JPS6134431B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention has the following reaction formula: Accordingly, the present invention relates to a new process for the direct epoxidation of olefins using hydrogen peroxide in the presence of a catalyst in the liquid phase. The present invention continuously removes the water produced during the reaction and the water introduced together with hydrogen peroxide from the reaction system by distillation or azeotropic distillation or, in some cases, by entrainment simply by the vapor pressure of the water. It is characterized by being removed.

Olefin epoxide is an extremely important compound industrially in terms of its production volume and uses.

The oldest method for epoxidizing olefins is known as the chlorohydrin method, in which olefins are reacted with chlorine in an alkaline medium to obtain chlorohydrin. It consists of obtaining the epoxide by dechlorohydration using a base such as a base. Although this method is very widely practiced, it cannot be used to date due to energy consumption or ecological considerations. In the above method, the consumption efficiency of chlorine is not very good, and besides the epoxide there are by-products which are completely worthless and pollutants, namely the organic chlorinated derivatives corresponding to the olefins used and the chloride of lime. is generated.

A more recent and less polluting method is to epoxidize olefins using hydroperoxides in an organic medium in the presence of a catalyst. However, in addition to the epoxide, this process produces an amount of alcohol which is of no use value and which significantly affects the economics of the process, corresponding to the hydroperoxide initially used.

Similarly, various methods of epoxidizing olefins using molecular oxygen have been studied. However, in the case of this method, it is well known that as far as ethylene is concerned, satisfactory results can be obtained by using catalysts based on silver, for example, but when applied to other olefins other than ethylene, The disadvantage is that the selectivity is poor in both cases.

Generally, hydrogen peroxide is used as the oxidizing agent because it is a non-fouling chemical. However, in the absence of an activator, hydrogen peroxide is not inactive toward olefins, but it exhibits only low activity. Therefore, various methods have been proposed using peracids such as peracetic acid, performic acid or perpropionic acid (see, for example, Belgian Patent No. 838068). However, since epoxides are unstable in acidic media, it is difficult to carry out this method in practice.

Compared to the above methods, which have the disadvantage of requiring peroxide synthesis when producing epoxides,
Various other catalytic epoxidation methods have been proposed that are advantageous over the above methods in that they do not use peroxides. For example, it has been proposed to use oxides or oxyacids that are derivatives of transition metals such as molybdenum, tungsten, vanadium, cerium, etc. in an aqueous medium. However, these methods are unsatisfactory in that the products obtained are primarily the corresponding glycols rather than the desired epoxides.

It has also been proposed to use peroxodo complexes of the transition metals (see French Patent No. 2082811).
Although these complexes are good epoxidizing agents, there are major problems in the in situ regeneration of the complexes, so that the process cannot be carried out economically.

It is an object of the present invention to provide a new process for carrying out epoxidation using hydrogen peroxide in the presence of a catalyst, which does not have the above-mentioned disadvantages and yet has a high selectivity and a very long service life. An object of the present invention is to provide a method for epoxidizing olefins, which is characterized in that it can be carried out extremely easily using a catalyst.

The process of the invention is carried out in the presence of an effective amount of transition metals of groups A, A and A of the periodic table or inorganic or organic derivatives of these elements, and in the presence of water or an aqueous solution formed during the reaction. olefin and hydrogen peroxide in an organic solvent under such temperature and pressure conditions that the water introduced into the reaction system by hydrogen peroxide when used in the form of This is a method for catalytic oxidation of olefins carried out in the liquid phase.

Preferably, the olefin used in the method of the invention is of the formula: In the above formula, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and each has a hydrogen atom or a carbon number of 1 to 30
A hydrocarbon group consisting of a linear or branched alkyl group, an optionally branched cycloalkyl group having 3 to 12 carbon atoms, or a benzene ring having 6 to 12 carbon atoms and optionally substituted with an alkyl group. or R ₁ and R ₂ or R ₃ and R ₄ together represent a straight or branched alkylene group having 3 to 11 carbon atoms; or
R ₁ and R ₃ or R ₂ and R ₄ together represent a straight or branched alkylene group having 1 to 10 carbon atoms. These radicals R ₁ , R ₂ , R ₃ and R ₄ optionally contain functional groups stable in the reaction medium, such as hydroxy groups, chlorine, fluorine, bromine, iodine, nitro groups, alkoxy groups, such as methoxy group, an amino group, a carbonyl group, an acid group, an amide group, a nitrile group. R ₁ , R ₂ , R ₃ and R ₄ can be unsaturated radicals, so that among the olefins used in the invention there are also polyolefins, such as dienes, trienes, optionally in conjugated form,
Included.

