FR3051790A1 - PROCESS FOR OXIDATION OF UNSATURATED FATTY ACID AND REACTION SYSTEM FOR IMPLEMENTING SUCH A METHOD - Google Patents

Abstract

The invention relates to a process for oxidizing an unsaturated fatty acid with singlet oxygen, which comprises preparing a reaction system containing at least one unsaturated fatty acid and molybdate ions, in a mixture of water and an alcohol capable of solubilizing the unsaturated fatty acid, this reaction system being free of exogenous emulsifying agent; and the addition of hydrogen peroxide in this reaction system. This process makes it possible to carry out, in a controlled manner, the allylic oxidation or the epoxidation of the unsaturated fatty acid.

Description

The present invention is in the field of the transformation of oleochemical products into valuable derivatives. More particularly, it relates to a process for oxidation of an unsaturated fatty acid by singlet oxygen, in particular allylic oxidation of an unsaturated fatty acid by singlet oxygen insertion, and a reaction system for the implementation of of such a process. The invention also relates to the use of ion exchange resin supporting molybdate ions for the production of singlet oxygen. It furthermore relates, on the one hand, to a process for forming an allyl monoalcohol, more specifically a hydroxylated fatty acid, from an unsaturated fatty acid, and, on the other hand, to a process for forming an a diol from an unsaturated fatty acid, each of these processes using a process for oxidizing an unsaturated fatty acid with singlet oxygen according to the invention.

Oxygenated oils, as well as the fatty acids that compose them, that is to say acids with a carbon chain of 4 to 36 carbon atoms, are products of high added value for the oleochemical industry. Oleochemistry, which refers to physico-chemical transformation operations applied to animal and vegetable oils and fats, is used in many fields of industry, such as the cosmetic, chemical and pharmaceutical fields, in which it occupies a place important given current trends in sustainable development and environmental legislation. Thus, new processes based on the use of oleochemical products are being developed all over the world. Like the biological pathways, chemical oxidation processes of fatty acids derived from vegetable or animal oils and fats have been developed, aimed at obtaining hydroxylated fatty acids. The hydroxylated fatty acids have one or more hydroxyl groups on their hydrophobic chain, which gives them very specific physicochemical properties, such as high viscosity and reactivity. These properties make them particularly attractive for many applications. especially in the fields of organic chemistry, as chemical intermediates; polymers, especially for the manufacture of polyurethanes; lubricants; building, especially for the manufacture of coatings, cements, coatings, etc. ; cosmetics, especially for the manufacture of varnishes; but also pharmacy and medicine; etc.

In particular, oleic acid extracted from an oil, such as sunflower oil, can be hydroxylated at its ethylenic double bond, to selectively obtain the 9-hydroxystearic acid, 10-hydroxystearic acid and 9,10-hydroxystearic acid. hydroxystearic acid, which can be used as intermediates of polymerization reactions, in particular for the manufacture of biopolymers.

In general, the chemical processes for obtaining hydroxylated fatty acids can carry out monohydroxylation reactions or dihydroxylation reactions of the double-bonds of unsaturated fatty acid chains, to lead, respectively, to mono derivatives. alcohols and oleochemical diols.

The dihydroxylation reactions may be direct, or involve an epoxide intermediate, which is then hydrolysed.

Direct dihydroxylation processes, allowing the formation of vicinal diols (1,2-diol) by reacting an olefin with a solution of potassium permanganate (ΚΜηθ4) or osmium tetroxide (OSO4), have been known for a long time ( US 2,265,143, Bader, 1948). These methods have, for example, been applied to oleic acid to give 9,10-dihydroxystearic acid (Foglia et al., 1977, Julien-David et al., 2008).

However, such processes require the implementation of several post-treatment operations, such as the removal of reduced metals and the neutralization of the media, and thus these processes produce hazardous effluents by the nature of metals containing them . In addition, the ΚΜηθ4 reaction only works with stoichiometric amounts of substrate and catalyst, but the overoxidation of the products is very poorly controlled, which causes the formation of secondary products in large quantities, up to 20%. Other more refined processes use catalysts based on osmium oxide (Os), ruthenium (Ru) and zeolite, etc., which are very expensive.

The synthesis of diols by intermediate formation of epoxides and then hydrolysis of these epoxides is commonly used in the functionalization of oils and fats. Epoxides are generally obtained by four technologies: the use of peracids in the presence of acid or enzymes as catalysts, a well-known method for industrial epoxidation (Warwel et al., 1995); the use of organic or inorganic peroxides (Sharpless et al., 1983); the use of halohydrins; or the use of molecular oxygen, which is the least expensive and most environmentally friendly method, but which is effective only for simple molecules.

None of these technologies is, however, completely satisfactory, especially from an ecological point of view.

Chemical monohydroxylation reactions lead to oleochemical monoalcohols. They are generally carried out by two synthetic routes, implementing either hydroboration or oxidation of unsaturated fatty acids.

The hydroboration reaction of the unsaturated fatty acids makes it possible to produce saturated hydroxylated fatty acids. For example, hydroboration of methyl esters of fatty acids with diborane was proposed as early as 1959 (Fore et al., 1959). The sensitivity to air and hydrolysis of borane compounds, however, makes it difficult to develop hydroboration processes.

The oxidation reaction of the unsaturated fatty acids involves selenium dioxide (SeOa) or singlet oxygen (02O2) to obtain unsaturated hydroxylated fatty acids. In particular, selenium dioxide (SeOa) in the presence of tert-butyl hydroperoxide (TBHP) has proved very effective for the hydroxylation of unsaturated fatty acids in a single step. However, selenium dioxide causes the overoxidation of alcohols and generates two types of by-products in a significant amount, by-products whose removal is particularly difficult, making such a process unusable on an industrial scale. The oxidation of unsaturated fatty acids by singlet oxygen is a known process in photochemistry (Choe et al., 2005, Watabe et al., 2007). This method presents in particular no problem of over oxidation of the alcohols formed. In addition, the use of singlet oxygen for the oxidation of fatty acids makes it possible to avoid the secondary decompositions commonly observed for autoxidation reactions, such as the formation of aldehydes, the splitting of the double bond, polymerizations, etc. Singlet oxygen, conventionally designated by is a highly reactive oxygen species that is commonly used for many applications in organic synthesis. Singlet oxygen more particularly corresponds to the first excited state of the oxygen molecule. It has an excess of energy compared to the fundamental oxygen O2. In particular, singlet oxygen exhibits selective reactivity to unsaturated substrates. The singlet oxygen is generally produced by the so-called photosensitization method, during which a molecule, called photosensitizer, typically a dye with a high absorption power, excited by light, transfers its energy to oxygen and oxygen. active in singlet oxygen.

For example, the oxidation of oleic acid by singlet oxygen produced by photosensitization generates hydroperoxides of allylic fatty acids which are then reduced to give 10-hydroxy-8 (E) -octadecenoic acid and the acid. 9-hydroxy-10 (E) -octadecenoic (Choe et al., 2005, Watabe et al., 2007). Montera de Espinosa et al. (2009) applied such a method, which performs the oxidation of triglycerides by singlet oxygen produced by photosensitization using a porphyrin, tetraphenyl porphyrin (TPP), with sunflower oil with oleic acid content greater than 90 %, to give a mixture of unsaturated hydroxylated triglycerides. These polyhydroxy triglycerides can be used for the synthesis of acrylic polymers, which have shown considerable interest as surfactants and in polyurethanes (Lligadas et al., 2010).

However, in general, the need for the combination of efficient illumination with oxygen in the air, as well as the photolability of many dyes / catalysts, are major disadvantages for the implementation of photosensitization processes in industrial conditions.

Thus, there remains a need for a process for performing the oxidation of unsaturated fatty acids, to obtain epoxy or hydroperoxide derivatives, efficiently and with high yield and selectivity, which can be easily implemented, including in industrial conditions, and which is respectful of the environment. In order to provide such a method, the present inventors have been particularly interested in singlet oxygen oxidation techniques, by searching for methods other than photosensitization to produce singlet oxygen.

They are thus interested in another method known in itself for the production of singlet oxygen, more precisely to the so-called method of catalytic disproportionation of hydrogen peroxide. Such disproportionation is typically carried out in an alkaline medium in the presence of a catalyst such as a metal ion. This method is a safe and inexpensive alternative to photosensitization. In particular, it has been proposed by the prior art to produce singlet oxygen under the action of alkaline molybdates in the presence of an excess of hydrogen peroxide in a basic aqueous medium (Aubry, 1985). The oxidation by the H2O2 / Μ 0 θ 4 system advantageously makes it possible to produce singlet oxygen efficiently and quantitatively.

The mechanism of formation of singlet oxygen from a H2O2 / MoO / 'system has been investigated by the prior art. The addition of hydrogen peroxide to molybdate ions generates reactive peroxomolybdate intermediates, including triperoxomolybdate ΜοΟ (θ2) 3 'which is the main precursor of singlet oxygen. The importance of the nature of the reaction medium on the production and the lifetime of singlet oxygen has been underlined by the prior art. Several methods have been proposed to promote this production, such as the use of dipolar aprotic solvents, or the use of microemulsions based on water and an immiscible organic solvent (Borde et al., 2008).

The present inventors have now discovered that, quite surprisingly and advantageously, it is possible to carry out the oxidation of unsaturated fatty acids, to form intermediates which can easily be converted into alcohols, be they mono- alcohols or polyols, especially hydroperoxide intermediates or epoxides, in a controlled manner, and in a simple manner and with a particularly high yield and selectivity, by reaction with singlet oxygen produced in situ chemically in a reaction system of particular composition. More particularly, this reaction system is of the ternary type, based on water, an alcohol capable of solubilizing the unsaturated fatty acid which must be oxidized, and of this unsaturated fatty acid itself as the third component of the medium. . The present invention thus advantageously takes advantage of the surfactant properties of unsaturated fatty acids, more precisely in their carboxylate form, to form, without the addition of any exogenous emulsifying agent, a reaction medium in the form of an emulsion which proves particularly and surprisingly favorable to the in situ production of singlet oxygen, the prolongation of its lifetime in the medium and the realization of the oxidation reaction of the unsaturated fatty acid by singlet oxygen thus produced in if you.

In this ternary medium, the fatty acid in carboxylate form plays both a reactive and a surfactant role. Under conditions of neutral or basic pH, the carboxylate species of the unsaturated fatty acid is immediately formed in the reaction medium. Under conditions of initial acidic pH, it has been observed by the present inventors that, quite advantageously, there is a self-regulation of the pH in the medium, which causes the formation of the carboxylate species of the Unsaturated fatty acid in the reaction medium, the species of which the present invention advantageously takes advantage of the surfactant properties. Alcohol plays a role both solvent of the fatty acid and co-surfactant. All of these constituents promote contacting the different reactants with each other in the reaction system, and obtaining a particularly high reaction efficiency. In addition, it has also been observed by the present inventors that it is possible, by a suitable adjustment of the operating conditions, and in particular of the pH of the reaction system, at least in homogeneous catalysis, to specifically orient the reaction towards: the so-called allylic oxidation of the unsaturated fatty acid, by insertion of singlet oxygen, with migration of the double bond and cis-trans isomerization, so as to form hydroperoxides in alpha or beta of the double bond ; This makes it possible to form monoalcohols whose hydroxyl function is in the same position, after reduction of the corresponding allylic hydroperoxides obtained. This reaction is obtained, in particular by homogeneous catalysis, under conditions of basic or neutral pH; or the epoxidation of the unsaturated fatty acid with disappearance of the double bond. The epoxide thus obtained can in particular be used to form a diol. This reaction is obtained, in particular by homogeneous catalysis, under acidic pH conditions.

Such a control of the specific orientation of the reaction is furthermore advantageously obtained irrespective of the position of the double bond on the carbon chain.

Such results were not particularly predictable works of the prior art. Indeed, it is clear from these studies that the singlet oxygen produced by the H2O2 / MoO / 'chemical system has a very short lifetime. about a few microseconds. It thus appears important for the oxidation of a substrate to be effective, that this substrate is a good deactivator of singlet oxygen, that is to say that it easily deactivates the singlet oxygen by capturing it. This is not the case for unsaturated fatty acids, so that their oxidation by reaction with singlet oxygen produced in situ chemically, to form hydroperoxides or epoxides in a controlled manner and with a high yield and selectivity. is thus all the more surprising.

According to a first aspect, it is thus proposed by the present invention a process for oxidizing an unsaturated fatty acid with singlet oxygen, in particular to produce an epoxide or allyl hydroperoxides. This process comprises: - the preparation of a reaction system containing at least unsaturated fatty acid and molybdate ions, in a mixture of water and an alcohol capable of solubilizing said unsaturated fatty acid, this reaction system being free from exogenous emulsifier; and the addition of hydrogen peroxide in this reaction system. The unsaturated fatty acid may in particular be contained in a vegetable or animal oil, or in a semi-purified extract obtained from a vegetable or animal oil or fat. It may otherwise be introduced in substantially pure form into the reaction system.

By "the reaction system being free from exogenous emulsifying agent" is meant that the reaction system does not comprise any additional emulsifying agent relative to the carboxylate of the unsaturated fatty acid that forms spontaneously in the reaction system, and in particular no compound which is introduced into the reaction system in a form having emulsifying properties.

The process according to the invention advantageously makes it possible to carry out the oxidation in situ, by singlet oxygen, of oleochemical bases, that is to say bases resulting from physicochemical transformation (s) applied (s). ) to animal and vegetable oils and fats, and unsaturated triglycerides.

