JPS6127374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing olefins having a branched structure and 2 to 4 double bonds. A variety of these olefins are used as base materials for more valuable products, and some of them are of interest as intermediates in aromatic chemicals.

This olefin is represented by the following formula.

In the formula, R ¹ , R ² and R ³ are each an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X is 8 is an alkylene group having up to 1 carbon atoms.

Compounds of formula () are usually not readily available, and the methods developed to make them starting from more easily obtained materials are often not only complicated but also usually reduce the overall yield. It includes various process steps that lead to

It has now been discovered that the desired compounds of formula () can be obtained directly by disproportionation of other suitably available olefins with isoolefins.

According to the present invention, the compound of formula () is a compound represented by the following formula: In the formula R ¹ , R ² , R ³ , R ⁴ and X have the meanings given above and R ⁵ represents an alkyl group having 1 to 4 carbon atoms. It is produced by reacting with an isoolefin represented by the following formula in the presence of an olefin disproportionation catalyst.

In the formula, R ⁶ and R ⁷ are each an alkyl group having 1 to 4 carbon atoms.

In the compounds of formulas () and (), R ¹ and R ² are preferably lower alkyl groups, ie methyl or ethyl groups. R ⁴ is preferably a methyl group, or more preferably a hydrogen atom.

The alkylene group X is, for example, ethylene-, 1,2-
Propylene, 1,3-propylene- and 2,3
It can be a -propylene- group, with an ethylene group being particularly preferred.

In the reaction of a compound of formula () with a compound of formula (), two types of disproportionation products are produced: a compound of formula () and a compound represented by the following formula.

Particularly favorable results are obtained when compounds of the formula () in which R ⁵ represents a methyl group are reacted with the more reactive isoolefins of the compounds of the formula (), in particular isobutene and methylbutene-1.

Thus, according to a preferred embodiment of the method, 2.
6-dimethylocta-2,6-diene reacts with isobutene to form 2,6-dimethylhepta-1,5-
Diene (isononadiene) and 2-methylbutene-
2. According to another embodiment, 2,4,6-trimethylocta-2,6-diene and isobutene are converted to 2,4,6-trimethylhepta-1,5-diene and 2-methyl-butene-2. . The methyl-substituted heptadiene is of interest as an intermediate for aromatic chemicals such as hydroxycitronellal and its congeners. Regarding the production of hydroxycitronellal from isonadiene, reference is made to the co-pending Japanese Patent Application No. 136964/1983.

The process is carried out in the presence of a suitable disproportionation catalyst. For example, if the reaction proceeds in a batch operation, homogeneous catalysts can be used;
It is usually preferred to use a heterogeneous catalyst system. Catalyst Reviews 3 (1969)
Described on pages 37-60. Catalysts consisting of one or more transition metal oxides are recommended, for example group metal oxides such as Re ₂ O ₇ supported on a support such as aluminum oxide or tungsten oxide supported on silica. Preferred catalyst systems are alkali metal and alkaline earth metal oxides,
For example, it contains one or more promoters such as potassium oxide and cesium oxide. A small amount as accelerator, usually 0.1-10%, preferably 1
Particularly preferred is a catalyst consisting of 5-70% by weight Re ₂ O ₇ supported on gamma alumina containing potassium oxide in the range from 2% to 2%.

Suitable reaction temperatures are typically -20 to 200°C. At temperatures higher than this, the results are often adversely affected because undesirable side reactions occur. When using catalysts containing rhenium oxide, reaction temperatures of 20 to 100°C are very satisfactory; furthermore, temperatures of 20 to 80°C are selected;
When using catalysts containing tungsten oxide, slightly higher temperatures are required, for example 120-150°C. The pressure may range from 1 to 150 bar, with a range from 1 to 100 bar being suitable for most purposes, and a range from 1 to 25 bar being preferred.

The isoolefin of formula () is conveniently applied in molar excess over the olefin of formula (). Molar ratios up to 50:1 mol are suitable;
A molar ratio of up to 1 is preferred.

Advantageously, the reaction is carried out in continuous mode. A preferred method of operation consists of feeding the reactants at one end of a tubular reactor containing the disproportionation catalyst, or containing it and an inert material, and collecting the product mixture at the other end. Solvents or diluents are not required, but may be used if desired. Suitable solvents include alkanes having 5 to 14 carbon atoms, such as heptane, cyclic or bicyclic alkanes, such as cyclohexane, pinane or 1-isopropenyl-
Included are aromatic compounds such as 2,3-dimethylcyclopentane, toluene, xylene and halogenated benzenes, such as chlorobenzene.

Compounds of formula () can generally be easily prepared when they are not available on their own.
A very preferred method for preparing compounds of formula () when R ⁵ represents a methyl group consists in double bond isomerization of compounds of the formula below.

For example, dihydrocimene (2,6-dimethylocta-2,6-diene) is conveniently prepared by isomerization of dihydromircene (2,6-dimethylocta-2,7-diene). If, in addition to R ⁵ , R ¹ and/or R ² also represent a methyl group, compounds of formula () can be prepared from their double bond isomers containing two terminal unsaturated bonds. Thus, dihydrocimene is alpha dihydromyrcene (2,6-dimethylocta-1,7
- diene).

According to a preferred embodiment of the invention, the process is carried out by means of a compound of formula () when R ⁵ is methyl formed in situ, i.e. from a mixture containing a compound of formula (). This is accomplished by feeding the mixture with an isoolefin reactant of the formula () to subject it to unsaturation without liberating the compound.

