composition of the geraniol mixture at different levels of hydrogen adsorption. In the following table, the percent of hydrogen theory is the ratio in percent of the moles of hydrogen adsorbed per moles of hydrogen theo- 1 retically required to saturate one double bond of the geraniol present.

Hydrogen Geraniol Citronellol Dimethyl- Theory Weight Weight octanol Percent Percent Percent Weight Percent The data of the above table indicates that when about 72.5 percent of hydrogen has been adsorbed there has been little change in the contents of geraniol, citronellol or dimethyloctanol, with most of the hydrogen reacting with the small amount of terpenic hydrocarbons originally From about 72 to 87 percent of hydrogen theory, however, there is a substantial conversion of the geraniol to the citronellol of about a 28 percent net increase in the citronellol level, while at the same time there is substantially no change in the level of the dimethyloctanol, indicating an extreme selectivity 6 Example 111 A noncommercial geraniol mixture containing only about 2 to 4 percent by weight of non-alcoholic terpenic hydrocarbons was hydrogenated according to this invention by the following procedure. I

This geraniol mixture had the following composition:

(1) By analysis for hydroxyl content, percent by weight- C hydrocarbons 96 to 98 Terpene hydrocarbons 2 to 4 (2) By gas-liquid chromatography analysis, percent by weight- Geraniol 53.7 Citronellol 42.7 Dimethyloctanol 3.9

Approximately 530 grams of this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 10.6 grams of Raney cobalt catalyst. Hydrogen was then charged to the autoclave and the mixture was heated to about 130 C. and hydrogenated at pressures of about 300 to about 230 pounds per square inch gage. As the hydrogenation proceeded, the refractive index of the charge material decreased and when a value of 1.4565 was reached, which was assumed to indicate almost complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogenation product was recovered and analyzed 'by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge:

At the termination of the hydrogenation about 1.85 moles of hydrogen had been adsorbed. This amount of hydrogen represents substantially about a one-mole theory based upon the moles of geraniol (1.85). present initially in the geraniol mixture.

The progress of the hydrogenation and the extreme selectivity of the Raney cobalt catalyst in effecting hydrogenation of only the double bond in. the 2 position of the geraniol is demonstrated by the following data which represents the composition of the geraniol mixture at difierent levels of hydrogen adsorption. In the following table the percent hydrogen theory is the ratio in percent of the moles of hydrogen adsorbed per moles of hydrogen theoretically required to saturate one double bond of the geraniol present.

Hydrogen Geraniol Citronellol Dimethyl- Theory, Weight Weight octanol Percent Percent Percent Weight Percent O 53. 7 42. 7 3. 9 68 24. 4 69. 6 6. 0 76. 5 15.9 77. 9 6.3 81. 5 12. 7 80. 4 6. 9 9O 9. 83. 4 7. l 100 3. 1 88. 1 8. 8

The above table of data indicates that, in the hydrogenation of a mixture containing about equal parts of geraniol and citronellol, the Raney cobalt catalyst eifects hydrogenation of only the double bond in the 2 position of the geraniol to the substantial exclusion of the double bond in the 6 position of the citronellol. This selectivity A commercial geraniol mixture was hydrogenated in the presence of cobalt oxide catalyst which is not according to this invention by the following procedure.

This geraniol mixture had the (following composition:

(1) By analysis for hydroxyl content, percent by weight C hydrocarbons 87 Terpene hydrocarbons 13 (2) By gas-liquid chromatography analysis, percent by weight- Geraniol 55 Citronellol 35 Dimethyloctanol 4 Approximately 530 grams of this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 10.3 grams of cobalt oxide. Hydrogen was then charged to the autoclave and the mixture was heated to about 1.25" to 145 C. and hydrogenated at pressures of about 300 to 150 pounds per square inch gage. As the hydrogenation proceeds, the refractive index of the charge material decreases and when a value was reached which was assumed to indicate complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixtwo to about 25 C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the initial charge:

Product Weight, Percent Charge Weight, Percent Net Change, Percent Geraniol 4 Citronellol 69 Dimethyloctanol 16 Minn- At the termination of the hydrogenation about 2.4 moles of hydrogen had been adsorbed. This amount of hydrogen represents about a 26 percent excess based upon the moles of geraniol (1.9) present initially in the geraniol mixture.