The process according to the invention is simple to implement, at low cost and by means of environmentally friendly reagents.

It also makes it possible, by means of a single molecular system, to carry out several types of reactions, depending on the particular operating conditions implemented, in particular as a function of the pH in the reaction system, in order to obtain either allyl hydroperoxides or a epoxide.

Under certain operating conditions, more precisely at basic or neutral pH, the addition of singlet oxygen in the olefinic CH bond of the unsaturated fatty acid may thus lead, according to the invention, to the formation of a hydroperoxide group with migration. of the double bond of the unsaturated fatty acid and its isomerization in trans configuration.

Thus, in particular embodiments of the invention, the pH of the reaction system is maintained at a value greater than or equal to 7, preferably between 9 and 12, and preferably greater than or equal to 10 and less than 12. The process according to the invention then carries out the allylic oxidation of the unsaturated fatty acid by insertion of singlet oxygen, to form allyl hydroperoxides. These allylic hydroperoxides can then be reduced to the corresponding allylic alcohols, for example by means of sodium sulphite or sodium borohydride. In the remainder of the present description, this reaction will be referred to as the allylic oxidation term. The allylic oxidation consists of the oxygenation of the organic environment around the unsaturation of the oleochemical base or of the unsaturated triglyceride, this oxidation generating the migration of the double bond and the hydroxylation in alpha or beta of this double -liaison. The process according to the invention makes it possible to carry out this reaction with a particularly high yield and selectivity. For example, carried out for the allyl oxidation of oleic acid on a laboratory scale, the process according to the invention makes it possible, after reduction of the hydroperoxide intermediates formed, to obtain hydroxylated fatty acids with a yield as high as 98%. By way of example, the two successive reactions of allylic oxidation, and then of reduction of the hydroperoxides formed at the end of this step, can be illustrated by the following reaction scheme A, for the example of oleic acid as unsaturated fatty acid:

Reaction Scheme A The insertion of singlet oxygen at the oleic acid double bond leads to the migration of this double bond, as indicated by the arrows, and to the production of two hydroperoxides which make it possible to form, after reduction, monounsaturated fatty acid hydroxylated in position 9, and monounsaturated fatty acid hydroxylated in position 10, these two molecules being in trans configuration.

The adjustment of the pH of the reaction system can be carried out by any conventional method in itself for the skilled person, in particular, for the basic pH, by adding sodium hydroxide in the reaction system.

In other operating conditions, more particularly at acidic pH, at least in homogeneous catalysis, the process according to the invention makes it possible to obtain oleophilic epoxides as well as short-chain fatty acids.

Thus, in particular embodiments of the invention, the pH of the reaction system is set, prior to the step of adding hydrogen peroxide in the reaction system, to a value of less than 7, preferably between 4 and 6. The process according to the invention then performs the oxidation of the unsaturated fatty acid to form an epoxide. This epoxide can in particular be hydrolyzed to a diol. In the remainder of the present description, this reaction will be referred to as the epoxidation term. By way of example, the two successive reactions of epoxidation followed by hydrolysis of the epoxide formed at the end of this step can be illustrated by the following reaction scheme B, for the example of oleic acid. as unsaturated fatty acid:

Reaction Scheme B Oxidation by singlet oxygen at the double bond of oleic acid causes the formation of an epoxide, which itself allows to form, after hydrolysis, a diol, acid 9, 10-dihydroxystearic acid, initially replacing the double bond.

The oxidation process according to the invention can be applied to all forms of the fatty acid, in particular to the acidic forms, and to the salt forms. In particular embodiments of the oxidation process according to the invention which will be described in more detail hereinafter, relating to heterogeneous catalysis, the oxidation process also applies successfully to the acid ester forms. advantageously without observing the hydrolysis of the fatty acid ester function.

Thus, the process according to the invention makes it possible to carry out the oxidation of an unsaturated fatty acid both in acid form, in salt form and in ester form. The salt forms and the esterified forms of the unsaturated fatty acid are thus encompassed in the expression "fatty acid" within the meaning of the present invention.

According to particular embodiments, the oxidation process according to the invention also satisfies the following characteristics, implemented separately or in each of their technically operating combinations.

The various operating parameters of the process are in particular fixed as indicated below, each of the indicated value ranges making it possible to obtain a particularly high reaction yield in the desired reaction route.

In particular embodiments of the invention, the addition of hydrogen peroxide in the reaction system is carried out gradually, preferably by introducing into the reaction system an aqueous solution of hydrogen peroxide, and preferably at a rate of more than 3.0 mmol of hydrogen peroxide per minute, especially from 3.0 mmol to 4.9 mmol of hydrogen peroxide per minute. For example, it can be implemented an aqueous solution of hydrogen peroxide 50% w / w. This solution is then preferably introduced into the reaction system at a flow rate greater than 0.17 ml / min, especially between 0.17 and 0.28 ml / min.

Preferably, the addition rate of the aqueous solution of hydrogen peroxide in the reaction system is chosen, in conjunction with the molar amount of hydrogen peroxide to be introduced relative to the molar amount of unsaturated fatty acid present in the reaction mixture. reaction medium, so as to obtain a duration of addition of hydrogen peroxide greater than or equal to 30 minutes, preferably between 2 and 5 hours, especially between 2 and 4 hours, and for example equal to about 3 hours.

When the process according to the invention is applied for carrying out an epoxidation reaction of the unsaturated fatty acid, as indicated above, the hydrogen peroxide is preferably introduced into the reaction system at the rate of 4.2 mmol per minute. This corresponds to a rate of addition of an aqueous solution of hydrogen peroxide of 0.24 ml / min.

When the process according to the invention is applied for carrying out an allyl oxidation reaction of the unsaturated fatty acid, as indicated above, the hydrogen peroxide is preferably introduced into the reaction system at a rate of 3.7 mmol per minute. This corresponds to a rate of addition of an aqueous solution of hydrogen peroxide of 0.21 ml / min. The addition of hydrogen peroxide is preferably carried out with stirring, for example at a speed of 600 rpm.

In particular embodiments of the invention, the process comprises, after the step of adding hydrogen peroxide in the reaction system, a step of stirring the reaction medium obtained for a duration greater than or equal to at 1 hour, and preferably at least 2 hours. Such a step advantageously makes it possible to optimize the yield of the oxidation reaction.

Preferably, the total duration of the addition step of hydrogen peroxide in the reaction system and of the stirring step of the reaction medium obtained is greater than or equal to 4 hours, preferably between 5 and 7 hours.

In particular embodiments of the invention, the step of adding hydrogen peroxide in the reaction system, and optionally the stirring step of the reaction medium obtained, are carried out at a higher temperature. at 25 ° C, preferably between 50 and 85 ° C, and preferably between 50 and 75 ° C. Such temperature ranges promote the stability of the emulsion that forms in the reaction system, and activate the ionic and nonionic entities at the interfaces of the phases of the emulsion. A particularly preferred temperature range within the scope of the invention is the range from 55 to 75.degree. C., and more particularly from 65 to 75.degree. C., both for an epoxide reaction of the unsaturated fatty acid with oxygen. singlet, only for an allyl oxidation reaction of the unsaturated fatty acid by singlet oxygen insertion.

In particular embodiments of the invention, the alcohol capable of solubilizing the unsaturated fatty acid is chosen from ethanol and methanol. It may otherwise be butanol, octanol, etc.

The volume ratio between the water and the alcohol in the mixture of water and an alcohol capable of solubilizing the unsaturated fatty acid to be oxidized, for example the ratio of water to ethanol, is preferably between 1/1 and 1/9, preferably between 1/1 and 1/5, and in particular 1/1 and 1/2.

A water / alcohol ratio of about 1/1 will be more particularly preferred for the allylic oxidation reactions, while a water / alcohol ratio of about 1/2 will be more particularly preferred for the epoxidation reactions. By way of example, when the unsaturated fatty acid is oleic acid, and the alcohol is ethanol, an oleic acid / water / ethanol volume ratio of 2: 5: 5 will be more particularly preferred for allyl oxidation reactions, and a ratio of 1/1/2 will be more particularly preferred for the epoxidation reactions. Such ratios make it possible in particular to obtain a particularly high yield of oxidation reactions, and high reproducibility in the results obtained, in particular in homogeneous catalysis.

Molybdate ions may be introduced into the reaction medium in salt form, for example sodium molybdate dihydrate.

In particular embodiments of the invention, the molybdate ions are present in the reaction system in an amount in mol of between 4 and 9% relative to the number of moles of the unsaturated fatty acid to be oxidized, preferably between 6 and 9 mol% relative to the number of moles of said unsaturated fatty acid. Such a characteristic advantageously makes it possible to further increase the conversion rate of the unsaturated fatty acid, and to reduce the amount of by-products formed for each oxidation route chosen.

When the process according to the invention is applied for carrying out an epoxidation reaction of the unsaturated fatty acid, as indicated above, the molybdate ions are preferably introduced into the reaction system in a quantity in moles about 6.6% relative to the number of moles of the unsaturated fatty acid to be oxidized.

When the process according to the invention is applied for the implementation of an allylic oxidation reaction of the unsaturated fatty acid, as indicated above, the molybdate ions are preferably introduced into the reaction system in an amount of moles of about 8.8% based on the number of moles of the unsaturated fatty acid to be oxidized.

As for the hydrogen peroxide, it is preferably introduced into the reaction system in a proportion of at least 6 molar equivalents, preferably at least 9 molar equivalents, relative to the unsaturated fatty acid. Here again, such a characteristic contributes to increasing the yield of the allyl oxidation reaction of the unsaturated fatty acid by the process according to the invention.

When the process according to the invention is applied for carrying out an epoxidation reaction of the unsaturated fatty acid, as indicated above, the hydrogen peroxide is preferably introduced into the reaction system at a rate of at least 9 molar equivalents, preferably 9 to 13 molar equivalents, based on the unsaturated fatty acid.

When the process according to the invention is applied for carrying out an allylic oxidation reaction of the unsaturated fatty acid, as indicated above, the hydrogen peroxide is preferably introduced into the reaction system at a rate of from 13 to 21 molar equivalents, preferably about 14 molar equivalents, based on the unsaturated fatty acid.

The hydrogen peroxide may in particular be introduced into the reaction medium in the form of an aqueous solution, for example concentrated to 50% by volume of hydrogen peroxide.

The process according to the invention can be carried out in homogeneous catalysis, that is to say in which the molybdate ions are in free form in the reaction system.

In preferred embodiments of the invention, the oxidation process is carried out in heterogeneous catalysis. Thus, the molybdate ions are present in the reaction system in the form supported by an organic anion exchange resin. The catalyst thus obtained is then advantageously easy to separate from the reaction system, and it can be reused for several successive oxidation cycles. The method according to the invention is therefore more economical to implement, and even easier because it requires fewer purification steps of the reaction products.

In addition, it has been found by the present inventors, quite surprisingly, that the use of molybdate ions in resin-supported form increases the efficiency of the oxidation reaction, and decreases the duration thereof. We shall not prejudge here the phenomena underlying such an advantageous result. It can be assumed, however, that the supported form of the molybdate ion catalyst prevents close contact between the unsaturated fatty acid and the intermediate forms of peroxomolybdate formed during the process of producing singlet oxygen, more particularly the forms of molybdate capable of reacting. in the medium to form undesirable side products.

According to the present invention, it is preferably implemented a basic resin, advantageously to adjust the pH of the reaction system without using additional exogenous base.

Examples of resins that can be used in the context of the invention are copolymers of styrene and divinylbenzene, such as the resin sold under the name Lewatit® K7367, or Lewatit® MP 600 resin, Amberlite® resin. IRA 410 or Amberlite® IR 120H resin.

For example, the process according to the invention has been applied for the allyl oxidation of oleic acid with, as a catalyst in the reaction system, molybdate ions supported on the Lewatit® K7367 anion exchange resin. A conversion rate of the order of 100% was obtained, with regeneration of the catalyst without loss of efficiency over three cycles for the resin.

Ion exchange resins which are particularly preferred in the context of the invention are macroporous type resins, which have in particular a good adsorption capacity for molybdate ions, and make it possible to obtain particularly high catalytic yields. However, the invention also extends to other types of resins, in particular to microporous resins, in gel form, etc.

Preferably, the adsorption step is carried out by bringing the resin into contact with an aqueous solution of molybdate ions. This contacting can be carried out in an acid medium as well as in a basic medium. The use of a basic medium is particularly advantageous in that it makes it possible to obtain a very good yield of the subsequent allyl oxidation reaction of the unsaturated fatty acid, without it being necessary. to add an exogenous base in the reaction medium.

In particular embodiments of the invention, the process comprises a step of adsorbing the unsaturated fatty acid on the anion exchange resin supporting the molybdate ions, prior to the preparation step of the reaction system by bringing said resin into contact with the mixture of water and said alcohol. This step is preferably carried out in a dry medium, by contacting the resin supporting the molybdate ions with the unsaturated fatty acid, preferably under mild heating, for example at about 40 ° C. Such a characteristic advantageously increases the yield of the process according to the invention, applied to the allylic oxidation of the unsaturated fatty acid, with respect to the modes of implementation in which the unsaturated fatty acid is introduced in free form into the system. reaction.

