EP3902782A1

EP3902782A1 - Purification of alkyl hydroperoxide by distillation in the presence of methanol and water

Info

Publication number: EP3902782A1
Application number: EP19848899.1A
Authority: EP
Inventors: Bruno Van Hemelryck; Serge Hub; Philippe Maj
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2018-12-26
Filing date: 2019-12-20
Publication date: 2021-11-03
Also published as: WO2020136335A1; FR3091283B1; FR3091283A1

Abstract

The invention relates to a method for purifying an alkyl hydroperoxide from dialkyl peroxide thereof, involving a step of distillation in the presence of methanol and water.

Description

PURIFICATION OF ALKYL HYDROPEROXIDE BY DISTILLATION IN THE PRESENCE

METHANOL AND WATER

FIELD OF THE INVENTION

The present invention relates to a method of separation and purification by means of extractive distillation of organic peroxides, and more particularly the separation of dialkyl peroxides of the general formula R1-OO-R2 with Ri and R ₂ alkyl structures of C to C, identical or not, possibly being cyclic.

Thus, more specifically but not limited to this application, the present invention relates to the purification of alkyl hydroperoxides, from mixtures containing dialkyl peroxides as defined above.

This invention is applicable in particular, but not exclusively, during the production of organic peroxides obtained by synthesis of alkyl hydroperoxides containing the peroxide dialkyl impurities. This invention therefore makes it possible to obtain with improved purity organic peroxides of the peresters type such as tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate of monoperoxypercarbonate type 00 tert-butyl-0- (2-ethylhexyl) - perketal-type monoperoxycarbonate such as 2,2-di-tert-butyl-peroxybutane, 2,2-di-tert-amyl-peroxybutane of hemi-perketal type or peroxide ether such as 1, 1 - dimethyl-propyl-1-methoxy-cyclohexyl peroxide and of dialkyl or aryl peroxides such as 2,5-dimethyl-2,5-di- (tert-butylperoxy) peroxide - hexane, tert-butyl-cumyl peroxide, di (tert-butyl-peroxy-isopropyl) -benzene ...

The alkyl hydroperoxides are typically tertiary amyl hydroperoxide (hereinafter abbreviated as TAHP) and tertiary butyl hydroperoxide (hereinafter abbreviated as TBHP).

TECHNICAL BACKGROUND

Alkyl hydroperoxides are commonly used as raw materials to produce crosslinkers, intended to be mixed with polymers, such as polyester, ethylene-vinyl acetate or even ethylene-propylene-diene monomer. They are also used in the production of polymerization initiators, for example that of polystyrene or polyethylene.

In general, the alkyl hydroperoxides present on the market contain impurities, mainly represented by dialkyl peroxides, derived from the hydroperoxides in question. Indeed, alkyl hydroperoxides are conventionally obtained by acid catalysis, resulting in the formation of dialkyl peroxides associated, generally present between 3 and 30% by weight relative to the total weight of the composition of alkyl hydroperoxides.

These dialkyl peroxides are not desired in association with their respective alkyl hydroperoxides and represent the primary source of harmful / negative contamination in the synthesis of crosslinkers and polymerization initiators.

Thus, these impurities obtained in the raw materials hydroperoxides of alkyl, enter into the process of production of crosslinkers for polymers and initiators of polymerization. This has the direct consequence of lowering the purity of the products obtained. For certain applications such as low density polyethylene obtained by peroxy initiation under very high pressure, the presence of dialkyl peroxide in the initiators can be a source of poor thermal reaction profiles, thus adversely affecting the implementation of the polymerization.

Research has therefore been carried out to purify the crosslinkers and the polymerization initiators, in other words to remove these impurities, more particularly in this case dialkyl peroxides. Unfortunately, the results obtained are not satisfactory at present: the purification yields are low, the organic peroxides treated are partially degraded.

Thus, it appears necessary to find a process for eliminating these impurities, and in particular dialkyl peroxides, in the raw materials, i.e. alkyl hydroperoxides, while preserving the physicochemical properties of the latter.

There are different modes of purification of alkyl hydroperoxides, well known to those skilled in the art, such as for example washing by salt formation, to which the document FR 2455036 refers. The alkyl hydroperoxides are conventionally soluble in water but generally their associated dialkyl peroxides are much less so. The alkyl hydroperoxides react with a base such as, for example, sodium hydroxide (NaOH) or potassium hydroxide (KOH), to form a salt of alkyl hydroperoxide soluble in water. Thus by decantation, the salt and the organic compounds insoluble in water, including the dialkyl peroxides, are separated. Then, when the use of the alkyl hydroperoxide and not that of its salt is required in the subsequent synthesis of the polymerization initiator or of the crosslinker, the alkyl hydroperoxide salt is acidified, for example with using an aqueous solution of sulfuric acid, to reform the alkyl hydroperoxide. The alkyl hydroperoxide is thus recovered by phase shift or by extraction with a solvent, for example a hydrocarbon. The major drawbacks of this technique come on the one hand from its low productivity if we consider that the same reactor performs the stages (salt formation / decantation, re-acidification / extraction), on the other hand from the formation of effluents saline aqueous. The aqueous effluents formed during acidification, such as for example potassium sulphate, must be treated. In addition, the use of base and acid increases production costs. Finally, the dialkyl contents obtained remain too high.