The results of the hydrogenation indicate that compared to Raney cobalt catalyst, the cobalt oxide catalyst is not selective in attacking only the double bond in the 2 position because at the termination of the hydrogenation,

'therehas been only a net increase of 34.2 percent in the level of the citronellol while the dimethyloctanol level has increased 12.9 percent to a final level of 16.9 percent of the mixture.

T Example V i (2) By gas-liquid chromatography analysis, percent by weight- Geraniol 55 Citronellol 35 Dimethyloctanol 0 Approximately 1000 grams of "this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 13.3 grams of Raney nickel catalyst and 18.5 grams of water. Hydrogen was then charged to the autoclave and the mixture was heated to about C. and hydrogenated at pressures of about 300 to pounds per square inch gage. As the hydrogenation proceeded, the refractive index of the charge mixture decreased and when a value was reached which was assumed to indicate almost complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogen product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge.

Product Charge Net Change, Weight, Weight, Percent Percent Percent Geraniol 9. 9 55 45. 1 Citronellol 60. 9 35 +25. 9 Dimethyloctanol 29. 4 0 +29. 4

At the termination of the hydrogenation, approximately 3.98 moles of hydrogen had been adsorbed. This amount of hydrogen represents about a 10.3 percent excess based upon the moles of geraniol (3.57) present initially in the geraniol mixture.

The progress of the hydrogenation and the low selectivity of the Raney nickel catalyst, as compared with Raney cobalt catalyst, in effecting hydrogenation of only the double bond in the 2 position of geraniol is demonstrated by the following data which represents the composition of the geraniol mixture at different levels of hydrogen adsorption. In the following table, the percent hydrogen theory is the ratio in percent of the moles of hydrogen adsorbed per moles of hydrogen theoretically required to saturate one double bond of the geraniol present.

Hydrogen Geranlol Citronellol Dimethyl- Theory, Weight Weight octanol Percent Percent Percent Weight Percent The above table of data indicates the poor selectivity of the Raney nickel catalyst in the hydrogenation of the double bond in the 2 position of geraniol. For example, even at low levels of hydrogen adsorption (15.6 percent of theory) there is a substantial production of dimethyloctanol of about a 9 percent net increase with an almost negligible net increase in the quantity of the desired citronellol indicating that the reaction is principally the reduction of the double bond in the 6 position of the citronellol originally present in the mixtures or that formed from the geraniol. Moreover, at the termination of the hydrogenation when there remains a substantial quantity of unreacted geraniol of almost 10 percent, the mixture contains about 30 percent of the highly undesirable dimethyloctanol.

Example VI A commercial geraniol mixture was hydrogenated in the presence of a nickel kieselguhr catalyst which is not according to this invention by the following procedure.

This geraniol mixture had the following composition:

Geraniol 54.3 Citronellol 29.3 Dimethyloctanol Approximately 1000 grams of this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 50 grams of a nickel kieselguhr catalyst identified as Girdler catalyst, G49-A, Hydrogen was then charged to the autoclave and the mixture heated to about 35 C. and hydrogenated at pressures of about 300 to 270 pounds per square inch garge. As the hydrogenation proceeded the refractive index of the charge mixture decreased and when a value was reached which was assumed to indicate almost complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge:

At the termination of the hydrogenation, approximately 7.3 moles of hydrogen had been adsorbed. This amount of hydrogen represents about a 31 percent excess based upon the moles of geraniol (3.5) present initially in the geraniol mixture.