When the unsaturated fatty acid and the molybdate ions are supported on the anion exchange resin, the volume ratio between the water and the alcohol capable of solubilizing the unsaturated fatty acid is preferably between 1/4 and 1. / 9, especially about 1/5. In such reaction systems, the unsaturated fatty acid is well solubilized, and particularly high yields are obtained. Hydrogen peroxide is preferably introduced into the reaction system in an amount of greater than or equal to 5.3 mmol per minute. This corresponds to a rate of addition of an aqueous solution of hydrogen peroxide greater than or equal to 0.30 ml / min.

The method according to the invention may further comprise a final regeneration step of the resin supporting the molybdate ions, for a subsequent implementation.

In particular embodiments of the invention, the oxidation process comprises a final step of reducing the residual hydrogen peroxide in the reaction medium, for example by means of sodium sulphite.

The process according to the invention can be applied to the oxidation of any unsaturated fatty acid. It can in particular be applied to the oxidation of oleic acid, in particular extracted from a sunflower oil, rapeseed oil, soybean oil, palm oil, etc., to synthesize a hydroxylated fatty acid of carbon chain C18.

Otherwise, the unsaturated fatty acid may be selected from ω-unsaturated fatty acids, such as undec-10-enoic acid, hydroxylated monounsaturated fatty acids, such as (E) -10-hydroxyoctadec-8- enoic acid, (E) -9-hydroxyoctadec-10-enoic acid, (Z) -12-hydroxyoctadec-9-enoic acid, monounsaturated fatty acids with long carbon chain, preferably in C 8: 1 to C 24 : 1, for example C20: 1 to C24: 1, such as (Z) -docos-13-enoic acid, and polyunsaturated fatty acids, especially diunsaturated fatty acids, such as (9Z, 12Z) -octadecanic acid; -9,12-dénoïque.

The oxidation process according to the invention can also be applied to a single unsaturated fatty acid as well as to a mixture of unsaturated fatty acids.

In particular embodiments of the invention, the water or alcohol capable of solubilizing the unsaturated fatty acid is deuterated. Preferably, the water and the alcohol capable of solubilizing the unsaturated fatty acid are deuterated. Such a characteristic advantageously has the effect of increasing the yield of the reaction, by increasing the lifetime of the singlet oxygen which is formed in the reaction medium.

When, in accordance with a preferred embodiment of the invention, the process is carried out at basic or neutral pH, particularly favoring the allyl oxidation reaction route of the unsaturated fatty acid, preferably the preparation of the The reaction system comprises the following succession of steps: - mixing of the unsaturated fatty acid and an aqueous solution containing a base, in particular sodium hydroxide, - optionally, heating at a temperature above 25 ° C., for example approximately 50 ° C, and successive introduction into the mixture of the unsaturated fatty acid and the base, molybdate ions, and the alcohol capable of solubilizing the unsaturated fatty acid.

Such a succession of steps is quite advantageous, in particular in that, initially, the mixture of unsaturated fatty acid and of the basic aqueous solution makes it possible to form the carboxylate form of the unsaturated fatty acid, which has surfactant properties. The presence of this carboxylate group increases the solubility in water of the fatty acid, and forms a particularly stable oil / water emulsion. A rise in temperature above 25 ° C, for example at 50 ° C, contributes to the stability of this emulsion. The molybdate ions introduced into the mixture then advantageously have a better solubility in the aqueous phase of the emulsion formed, which becomes less dense. The addition of alcohol at this stage helps to reorganize and reinforce the stability of the emulsion already present, by its co-surfactant properties.

In addition, the reaction of singlet oxygen with the unsaturated fatty acid leads to the formation of oxygenated fatty acids, whose physicochemical properties differ from those of simple fatty acids. The presence of the oxygen function improves the solubility of these compounds in the solvents, which contributes to the in situ stability of the emulsion formed in the reaction medium. All of these characteristics contribute to increasing the yield of the allyl oxidation reaction.

Preferably, a base, preferably the same as that used in the first preparation step of the reaction system, is further introduced into the reaction medium during the addition of hydrogen peroxide, so as to always maintain the pH in the reaction medium. the desired range of values. This base is preferably introduced into the reaction medium in substantially pure form, in particular in solid form or, for the liquid bases, undiluted form, and at regular intervals throughout the duration of addition of hydrogen peroxide. Such a continual supply of the base in the reaction medium also contributes to maintaining the stability of the emulsion formed in the reaction medium by the carboxylate form of the unsaturated fatty acid. This advantageously has the effect of promoting the in situ production of singlet oxygen, and improving its lifetime in the reaction medium.

When, in accordance with a preferred embodiment of the invention, the process is carried out at acidic pH, particularly favoring the epoxidation reaction pathway of the unsaturated fatty acid, preferably, the preparation of the reaction system comprises the succession of the following steps: - mixing molybdate ions and water, - and successive introduction in this mixture, the alcohol capable of solubilizing the unsaturated fatty acid, and unsaturated fatty acid.

Such a succession of steps is quite advantageous from the point of view of the reaction efficiency obtained. In particular, the molybdate ions dissolved in the water in the first stage easily penetrate into the cavities formed by the water at the moment when the emulsion will be formed in the reaction medium, thus increasing its surface of subsequent contact with the peroxide of hydrogen. The successive addition of the alcohol then the unsaturated fatty acid then advantageously makes it possible to solubilize the fatty acid and to promote its contact with the aqueous phase. When the volume of alcohol is greater than the volume of the water, the alcohol has the effect of dispersing the aqueous phase, which also has the effect of increasing the contact area between the unsaturated fatty acid and the water .

Moreover, the subsequent step of adding hydrogen peroxide in the form of an aqueous solution brings about important modifications in the reaction system. The supply of water which it entrains in the reaction medium has the effect of stabilizing the structure of the emulsion and of promoting exchanges of the peroxomolybdate complexes formed in the reaction medium, between the aqueous phase in which they are formed and the phase lipid where they oxidize the double bond of the fatty acid. In addition, the reaction of singlet oxygen with the unsaturated fatty acid leads to the formation of epoxidized fatty acids, the physicochemical properties of which differ from those of simple fatty acids. The presence of the epoxide function improves the solubility of these compounds in the solvents, which contributes to the in situ stability of the emulsion formed in the reaction medium.

According to another aspect, the present invention relates to a reaction system for carrying out a process for the oxidation of an unsaturated fatty acid according to the invention, this process satisfying in particular one or more of the above characteristics. or below. This reaction system contains at least said unsaturated fatty acid and molybdate ions in a mixture of water and an alcohol capable of solubilizing said unsaturated fatty acid. It is also free of exogenous emulsifying agent.

Such a reaction system advantageously constitutes an organized and stabilized system, particularly favorable for the production of singlet oxygen after addition of hydrogen peroxide, as close as possible to the unsaturated fatty acid to be oxidized, and to the oxidation reaction of this fatty acid unsaturated by this singlet oxygen. Thus, the reaction system according to the invention is particularly favorable for the oxidation of oleochemical bases and unsaturated triglycerides, at the oil / water interface, without assistance of any exogenous emulsifying agent.

This reaction system may meet one or more of the characteristics described above with reference to the oxidation process according to the invention.

Another aspect of the invention relates to the use of anion exchange resin supporting molybdate ions for the production of singlet oxygen. This resin may meet one or more of the characteristics described above with reference to the process for oxidizing an unsaturated fatty acid according to the invention.

In particular, this anion exchange resin is preferably a macroporous resin. It is preferentially a basic resin.

In preferred embodiments of the invention, the anion exchange resin is subjected to a hydrophobation treatment, by absorption of molecules of a compound of hydrophobic character, prior to its implementation for the production of singlet oxygen. This hydrophobation step is preferably carried out in a dry medium.

The hydrophobic compound may in particular consist of an unsaturated fatty acid.

According to other aspects, the present invention relates, on the one hand, to a process for forming an allylic monoalcohol from an unsaturated fatty acid, and, on the other hand, to a process for forming a diol from of an unsaturated fatty acid, each of these processes implementing an oxidation process according to the invention, in particular responding to one or more of the above characteristics, in particular implemented, for the first, at basic pH or neutral, and in particular implemented for the second, at acidic pH.

Thus, in one aspect, the present invention relates to a process for forming an allyl monoalcohol from an unsaturated fatty acid, comprising carrying out a method of oxidizing an unsaturated fatty acid with oxygen. singlet according to the invention, in particular carried out at basic or neutral pH, followed by a final step of reduction, preferably in situ, of allyl hydroperoxide formed at the end of this oxidation process, preferably by introduction of a solution of sodium sulfite or sodium borohydride in the reaction system.

In another aspect, the present invention relates to a method of forming a diol from an unsaturated fatty acid, comprising carrying out a method of oxidizing an unsaturated fatty acid with singlet oxygen according to the invention, especially at acidic pH, followed by a final step of hydrolysis, preferably in situ, of the epoxide formed at the end of this oxidation process, preferably in acidic medium.

Included here, in the term diol, are poly-diols which may be formed from polyunsaturated fatty acids by an oxidation process according to the invention, followed by a step of hydrolysis of the polyepoxides and obtained.

The process for oxidizing an unsaturated fatty acid according to the invention, the process for forming a diol from an unsaturated fatty acid and / or the process for forming an allyl monoalcohol from an acid unsaturated fat, may comprise a final stage of post-treatment, including in particular the addition of ethyl acetate in the reaction medium, the acidification to an acidic pH, in particular of about 4, and then the separation of the organic phase and the aqueous phase, preferably by centrifugation, and recovering the organic phase for drying and concentration, after any washing phases.

The compounds obtained in accordance with the invention, in particular oleophilic monohydroxyallyl compounds, which have the particular feature of possessing unconventional ethylenic groups resulting from the migration of double bonds, advantageously find application in many fields, such as the plastics, coatings, polymers, building, etc.

Furthermore, according to other aspects, the present invention relates to the α-hydroxy-epoxy fatty acids that can be obtained by a singlet oxygen oxidation process in accordance with the present invention, from hydroxylated unsaturated fatty acids. indicated below: - 7- (3- (1-hydroxynonyl) oxiran-2-yl) heptanoic acid, obtainable from the fatty acid (E) -10-hydroxyoctadec-8-enoic acid , of general formula:

9- (3-heptyloxiran-2-yl) -9-hydroxynonanoic acid, obtainable from (E) -9-hydroxyoctadec-10-enoic fatty acid, of general formula:

The features and advantages of the invention will emerge more clearly in the light of the following examples of implementation, provided for illustrative purposes only and in no way limitative of the invention, with the support of FIGS. 1 to 7, in which: FIG. 1 represents a graph showing the conversion rate of oleic acid (XAO), the rate of epoxide formation (YEP) and the rate of formation of monoalcohols (YHFA) as a function of the molar ratio of molybdate ions / oleic acid; at the end of the implementation of a process for oxidation of oleic acid according to the invention at acidic pH; FIG. 2 represents a graph showing the conversion rate of oleic acid (XAO), the rate of epoxide formation (YEP) and the rate of formation of monoalcohols (YHFA) as a function of the molar ratio of hydrogen peroxide H2O2. oleic acid AO, after the implementation of a process for oxidation of oleic acid according to the invention at acidic pH; FIG. 3 represents a graph showing the conversion rate of oleic acid (XAO), the epoxide formation rate (YEP) and the amount of residual hydrogen peroxide (H2O2) as a function of the agitation time of the reaction medium after the complete addition of hydrogen peroxide (H2O2), during the implementation of a process for oxidation of oleic acid according to the invention at acidic pH; FIG. 4 represents a graph showing the relative percentage of oxirane in the reaction medium at the end of the implementation of a process for epoxidation of oleic acid according to the invention, as a function of time and for different temperatures; the indicated values representing the average obtained over two tests; FIG. 5 represents a graph showing the percentage of hydroxy allylic compounds formed, as a function of the initial concentration of oleic acid (AO) in ethanol, after the implementation of an oxidation process. oleic acid with singlet oxygen according to the invention, at basic pH; FIG. 6 represents a graph showing the conversion rate of oleic acid (XAO), the degree of formation of monoalcohols (YHFA) and the rate of formation of epoxide (YEP) as a function of the molar ratio of catalyst molybdate ions / acid oleic (AO), after the implementation of a process for oxidation of oleic acid according to the invention at basic pH; and FIG. 7 represents a graph showing the degree of conversion of oleic acid (XAO), the rate of formation of monoalcohols (YHFA) and the rate of formation of epoxide (YEP) as a function of the molar ratio of H2O2 / oleic acid. (AO), after the implementation of a process for oxidation of oleic acid according to the invention at basic pH. A / Experimental Protocols A. 1 / Gas Chromatography (GC) Analysis

GC analyzes were performed using a Varian 3900 GC Capillary Column CP-Select CB for fused silica WCOT (50m x 0.25mm x 0.25pm). The oven temperature program was as follows: 100 ° C. for 5 minutes, followed by an increase of 5 ° / min. To 180 ° C., held at 180 ° C. for 10 minutes and then increased to 45 ° / min. at 250 ° C, and held at 250 ° C for 8 min. The temperature of the injector was set at 250 ° C. The measurements were made in splitless and split split mode (ratio 1: 100) using helium as a carrier gas (flow rate 1.2 ml / min). The analysis was carried out after methylation of the fatty acids with trimethylsulfonium hydroxide (TMSH) dissolved in tert-butyl methyl ether (TBME). For quantitative analysis, pentadecanoic acid (Cl 5: 0) served as an internal standard. A.2 / Protocol for determining the eooxvde index

The oxirane oxygen content of each sample was determined using the direct method with 0.2 N hydrochloric acid solution in diethyl ether (adapted from Cd 9-57). The procedure followed is as follows: 0.5 g of 9,10-epoxystearic acid are solubilized in 5 ml of diethyl ether, followed by 10 ml of 0.2 N hydrochloric acid (HCl) in diethyl ether. The mixture is stirred at ambient temperature for 3 h. At the end of the reaction, 50 ml of 95% ethanol are added. The unreacted HCl is titrated with 0.1 N KOH potassium hydroxide solution in ethanol. A few drops of phenolphthalein indicator are also added. The percentage of oxirane content is thus calculated by known mathematical formulas. B / Process for the epoxidation of oleic acid B.1 / General protocol

Unless otherwise indicated, the general protocol of the method implemented is as follows.