Examples of unsaturated compounds that can be epoxidized by the method of the invention are: ethylene, propylene, butene, butadiene,
Pentene, 1-hexene, 3-hexene, 1-peptene, 1-octene, diisobutylene, 1-nonene, limonene, pinene, myrcene, camphene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1 -Pentadecene, 1
- hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-icosene, trimers and tetramers of propyrene, polybutadiene,
Styrene, α-methylstyrene, divinylbenzene, indene, stilbene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclooctadiene, cyclodecene, cyclododecatriene, dicyclopentadiene, methylene, cyclopropane, methylene, cyclopentane, methylene, cyclohexane , vinyl, cyclohexene, methyl, allyl, ketone, allyl chloride, allyl bromide, acrylic acid, methacrylic acid, crotonic acid, vinyl acetate, crotyl chloride, methallyl chloride, dichlorobutene, allyl, alcohol, allyl carbonate, allyl acetate, acrylic acid or alkyl methacrylates, diallyl maleates, diallyl phthalates, unsaturated glyceric acids, such as soybean oil, sunflower oil, corn oil, cottonseed oil, olive oil, ricin oil, cod oil, peanut oil, tol oils, oleic and linseed oils, unsaturated fatty acids such as oleic acid, linolenic acid, bilicic acid
erucic acid, oleosteraric acid, myristoleic acid, palmitoleic acid, ricanic acid, ricinoleic acid, arachidonic acid and its esters.

The catalysts used in the process of the invention are metals of groups A, A and A of the periodic table, which metals may be present in metallic form or in varying degrees of oxidation (valence).
in the form of a metal complex in which is zero, or
They can be used in the form of inorganic or organic derivatives of metals present with varying degrees of oxidation (valence). Preferably the metals are molybdenum, tungsten, vanadium, chromium and titanium.

Inorganic derivatives of these metals include oxides, oxide mixtures, hydroxides, oxyacids, heteropolyacids, salts and esters thereof; derived from organic carboxylic acids or sulfonic acids having anions that are stable and stable under the reaction conditions.

The metal complexes mentioned above are mainly complexes called organometallic complexes, in which the transition metal has an oxidation degree (valence) of 0 to +6 and is surrounded by organic bonding groups and/or inorganic bonding groups. has been done.

These organometallic compounds usually have the advantage that they are relatively easily soluble in organic solvents and therefore the catalyst can be used in a homogeneous system. However, there is no major disadvantage in using insoluble catalysts; this is because, when the reaction system is heterogeneous, in order to effectively contact the various reactants in the reaction system, This is because it is sufficient to vigorously stir the reaction system.

Examples of catalysts that can be used in the present invention are as follows: molybdenum, tungsten, chromium,
Vanadium, titanium, zirconium, niobium; metal carbonyl, Mo(CO) ₆ , W(CO) ₆ ; oxide, MoO ₂ , Mo ₂ O ₅ , Mo ₂ O ₃ , MoO ₃ , WO ₂ ,
W ₂ O ₅ , WO ₆ , CrO ₂ , Cr ₂ O ₃ , Cr ₂ O ₃ , VO ₂ ,
_{V2O3 , V2O5 , ZrO2} , TiO, _TiO2 , _{Ti2O3 ,}
NbO ₂ , Nb ₂ O ₃ , Nb ₂ O ₅ , the sulphides MoS ₂ ,
MoS ₃ , MoS ₄ , Mo ₂ S ₃ , Mo ₂ S ₅ , WS ₂ , WS ₃ ,
_CrS , _{Cr2S3 , V2S3} , _V2S5 , _ZrS2 , TiS, _{TiS2 ,}
Ti ₂ S ₃ ; molybdenum, tungsten, chromium, vanadium, zirconium, titanium oxychloride, fluoride, chloride, bromide, iodide, nitrate, sulfate, phosphate, pyrophosphate, polyphosphate , borate, carbonate, formate, acetate, propionate, butyrate, isobutyrate, caproate, caprylate, laurate, naphthenate, stearate, oxalate, succinate. acid salt,
Glutarate, Adipate, Benzoate, Flutarate, Molybdenum, Tungsten, Titanium,
benzenesulfonates of chromium, zirconium and vanadium; complexes such as acetyl acetonate and phthalocyanine; to the above acids such as molybdic acid, tungstic acid, vanadic acid, chromic acid, phosphomolybdic acid, tungstic acid, arsenomolybdic acid or tungstic acid; Corresponding heteropolyacids and alkali metal or alkaline earth metal salts of the above acids.

