Method for producing multi-unsaturated hydrocarbons

Abstract

Disclosed is a method for producing a multi-unsaturated hydrocarbon by isomerizing myrcene in the presence of CuCl as catalyst.

Description

METHOD FOR PRODUCING MULT I -UNSATURATED HYDROCARBONS Background

[0001] Ocimene (3, 7-dimethyl-l, 3, 6-octatriene) is used in perfumery for its sweet herbal scent and is believed to exhibit plant defense and have anti-fungal properties . Ocimene has been prepared from pinene (US 3, 616, 372 A) or from purified myrcene 90 ( 7-methyl-3-methylene-l , 6-octadiene) using RhCla as a catalyst (Scheme 1 ) . This reaction includes the use of 8 molar % acetyl chloride (AcCl) and 6.25 wt% isopropanol ( IPA) . The reaction yield to ocimene under these conditions is 72% .SCHEME 1

[0002] When RhCla is used as catalyst, myrcene 90 is required because the impurities ( e. g. , sulfur) of other myrcene preparations affect catalyst activity. The most common method to produce myrcene industrially is through the pyrolysis of p-pinene, which is extracted from pine or spruce resins or obtained by distillation and desulphurization of crude sulphate turpentine (CST) . To remove impurities in the myrcene, exhaustive extraction processes are required. In addition, Rh is a scarce metal that is difficult to recover and in many cases is not reusable, i . e. , it is deactivated after single . Thus, the use of purified myrcene and RhCla catalyst significantly increase the cost of ocimene production .

[0003] Therefore, needed in the art is a cost effective, high yield method for producing ocimene . The present invention addresses this need in the art .Summary of the Invention

[0004] This invention provides a method for producing ocimene, a multi-unsaturated hydrocarbon, by isomerizing myrcene in the presence of CuCl, e. g. , 0.1 wt% to 0.5 wt% CuCl . In some aspects, the method further includes between 8 wt% and 15 wt% AcCl . In other aspects, the method is carried out at a reaction temperature in the range of 70°C to 80°C. In still other aspects, the reaction optionally includes an antioxidant .Detailed Description of the Invention

[0005] As used herein, the terms "comprises, " "comprising, " "includes, " "including, " "has, " "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus . Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or . For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present) , A is false (or not present) and B is true (or present) , and both A and B are true (or present) .

[0006] Also, use of "a" or "an" are used to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise .

[0007] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs . In case of conflict, the present specification, including definitions, will control . Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0008] When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and / or lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range . For example, when a range of "1 to 10" is recited, the recited range should be construed as including ranges "1 to 8 , " "3 to 10, " "2 to 7 "1.5 to 6, " "3.4 to 7.8, " "1 to 2 and 7-10, " "2 to 4 and 6 to 9, " "1 to 3. 6 and 7.2 to 8.9, " "1-5 and 10, " "2 and 8 to 10, " "1.5-4 and 8, " and the like .

[0009] The present disclosure illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations that are not specifically disclosed herein. While compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods also can "consist essentially of" or "consist of" the various components or steps, unless stated otherwise .

[0010] A person of ordinary skill in the art appreciates that some chemical compounds in this disclosure have chiral center, carbon-carbon double bond, and / or cyclic structure . Unless explicitly indicated, a chemical compound in this disclosure includes its stereoisomers, such as enantiomers and diastereomers .

[0011] CuCl has been found to be a cost-effective alternative catalyst to RhCla for preparing ocimene from myrcene . Advantageously, the reaction proceeds independent of the amount of CuCl and the presence of impurities in the myrcene . Given the reduced cost of CuCl as compared to RhCla, the low level of catalyst needed, and reduced reliance upon purified sources of myrcene, the present method provides a significant cost savings over conventional methods for producing ocimene .

[0012] Accordingly, this invention provides a method for producing ocimene by isomerizing myrcene in the presence of CuCl . As is conventional in the art, the term "isomerizing, " "isomerize, " or "isomerization" refers to the process in which a molecule is transformed into an isomer with a different chemical structure . In accordance with this invention, myrcene is isomerized into cis-beta-ocimene and / or trans-beta-ocimene .

[0013] As indicated, the source or raw material containing myrcene is not particularly critical to this invention given that impurities typically found in myrcene preparations have little impact on the CuCl-mediated reaction. In this respect, the myrcene may be directly obtained from the pyrolysis of beta-pinene . Ideally, however, the raw material used in accordance with this method is composed substantially of myrcene, i . e. , the raw material contains at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90% myrcene . Alternatively stated, the raw material contains less than about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% impurities, i . e. , compounds other than myrcene . In some aspects, the reactionincludes between 70% and 95% raw material comprising myrcene, or more preferably 75% and 90% raw material comprising myrcene .

[0014] The amount of CuCl used in the isomerization reaction may be in the range of between 0. 1 wt% and 0.5 wt% CuCl . In some aspects, the amount of CuCl is ideally between 0.1 wt% and 0.2 wt% . In particular aspects, the amount of CuCl is preferably 0.125 wt% .