The above isomerization of compounds containing one or two terminal double bonds into compounds of formula () is preferably carried out in the presence of an alkaline isomerization catalyst. Recommended catalysts include supported alkali metal catalysts and combinations thereof, such as potassium and/or sodium on alumina and regenerable catalysts, such as alumina and alkali metal compounds such as potassium carbonate or sodium oxide, preferably supported on a support. These alkali metal compounds are included. A preferred catalyst consists of potassium oxide on gamma-alumina in which the amount of alkali metal oxide is 1-20% by weight, preferably 2-5% by weight.
Non-alkaline catalysts such as carbonyls of transition metals, such as rhodium carbonyls and iron carbonyls, are also used.

The isomerization is suitably carried out at a temperature in the range 20-200°C,
It is carried out at a temperature of 50 to 180°C, and temperatures of 80 to 150°C are particularly preferred.

Any suitable method may be chosen to liberate the compound of formula (). Although it is usually preferred to separate the desired compounds from the product mixture by distillation, other methods such as chemical separation methods may be applied if desired.

The invention will be further illustrated by the following examples.

Example (a) Preparation of 2,6-dimethylocta-2,6-diene (starting material) Gamma-alumina (Ketjen CK300, 25g)
was baked at 500℃ for 2 hours, and then heated with metallic sodium (0.25℃) at 200℃ under nitrogen atmosphere.
g). 20 soaked alumina
After cooling to ℃, 2,6-dimethylocta-
2,7-diene (75ml) was added.

Within 5 minutes of addition, the starting material was converted to the desired 2,6-dimethylocta-2,6- with a selectivity of 85%.
Gas-liquid chromatography showed complete isomerization to the diene. This diene could be purified by distillation at atmospheric pressure with a boiling point of 172-3°C.

(b) Production of 2,6-dimethylocta-1,5-diene (isononadiene) An olefin disproportionation catalyst was produced as follows.

Gamma-alumina (Ketjen CK300) was first soaked with an aqueous potassium carbonate solution, dried at 120°C and then treated with a solution of rhenium heptoxide. After drying at 120°C for 3 hours, the catalyst was calcined at 500°C for 3 hours. The catalyst thus prepared contained 14% by weight of Re ₂ O ₇ and 1.3
Contained % K ⁺ by weight. The catalyst was activated by heating at 500° C. for 3 hours in a stream of pure nitrogen before use.

Disproportionation catalyst (10g), 2,6-dimethylocta-2,6-diene (25g), isobutene (50g)
A mixture of g) and n-heptane (25 g) was stirred in an autoclave for 3 hours at 30°C. At the end of this period the conversion of starting material is 85% and the selectivity to the desired product is 90%.
% was confirmed by gas-liquid chromatography. Pure 2,6-dimethylhepta-1 with a boiling point of 139°C at normal pressure by fractional distillation.
5-diene was obtained.

Example (a) Preparation of 2,6-dimethylocta-2,6-diene (dihydroocimene) Soaking 4% by weight of potassium carbonate and 575
5 g of a fixed bed catalyst consisting of spherical gamma-alumina calcined for 16 hours at °C were fed into a tubular reactor equipped with a thermowell.

In a continuous experiment, 2,6-dimethylocta-2,7-diene was fed at a weight hourly space velocity of 1.0. The temperature was maintained at 165°C and the pressure at atmospheric. After a reaction time of 24 hours, the conversion was 93%. The overall yield of isomerized product is 90% and 2,6-dimethylocta-2,6
- Selectivity to diene was 77%.

(b) Example of disproportionation of generated dihydrooocimene
Achieved in the same way as (b).

Claims (1)

[Claims] 1. A compound represented by the following formula: In the presence of a disproportionation catalyst, reacting with an isoolefin represented by the following formula, A method for producing a branched olefin having the following formula: [In each of the above formulas, R ¹ , R ² , R ³ , R ⁵ , R ⁶ and R ⁷ are each an alkyl group having 1 to 4 carbon atoms, and R ⁴ is an alkyl group having 1 to 4 carbon atoms. and X is an alkylene group having up to 8 carbon atoms. 2. The method according to claim 1, characterized in that a compound of formula () is used in which R ⁵ is a methyl group. 3. The method according to claim ¹ or ² , characterized in that a compound of formula () is used, in which R 1 and R 2 are a methyl group or an ethyl group, and R ⁴ is a hydrogen atom. 4. Process according to any one of claims 1 to 3, characterized in that an isoolefin of formula () is used, in which R ⁶ and/or R ⁷ are methyl groups. 5. Claims 1-4, characterized in that a compound of formula () is used, in which X is an ethylene group.
The method described in any of the above. 6. The method according to any one of claims 1 to 5, characterized in that a heterogeneous disproportionation catalyst is used. 7. Process according to claim 6, characterized in that rhenium oxide supported on gamma alumina is used as catalyst. 8. Process according to claim 6 or 7, characterized in that a catalyst containing 0.1-10% potassium oxide is used as promoter. 9. The method according to any one of claims 2 to 8, characterized in that a compound of formula () obtained by double bond isomerization of a compound represented by the following formula is used. 10. Process according to claim 9, characterized in that a compound of formula () produced in situ is used. 11 Claim 9 or 10, characterized in that an alkaline double bond isomerization catalyst is used.
Method described. 12. The method according to claim 11, characterized in that a catalyst containing a potassium compound is used.