It is of course possible to use mixtures of the abovementioned catalysts. Heterogeneous catalysts can also be immobilized on supports such as alumina, silica, silicates of alumina, zeolites, and optionally polymers according to known methods.

The reaction medium must be such that it completely dissolves the hydrogen peroxide solution under the reaction conditions. In other words, the reaction system of the present invention must have a single liquid phase. Furthermore, the reaction medium must be as inert as possible towards the reactants and the epoxide formed. The reaction may in some cases be carried out without the use of a solvent by contacting the reactants, olefin, with hydrogen peroxide. In this case, however, a sufficiently high ratio of olefin:H ₂ O ₂ moles is required, preferably from 2 to 200, in order to ensure that the reaction takes place.

It will usually be preferred to carry out the reaction in an organic inert solvent or mixture thereof, such as:
Primary, secondary or tertiary alcohols having 1 to 6 carbon atoms, such as methanol, ethanol, n-
Propanol, isopropanol, 1-butanol, 2-butanol, tertiary butanol, amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, glycerin;
Oxide ethers, such as ethyl ether, isopropyl ether, dioxane, tetrahydrofuran; oligomers of ethylene oxide, propylene oxide; ethers of the above oligomers, such as dimethoxydiethylene glycol, diethoxyethylene glycol, diglyme, esters such as alcohols or the customary glycols. formate or acetate ester of. Other suitable solvents are dimethylformamide, nitromethane and triethyl, trioctyl and ethylhexyl phosphate.

When epoxidizing an olefin compound according to the method of the invention, hydrogen peroxide and the olefin are mixed in a solvent in the presence of a catalyst and the water introduced by the hydrogen peroxide and the water formed during the reaction are continuously mixed. contact while distilling. The reaction temperature is 0-120°C, preferably 70-100°C. Depending on the reaction temperature chosen and the reaction system used (olefin and solvent), water removal may be carried out at low pressure if the reaction is carried out at low temperature or at atmospheric pressure, or at about 100% When carried out at 0.degree. C., water removal can also be carried out under pressure, especially in the case of light olefins. Therefore, the pressure is 20
It can be varied between mmHg and 100 bar.

Depending on the boiling point of the olefin, solvent and epoxide, water removal may be accomplished by simple distillation.
Water can also be removed azeotropically by taking advantage of the fact that water and olefins are azeotropic, or by adding co-solvents having such properties to the reaction medium. Examples of co-solvents are benzene, toluene,
n-pentane, cyclohexane and anisole. Finally, water can also be entrained by the gas by passing the gas through the reaction medium, taking advantage of the vapor pressure of water at a given temperature; It can be olefin itself.

The reaction temperature is naturally selected depending on the stability of the hydrogen peroxide in the chosen reaction medium. When carrying out the reaction at high temperatures (80-120°C), it is preferable to use an acidic medium. However, since epoxides are unstable in this type of medium, organic or inorganic compounds acting as buffers, such as tertiary amines,
It is advantageous to add pyridine, alkali metal phosphates or acetates.

The reaction time is determined by the catalyst, solvent and olefin used. Reaction times can range from a few minutes to 100 hours or more. Although the reactants may be used in equimolar amounts, it is also possible to use less or less of one reactant. For example, 0.1 to 50 moles of olefin per mole of hydrogen peroxide (i.e., 0.02 to 10 moles of hydrogen peroxide per mole of olefin).
mol) may be used, but it is preferred to use 1 to 10 mol.

The catalyst contains 0.0001 to 1 metal per mole of hydrogen peroxide.
used in the proportion of g atoms. However, it is preferred to use 0.001 to 0.1 g atoms of metal per mole of hydrogen peroxide.

The amount of solvent or solvent mixture is that necessary to maintain a single liquid phase and prevent sedimentation phenomena. The amount of solvent is usually about 25% of the total volume of the reaction medium.
~55%.

