US2975170A - Process for manufacturing terpeneless essential oils - Google Patents

Description

March 14, 1961 A. B. HERRICK ET Al. 2,975,170

PROCESS FOR MANUFACTURING TERPENELESS ESSENTIAL OILS Filed May 14, 1958 n l A I I I I LOO 2.00 3.00 4.00

Volume of Methanol Eluent Collected (liters) SEPARATION OF TERPENES FROM OXYGENATED COMPOUNDS OF ESSENTIAL OIL OF PETITGRAIN (ELUTION WITH ALCOHOL AFTER ABSORPTION BY RUBBER) al -14:? W

ATTORNEY United States atent PROCESS FOR MANUFACTURING TERPENELESS ESSENTIAL OILS Aaron 'Brown Herrick, Cedar Grove, and James R. Trowbridge, Glen Rock, N.J., assignors to Colgate-Palmolive Company, New York, N.Y., a corporation of Delaware Filed May 14, 1958, Ser. 'No. 735,213

7 Claims. (Cl. 260-2366) This invention relates to a process for removing terpene hydrocarbons from essential oils. More particularly the invented process is one in which terpene hydrocarbons are preferentially absorbed from an essential oil by a' I particulate solid material, terpeneless essential oil being volatility at room temperature.

Almost all of the essential oils contain a significant proportion of terpenes. In the cases of citrus oils, such as lemon, orange, grapefruit, lime and mandarin oils, to name a few, the terpenes constitute a major propor tion of the essential oil. Other oils, such as petitgrain (bigarade, Paraguayan, South American), bergamot, lavender, pirnenta berry, leaf, stem and bud clove oils, bay leaf, Sassafras and geranium, for examples, are com para-tively low in terpene content, having a minor proportion, generally less than about 30% of such compounds. 1

In some perfumery, cosmetic and flavor applications of essential oils the terpene content performs a useful function and is a desirable constituent of the essential oil employed. However, there is a large number of products and applications in which the terpenes are either harmful or undesirable. 1

Terpenes are generally of lower solubility in aqueous or alcoholic compositions thanare the oxygenated com-- ponents of the essential oils. In flavors intended for use in aqueous mixture, solution oremulsion, the terpenes are often insufliciently dispersible and usually rise to the top of the product, e.g., a soft drink or fruit juice, and form an unsightly oily layer, often of unpleasant taste. The oxygenated constituents of the essential oils, which are much more readilyemulsified or otherwise dispersed, do not give rise to this problem. Additionally, these essential oil constituents, such as alcohols, esters, ketones, aldehydes, acids and others, contribute to the more desirable perfume or flavor note of the oils and are not as not of satisfactory stability for many erfumery and flavor applications and natural oils containing themtend to be oxidized causing the production of unwanted odors and flavors. The oxidation of the terpenes may sometimes result in products which very se riously detract from the value and utility of the essential oils.

According to the present invention there is provided a process for removing terpenes from essential oils which comp'risescontacting' an essential oil containing OdOI'lfr. erous compounds and terpenes with a solid absorbent. material of high surface/volume ratio, whichmaterial has a greater aflinity. for'the terpenes than for the odoriferous compounds, and recovering essential oil from which terpenes have been'removed.

A'number of commercially important essential oils has been listed above. The present process is applicable to removal of terpene hydrocarbons from those oils but is not to be restricted thereto since it finds general use in removing terpenes and preparing terpeneless products from a wide variety of terpene-containing essential oils. By the term terpene it is meant those hydrocarbons of empirical formula C H and C H the mono-terpenes and sesquiterpenes which are considered to be the major insoluble and unsuitable constituents of the essential oils. As examples of these compounds may be mentioned alpha and beta pinenes, myrcene, dipentene, ocimene, terpinolene, d-limonene, gamma-terpinene, phellandrene, thujene, sesquicitronellene, bisabolene, beta-caryophyllene and cadinene. Essential oils usually consist substantially of mixtures of the terpenes and several more oxygenated odoriferous compounds. In the present process the terpenes are removed from the other constituents of the essential oil due to the action of a solid absorbent,