In a reactor, a precise amount of Na2MoO4.2H2O and water are added and the mixture is stirred until complete solubilization of the catalyst. Then, absolute ethanol and oleic acid are successively introduced into the reactor with stirring (600 rpm). The whole mixture is then heated to 65 ° C. The pH of this reaction system is between 4 and 6.

An amount of 50% w / w aqueous H2O2 solution is added slowly through an electric syringe pump over a period of several hours. After stirring for a further 2 h at 65 ° C., a saturated aqueous solution of sodium sulphite Na 2 SO 3 (8.89 g, 70.53 mmol) in 25 ml of water is added to the reaction medium, using a light bulb. bromine. The temperature of the medium is raised to 70 ° C. and the stirring of the medium is maintained at the same speed (600 rpm) for 30 minutes. At the end of the reaction, the reaction medium is cooled to room temperature.

The reaction medium is then subjected to the following post-treatment steps.

A volume of 50 ml of ethyl acetate (AcOEt) is added to the reaction medium, which makes it possible to destabilize the emulsion and to solubilize the organic phase. The medium is then slightly acidified with 4N hydrochloric acid (HCI) solution to pH = 4 (10 ml) and stirred (200 rpm) for 2-5 min. This step ensures a better recovery of the acids, and the total release of carboxylic groups of fatty acid.

The aqueous and organic phases are separated by centrifugation at a speed of 5000xg for 10 min at θ '.

The implementation for this step of the centrifugation technique is particularly advantageous because it effectively separates the aqueous phase and the organic phase, and the species present therein, by eliminating several washing steps of the process. reaction medium with chemical salts. This step is all the more important that during the oxidation reaction, phenomena of "salting in" and "salting out" occur, ie solubilization of the organic phase in the aqueous phase, as well as a release of the catalyst from the aqueous phase to the organic phase.

Each phase is then washed separately with a saturated aqueous solution of sodium bicarbonate NaHCOa (10%). The whole is then extracted with ethyl acetate (3 × 50 ml), and the organic fractions are combined, dried with magnesium sulfate MgSO 4 anhydrous, filtered and then concentrated under reduced pressure. B.2 / Variation of the molar ratio Na? MoO4.2H? 0 / oléigue acid

The oxidation process is carried out for different molar ratios of molybdate ions relative to oleic acid, of between 1.1% and 10.1%. The other operating parameters are set as follows: oleic acid / H 2 O 2 molar ratio (1 / 5.6), H 2 O 2 addition rate (0.17 ml / min), H 2 O 2 addition time (4 hours). An ethanol / water volume ratio of 7/1 for a total volume of 70 ml is employed.

The amount of oleic acid consumed and the amount of epoxide formed at the end of the reaction are determined by GPC, according to the protocol indicated above, as well as the amount of secondary reaction products which are the monoalcohols (HFA) resulting from the other oxidation route, the allylic oxidation route. The conversion rate of oleic acid (XAO) and the rates of formation of epoxide (YEP) and monoalcohols (YHFA) are deduced. The results obtained are shown in FIG.

These results show that a mole ratio molybdate catalyst / oleic acid catalyst between about 6% and 8%, illustrated by the shaded area in Figure 1, particularly favors a high oleic acid conversion and a high yield of epoxide . It has moreover been obtained that a molar ratio of 6.6% allows an oleic acid conversion of 85.3% and a maximum yield of 9,10-epoxystearic acid of 71, 0%. At lower ratios, especially from 1.1 to 4.4%, the conversion of oleic acid increases with increasing amounts of the catalyst, but the reaction remains partial. Above 8%, especially 8.8 to 10.1%, the conversion of oleic acid is almost complete (99%), but no increase in the amount of epoxide formed is observed, but a slight increase in the products of the competing allyl oxidation reaction of oleic acid. B.3 / Variation of the molar ratio HpO? / oleic acid

The oxidation process is carried out for different molar ratios of hydrogen peroxide (H2O2) relative to oleic acid (AO), of between 2.8 and 17.9 equivalents. For this purpose, a ternary system consisting of A0 / EtOH / H20 (4/7/1 v / v / v) with a slightly acidic pH (between 5 and 6) is used, in a total volume of ethanol and 70 ml water. The experiments are carried out for 11 h and with an H2O2 addition rate of 0.17 ml.min '

The amount of oleic acid consumed and the amount of epoxide formed at the end of the reaction are determined by GPC, according to the protocol indicated above, as well as the amount of secondary reaction products which are the monoalcohols (HFA) resulting from the other oxidation route (allylic oxidation route). The conversion rate of oleic acid (XAO) and the rates of formation of epoxide (YEP) and monoalcohols (YHFA) are deduced. The results obtained are shown in FIG.

It can be seen that the charge in FI2O2, which makes it possible to increase the conversion of oleic acid and the epoxide yield as much as possible, is between 9.0 and 13.0 equivalents, as shown by the shaded area in FIG. Beyond, there is a plateau. The reaction no longer evolves, and the epoxide formed tends to slightly degrade by opening its oxirane ring to give the corresponding diol. For example, at 11.3 eq. in H2O2, a total conversion of oleic acid is observed for a yield of 81.4% in 9,10-epoxystearic acid. B.4 / Variation of the addition rate of HpO? The evaluation of the influence of the H2O2 addition rate on the epoxidation reaction is carried out for different addition rates: 0.17; 0.24; 0.28; 0.35 and 0.47 ml.min '

The other operating parameters are fixed as follows: molar ratio of molybdate ions relative to oleic acid (6.6%), amount of oleic acid (62.0 mmol), total amount of hydrogen peroxide (aqueous solution at 50% w / w, 745.0 mmol, 12.0 equiv). An ethanol / water volume ratio of 7/1 for a total volume of 70 ml is employed. The results obtained are shown in Table 1 below.

Table 1 - Influence of Hydrogen Peroxide Addition Rate on Oleic Acid Epoxidation Reaction by Singlet Oxygen

These results show that conversion of oleic acid and epoxide yields are better for the lower flow rates, i.e., for the longer hydrogen peroxide addition times. For a flow rate between 0.17 and 0.28 ml.min, a total conversion of oleic acid with high yields (80-87%) of 9,10-epoxystearic acid is observed. B.5 / Variation of stirring time after addition of HpQp The experiment described in B.4 / above, corresponding to a total addition time of hydrogen peroxide of 3 h, is continued after the end the addition of hydrogen peroxide. Samples of 1 ml of the reaction medium are made from 15 min after the complete addition of H 2 O 2 and then at 5 different times from this addition: 30; 60; 120; 180; and 240 min.

The amount of oleic acid consumed and the amount of epoxide formed at the end of the reaction are determined by GC, according to the protocol indicated above, as well as the amount of residual hydrogen peroxide. The conversion rate of oleic acid (XAO) and epoxide formation rates (YEP) are deduced for each sample. The results obtained are shown in FIG.

These results show that a duration of 120 min is sufficient for an almost complete decomposition of hydrogen peroxide and for a total conversion of oleic acid and epoxidized fatty acid at high yields (84.6%). B.6 / Variation of the reaction temperature The influence of the temperature is evaluated by carrying out the process at 8 different temperatures (T ° = 25'Ό, 45'Ό, 55'Ό, 65'Ό, 75 ' Ό, 85 ^, 105'G and 120Ό), for the step of adding hydrogen peroxide and subsequent stirring. The reaction conditions are as follows: AO (62.0 mmol, 1 eq), H2O2 (745.0 mmol, 12.0 eq.), Na2MoO4.2H2O (6.6 mol% relative to AO), Acid oleic / ethanol / water (4/7/1 v / v / v), at a flow rate of 0.24 ml.min -1 H 2 O 2, stirring for 7 h.

The results obtained, in terms of pH of the reaction medium, oleic acid conversion rate, epoxide formation rate, monoalcohols (concurrent allyl oxidation route), and rate of diol formation by hydrolysis acid in situ of the epoxide, are shown in Table 2 below.

Table 2 - Influence of Temperature on the Epoxidation Reaction of Oleic Acid (AO) by Singlet Oxygen

These results show that the optimal temperatures of the epoxidation reaction are between 55 ° C and 75 ° C for optimal production of the epoxide (82-88%) with a high selectivity (77-85%). At lower temperatures (25 ° C and 45 ° C), oleic acid conversion is lower. Above a temperature of 85 ° C, a high conversion of oleic acid but a decrease in epoxide yields is observed.

In order to better evaluate the impact of temperature on the oxidation reaction, a series of kinetic monitoring is performed on the yields of epoxides. For these experiments, the addition of the hydrogen peroxide is carried out over 4 h 15 to 0.17 ml / min. The other operating parameters are set as indicated above. The evolution over time of the molar composition of the reaction medium into epoxidized fatty acids is studied at different temperatures (45 ° C., 55 ° C., 65 ° C., 75 ° C. and 85 ° C.) by determining the epoxide number (OOexp) of the fatty acids present in the reaction medium, according to the protocol indicated above. The oxirane oxygen content of each sample is determined using the direct method with a solution of hydrochloric acid (HCl) in diethyl ether described in A.2 / above. The iodine number is determined using a Wijs solution. The content of each sample taken made it possible to draw the curves of the relative percentage of oxirane formed over time, illustrated in FIG.

These results show a significant production of epoxidized fatty acids for all temperature conditions. At the end of the reaction, the yields of oxiranes (92%) are higher for the temperatures of 65 ° C. and 75 ° C.

B.7 / Variation of the pH All the preceding experiments are carried out for a pH of the slightly acidic medium. In order to better appreciate the impact of the pH in the reaction system, the oxidation of oleic acid is carried out at 65 ° C. and at different pHs of the reaction medium. For this purpose, the alkali is provided by sodium hydroxide (NaOH, solid) while the acidity is provided by hydrochloric acid (HCl, 37% solution).

The other operating parameters are as follows: AO (62.0 mmol, 1 eq.), H2O2 (50%, 745.0 mmol, 12.0 eq.), Na2MoO4.2H2O (6.6 mol% relative to AO). ), flow rate of 0.24 ml.min 'of H2O2, 3 h of addition of H2O2, 7h total reaction.

The results obtained, in terms of pH of the reaction medium, oleic acid conversion rate, epoxide formation rate, monoalcohols (concurrent allyl oxidation route), and rate of diol formation by hydrolysis acid in situ of the epoxide, are shown in Table 3 below.

Table 3 - Influence of pH on the epoxidation reaction of oleic acid (AO) by singlet oxygen

These results show that whatever the pH of the reaction system, the conversion of oleic acid is high. This confirms that the AO / EtOH / H 2 O reaction system is well suited for the oxidation of oleic acid. At slightly acidic pH (6.0 <pH <5.3) it is further apparent that the peroxomolybdate complexes are capable of completely converting oleic acid and selectively producing 9,10-epoxystearic acid. B.8 / Variation of the ratio by volume of water and alcohol

In conclusion of the above study factor by factor in the reaction medium A0 / EtOH / H20 and in the presence of the catalyst / oxidant system (H2O2 / M0O4.2H2O), the optimal conditions for carrying out the reaction of epoxidation of oleic acid by singlet oxygen produced by catalytic disproportionation of hydrogen peroxide are fixed as follows: 62.00 mmol of oleic acid (1 eq.), 4.09 mmol of Na2MoO4.2H2O (6.6 mol% ), 745.00 mmol H 2 O 2 (50%, 12.0 equiv), a pH = 5-6, 65 ° C temperature, stirring 600 rpm, a rate of addition of H2O2 to 0.24 ml .min 'for a total reaction time of 5 hours. These conditions lead to a total conversion of oleic acid and a very high yield of 9,10-epoxystearic acid of 87.6% for a selectivity of 82%. The influence of the volume ratio of water and alcohol is tested under these operating conditions.

A series of 9 experiments varying the volume composition of the A0 / EtOH / H20 reaction medium made it possible to determine and validate mathematical models. Oleic acid - ethanol - water mixtures were determined by a centered Scheffé network. In a defined field of study containing at least 50% ethanol, the minimum yield is 32% and corresponds to an oleic acid / ethanol / water mixture in the proportions 40/50/10 by volume. The best yield is 90% obtained for an oleic acid / ethanol / water mixture in the proportions 25/50/25 by volume. In these proportions, the side reactions of allylic oxidation and dihydroxylation of oleic acid are minimized. In addition, the reproducibility of the oxidation is 90% ± 0.5% after 4 tests. B.9 / Catalyst recycling test

A recycling test of the Na 2 MoO 4 .2H 2 O catalyst is carried out. For this purpose, the reaction, carried out according to the optimized operating parameters described above, is stopped at the end after 5 hours of reaction, then the medium is allowed to cool to room temperature, without the addition of sodium sulfite. Then, the medium is centrifuged at a rate of 5000xg at 0 ° C for 25 min. The gray solid on the pellet is recovered and reused for a new oxidation reaction according to the same protocol. It is in parallel carried out a so-called white test, without catalyst.