The reactants can be used in their customary commercially available forms. In particular, hydrogen peroxide can be used in the form of a commercially available aqueous solution with a concentration of 30 to 70% by weight. However, in the method of the present invention, when considering the continuous removal of water present in the reaction medium, it is preferable to use an aqueous peroxide solution with a concentration of 70% by weight or more, especially 85 to 95% by weight. Naturally, this is preferable. Therefore, it is preferable to previously dissolve concentrated hydrogen peroxide in the solvent used as the reaction medium and to carry out the reaction using the thus obtained dilute organic solvent solution.

Examples of the present invention are shown below. The selectivity shown in the examples is the number of moles of epoxide produced relative to the number of moles of hydrogen peroxide reacted.

Example 1 Magnetic Stirrer and Florentine
In a 500 c.c. reaction vessel equipped with an attached reflux condenser were added 41 g of amyl alcohol, 0.05 g of molybdenum oxide (MoO ₃ ), 0.3 g of disodium phosphate (Na ₂ HPO ₄ ), and 41 g of cyclohexene.
(0.5 mol) was charged. The mixture was heated to the boiling point of cyclohexene, 81 DEG C., and 5.7 g (0.05 mol) of a 30% by weight aqueous hydrogen peroxide solution was added over 12 minutes. The reaction was allowed to run for 2 hours, during which water was removed by azeotropic distillation with cyclohexene and the temperature was kept at 80-90°C.
It was kept at ℃. 0.012 moles of hydrogen peroxide remained in the reaction medium, while gas chromatography showed that 0.024 moles of cyclohexene epoxide had formed. In this case, the hydrogen peroxide conversion rate was 76% and the selectivity was 63%.

Example 2 0.1 mol of molebutyl acetyl as catalyst
The same method as Example 1 was repeated except that acetonate was used. After 2 hours of reaction, chemical analysis detected 0.014 mol of hydrogen peroxide, and gas chromatography confirmed the formation of 0.034 mol of cyclohexene epoxide. Hydrogen peroxide conversion rate 72%, selectivity 94%.

Example 3 In a stainless steel reaction vessel with an effective volume of 3, 200 c.c. of amyl alcohol, 5 g of molybdylacetylacetonate, and disodium phosphate were added.
5 g of Na ₂ HPO ₄ was charged. The reaction vessel was sealed and 420 g (10 mol) of liquid propylene was introduced by means of a pump. The mixture was heated to 85°C and held at this temperature. The propylene boiled at 40 bar and the heating was adjusted so that 12.6 moles of propylene were distilled off per hour. Then, using a dispensing pump, the concentration is 70% by weight.
48.5g (1 mol) of hydrogen peroxide solution per hour
and 533 g of propylene per hour (12.7 mol per hour). Water introduced into the reaction system,
The water produced by the reaction and the propylene oxide produced were entrained by the distilled propylene gas and condensed at 0°C. In this way, 81.7 g of a 60.3% by weight aqueous propylene oxide solution was obtained per hour.
The yield of propylene oxide was 85% based on the hydrogen peroxide used.

Example 4 A glass reactor with a capacity of 300 c.c. was charged with 41 g of amyl alcohol, 82 g (1 mole) of cyclohexene, 0.1 g of vanadyl acetylacetonate, and 0.1 g of disodium phosphate in sequence. This mixture was heated to 81°C, the boiling point of cyclohexene, and then
2.5 g (0.05 mol) of a 67.4% by weight aqueous hydrogen peroxide solution was charged. The reaction was carried out for 1 hour, during which water was continuously removed by azeotropic distillation with cyclohexene and the temperature was maintained at 80-90°C. After one hour of reaction, it was found that 0.01 mole of unreacted hydrogen peroxide remained in the reaction medium and 0.018 mole of cyclohexene, epoxide had been produced. Hydrogen peroxide conversion rate 80%, selectivity 45%.

Example 5 Diethylene glycol dimethyl ether was added to a glass reaction vessel with a capacity of 300 c.c.
CH ₃ OCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₃ 87g, cyclohexene 82g (1 mol), molybdenum hexacarbonyl Mo(CO) ₆ 0.2g, disodium phosphate 0.15g
and 6.6 g (0.068 mol) of cyclohexene epoxide were charged. Boiling point of cyclohexene mixture
70% by weight aqueous hydrogen peroxide solution dissolved in 20g of solvent heated to 81°C for 0.5 hours 2.81
g (0.058 mol) was introduced. In the meantime, water was continuously removed from the reaction medium by azeotropic distillation with cyclohexene. After the addition is complete, the reaction medium contains
The presence of 0.006 mole hydrogen peroxide and 0.115 mole cyclohexene epoxide was confirmed. Hydrogen peroxide conversion rate 89.7%, selectivity 87%.