The progress of the hydrogenation and the low selectivity of the nickel catalyst, as compared to the Raney cobalt catalyst in eifecting hydrogenation of only the double bond in the 2 position of geraniol is demonstrated by the following data which represents the composition of the geraniol mixture at different levels of hydrogen adsorption. In the following table, the percent hydrogen theory is the ratio in percent of the moles of hydrogen adsorbed per moles of hydrogen theoretically required to saturate one double bond of the geraniol present.

Hydrogen Geraniol Citronellol Dimethyl- Theory, Weight Weight octanol Percent Percent Percent Weight Percent The above table of data indicates the poor selectivity of the nickel catalyst in effecting hydrogenation of the double bond in the 2 position of geraniol even at very mild hydrogenating temperatures of about 35 C. For example, even at low levels of hydrogen adsorption (27 percent of theory) there is already significant formation of the undesired dimethyloctanol of the order of a percent net increase. Moreover, near the end of the hydrogenation when there remains only about 4 percent geraniol there is a 28.8 percent net increase of the dimethyloctanol and at the end of the hydrogenation with about 0.5 percent geraniol remaining, the mixture contains as much as 46 percent dimethyloctanol.

10 Example VII A commercial geraniol mixture was hydrogenated in the presence of a palladium charcoal catalyst which is not according to this invention by the following procedure.

This geranoil mixture had the following composition:

(1) By analysis for hydroxyl content, percent by weight- C alcohols 87 Terpene hydrocarbons 13 (2) By gas-liquid chromatography analysis, percent by weight Geraniol 55 Citronellol 35 Dimethylo'ctanol 4 Approximately 530 grams of this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 10.6 grams of palladium charcoal catalyst containing 2 percent by weight of palladium. Hydrogen was then charged to the autoclave and the mixture heated to about C. and hydrogenated at pressures of about 300 to pounds per square inch gage. As the hydrogenation proceeded the refractive index of the the charge mixture decreased and when a value was reached which was assumed to indicate almost complete conversion of the geraniol, the hydrogenation was stopped by cooling the mixture to about 25 C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge:

Product Charge N ct Change,

Weight, Weight, Percent Percent Percent Geraniol 4. 6 55 50. 4 Citronellol 30. 4 35 4. 6 Dimethyloctanol 24. 4 4 20. 4

Example XIII The hydrogenation as described in Example VII was repeated, except that a lower temperature of 45 to 60 C. was utilized in an attempt to effect less severe hydrogenation. The results, however, as indicated in the following table were substantially the same, with no catalyst selectivity and with an actual decrease in the original level of the citronellol in the geraniol mixture.

Product Charge Net Change, Weight, Weight, Percent Percent Percent Geraniol 4. 7 55 50.3 Citronellol 30. 2 35 4. 8 Dimethyloctanol 24. 2 4 +20. 2

Example IX A commercial geraniol mixture was hydrogenated in the presence of a platinum oxide catalyst which is not according to this invention by the following procedure.

This commercial geraniol mixture had the following composition:

11 (1) By analysis for hydroxyl contents, percent by weight- C alcohols 87 Terpene hydrocarbons 13 (2) By gas-liquid chromatography analysis, percent by weight Geraniol 55 Citronellol 35 Dimethyloctanol 4 Approximately 15.4 grams of this geraniol mixture were charged into a stainless steel, stirred autoclave containing about 001 gram of platinum oxide catalyst. Hydrogen Was then charged to the autoclave and heated to about substantial production of the desired citronellol of as high as about a 55 percent net increase in level which results in products containing as much as 90 percent citronellol by weight.

The excellent selectivity of the Raney cobalt catalyst may be compared in the following table with the selectivity of other hydrogenation catalysts where it may be observed that the other catalysts, even cobalt containing catalyst such as cobalt oxide, are not comparably selective in the hydrogenation of geraniol to citronellol. Moreover, the data of the following table indicate that the use of such other catalysts in the hydrogenation results in both low production of citronellol and high production of dimethyloctanol and even, in the instance of platinum oxide, actually results in a decrease in the amount of the citronellol 110 to 75 C. and hydrogenated at pressures of about originally contained in the hydrogenation charge.