The results obtained, in terms of oleic acid conversion rate and epoxide formation rate, for each cycle are shown in Table 4 below.

Table 4 - Evaluation of the Recyclability of the Catalyst for the Implementation of a Process for the Epoxidation of Oleic Acid by Singlet Oxygen According to the Invention

These results show that all the experiments allow the conversion of oleic acid. In the presence of catalyst, the conversion of oleic acid is more pronounced for the first and second cycles. B. 10 / Implementation on a larger scale

The epoxidation process carried out under the optimum conditions defined above is evaluated on larger amounts of oleic acid (100 g and 200 g). The reaction is conducted in a batch reactor of 2 L jacketed with a thermometer, so as to control the temperature of the reaction medium. The results obtained, in terms of oleic acid conversion rate, epoxide formation rate and monoalcohols formation rate (concurrent allylic oxidation route) are shown in Table 5 below.

Table 5 - Epoxide yield of a process for epoxidation of oleic acid with singlet oxygen in accordance with the invention

These results show that the optimized system is well suited for the epoxidation of oleic acid on a large scale. From the scale of 20 g of oleic acid to a scale of 200 g, the conversion rates are very high, as are the yields of epoxide. C / Process for forming a diol from oleic acid

A process for forming a diol from oleic acid is carried out by the following two successive steps, according to the reaction scheme B indicated above. C.1 / Epoxidation of oleic acid

In a 1 liter reactor, a precise amount of Na2MoO4.2H2O (1.00 g, 4.09 mmol) and water (23 mL) are added and the mixture is stirred until complete solubilization of the catalyst. Then, 46 ml of absolute ethanol and 62.00 mmol of oleic acid are successively introduced into the reactor with stirring (600 rpm). The whole mixture is then heated to 65 ° C. An amount of 50% w / w aqueous H2O2 solution (25.34 g, 745.00 mmol) was added slowly through an electric syringe pump over a period of 3 h (0.24 ml. After stirring for a further 2 h at 65 ° C, a saturated aqueous solution of sodium sulfite Na 2 SO 3 (8.89 g, 70.53 mmol) in 25 ml of water is added to the reaction medium at room temperature. The temperature of the medium is raised to 70 ° C. and the stirring of the medium is maintained at the same rate (600 rpm) for 30 minutes at the end of the reaction. is cooled to room temperature.

The reaction medium is then subjected to the post-treatment described above.

19 g of 9,10-epoxystearic acid are obtained, the structure of which is confirmed by physico-chemical analyzes (yield 89.5%). C.2 / Hydrolysis of the epoxy obtained

After the 5 hours of reaction described in C.1 /, the reaction being complete, an aqueous solution of 0.5 N ethanolic sulfuric acid is slowly added in the medium to a pH value of between 1 and 2 ( midnight blue coloration of the middle). The reaction mixture is stirred under heat (50 ° C.) for 2 hours. 25 ml of an aqueous Na 2 SO 3 solution (8.94 g, 0.07 mol) are then added to the stirred reaction mixture, followed by 100 ml of petroleum ether. The ether phase is separated by centrifugation (5000xg speed at 5 ° C for 15 min). This phase is washed with a saturated aqueous solution of sodium bicarbonate (2 × 50 mL), then with a saturated aqueous solution of sodium chloride (2 × 100 mL) and dried with anhydrous MgSO 4. Removal of the solvent yields 18.85 g (59.56 mmol, 96%) of 9,10-dihydroxystearic acid. D / Epoxidation process for other unsaturated fatty acids

An oxidation process according to the invention, carried out according to the optimum conditions defined in B.9 / above, is applied to various other unsaturated fatty acids, more particularly: l'-unsaturated fatty acid (acid undec-10- enoic), hydroxylated fatty acids ((E) -10-hydroxyoctadec-8-enoic acid, (E) -9-hydroxyoctadec-10-enoic acid, and (Z) -12-hydroxyoctadec-9-enoic acid), a fatty acid with a very long carbon chain ((Z) -docos-13-enoic), but also on a diunsaturated fatty acid ((9Z, 12Z) -octadeca-9,12-denoic acid). GPC analysis after implementation of the above written post-treatment shows that the oxidation of these compounds leads to the production of C 11, C 18 and C 22 fatty acid epoxies. The structures of the compounds have been validated by mass spectrometry (MS), nuclear magnetic resonance (NMR and FTIR).

Table 6 below summarizes the results obtained.

Table 6 - Epoxide yields of epoxidation processes of various unsaturated fatty acids by singlet oxygen in accordance with the invention

The results above show that the optimized system is well suited for the epoxidation of unsaturated fatty acids, regardless of the position of the carbon-carbon double bond on the carbon chain. These high conversions led to the synthesis of epoxides of carboxylic acids with high yields (69% -87%), for all oxidation reactions: the oxidation of undec-10-enoic acid in mono-ω epoxy, 9- (oxiran-2-yl) nonanoic acid; oxidation of (Z) -docos-13-enoic acid to 12- (3-octyloxiran-2-yl) dodecanoic acid; the oxidation of (9Z, 12Z) -octadeca-9,12-denoic acid to three epoxides (diepoxy acid (8- (3 - ((3-pentyloxiran-2-yl) methyl) oxiran-2-yl) octanoic, 47%), monoepoxy acids ((Z) -8- (3- (oct-2-en-1-yl) oxiran-2-yl) octanoic acid and (Z) -11- (3-pentyloxiran-2- yl) undec-9-enoic, 33%); oxidation of (Z) -12-hydroxyoctadec-9-enoic acid to 8- (3- (2-hydroxyoctyl) oxiran-2-yl) octanoic acid; the oxidation of the mixture of (E) -10-hydroxyoctadec-8-enoic and (E) -9-hydroxyoctadec-10-enoic acids to α-hydroxy-epoxy (52% for 9- (3-heptyloxiranic acid); 2-yl) -9-hydroxynonanoic acid and 48% for 7- (3- (1-hydroxynonyl) oxiran-2-yl) heptanoic acid E / Process for forming monoalcohols from oleic acid via a reaction of EIV / General Protocol

Unless otherwise indicated, the general protocol of the process used, responding to the reaction scheme A presented above, is as follows.

In a 1 liter reactor, the oleic acid is placed under mechanical stirring. An aqueous solution of 0.25 N sodium hydroxide is added to raise the pH to a value between 10 and 12, then the mixture is heated to 50 ° C until a slight lightening of the initially cloudy medium. Then Na2MoO4.2H2O and absolute ethanol are added successively. The temperature of the reaction medium rises to 65 ° C.

The adequate amount of H2O2 in 50% w / w aqueous solution is added through an electric syringe pump over a period of several hours. At the same time, a quantity of solid sodium hydroxide is added to the reaction medium, in fractions introduced every 10 min, in order to maintain the pH between 10 and 12.

After complete addition of all reagents, the reaction is stirred for a further 2 hours. At the end of the reaction, a saturated aqueous solution of sodium sulfite Na 2 SO 3 (15.63 g, 124 mmol) in 50 ml of water is added to the reaction medium still at 65 ° C., using a sodium hydroxide solution. bromine, so as to reduce the residual hydrogen peroxide, as well as hydroperoxides of oleic acid formed in the reaction medium (the latter reduction reaction to produce the targeted monoalcohols). The temperature of the medium rises to 70 ° C. and the agitation of the medium is maintained at the same speed (600 rpm) for a period of 30 minutes to 1 hour.

The reaction medium is then subjected to a post-treatment identical to that described above in part B /.

E.2 / pH variation

Experimentally, the alkali of the systems is obtained in the following manner: the oleic acid is pre-mixed in the alkaline water consisting of 0.5 g of sodium hydroxide NaOH (0.2 eq.) And 35 ml of milli-Q water. . In order to avoid foaming, the mixture is heated to 50 ° C until a slight lightening of the initially cloudy medium. Then the necessary amount of Na2MoO4.2H2O and ethanol are added successively. Another 1.5 g of solid sodium hydroxide is added during the addition of H2O2 in order to maintain the basic pH. The reaction conditions are as follows: H 2 O / EtOH (1/1 v / v), AO (62.0 mmol, 1 eq), H 2 O 2 (50%, 350.0 mmol, 5.6 eq.), Na2MoO4.2H2O (4.4 mol% relative to AO).

Table 7 below shows the values of the oleic acid conversion rate, the monoalcohol formation rate, and the epoxide formation rate (concurrent oleic acid epoxidation route) recorded in FIG. absence of soda and in the presence of soda.

Table 7 - Influence of the pH on a process of allylic oxidation of oleic acid by insertion of singlet oxygen according to the invention

In the absence of sodium hydroxide, the macroscopic system is heterogeneous while in the presence of sodium hydroxide, the system is almost homogeneous milky, translucent, characteristic of a fine emulsion. These results show that the reaction system (A0 / A0 ') / EtOH / H2O (0.6 / 1/1 v / v / v), which is formed in the reaction system under basic conditions, has a substantially considerable selectivity for the reaction. production of hydroxy allylic only for the formation of the epoxide. This organized system particularly favors the accumulation of ^ 02. In particular, the fine emulsion constituted by this system benefits from the stability afforded by the surfactant properties of the oleic acid salt (R-COO 2, Na 2) and the co-surfactant properties of ethanol. In addition, in this system, the presence of ethanol advantageously makes it possible to reduce the rise in temperature of the reaction medium at the time of addition of the hydrogen peroxide. E.3 / Variation of oleic acid concentration in ethanol

Another series of experiments is performed to evaluate the concentration of oleic acid in the reaction solvents relative to the desired hydroxyl acid yields. The reaction conditions are as follows: AO (62.0 mmol, 1 eq.), H2O2 (50%, 350.0 mmol, 5.6 eq.), Na2MoO4.2H2O (4.4 mol% relative to AO). ), flow rate of H 2 O 2 0.17 ml.min -1 and addition time 4 h, volume ratio water / ethanol (1/1).

The initial concentration of oleic acid in ethanol is varied. Efficiency is expressed as the amount of hydroxy allylic compounds formed in the reaction crude. For oleic acid concentrations of less than 1.7 mol.l -1 in ethanol, a quantity of sodium hydroxide is adjusted in the aqueous phase to maintain the pH between 9.0 and 9.5. The results obtained are shown in FIG. 5. The hydroxylated fatty acid amounts obtained show that a concentration of oleic acid in ethanol of between 1.0 mol.l -1 and 1.5 mol.l -1 ( illustrated by the shaded area in Figure 5) promotes better synthesis of allylic hydroxyl fatty acids.

The initial concentration of 1.24 mol / l of oleic acid in ethanol is retained for the following experiments. More particularly, the optimized reaction system used in the following experiments comprises oleic acid, ethanol and water in the ratio 2/5/5 by volume. E.4 / Variation of soda concentration

The experiments are carried out at amounts of sodium hydroxide of between 0.8 and 2 equivalents relative to oleic acid. The operating procedure consists of preparing a basic aqueous solution with 0.2 equivalents of NaOH as described above, the remainder of the sodium hydroxide being added simultaneously with the hydrogen peroxide.

The operating conditions are as follows: AO (62.0 mmol, 1 eq.), H2O2 (50%, 350.0 mmol, 5.6 eq.), Na2MoO4.2H2O (4.4 mol% relative to AO) flow rate of H2O2 0.17 ml.min -1 and addition time 4 h.

The amount of oleic acid consumed and the amount of monoalcohols formed at the end of the reaction are determined by GPC, according to the protocol indicated above, as well as the amount of secondary reaction products which are the epoxides resulting from the other route. oxidation, the epoxidation route. The conversion rate of oleic acid (XAO) and the rates of epoxide formation (YEP) and monoalcohols (YHFA) are deduced. The results obtained are shown in Table 8 below.

Table 8 - Influence of the molar amount of NaOH with respect to oleic acid, on a process for the allylic oxidation of oleic acid by insertion of singlet oxygen in accordance with the invention

These results show that for the amounts of NaOH between 0.8 eq. and 1.6 eq, the selectivity to hydroxy is the highest. The measurement of the pH between the initial reaction mediums and the final reaction media shows that the allyl oxidation of oleic acid is favored when the pH of the reaction medium is between 9 and 12, and better still for the reaction systems whose pH is in the range [10; 12 [.