The solid material having a greater aflinity for the terpene hydrocarbons than for the other odoriferous components of the natural essential oils is one which perfer-. entially absorbs the terpenes. The mechanism of this absorption is apparently one in which the solid acts as a preferential solvent for the terpene molecules. Such action is evidenced by the pronounced swelling of some absorbents when in contact with terpenes. For the sake of simplicity the term absorption will be employed in this specification to denote the act-ionof the solid employed even though adsorption may also take place. The solid will be characterized as an absorbent. P j k l The solid absorbent material has a high surface/ volume ratio to promote intimate contact between essential oil' and absorbent and thereby obtain high effectiveness of' the absorbent in separating terpenes from the oxygenated components of the essential oils. To obtain a high surface/volume ratio the absorbent may be in fine particles or may be of larger size but of porous, perforated or spongy structure, possessing many intercornmunicating voids or passageways through which essential oil solution may flow and on and through thewalls of which terpenes may be absorbed. Whether the absorbent is in particulate or other useful form it is sufliciently formretaining to leave interstices adequate for passage of essential oil when the absorbent is packed in a column. Where the absorbent is controllably com- 1 pressible the sizes of interstices can be regulated by the packing force applied, thereby resulting in a versatile column of various regulatable flow rates and degrees of absorbency. f

It has been found that those absorbents which are non a polar exert a preferential afiinity for terpenes inessential oils. Unlike the polar adsorbents, such as alumina, silica gel, magnesia and so forth, the non-polar absorbents do not tend to react with the oils being processed and do not preferentially sorb the oxygenated odoriferousk constituents. Among the non-polar absorbents highly; Q polymeric products,such as -rubbers and non-polar'members of the class commonly referred to as plastics are suitable in the present processes. These materials are characterized as non-polar in this specification although they are sometimes considered as being of low polarity when compared with the highly polar adsorbents men' tioned above. Azfew examples of suitablejjpolymeri absorbents are processed natural rubber, prefer-abl only slightly vulcanized, Buna S, neoprene and siliconerubbers Various plastics'may also be employed, such; as 7 vinyl chloride, polyvinylidene chloride, polyethv other lower alkylene polymers, polystyrene, such as Dacron, and so forthL Usually it'is preferable to use the softer, more elastorneric forms of these organic polymers, which often are more absorbent and have a greater afiinity for terpenes, but harder plastics may also be usefully employed providing that they are of sutficient absorbency.

Usually the polymeric absorbent is granulated or otherwise reduced in size to particles having a maximum diameter of about 0.1 inch. Generally, the ground absorbent should be no smaller than 0.001 inch in diameter. To facilitate regular flow without channelling the particles should be of about the same size. However, so long as the powdered solid is separable from the liquid media employed and sufiioient contact is obtained with the essential oil being treated sizes outside the range given may find use. Grinding of the elastomeric polymers and the thermoplastic absorbents may be facilitated by lowering the temperature of the absorbent before size reduction, as by chilling with Dry Ice.

The particulate absorbent is preferably packed in a container through which the natural essential oil can be passed. In this packed container the absorbent may be considered to act as if it were a multiplicity of plates in a distilling column, each successive layer of absorbent tending to hold back the flow of some of the terpene content of the feed to that layer. Thus, after passing the natural essential oil through a packed tower or column of polymeric non-polar absorbent the terpene has been stripped from the valuable odoriferous oxygenated components of the oil. In many instances the terpene is so strongly 'attracted by the non-polar absorbent that a batch-type separation may be carried out successfully. This type of process is especially applicable when the essential oil is comparatively low in terpene content.

When the non-polar absorbent employed possesses some adhesive properties particles thereof tend to be loosely held together and are sometimes removable from an absorption column as a unit. Providing that the compacting of the absorbent is'not. so great as to make it into an impenetrable mass this light cementing action is of advantage because it promotes retention of the packing in position and diminishes settling of the absorbent during use. The resiliency of the non-polar packing also causes it to resist sifting.

If used as a sponge having interconnecting voids the resilient and elastomeric absorbents can be inserted and removed as a unit and, as previously mentioned, can be easily adjusted in solid/void ratio by regulated compression, giving various controllable flow rates and degrees of absorption. Such unitary absorbents can be partially freed of terpenes and solvent after the deterpenation of essential oil, by squeezing, or alternate compression and relaxation of the sponge absorbent in a desorbing solvent. They are easier to handle during regenerative operations and require a minimum of effort to be re-set in the column for use in another absorption.