Charge Weight Percent Product Weight Percent Net Change Percent Example Catalyst Geranlol C1tron- Dimethyl- Geraniol Citron- Dimethyl- Geraniol Citron- Dimethylellol octanol ellol oct anol ellol oetanol Raney cobalt 55 35 4 4 84 5 51 +49 +1 Raney cobalt 60 36. 3 3. 9 0 91. 1 9.03 60 +54. 8 +5. 13 Raney cobalt. 53. 7 42. 7 3.9 3. 1 88. 1 8. 8 50. 6 +45. 4 +4. 9 Cobalt oxide 55 35 4 4. 1 69.2 16. 9 51. 9 +34. 2 +12. 9 Raney Nickel 55 35 0 9. 9 60. 9 29. 4 45. 1 +25. 9 +29. 4 Nickel Kieselguhr 54. 3 29. 3 0 0. 5 52. 7 46. 8 53. 8 +23. 4 +46. 8 Palladium Chareoal 55 35 4 4.6 30. 4 24.4 50. 4 -4. 6 +20. 4 Palladium Charcoal... 55 35 4 4. 7 30. 2 24. 2 50. 3 4. 8 +20. 2 Platinum oxide 55 35 4 0 40. 2 51. 0 55 +5. 2 +47. 0

500 to 300 pounds per square inch gage. As the hydrogenation proceeded, the refractive index of the geraniol mixture decreased and when a value was reached which indicated that almost all of the geraniol in the geraniol mixture had been converted, the hydrogenation was stopped by cooling the mixture to about C.

The hydrogenation product was recovered and analyzed by gas-liquid chromatography methods to indicate the following composition as contrasted with that of the charge:

Product Charge Net Change, Weight, Weight, Percent Percent Percent Geraniol O 55 55 Citronellol 40. 2 +5. 2 Dirnethyloctanol 51. 0 4 +47. 0

At the termination of the hydrogenation approximately 0.06 mole of hydrogen had been adsorbed. This amount of hydrogen represents about a 9 percent excess based upon the moles of geraniol (0.055) initially present in the geraniol mixture.

The above data demonstrates the non-selectivity of platinum oxide catalyst in the hydrogenation of geraniol for while there is only a net increase in the level of the citronellol of about 5 percent, there is a net increase in the level of the dimethyloctanol of about 47 percent.

Example X I claim as my invention:

A process for the production of citronellol without substantial formation of dimethyloct anol from a mixture of geraniol and citronellol which comprises subjecting said mixture to reaction with hydrogen in the presence of from about 1% to about 25% by weight of Raney cobalt catalyst resulting from the alkali digestion of aluminum-cobalt alloy, said reaction being at a temperature of from about 25 C. to about 200 C. and a pressure of from about 50 to about 550 pounds per square inch to selectively hydrogenate only the double bond in the 2-position of the geraniol to the substantial exclusion of the double bond in the 6-position of the geraniol, the citronellol in admixture with the geraniol, and the citronellol formed by the reaction, and recovering the citronellol.

References Cited by the Examiner FOREIGN PATENTS 6/ 1917 Germany.

OTHER REFERENCES don), vol. 8 (1958), pp. 492-495.

Berkman et al.: Catalysis (1940), p. 263.

Escourrou: Les Parfums de France (1925), pp. 86- 102.

Grignard et al.: Bull. Soc. Chim (FL), vol. 37 (1925), pp. 542-8.

Ishimura et al.: Chem. Abstracts, vol. 41 (1947), p. 4445.

Marullo: Chemical Abstracts, vol. 51 (1957), p. 12'128h.

Simonsen: The Terpenes, vol 1, 2nd ed., 1947, p. 88.

LEON ZITVER, Primary Examiner.

J. E. EVANS, T. G. LDILLAHUNTY,

Assistant Examiners.