Example 6 (comparative example) Example 2 was repeated without removing the water introduced and the water produced by the reaction together with the hydrogen peroxide. After 2 hours of reaction at 88°C, iodometric analysis revealed that no hydrogen peroxide was present. Furthermore, gas chromatography confirmed the production of 1.2 g of cyclohexene epoxide. Therefore, the conversion rate of hydrogen peroxide is
100%, but the selection rate is 26%.

Example 7 82 g (1 mol) of cyclohexene, 62 g of diethylene glycol monoethyl ether,
0.2 g of disodium phosphate and 0.2 g of powdered metal molybdenum were charged. The mixture is brought to a boil with reflux cooling, then diethylene glycol
13.5g of monoethyl ether and 2.6g of 70% hydrogen peroxide
g (0.054 mol) was introduced over a period of 40 minutes. During this time, water in the reaction medium was continuously removed by azeotropic distillation. After 1 hour of reaction, it was confirmed that 0.017 mol of unreacted hydrogen peroxide and 2.25 g (0.023 mol) of cyclohexene epoxide were present in the mixture. Hydrogen peroxide conversion rate 68.5% selectivity
62%.

Example 8 Powdered metal tungsten instead of molybdenum
Example 7 was repeated using 0.2g. After 90 minutes of reaction, there is no unreacted hydrogen peroxide in the reaction medium.
0.007 mol, and cyclohexene epoxide 2
g (0.021 mol) was observed; therefore, the hydrogen peroxide conversion was 87% and the selectivity was 44.6%.

Example 9 Example 7 was repeated using 0.2 g of molybdyl acetylacetonate instead of molybdenum metal. After 1 hour of reaction, the presence of 0.001 mol of unreacted hydrogen peroxide and 4.1 g (0.042 mol) of cyclohexene epoxide was observed in the reaction mixture: therefore, the hydrogen peroxide conversion was 98.2% and the selectivity was 79.2%.
It is.

Example 10 82 g (1 mol) of cyclohexene in the reaction vessel,
Diethylene glycol monoethyl ether 52
g, 0.2 g of disodium phosphate and 0.17 g of molybdic acid of formula (NH ₄ ) ₂ O.4MoO ₃ were charged. Bring the mixture to a boil with reflux cooling,
Next, a solution of 2.4 g (0.049 mol) of 70% hydrogen peroxide dissolved in 20 g of diethylene glycol monoethyl ether was added over 30 minutes. Water was continuously removed by azeotropic distillation. After 1 hour of reaction, 1 mmol of unreacted hydrogen peroxide and 4.7 g (0.048 mol) of cyclohexene epoxide were found to be present in the reaction medium; therefore, the hydrogen peroxide conversion was
97.9%, the selection rate is 100%.

Example 11 Instead of molybdic acid, Rec.Trav.Chim. 92 ,
Cyclohexanediol molybdate (C ₆ H ₁₁ O ₂ ) prepared by the method described in 253 (1973)
Example 10 was repeated using 0.359 g of _MoO2 . 30
After a minute of reaction, all hydrogen peroxide was consumed and 3.3 g of cyclohexene epoxide was added to the reaction medium.
(0.034 mol) was found to be present: therefore the conversion is 100% and the selectivity is 69.4%.

Example 12 Tungstic acid 0.2 instead of metal tungsten
Example 8 was repeated using g. After 30 minutes of reaction, there was 0.004 mole of unreacted hydrogen peroxide in the reaction medium and cyclohexene epoxide.
3.8 g (0.039 mol) were present; therefore, the hydrogen peroxide conversion was 92.6% and the selectivity was 78%.

Example 13 A reaction vessel was charged with 82 g (1 mol) of cyclohexene, 47 g of diethylene glycol dimethyl ether, 0.2 g of disodium phosphate, and 0.2 g of zirconium acetylacetonate. Boil while cooling under reflux, then add 2.7 g of 70% H ₂ O ₂ to 20 g of diethylene glycol dimethyl ether.
(0.055 mol) was added over an hour. Hydrogen peroxide in the medium after 1 hour reaction
0.011 moles and 0.96 g of cyclohexene epoxide
(0.01 mol) was present: therefore the conversion was 80
%, and the selection rate is 22.7%.