The speed of flow of essentialoil through a column of absorbent may be increased and the degree of contact with the absorbent may beirnproved by first dissolving or dispersing the oil in a suitablesolvent or other liquid medium. The medium employed is one that is at least comparatively polar in nature and preferably is strongly polar, comparable in polarity to methanol.

the lower aliphatic organic alcohols, e.g., methanol, ethano], isopropanol, although those of up to 6 carbonatoms are useful. The lower ketones, e.g.,' acetone, methyl ethyl ketone, ethyl ketone and the lower ether s, e.g.,

ethyl ether, also usually having no more than 6 carbon atoms to the molecule, are useful solvents in mixture with the lower alcohols. The lower ketones, ethers and other solvents of lower polarity than the lower aliphatic- Of the solvents which may be used included among the best are Often these solvents can be usedif polarity is increased by mixing with lower alcohol or other suitable polar solvent. Addition of a small amount of water to solvents with which it is miscible also satisfactorily increases the polarity thereof and makes them useful in the present processes. Usually the water present in such adjusted solvents will be less than 5% but more may be used if it is miscible with the solvent and does not render insoluble the essential oil components.

Before contacting the solution of natural essential oil with the absorbent it is usually advantageous to wet the absorbent with polar solvent and displace air or other gas from the absorbing surface. The presence of gas bubbles within the absorbent interstices is generally undesirable since it both limits free flow of the liquid phase and diminishes the area of contact of absorbent with solution of essential oil.

The choice of solvent is to some extent dependent on the character of the absorbent material itself, particularly its solubility. It has been found that the comparatively polar solvents usually do not dissolve or plasticize the elastomers or other polymeric absorbents and the various granules do not coalesce or adhere too strongly. On the other hand the relatively non-polar solvents, such as petroleum ether, and other hydrocarbons, either aliphatic or aromatic, tend to dissolve or fuse the usual non-polar absorbents, which action will make the column inoperative for the present processes.

The oxygenated polar solvents aid in keeping the odoriferous essential oil components in solution and unabsorbed by the polymeric absorbent. Where some ab sorption has taken place they assist in removal of these desired aromatic essences, allowing the terpenes to be held back by the absorbent. After the solution of essential oil in polar solvent has been brought into contact with a packed column of absorbent, additional solvent may be passed through the container to completely remove the oxygenated components of the oil. By flow of even more solvent the terpenes themselves can he removed.

The point of demarkation in the flow of desired oxygenated compounds and terpenes may be established by any suitable detection method. The effluent may be separated into 'a multiplicity of cuts which can later be analyzed and re-blended as desired. Alternatively, a chemical or physical test may be applied to the effluent to determine when the first terpenes are removed from the column, at which point the separation of solution of desired essences from terpene solution is made. Preferably, the efiluent is passed through a continuous recording refractometer and the desired oxygenated essences are collected as indicated by the variations in refractive index charted by this instrument. Other instruments, such as infrared and ultraviolet spectrometers; may be adapted to the described processes. In some instances it may also be advantageous to make separations of the .various oxygenated components, e.g., alcohols from esters and the described techniques lend themselves readily to such applications.

In a preferred embodiment of the invented process the essential oil employed contains a minor proportion of terpene hydrocarbon. Minor amounts of other hydrocarbons may also be present but the essential oil itself preferably possesses a major proportion of odoriferous oxygenated constituents. This natural oil is first dissolved in a sufficient amount of suitable polar solvent, selected because of its compatibility with the absorbent and solutes and its utility in improving the separation of terpenes from the desired components of the essential oil. The comparatively broad range of polarities of alcohols and mixed solvents previously described and their gradations V of absorption characteristics assure the availability of a solvent. particularly adapted to etficiently separate the essential oil-fractions. After the absorbent has been selectd'it may be slu rriedwith'a'polar solvent, usually the tomeric absorbents due to the swelling action of absorbed terpenes columns are packed loosely enough. to allow good flow throughout the process. The solution of oil is the unwanted terpenes.

allowed to pass through the container of absorbent and effluent is collected. Additional quantities of solvent are added and the flow through the column is maintained at a desirable rate. A continuously registering instrument for measuring physical characteristics is employed on the eflluent to ascertain when the desired separations have been effected and the efliuent is collected accordingly. Afterward, if any terpenes remain on the column their desorption may be speeded by addition of a less polar solvent. The oxygenated essential oil constituents may be recovered from the polar solvent by careful dis-tillation or evaporation. In some instances they may be used directly as solvent solutions. For example, when ethanol is the solvent there will often be no need to remove it completely from the terpeneless oils useful in perfumery.