[0015] To form HC1 in si t u , preferably the reaction is carried out in the presence of acetyl chloride (AcCl) and isopropanol . In some aspects, the reaction includes between 4 wt% and 15 wt% AcCl, preferably between 8 wt% and 15 wt% AcCl . In a particular aspect, the reaction includes between 12 wt% and 15 wt% AcCl . In other aspects, the amount of isopropanol is in the range of 2 wt% to 9 wt% or more preferably 4 wt% to 8 wt% .

[0016] In particular aspects, the reaction is carried out in the absence or substantial absence of a solvent . Accordingly, in some aspects, ocimene is prepared by isomerizing myrcene in the presence of CuCl in the presence of no more than 5%, 2%, 1%, 0.5%, 0.25%, 0.1%, 0.05%, 0.01%, or preferably 0% solvent by weight of the reaction mixture . The absence or substantial absence of solvent is a significant improvement in the preparation of ocimene .

[0017] The temperature at which the isomerization reaction can be carried out is ideally between 50°C and 100°C, or more preferably in the range of between 70°C and 85°C, most preferably 75°C and 80°C . Ideally the reaction is carried at atmospheric pressure and / or in batch mode . However, in some cases, the reaction may be carried out under reduced pressures conditions, e . g. , between 0.5 and 100 mbar .

[0018] In particular aspects of this invention, ocimene is produced from myrcene in a reaction containing 15 wt% AcCland 0.125 wt% CuCl, wherein the reaction is carried out at 80°C .Example 1 : Synthesis of Ocimene

[0019] Myrcene, directly obtained from a pyrolsis reaction, and with no additional solvent added, was used in the synthesis of ocimene . The myrcene content of the substrate loaded into the reactor was generally in the range of 78-85 wt% . The temperature of the reactor was set to a temperature appropriate for acetyl chloride (AcCl) addition (typically 30°C) . Subsequently, approximately half of the amount of isopropanol ( IPA, 7 wt% total) used in the reaction is loaded into the reactor . The catalyst is then charged in the reactor and the rest of IPA is immediately added. AcCl is loaded at a controlled rate (typically at an addition rate of 2 hours) . Once all the AcCl is loaded into the reactor, the temperature is set at the desired reaction temperature (70-100° ) . Samples are collected periodically and analyzed by gas chromatography (GC) . Toluene is employed as internal standard for the GC-based quantification.Example 2 : Evaluation of Alternative Catalysts

[0020] Different catalysts (Table 1 ) were tested for their ability to convert myrcene from a crude sulphate turpentine (CST) source into ocimene . The amount of isopropanol used was 4.5-5 wt% and the amount of AcCl used was 4.5 wt%, unless otherwise indicated. This analysis indicated that CuCl could efficiently catalyze the conversion of myrcene to ocimene with a high degree of selectivity.TABLE 1* AcCl, 7.5 wt% .Example 3 : Dependence of CuCl Activity on Raw Material

[0021] To determine whether CuCl reactivity was dependent upon the source of raw material, the reaction was repeated using different sources of myrcene . The reactions were carried out at 80°C using 15 wt% AcCl and 0.125 wt% CuCl . The different sources of myrcene included myrcene 90 (myrcene from gum turpentine, 90% myrcene) , distilled myrcene and 74-80% myrcene . The results of this analysis indicated that, contrary to RhCla, impurities had no effect on the catalytic activity of CuCl .Example 4 : Process Parameter Modifications

[0022] The effect of temperature on ocimene production was analyzed in reaction containing 4.0 wt% AcCl, 7.0 wt% IPA and 0.44 wt% CuCl . The results of this analysis are presented in Table 2 .TABLE 2

[0023] Changes in AcCl amount on ocimene production was analyzed in reaction containing 7.0 wt% IPA and 0.44 wt% CuCl at a temperature of 80°C . The results of this analysis are presented in Table 3.TABLE 3

[0024] Changes in IPA amount on ocimene production was analyzed in reaction containing 8.0 wt% AcCl and 0.44 wt%CuCl at a temperature of 80°C . The results of this analysis are presented in Table 4 .TABLE 4* Catalyst loading 0.22 wt% .

[0025] Changes in catalyst amount on ocimene production was analyzed in reaction containing 8.0 wt% AcCl and 0.45 wt% IPA at a temperature of 80°C . The results of this analysis are presented in Table 5.TABLE 5* 7 wt% IPA.

Claims

What is claimed is :

1. A method for producing ocimene comprising isomerizing myrcene in the presence of CuCl thereby producing ocimene .

2. The method of claim 1, wherein the CuCl is present in an amount in the range of 0.1 wt% to 0.5 wt % .

3. The method of claim 1, further comprising between 8 wt% and 15 wt% AcCl .

4. The method of claim 1, wherein said method is carried out at a reaction temperature in the range of 70°C to 85°C .

5. The method of claim 1, further comprising an antioxidant .

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