Under the operating conditions used, the optimum consumption of sodium hydroxide is around 1.3 equivalents relative to oleic acid, for a particularly high selectivity to hydroxy allylic (78.3%). E.5 / Variation in the process of preparation of sodium oleate

Since the addition of sodium hydroxide in oleic acid produces sodium oleate, in order to validate the operating protocol and the roles played by NaOH in the reaction system, the reaction media are prepared according to four different protocols. All tests are carried out with a molar ratio of AO / NaOH corresponding to 1 / 1.3. The addition of H2O2 and the post-reaction treatments are identical to those described in the previous experiment. - Protocol 1 (PI)

This protocol consists of pre-preparing 62 mmol of oleic acid in 50 ml of a basic aqueous solution containing 0.2 equivalents of 50% NaOH (0.0124 N). After a slight lightening of the initially cloudy medium, 50 ml of absolute EtOH and 4.4 mol% of Na2MoO4.2H2O are added successively. At 65 °, 5.6 eq of 50% aqueous H2O2 and 1.1 eq. of NaOH are introduced into the medium simultaneously. After different washing of the reaction medium at the end of the reaction, the organic phase gives a clear and thick yellow oil. - Protocol 2 (P2):

In a stirred batch reactor, 62 mmol of oleic acid and 1.3 eq of NaOH are introduced and the mixture is then stirred. Then the corresponding EtOH / H2O (1/1 v / v) mixture is poured and 4.4 mol% of Na2MoO4.2H2O are added. The reaction mixture is heated to 65 ° C. 5.6 eq of 50% aqueous H2O2 are added. At the end of the reaction, a viscous, colorless liquid is obtained, which foam enormously. Protocol 3 (P3): 62 mmol of a finely ground powder of sodium oleate is placed in a batch reactor, and the corresponding EtOH / H20 mixture (1/1 v / v) and 4.4 mol% of Na2MoO4.2H20 are added. The mixture is stirred. At 65 ° C., 5.6 eq. Of 50% aqueous H2O2 are introduced into the reactor. At the end of the reaction, a whitish viscous oil is obtained. - Protocol 4 (P4):

It is the same protocol as P2, but we add 0.3 eq. of NaOH in the medium during the addition of 5.6 eq of 50% aqueous H2O2 at 65 ° C. The mixture obtained at the end of the reaction is a very pale yellow oil. All the results obtained, in terms of pH variation of the initial and final reaction systems, as well as conversion rates of oleic acid or sodium oleate (XAO) and rate of formation of monoalcohols (YHFA ) are shown in Table 9 below.

Table 9 - Influence of the preparation protocol of the reaction system on a process for the allylic oxidation of oleic acid by insertion of singlet oxygen in accordance with the invention

From these results, it is noted that the PI protocol, with a reaction pH of between 9.02 and 10.97, makes it possible to have high yields of allylic hydroxyl fatty acids.

By using with sodium oleate formed in situ as a substrate (protocol P2), or for emulsions formed by ex-situ sodium oleate (P3 and P4 protocols), the reaction yields are lower.

Such a result could in particular result from the fact that in the reaction system resulting from the P1 protocol, carboxylic groups of free fatty acids (oleic acid) and carboxylate groups of fatty acid salt (sodium oleate) coexist. The fatty carboxylic acid / fatty acid salt equilibrium of the reaction system would give it an appropriate character for the in situ production of O 2 O, its accumulation, its reactivity and its allylic regioselective insertion onto oleic acid.

These results demonstrate that the maintenance of the pH during the oxidation process at a particular level, between 9 and 12, promotes the continuous formation of singlet oxygen, and the production of hydroxy allylic fatty acids with high yield and selectivity. E.6 / Variation of the Na 2 MoO 4 .2H 2 O / oleic acid molar ratio The study of the conversion of oleic acid as a function of increasing amounts of the catalyst in the reaction is studied. For these tests, catalyst quantities of between 1.1% and 10.1% relative to the number of moles of oleic acid are tested under the following experimental conditions: oleic acid / NaOH / H 2 O 2 molar ratio (1/1, 3: 5.6), H2O2 addition rate (0.17 mL.min -1). The emulsified system used consists of A0 / EtOH / H 2 O in the volume ratio 2/5/5.

The amount of oleic acid consumed and the amount of monoalcohols (HFA) formed at the end of the reaction are determined by GPC, according to the protocol indicated above, as well as the amount of secondary reaction products which are the epoxides resulting from the reaction. another oxidation route, the epoxidation route. The conversion rate of oleic acid (XAO) and the rates of epoxide formation (YEP) and monoalcohols (YHFA) are deduced. The results obtained are shown in FIG.

These results show that for increasing amounts of catalyst from 1.1% to 8.8%, there is a marked improvement in the yields of hydroxylated fatty acids. Above 8.8%, there is a slight loss of the desired products. The molar ratio of 8.8% (ie 0.21 equivalents) seems to be the most efficient in that it makes it possible to obtain a conversion of 88.8% of oleic acid and a selectivity of 81.5% and a high yield of HFA (72.4%). E.7 / Variation of the molar ratio HpO? The influence of the hydrogen peroxide concentration in the emulsions formed for the allyl oxidation reaction of oleic acid by singlet oxygen is evaluated. To do this, the experiments were carried out with amounts of hydrogen peroxide ranging from 2.8 to 28.2 molar equivalents relative to oleic acid.

The operating conditions are as follows: AO (62.0 mmol, 1 eq.), NaOH (80.6 mmol, 1.3 eq.), Na 2 MoO 4 .2H 2 O (8.8 mol% relative to AO), addition of H2O2 (0.17 ml.min -1).

Reactions were evaluated on 11 h.

The amount of oleic acid consumed and the amount of monoalcohols (HFA) formed at the end of the reaction are determined by GPC, according to the protocol indicated above, as well as the amount of secondary reaction products which are the epoxides resulting from the reaction. another oxidation route, the epoxidation route. The conversion rate of oleic acid (XAO) and the rates of epoxide formation (YEP) and monoalcohols (YHFA) are deduced. The results obtained are shown in FIG. 7.

It appears that the gain in hydroxy allylic during the reaction is directly related to the amount of H2O2 added. Overall, it can be seen that according to the increasing amounts of hydrogen peroxide, the allyl oxidation reaction of oleic acid is more favored. Between 13.0 and 21.0 equivalents of H2O2 with respect to oleic acid (zone shown in gray in FIG. 7), the reaction conditions are the most favorable for the total allylic oxidation of oleic acid to HFA. (-88%).

For the rest of the experiments, the amount of H2O2 is set at a value which makes it possible to obtain high yields of HFA: 14.1 eq. of H 2 O 2 with respect to oleic acid, in a reaction system comprising A 0 / EtOH / H 2 O (2/5/5 v / v / v). This corresponds to a total reaction time of 7 h and a 5 hour H 2 O 2 addition time at a rate of 0.17 ml / minute. Variation of the H 2 O 2 addition rate.

A kinetic study of the oxygenated water consumption by the Na2MoO4.2H20 catalyst is carried out by assaying H2O2 in the reaction medium. It reveals that the dismutation of H2O2 in basic medium is very fast. The high rate of decomposition of hydrogen peroxide also reveals that water is formed very rapidly in the reaction medium.

Addition rates (0.14, 0.17, 0.21, 0.28 ml.min -1) of H2O2 are evaluated.

The molar ratios of the different species in the presence are as follows: AO / NaOH / EtOH / H 2 O / Na 2 MoO 4 .2H 2 O (1 / 1.3 / 13.8 / 44.7 / 0.088).

The results obtained, in terms of conversion rate of oleic acid (XAO) and rate of formation of monoalcohols (YHFA) are shown in Table 10 below.

Table 10 - Influence of H2O2 addition rate on a process for allyl oxidation of oleic acid by insertion of singlet oxygen according to the invention

An increase in the temperature in the reactor is observed as a function of the feed rate of H2O2. The slower H2O2 feed rates prove to be the most advantageous in that they do not involve the management of large amounts of energy released during the reaction.

The above experimental data show a high yield of allyl monoalcohols irrespective of the H2O2 addition rates tested. E.9 / Variation of the reaction temperature

Experiments were performed for 8 different temperatures (T = 45 ° C, 55 ° C, 65 ° C, 75 ° C, 85 ° C, 105 ° C and 120 ° C).

The operating parameters are as follows: AO (62.0 mmol, 1 eq.), NaOH (80.6 mmol, 1.3 eq.) (24.8 mmol NaOH (ie 0.4 eq.) Initially, then 0.9 eq at the same time as hydrogen peroxide), H2O2 (874.0 mmol, 14.1 equiv), Na2MoO4.2H2O (8.8 mol% relative to AO), H2O2 (0.21 ml / min).

The results of these experiments, in terms of oleic acid conversion (XAO), monoalcohols formation rate (YHFA) and epoxide formation rate (YEP) (concurrent epoxidation reaction) are indicated in Table 11 below.

Table 11 - Influence of the temperature on an allyl oxidation process of oleic acid by insertion of singlet oxygen according to the invention

It is observed that between 55 ° C and 75'Ό, the degree of conversion of oleic acid is maximum. This high conversion of oleic acid is favored for the formation of hydroxy allylics with very high yields. The yields of hydroxylated fatty acids are maximum with high selectivity for a temperature of about 65 ° C. From 85 ° C and above, the conversion of oleic acid is high but falls in yields of monoalcohols. E.10 / Optimized protocol

In a 1 liter reactor, oleic acid (62 mmol) is placed under mechanical stirring. An aqueous solution of 0.25 N sodium hydroxide (NaOH, 50 ml, 12.50 mmol) is added and the mixture is then heated to 50 ° C until a slight lightening of the initially cloudy medium. Then Na2MoO4.2H2O (1.32g, 5.45mmol) and absolute ethanol (65ml) are added successively. The temperature of the reaction medium rises to 65 ° C.

An aqueous solution of 50% w / w H2O2 (29.72 g, 874.00 mmol) is then added via an electric syringe pump over a period of 4 hours (0.21 ml.min -1). . At the same time, a quantity of solid sodium hydroxide (2.50 g, 62.50 mmol) is added to the reaction medium, at a fraction of 104.2 mg / 10 min, in order to maintain the pH between 10 and 12. After complete addition of all the reagents, the reaction kept stirring for a further 2 hours. At the end of the reaction, a saturated aqueous solution of sodium sulfite Na 2 SO 3 (15.63 g, 124 mmol) in 50 ml of water is added to the reaction medium still at 65 ° C., using a sodium hydroxide solution. bromine. The temperature of the medium rises to 70 ° C and stirring of the medium is maintained at the same rate (600 rpm) for a period of 30 minutes to 1 hour.

These operating conditions lead to a total conversion of oleic acid and to a very high yield (96%) of a mixture of (E) -10-hydroxyoctadec-8-enoic acid and (E) -9-hydroxyoctadecene acid. 10-enoic, in proportions of 48% and 52%, respectively. E.11 / Demonstration of the production of sinqulet oxygen during the reaction and the mechanism of the alluvial oxidation reaction

Demonstration of cis-trans isomerization and the insertion of an oxygen molecule

The product obtained after the implementation of the process described in point E.10 / above has been analyzed in 1 H NMR nuclear magnetic resonance. The spectrum obtained shows signals between 5.3-5.7 ppm with a coupling constant J = 15.4 Hz, which are characteristic of a trans configuration double bond. The alpha proton of the resulting secondary alcohol (CH-OH) quadruplet function is responsible for signals between 3.9-4.1 ppm. The 2D NMR results (COZY, HSQC, HMBC) confirm that the alcohol function is good and allyl position of the double bond. These results show that the cis configuration double bond of oleic acid has become trans configuration, there has been isomerization of this double bond. In addition, this double bond has a hydroxy function in the allyl position, it has well produced an allyl oxidation of oleic acid.

Mass spectrometry, meanwhile, shows that the oxidation products have a mass / charge ratio of 298, which corresponds to an insertion of an oxygen atom (m / z = 16) on the oleic acid of departure (m / z = 282). Infrared spectrometric analysis shows the appearance of a 3405 cm -1 band characteristic of an -OH function. It also reveals that the 724 cm-1 band characteristic of the cis-carbon-carbon double bond has disappeared and that a new band at 968 cm -1 has appeared: this band is characteristic of a carbon-carbon double bond. trans carbon On the other hand, the analysis of the intermediate reaction products before reduction with sodium sulphite in 1 H NMR nuclear magnetic resonance and proves the presence of allyl hydroperoxides. In addition, determination of the peroxide value between oleic acid (4.05 ± 0.52 meq O 2 / kg of oil) and reaction products (18.35 ± 0.10 meq O 2 / kg of oil). oil), shows the increase in the peroxide content of intermediate products. This observation shows that there was insertion of oxygen molecules. All of these analyzes on the reaction products confirm the allylic insertion of an oxygen atom in oleic acid and an isomerization of the cis-carbon carbon double bond to a trans configuration. The reaction intermediates are hydroperoxides.

Demonstration of double-bond migration

The migration of the double bond is established by the oxidation of undec-10-enoic acid under the same conditions used for oleic acid and described in point E.10 / above. It is observed that the addition of hydrogen peroxide in the medium consisting of undec-10-enoic acid / NaOH / EtOH / H2O / Na2MoO4 in the molar ratio 1 / 0.8 / 13.8 / 44.7 / 0.088 leads to a total conversion of the substrate and the formation of 3 oxygenated products. The products are isolated by chromatography on silica gel (eluent: ethyl acetate / cyclohexane 50/50 v / v) and the structural analysis of the compounds is carried out by infrared spectroscopy (IR) and by NMR and the NMR characterization of the proton identified two 71% hydroxy allyl, including (E) -11-hydroxyundec-9-enoic (51%) and (E) -9-hydroxyundec-10-enoic (20%) acids, and epoxide, 9- (oxiran-2-yl) nonanoic acid at 20%.

This structural characterization reveals that the process according to the invention is suitable for the allylic oxidation or the epoxidation of undec-10-enoic acid.

Furthermore, the NMR analyzes and reveal the expected product, (E) -11-hydroxyundec-9-enoic acid, corresponding to the formation of an allyl primary monoalcohol. The multiplet observed between 5.45 ppm and 5.53 ppm in NMR as well as the two peaks at 131.3 ppm and 129.2 ppm in NMR are characteristic of the ethylenic group (HC = CH). Also, the doublet at 4.49 ppm in NMR and the peak at 68.5 ppm in NMR indicate the presence of a hydroxyl group carried by a carbon in the sp ^ hybridization state. Similarly, in comparison with the NMR and undec-10-enoic acid results, it is noted in NMR that there is disappearance of the two terminal ethylenic protons (= CH2) and disappearance of the carbon bearing these protons in NMR ' ^ C. Therefore, obtaining this predominantly cu-hydroxy fatty acid confirms that there has been a shift of the double bond from one carbon to another.