The following example is given to'illustrate the invented process. It is typical of the sharpness of the separations obtained by this particular method of reverse phase partition chromatographic purification of natural essential oils and must not be taken as limitative of the invention. All proportions in the example, specification and claims are by weight unless otherwise indicated.

Example A quantity ofgum rubber (Davolbrand) was chilled with Dry Ice and was ground to an average particle size of about 0.02 inch in diameter, as evidenced by the fact that it passed a 20 mesh U.S. sieve and'was partlyretained by a 40' mesh U .S. sieve. This powder was subjected to a continuous extraction with methanol at 64 C. for a period of about 24 hours, 450 gramsof the extracted rubber powder, from which soluble plasticizers and lower polymers had been removed, were slurried in methanol and packed into a column of desired degree of compression in a uniform absorbent bed 18 inches long and 2% inches in diameter. 5.1 grams of oil of petitgrain (South American, like Paraguayan). dissolved in 25 rials 'analyzing as linalool and linalool acetate, respectively, and the smaller peaks C and D are indicative of the comparatively non-polar compounds, terpenes and hydrocarbons present in this oil, the latter peak corresponding to ocimene. In this process the terpenes were separated from the desired aromatic essences by collecting the first 1.85 liters of eflluent apart from the subsequent 1.15 liters. To obtain concentrated oxygenated essences these are recovered from the solvent by a low temperature evaporation or distillation, preferably conducted at or below room temperature tominimize degradation of the delicate essences. The resultant terpeneless oil of petitgrain may be employed in the formulation of perfumes and flavors, or in scenting the better cosmetics.

As illustrated by the refractometer curve obtained during the process described in the example the oxygenated odoriferous essences of the essential oilsare removed from the absorbent well ahead of the terpenes. This allows an operator to make a clean separation without difliculty andto produce a terpeneless essential oil of very high purity. Where distillation techniques or solvent extraction methods are utilized in deterpenating essential oils it is often extremely difiicult, if not impossible, to obtain a completely terpeneless oil or to recover the oxygenated essences without losing some with terpenes can be economically separated often thehigherboiling sesquiterpenes remain with the oxygenated compounds.

thereof will be removed from the absorbent sufficiently the comparatively few cases where the terpene and a portion of the desired essence tend to flow from the column together it will be found that this condition can be easily corrected by changing the solvent or increasing the eifective length of column. The wide range of solvent polarities possible assures that solvents will be readily available which will allow easy purification of a large number of naturalessential oils. As is indicated by the curve of the drawing, if it is desired sometimes oxy genated components of essential oils can also be separated from one another by the described method and such operations have been effected. Similarly, the terpene portion of eflluent may be classified into different fractions to segregate individual terpenes. For example, in other work with the same process it has been found possible to separate d-limonene and alpha pinene from para cymene.

The present process is most advantageously applied to essential oils having only minor amounts of terpenes present. In such cases the amount of absorbent that when the oil contains only a minor part of terpenes and the column will have to be regenerated more frequently.

The efficiency of deterpenating essential oils of .high te'rpene content may be increased by first subjecting these oils to a conventional deterpenating process, such as dis I tillation or solvent extraction. Terpeneless oil of high quality can be obtained by this combined method because 1 theconditions of the distillation or solvent extraction" processes need not be severe since only a gross separation is required.