Example 14 82 g (1 mol) of cyclohexene in the reaction vessel,
Diethylene glycol monoethyl ether 47
g, 0.2 g of disodium phosphate and 0.2 g of molybdenum sulfate were charged. While cooling at reflux, heat this mixture and then add 70% hydrogen peroxide dissolved in 20 g of diethylene glycol monoethyl ether.
2.4 g (0.049 mol) of the solution was added over 30 minutes, during which time water was removed by azeotropic distillation. After the addition is complete, only traces of hydrogen peroxide are present in the reaction medium, while 3.3 g of cyclohexene epoxide
(0.034 mol) was present: therefore the conversion was
100%, and the selection rate is 69.4%.

Example 15 Chromic anhydride Cr ₂ O ₃ 0.2 instead of molybdenum sulfate
Example 14 was repeated using g. After 90 minutes of reaction, there were 0.003 mol of hydrogen peroxide and 0.2 g (0.002 mol) of cyclohexene epoxide in the reaction medium: the hydrogen peroxide conversion in this case was therefore 93.8% and the selectivity was It is 4.4%.

Example 16 A reaction vessel was charged with 62 g of diethylene glycol monoethyl ether, 2 g of a 25% by weight ammonia aqueous solution, and 0.2 g of titanium oxide TiO ₂ . The mixture was brought to the boil with reflux cooling, and then a solution of 2.6 g (0.053 mol) of 70% hydrogen peroxide in 20 g of diethylene glycol monoethyl ether was added over 30 minutes. During this time, water was removed from the reaction medium by azeotropic distillation. After 6 hours of reaction, there were 0.031 mol of unreacted hydrogen peroxide and 0.6 g (0.006 mol) of cyclohexene epoxide in the medium: the hydrogen peroxide conversion in this case was therefore 41.5% and the selectivity was 27.3%. It is.

Example 17 Example 16 was repeated using 0.2 g of niobium oxide, Nb ₂ O ₅ instead of titanium oxide. After 6 hours of reaction, there were 0.021 mol of hydrogen peroxide and 0.7 g (0.007 mol) of cyclohexene epoxide in the medium; therefore, in this case the hydrogen peroxide conversion was
60.3%, and the selection rate is 21.8%.

Claims (1)

[Scope of Claims] 1. Olefin is dissolved in hydrogen peroxide in a reaction medium consisting of one or more organic solvents that dissolve hydrogen peroxide.
Under a temperature of ~120℃ and a pressure of ~20mmHg ~100 bar,
In the method of epoxidizing with 0.02 to 10 moles of hydrogen peroxide per mole of olefin,
The use of catalysts consisting of or containing metals IVA, VA and VIA, or mixtures thereof, in amounts of 0.0001 to 1 g atom of metal per mole of hydrogen peroxide and the water introduced with the hydrogen peroxide and A process for the epoxidation of olefins, characterized in that during the reaction the water resulting from the reaction is continuously removed from the reaction medium by distillation or entrainment. 2. Process according to claim 1, wherein the catalyst used is molybdenum or tungsten. 3. Process according to claim 1, wherein the catalyst used is a derivative of a metal or an inorganic or organic complex of a metal. 4. The method according to claim 3, wherein the metal is molybdenum or tungsten. 5 Olefin has the general formula: (In the formula, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and each represents a hydrogen atom or a straight or branched alkyl group having 1 to 30 carbon atoms, or optionally a branched 3-carbon alkyl group. ~12 cycloalkyl groups or a hydrocarbon group consisting of a benzene ring having 6 to 12 carbon atoms and optionally substituted with a lower alkyl group; or R ₁ and R ₂ or R ₃ and R ₄ together represent a straight or branched alkylene group having 3 to 11 carbon atoms; or R ₁
and R ₃ or R ₂ and R ₄ together represent a straight or branched alkylene group having 1 to 10 carbon atoms. These groups R ₁ , R ₂ , R ₃ and R ₄ may optionally be substituted with functional groups stable in the reaction medium.
The method according to any of paragraph 4. 6. The method of claim 6, wherein the olefin is propylene. 7. The method according to any one of claims 1 to 6, wherein the solvent used is an oxide ether, an alcohol, a polyol or an ether or ester of an alcohol and a polyol. 8. The solvent used is an oligomer of ethylene oxide or propylene oxide, the corresponding methyl or ethyl ether, or the corresponding formic acid, acetic acid or propionic acid ester.
A method according to any one of claims 1 to 7.