Demonstration of the booster effect of deuterated water

The detection of singlet oxygen in the reaction medium is carried out using an indirect and qualitative method. This is the use of deuterated water (D2O) instead of water (H2O) in the oleic acid-ethanol-water reaction system. This experiment makes use of the fact that the lifetime of singlet oxygen ^ 02 is 15 times longer in D2O than in H2O. Different contents of D2O were tested under the operating conditions: AO (62.0 mmol, 1 eq.), H2O2 (50%, 350.0 mmol, 5.6 eq.), NaOH (1.3 eq. (a), 0.4 eq (b), and 0.2 eq (c)), Na2MoO4.2H2O (8.8 mol% relative to AO). Table 12 below shows the results obtained in terms of conversion rate of oleic acid (XAO), rate of formation of monoalcohols (YHFA) and rate of formation of epoxides (YEP) (concurrent reaction of epoxidation ).

Table 12 - Influence of the implementation of deuterated solvents on an allyl oxidation process of oleic acid by insertion of singlet oxygen in accordance with the invention

These results show that when the EtOH / H 2 O reaction mixture is fully deuterated (EtO D / D 2 O), the conversion of oleic acid is complete, and the HFA yield is almost quantitative. This demonstrates that the reaction system according to the invention generates singlet oxygen, and that the life of 022 O is significantly longer in the deuterated solvents compared to the same non-deuterated solvents. E.12 / Implementation on a larger scale

The allyl oxidation process carried out under the optimum conditions defined above is evaluated on larger amounts of oleic acid (100 g, 200 g and 500 g).

The reaction is carried out in a closed jacketed 3 L batch reactor equipped with a thermometer in such a way as to control the temperature of the reaction medium. The experiments are carried out according to the protocol described according to the optimal protocol described in point E.10 / above. For the amount of 500 g of oleic acid, suitable conditions were used (H 2 O 2 (50%, 18.3 eq), 75 ° C, 11 h, 1200 rpm).

The results obtained, in terms of oleic acid conversion rate, epoxide formation rate and monoalcohols formation rate (concurrent allylic oxidation route) are shown in Table 13 below.

Table 13 - Monoalcohol yield of a process for allyl oxidation of oleic acid with singlet oxygen according to the invention

These results show that the optimized system is well suited for the allylic oxidation of oleic acid, and the formation of (E) -10-hydroxyoctadec-8-enoic acid and (E) -9-hydroxyoctadec acid (10) monohydric alcohols. enoic on a large scale. From the scale of 20 g of oleic acid to a scale of 500 g, the conversion rates are very high, as are the yields of alcohols. F / Process for the formation of monoalcohols from oleic acid via an alumina oxidation reaction with sinaulin oxygen generated in situ in heterogeneous catalysis F.1 / General protocols

Unless otherwise indicated below, the operating protocols implemented are as follows.

Washing and drying the ion exchange resin - The resin is washed beforehand with deionized water (milliQ) and then with 95% ethanol until the effluent is colorless and of neutral pH. It is rinsed twice with diethyl ether (Et2O) and dried for a longer time at 45 ° C for 24 hours.

Adsorption of molybdate ions on the ion exchange resin - The resin-MoO4 material is prepared by wet impregnation according to the following procedure. In a 1-liter reactor equipped with a mechanical stirrer and a dropping funnel, 50.0 g of resin are placed, then 250 ml of a concentrated aqueous solution of Na 2 MoO 4 are added dropwise. 2.20 to 0.50 mol / l at room temperature, with stirring (200 rpm), for 2 h. After the addition of the alkaline solution, the medium is stirred for 4 hours. Then, the whole is transferred to an incubator equipped with a stirring table (202 movements / min) for 44 hours at room temperature. The impregnated resin is then washed and dried according to the protocol above.

Fixing the Unsaturated Fatty Acid on the Ion Exchange Resin - In a 250 ml reactor equipped with a mechanical stirrer, a ball cooler, a thermometer and a dropping funnel 20.00 g of grafted resin are placed in molybdate ions, then 20.00 g of fatty acid are added slowly. Then the medium is stirred (400 rpm) for 24 hours and 40Ό to promote contacting and adsorption of the fatty acid on the grafted resin. There is a swelling of the size of the beads of the grafted resins which are then hydrophobed.

Allyl oxidation of the unsaturated fatty acid on the ion exchange resin supporting molybdate ions and hydrophobed by the unsaturated fatty acid - In the reactor containing the resin on which the molybdate ions and the unsaturated fatty acid are adsorbed, the a mixture of 15 ml of water and 75 ml of ethanol. Then, the medium is heated to 50 ° C. with mechanical stirring (400 rpm). 22.24 g of 50% aqueous H2O2 (756.4 mmol) are then added dropwise over 2 hours (ie at a rate of 0.36 ml-min -1). After stirring for 6 h, the reaction is stopped. The resin is filtered. It is washed with small amounts of water. All the filtrate is returned to another reactor. A volume of 50 ml of dichloromethane (CH 2 Cl 2) is added and the medium is slightly acidified with a 4N solution of hydrochloric acid (HCl) until the pH = 3-4, then stirred (150 rpm) for 2 hours. at 5 min. The aqueous and organic phases are separated by centrifugation (centrifuge: SIGMA G16K) at a speed of 5000xg for 10 min at 0 ° C. Each phase is washed with a saturated aqueous solution of sodium bicarbonate NaHCOa (10%). The whole is then extracted with dichloromethane (3 × 50 ml) and the organic fractions are combined, dried with magnesium sulfate MgSO 4 anhydrous, filtered and then concentrated under reduced pressure. The crude product obtained gives a 1/1 molar mixture of two allyl hydroperoxides. Reduction of hydroperoxides to hydroxy allyl fatty acids - The mixture of allyl hydroperoxides is diluted with 30 ml of methanol and transferred to a 250 ml reactor equipped with a magnetic bar, a ball cooler, and a thermometer. The whole is placed in an ice bath so as to maintain the temperature of the medium at 90 °. Then, 1.3 equivalents of solid sodium borohydride (NaBH4) is slowly added under gentle stirring so that the temperature of the medium does not exceed 0.degree. When the reaction is complete (after 2 hours of reaction), 50 ml of a saturated solution of NH 4 Cl (10%) are introduced into the reactor to stop the reaction, and the pH is adjusted to 3. The medium is extracted according to protocol described previously in Example B /. Regeneration of the ion exchange resin supporting the molybdate ions - At the end of the oxidation process, the resin-MoO 4 - material is regenerated in the form of -OH with the aid of a concentrated 2M aqueous sodium hydroxide solution. In a 1-liter batch reactor equipped with a mechanical stirrer and a dropping funnel, 100.0 g of resin are weighed, then 300 ml of the sodium hydroxide solution (2 M) are added dropwise. ) at room temperature, with stirring (200 rpm), for 2 hours. After the addition of the alkaline solution, the medium is stirred for 2 hours. The impregnated resin is then washed and dried according to the protocol described above. It can be reused in a new cycle of adsorption experiment of Μοθ4 ^ "and allyl oxidation.

Purification of the Allylic Hydroperoxides by Flash Chromatography In order to obtain a high purity sample of allyl hydroperoxides, the oily residue obtained after oxidation of the unsaturated fatty acid is purified by flash chromatography on a silica column (Combiflashretrieve, Serlabo). 2 g of the mixture are deposited on a cartridge of 12 g of silica (diameter 35 mm, L 200 mm). The elution is carried out with a mixture of hexane / isopropanol / acetic acid: 229/20/1 by volume with a flow rate of 6 ml.min 3 ml fractions are recovered at the outlet of the system in test tubes and the Fractions of the same nature are collected and the solvent mixture is evaporated. The allylic hydroperoxide fraction is kept away from light. Its purity is monitored by 1 H NMR. F.2 / Use of a Macroporous Basic Anion Exchange Resin

Lewatit® commercial anion exchange resin K7367, marketed by Lanxess, is used. This strongly basic resin is formed of a matrix of styrene-divinylbenzene copolymer (DVB) bearing functional groups of quaternary ammonium type (-N 1 (CH 3) 3) which enable it to graft the Μ 0 4 4 anions. In addition, its macroporous structure (63-68% by mass in water) offers good accessibility of sites to the anion Μοθ4 ^ "and long-chain hydrocarbon substrate.

The exchange capacity Ce of this resin was determined, by a conventional method in itself, at a value equal to 1.19 ± 0.03 eq.

Under the operating conditions of the general adsorption protocol for the molybdate ions described above, the exact operating capacity of the resin is 0.484 mmol of Μ004 ions per gram of resin.

Oleic acid in solution

For these tests, the oxidation of oleic acid is carried out under conditions almost similar to those of the oxidation in homogeneous catalysis described in Example E / above, but without the addition of sodium hydroxide. These conditions are the following: mass ratio oleic acid / resin supporting the molybdate ions: 1/1, molar ratio oleic acid / H 2 O 2: 1 / 12.2, addition of aqueous H 2 O 2 for 30 min, reaction solvent: water / ethanol mixture (1/1 v / v), temperature: 65 ° C, stirring 400 rpm 'overall reaction time: 8 h.

In a 250 ml reactor, exactly 20.00 g of resin supporting the molybdate ions are introduced, and an emulsified mixture consisting of 20.00 g of oleic acid, 50 ml of water and 50 ml is added thereto. ethanol. The whole is brought to 50 ° C with stirring (400 rpm). Then 22.24 g of 50% aqueous H2O2 (756.4 mmol) is added dropwise over 30 minutes (at a rate of 1.44 ml.min -1). After stirring for an additional 7 hours, the reaction is stopped and the resin is filtered. Washing the resin with an additional volume of ethanol for 2 hours with stirring is necessary to release all the fatty acid molecules. The treatments of the total volumes of the filtrate and the reduction of the hydroperoxides are carried out according to the general protocol described above. At the end of the reaction, the degree of conversion of the oleic acid and the degree of formation of monoalcohol are determined as described above. An oleic acid conversion level of 88.3% and an allylic mono-alcohols formation rate of 58.9% are thus determined. The influence of the addition of an exogenous base on the yield of the reaction was also analyzed. For this purpose, the same protocol is applied for the following operating conditions: oleic acid AO (1 eq.), H2O2 (50%, 12.2 eq.), Resin (20.0 g), temperature (50 ^ 0) total time (6 h), stirring (400 rpm), and varying the proportions A 0 / EtOH / H 2 O, with or without the addition of exogenous sodium hydroxide as a source of alkalinity. The results obtained, in terms of conversion rate of oleic acid (XAO) and rate of formation of monoalcohols (YHFA) are shown in Table 14 below.

Table 14 - Yield of monoalcohols of a process for allyl oxidation of oleic acid by singlet oxygen in heterogeneous catalysis according to the invention - reaction at 65 ° C.

It is observed that the conversion rate of oleic acid is high regardless of the composition of the reaction system and regardless of the pH of the medium. The formation rates of monoalcohols (allyl hydroxylated fatty acids) are important for all the conditions tested, and particularly high in the system comprising a water / ethanol volume ratio equal to 1/5 (Tests No. 7 and 8, with or without sodium hydroxide ). It is further observed that the pH varies little during the reaction, making it advantageously unnecessary to add a base during the reaction, unlike the same reaction in homogeneous catalysis.

Oleic acid adsorbed in the ion-exchange resin by wet impregnation The adsorption of oleic acid on the resin is carried out by wet impregnation, according to the protocol below. In a 250 ml reactor, 20.00 g of resin containing ΜΜθθ ^ ^ ",,,,,,,,,,,,,,,,,,,,,, and slow stirring (200 rpm) are added slowly to an emulsion consisting of 20.00 g of oleic acid and 50 ml of water. Then the medium is stirred for 24 hours at 40 ° C to promote contacting and adsorption of oleic acid on the resin. After 24 hours, the resin beads are swollen and the reaction system is composed of three phases in the reactor: in the lower phase, a mixture of oil and resin, in the middle, a whitish aqueous phase, and in the upper phase a layer of yellow oil.

In the reactor containing this mixture of resin-MoO 4 and oleic acid / water emulsion, 50 ml of ethanol are introduced, then the whole is brought to 50 ° C., with stirring (400 rpm). 22.24 g of 50% aqueous H2O2 (756.4 mmol) are then added dropwise over 2 hours (at a rate of 0.36 ml.min -1). After stirring for a further 6 h, the resin is filtered. Washing the resin with an additional volume of ethanol for 1 hour is necessary to release all the fatty acid molecules. The filtrate treatments and the reduction of the hydroperoxides are carried out according to the general protocols described above.

The pH of this reaction system, initially equal to 3.35, is equal to 6.39 after the implementation of the oxidation process. The degree of conversion of oleic acid is 100%, and the degree of formation of the allyl monoalcohols is equal to 72.5%.

A similar experiment, in which the oleic acid has been brought into contact with the resin supporting the molybdate ions for a period of 48 h (instead of the 24 h previously described) makes it possible to obtain an allylic monoalcohol formation rate equal to 79.3%.

Oleic acid adsorbed in the ion-exchange resin by dry impregnation The adsorption of oleic acid on the resin is carried out by dry impregnation, according to the general protocol described above.