Although the invented process sential oils low in terpenes it is also distinctly advantageous in removing the valuable oxygenated odor and flavor essences from those essential oils which contain a high proportion of terpenes. In such cases only the initial solvent flow need be collected because in that portion will be contained all the desired oxygenated compounds. The terpenes, if offnegligible commercial value, may be removed from the absorbent by any: suitable solvent, it being unnecessary to save these com- In such instances the only consideration is to regenerate the absorbent and no special care need be taken to prevent decomposition of the absorbed material or to assure that it will be obtained in solution in a pounds.

desirable solvent.

would be held by the adsorbent.

causing some degradation thereof. been found that the odoriferous esters, e.g., the esters of higher alcohols and lower organic acids, tend to' deconi pose when in contact with polar adsorbents 'such 'asij alumina. Other reactions can result'due to the alkalinity a or acidity of some polar adsorbents. Even if there is no degradation of the perfume essence by the at In those cases where the mono- On the other hand, even when the invented process is applied to greatly different types of essential oils, it will be found that the oxygenated components" is best applied to-essorbent alone the desorptive and regenerative processes necessary may have an adverse eifect on the oxygenated odoriferous compounds of the essential oil. The invented process obviates the difliculties of such unsatisfactory techniques.

The above invention has been described in conjunction with an illustrative example and detailed descriptions of the invented process. It will be obvious to one skilled in the art that other variations and modifications of the invention can be made and equivalents can be substituted therein without departing from the principles revealed or being outside the purview of the claims or the process of the specification.

What is claimed is:

1. A process for removing terpenes from essential oils which comprises contacting an essential oil containing odoriferous compounds and terpenes with a solid absorbent material of high surface/volume ratio, which material has a greater afiinity for the terpenes than for the odoriferous compounds, and recovering essential oil from which terpenes have been removed.

2. A process for removing terpenes from essential oils which comprises contacting an essential oil containing odoriferous compounds and terpenes with a particulate solid absorbent material which has a greater afiinity for the terpenes than for the odoriferous compounds and recovering essential oil from which the terpenes have been removed.

3. A process for removing terpenes from essential oils which comprises contacting an essential oil containing odoriferous oxygenated compounds and terpenes with a comparatively non-polar particulate solid absorbent material which has a greater affinity for the terpenes than for the oxygenated compounds and contacting the mixture of absorbent and essential oil with a comparatively polar solvent to remove the terpeneless odoriferous oxygenated compounds.

4. A process for removing terpenes from essential oils containing odoriferous oxygenated compounds which comprises contacting a mass of particulate non-polar polymeric solid absorbent material with a solution of terpene-containing essential oil in a comparatively polar solvent and subsequently contacting the absorbent with polar solvent to remove the odoriferous oxygenated compounds free of terpenes.

pounds from the group consisting of'organic alcohols, esters and mixtures thereof, which comprises mixing the essential oil with an organic polar solvent, adding the essential oil in such a solvent to a column of particulate non-polar highly polymeric solid absorbent material and flowing through the column of absorbent containing essential oil a suitable low molecular weight polar solvent to remove the odoriferous oxygenated compounds free of terpenes.

6. A process for removing undesirable terpene hydrocarbons from essential oils containing oxygenated odoriferous compounds from the group consisting of higher organic alcohols, esters and mixtures thereof which comprises dissolving the essential oil in a suitable volatile organic alcohol of 1-3 carbon atoms, adding the solution of essential oil to a packed column of granular nonpolar highly polymeric solid absorbent material, flowing through the column of absorbent containing essential oil a suitable volatile organic alcohol of 1-3 carbon atoms to remove the terpene-free oxygenated odoriferous compounds from the absorbent and then making a lowtemperature separation of solvent from the odoriferous terpene-free alcohol.

7. A process according to claim 5 in which the essential oil contains a minor proportion of terpene hydrocarbons, the absorbent is a granulated rubber and methanol is the solvent for the essential oil.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Plachenov et al.: Chem. Abs., vol. 48, p. 3638 (1954), abstracting Zuhr. Priklad Khim., vol. 26, pp. 482-494 (1953).

Claims (1)

1. A PROCESS FOR REMOVING TERPENES FROM ESSENTIAL OILS WHICH COMPRISES CONTACTING AN ESSENTIAL OIL CONTAINING ODORIFEROUS COMPOUNDS AND TERPENES WITH A SOLID ABSORBENT MATERIAL OF HIGH SURFACE/VOLUME RATIO, WHICH MATERIAL HAS A GREATER AFFINITY FOR THE TERPENSES THAN FOR THE ODORIFEROUS COMPOUNDS, AND RECOVERING ESSENTIAL OIL FROM WHICH TERPENSES HAVE BEEN REMOVED.

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