At the end of the implementation of the oxidation process according to the invention, an oleic acid conversion rate of 100% is obtained, and a degree of formation of the allyl monoalcohols equal to 100% also.

Recycling of the resin supporting the molybdate ions

The recycling of the resin-MoO / "material is evaluated over three cycles of oxidation reaction of oleic acid with or without regeneration of the resin. For this purpose, it is carried out a step of adsorption of oleic acid by the resin, according to the general protocol described above, then the oxidation process with singlet oxygen, also according to the general protocol described. above, with the difference that after the filtration of the resin, the latter is washed with an additional 50 ml of ethanol for 1 hour to release all the organic molecules at 40 ° C. The resin is then filtered, dried under vacuum and then in an oven (45 ° C) for 1 h. it is weighed and reused directly, or regenerated for a new oxidation cycle, according to the general protocol above, by taking an equal mass of oleic acid. The filtrate treatments and the reduction of the hydroperoxides are carried out according to the general protocols described above.

The results obtained, in terms of conversion rate of oleic acid (XAO), rate of formation of monoalcohols (YHFA) and selectivity to monoalcohols (HFA) are given in Table 15 below.

Table 15 - Yield of monoalcohols of an allyl oxidation process according to the invention of oleic acid by singlet oxygen in heterogeneous catalysis, according to the cycles and the mode of recycling of the resin

These results show that after three reaction cycles, the conversion of oleic acid remains always total. The allylic oxidation of oleic acid with the MoO 2 resin recycled and having not undergone any regeneration step leads to high yields of allylic hydroxylated fatty acids (87-95%). As the resin is recycled, there is a small decrease in the yield of alcohols. Experiments with the regenerated resin as the allyl oxidation tests of oleic acid make it possible to obtain yields of allyl monohydroxy fatty acids of the order of 100% and without significant loss of efficiency on 3 cycles. F.3 / Use of other resins exchanging anions

The following commercially available anionic ion exchange resins (strong bases and weak bases) are used: Amberlite® IRA-400, IRA-410, and IRA-900, Amberlyst® A-26, and Lewatit® M-500, M -600, MP-600, and MP-64. All these resins comprise a DVB polystyrene matrix. Their main characteristics, as indicated by the suppliers, are shown in Table 16 below. The above general protocols are used for all these resins. The Lewatit® MP64 resin was first preconditioned in the form of percolation with a 1M aqueous hydrochloric acid solution in a column filled with resin. The temperature of the allyl oxidation reaction is set at 40 or 50 ° C. depending on the resins.

The results obtained, in terms of conversion rate of oleic acid (XAO) and rate of formation of monoalcohols (YHFA) are given in Table 16 below.

Table 16 - Yield of monoalcohols of allyl oxidation processes according to the invention of oleic acid by singlet oxygen in heterogeneous catalysis, for different resins - Amm. The results obtained show that all the resins tested lead to the conversion of oleic acid and to the production of allyl monoalcohols. Conversion rates of oleic acid are always greater than 75%. The yields in Germany are high for all the resins tested. The best results are obtained with macroporous resins Amberlite® IRA-400, Amberlyst® A-26, and Lewatit® MP-600. The structure of the matrix accompanied by the basicity of the resin, as well as its surfactant properties, give the reaction system an efficiency to produce singlet oxygen in situ at least equivalent to, or even superior to, homogeneous catalysts. For the very basic Amberlyst A-26 resin, the majority of the products are allylic ethyl perether fatty acids (69%) prior to the reduction of the peroxidic functions by NaBH4. This resin advantageously provides both the production of singlet oxygen, the insertion of this singlet oxygen on the ethylenic bonds, and the etherification of the hydroperoxides thus formed. This resin thus proves to be particularly advantageous for the direct synthesis of fatty acid alkyl perethers. G / Process for forming monoalcohols from other unsaturated aras acids via an alivl oxidation reaction with singlet oxygen generated in situ by heterogeneous catalysis

The general protocols described in Example F / above are applied to the oxidation of other monounsaturated fatty acids, more specifically: a acide-unsaturated fatty acid (undec-10-enoic acid), a hydroxylated fatty acid (acid (Z) -12-hydroxyoctadec-9-enoic), a fatty acid with a very long carbon chain ((Z) -docos-13-enoic), and a diunsaturated fatty acid (acid (9Z, 12Z) -octadeca-9, 12-dénoïque). The process has also been applied to monounsaturated fatty acid esters: glycerol monooleate and methyl oleate.

The structures of the compounds are validated by mass spectrometry (MS), nuclear magnetic resonance (^ H and Fourier transform infrared (FTIR).

The results obtained, in terms of fatty acid conversion rate (XAG) and rate of formation of monoalcohols (YFIFA) are shown in Table 17 below.

Table 17 - Monoalcohol yields of an allylic oxidation process according to the invention of unsaturated fatty acids with singlet oxygen in heterogeneous catalysis

These results show that the reaction system according to the present invention is well suited for the allylic oxidation of the selected substrates, whatever the position of the carbon-carbon double bond or the number of double bonds. The system is equally effective regardless of the length of the carbon chain, or whether the fatty acid is free or esterified. The tests lead to the formation of the desired hydroxy allylic with high fatty acid conversion rates (73% -100%). The yields of hydroxylated fatty acids are important for all tested compounds, including fatty acid esters.

With regard to these fatty acid esters, the difference in the acid values between the starting substrates and the products obtained show that the esters have not been hydrolyzed, and that the reaction products remain under Ester form.

In particular, the oxidation of glycerol monooleate leads to a yield of hydroxylated esters of 65%. The products of synthesis are (E) -2,3-dihydroxypropyl 10-hydroxyoctadec-8-enoate and (E) -2,3-dihydroxypropyl 9-hydroxyoctadec-10-enoate.

BIBLIOGRAPHIC REFERENCES

Aubry, 1985: Search for singlet oxygen in the decomposition of hydrogen peroxide by ore compounds in aqueous solutions. Journal of the American OH Chemists Society, 107: 5844-5849

Bader, 1948: The osmium tetroxide oxidation of some long-chain unsaturated fatty acids. Journal of the American OH Chemists Society, 70: 3938-3939

Borde et al., 2008: A Gemini Amphiphilic Phase Transfer Catalyst for Dark Singlet Oxygenation. Journal of Physical Organic Chemistry, 21: 652-658. Choe et al., 2005: Cemistry and reactions of reactive oxygen species in foods. Journal of Food Science, 70: R142-R159

Foglia et al., 1977: Oxidation of alkenes with use of phase transfer catalysis. Journal of the American Society Chemists Society, 54: A858-A861

Fore et al., 1959: Hydroboration of fats. I. Positional isomerism in the methyl oleate hydroboration reaction. Journal of Organic Chemistry, 24: 920-922

Julien-David et al., 2008: Synthesis of high-grade pure oxyphytosterols and (oxy) phytosterol esters: Part II. (Oxy) -sitosterol esters derived from oleic acid and 9,10-dihydroxystearic acid, Steroids, 73: 1098-1109

Lligadas et al., 2010: Plant oils as platform Chemicals for polyurethane synthesis: Current state-of-the-art. Biomacromolecules, 11: 2825-2835

Montero de Espinosa et al., 2009: A new route to acrylate oils: Crosslinking and properties of triglyceride acrylate from high oleic sunflower oil. Journal of Polymer Science Part A: Polymer Chemistry, 47: 1159-1167

Sharpless et al., 1983: On the mechanism of titanium-tartrate catalyzed asymmetric epoxidation. Pure and Applied Chemistry Journal, 55: 1823-1836

Warwel et al., 1995: Chemo-enzymatic epoxidation of unsaturated carboxylic acids. Journal of Molecular Catalysis B: Enzymatic, 1: 29-35

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Claims (25)

Process for the oxidation of an unsaturated fatty acid by singlet oxygen, characterized in that it comprises: the preparation of a reaction system containing at least said unsaturated fatty acid and molybdate ions, in a mixture of water and an alcohol capable of solubilizing said unsaturated fatty acid, said reaction system being free of exogenous emulsifying agent, and the addition of hydrogen peroxide in said reaction system. 2. Method according to claim 1, wherein the addition of hydrogen peroxide in the reaction system is carried out gradually, preferably by introducing into said reaction system of an aqueous solution of hydrogen peroxide, at the rate of more than 3.0 mmol of hydrogen peroxide per minute, especially from 3.0 mmol to 4.9 mmol of hydrogen peroxide per minute. 3. Method according to any one of claims 1 to 2, comprising, after the step of adding hydrogen peroxide in said reaction system, a step of stirring the reaction medium obtained for a duration greater than or equal to 1 hour, preferably greater than or equal to 2 hours. 4. Method according to any one of claims 1 to 3, wherein the step of adding hydrogen peroxide in said reaction system, and optionally the stirring step of the reaction medium obtained, are carried out. a temperature above 25 ° C, preferably between 50 and 85 ° C, and preferably between 50 and 75 ° C. 5. Method according to any one of claims 1 to 4, wherein the alcohol capable of solubilizing the unsaturated fatty acid is selected from ethanol and methanol. 6. Process according to any one of claims 1 to 5, wherein the volume ratio between water and alcohol capable of solubilizing said unsaturated fatty acid in said mixture is between 1/1 and 1/9. . 7. Process according to any one of claims 1 to 6, wherein the molybdate ions are present in the reaction system in a molar amount of between 4 and 9% relative to the number of moles of said unsaturated fatty acid, preferably between 6 and 9%, in moles relative to the number of moles of said unsaturated fatty acid. 8. Process according to any one of claims 1 to 7, according to which the hydrogen peroxide is introduced into the reaction system in a proportion of at least 6 molar equivalents, preferably at least 9 molar equivalents, relative to said fatty acid. unsaturated. 9. Process according to any one of claims 1 to 8, wherein the molybdate ions are present in free form in the reaction system. The process according to any one of claims 1 to 8, wherein the molybdate ions are present in the reaction system in anion-exchange-supported form. 11. A method according to claim 10, comprising a step of adsorbing the unsaturated fatty acid on the anion exchange resin supporting the molybdate ions, prior to the step of preparing the reaction system by placing said resin in contact with said resin and mixture of water and said alcohol. 12. Process according to any one of claims 1 to 11, according to which the unsaturated fatty acid is chosen from oleic acid, o-unsaturated fatty acids, hydroxylated monounsaturated fatty acids and long-chain monounsaturated fatty acids. preferably C18: 1 to C24: 1, and polyunsaturated fatty acids. 13. Method according to any one of claims 1 to 12, wherein the pH of the reaction system is maintained at a value greater than or equal to 7, preferably between 9 and 12, and preferably greater than or equal to 10 and less than 10. 12. 14. The method of claim 13, wherein the preparation of the reaction system comprises the following succession of steps: - mixture of the unsaturated fatty acid and an aqueous solution containing a base, - optionally, heating at a temperature to a value greater than 25 ° C, and successive introduction into the mixture of the unsaturated fatty acid and the base, molybdate ions, and the alcohol capable of solubilizing said unsaturated fatty acid. The process according to any one of claims 13 to 14, wherein a base is introduced into the reaction system during the addition of hydrogen peroxide, preferably in substantially pure form and at regular intervals throughout the duration of the reaction. adding hydrogen peroxide to said reaction system. 16. Process according to any one of claims 1 to 12, according to which the pH of the reaction system is fixed, prior to the step of adding hydrogen peroxide in said reaction system, to a value of less than 7, of preferably between 4 and 6. 17. The method of claim 16, wherein the preparation of the reaction system comprises the succession of the following steps: - mixing molybdate ions and water, - and successive introduction into said mixture, the alcohol capable of solubilizing said unsaturated fatty acid, and unsaturated fatty acid. 18. A process for forming an allyl monoalcohol from an unsaturated fatty acid, comprising carrying out a process for oxidizing an unsaturated fatty acid with singlet oxygen according to claim 1. at 15, followed by a final allyl hydroperoxide reduction step formed after said oxidation process. A process for forming a diol from an unsaturated fatty acid, comprising carrying out a process for oxidizing an unsaturated fatty acid with singlet oxygen according to any one of claims 1 to 12 and 16 to 17, followed by a final epoxide hydrolysis step formed at the end of said oxidation process, preferably in an acidic medium. 20. Reaction system for carrying out a process for the oxidation of an unsaturated fatty acid according to any one of claims 1 to 17, characterized in that it contains at least said unsaturated fatty acid and molybdate ions. , in a mixture of water and an alcohol capable of solubilizing said unsaturated fatty acid, and in that it is free of exogenous emulsifying agent. 21. Use of anion exchange resin supporting molybdate ions for the production of singlet oxygen. 22. Use according to claim 21, wherein the anion exchange resin is a macroporous resin. 23. Use according to any one of claims 21 to 22, wherein the anion exchange resin is subjected to a hydrophobation treatment, in particular by absorption of molecules of a hydrophobic compound, prior to its implementation for the production of singlet oxygen. 24. 7- (3- (1-hydroxynonyl) oxiran-2-yl) heptanoic acid obtainable from (E) -10-hydroxyoctadec-8-enoic fatty acid by an oxidation process according to any of claims 1 to 12 and 16 to 17. 25. 9- (3-heptyloxiran-2-yl) -9-hydroxynonanoic acid obtainable from (E) -9-hydroxyoctadec-10-enoic fatty acid by an oxidation process according to any of claims 1 to 12 and 16 to 17.