Another purification method is direct distillation, as described in document FR 2455036. The distillation of TAHP containing di-tert-amyl peroxide (DTA) is carried out in the presence of water under reduced pressure and at a temperature below 45 ° C, allowing the TAHP to be recovered at the bottom of the column. Distillation provides a composition of TAHP with a residue of 0.8% (8000 ppm) of DTA. These results remain insufficient, particularly for the use of TAHP as raw materials for the production of polymerization initiators. In addition, the loss of TAHP is significant, between 4 and 16%, due to a lack of selectivity during the separation of DTA, and / or to a thermal degradation of TAHP.

Current existing and proposed solutions for purifying alkyl hydroperoxides from their associated peroxides are insufficient. This is notably due to the lack of selectivity of the purification treatments, the low yields obtained, the production costs, but also to the safety conditions to be taken into account during the purification.

Indeed, it is important to note that organic peroxides are chemical in nature to decompose thermally, with in particular the formation of flammable vapors.

For reasons of safety and quality of the product to be purified, it is therefore important to limit the treatment temperature as well as possible, which makes the purification of organic peroxides all the more difficult.

At the present time, effective solutions are therefore sought in order to obtain a process for the purification of solutions of organic peroxides, more particularly of alkyl hydroperoxides, by elimination of dialkyl peroxide R1 -00-R2 defined above, this without loss or degradation of material, safely and with good yield. Thus, there is a strong need to obtain purified organic peroxide compositions comprising less than 1000 ppm of impurities, or even of the order of a hundred ppm.

SUMMARY OF THE INVENTION

Surprisingly, the Applicant has thus discovered that the implementation of a process comprising at least one step a) of distillation of a composition comprising alkyl hydroperoxide and dialkyl peroxide in the presence of methanol and water, allows the selective removal of dialkyl peroxide from the corresponding alkyl hydroperoxide.

One of the particularly interesting aspects of the present invention resides in the fact that the dialkyl peroxide is eliminated in the corresponding alkyl hydroperoxide, by entraining a reduced amount of this alkyl hydroperoxide during the process according to the invention. The removal of dialkyl peroxide from the corresponding alkyl hydroperoxide, with reduced loss of hydroperoxide, is particularly effective when the alcohol introduced into the distillation boiler is notably methanol.

By “alkyl hydroperoxide” is meant a compound of formula ROOH in which R represents an alkyl group, linear or branched, cyclic or non-cyclic, unsaturated or functionalized, or an aromatic group, optionally substituted, preferably having from 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms, more preferably 4 or 5 carbon atoms.

Preferably, said alkyl hydroperoxide is chosen from the group consisting of tert-butyl hydroperoxide, tert-amyl hydroperoxide, hexylene glycol hydroperoxide, tert-octyl hydroperoxide, hydroperoxide of tert-hexyl, 1-methyl-cyclopentyl hydroperoxide and 1-methyl-cyclohexyl hydroperoxide. Preferably, the water-soluble organic peroxide is chosen from the group consisting of tert-butyl hydroperoxide and tert-amyl hydroperoxide, more preferably still is tert-amyl hydroperoxide.

By “dialkyl peroxide” is meant a compound of formula R1-OO-R2 in which Ri and R ₂ are identical or different, and independently represent an alkyl group, linear or branched, cyclic or non-cyclic, unsaturated or functionalized, or an aromatic group, optionally substituted, preferably having from 4 to 8 carbon atoms, preferably from 4 to 6 carbon atoms, more preferably still 4 or 5 carbon atoms.

As dialkyl peroxide to be separated from the hydroperoxide, mention may be made of ditertiobutyl peroxide, ditertioamyl peroxide, di-3-hydroxy-1, 1-dimethylbutyl peroxide, di-tert-octyl peroxide, peroxide di-tert-hexyl, di (1-methyl-cyclopentyl) peroxide and di (1-methyl-cyclohexyl) peroxide. In particular, the dialkyl peroxide is symmetrical, that is to say that the groups framing the group 0-0 are identical.

The characteristics of the water-soluble organic peroxide described in relation to the concentration process above can be applied in the same way to the water-soluble organic peroxide in the context of the separation process.

Advantageously, said at least one water-soluble organic peroxide, preferably said at least one hydroperoxide, and said at least one dialkyl peroxide have identical groups R, Ri and R ₂ .

For example, the water-soluble organic peroxide is tert-butyl hydroperoxide and the dialkyl peroxide is ditertiobutyl peroxide.

Alternatively, the water-soluble organic peroxide is tert-amyl hydroperoxide and the dialkyl peroxide is ditertioamyl peroxide. Alternatively, the water-soluble organic peroxide is hexylene glycol hydroperoxide and the dialkyl peroxide is di-3-hydroxy-1,1-dimethylbutyl peroxide.

Alternatively, the water-soluble organic peroxide is tert-octyl hydroperoxide and the dialkyl peroxide is di-tert-octyl peroxide.

Alternatively, the water-soluble organic peroxide is tert-hexyl hydroperoxide and the dialkyl peroxide is di-tert-hexyl peroxide.

Preferably, the alkyl peroxide consists of tertiary amyl peroxide (DTA) or tertiary butyl peroxide (DI), even more preferably is tertiary amyl peroxide (DTA).

Thus, the present invention relates to a process for the separation of an alkyl hydroperoxide from a dialkyl peroxide comprising at least one stage of distillation of the composition comprising the alkyl hydroperoxide and said dialkyl peroxide in the presence of methanol and d 'water.

Other characteristics of this purification process are presented below:

preferably, the content by weight of methanol present in stage a) of distillation is greater by 5 times, preferably is greater by 10 times, preferably is greater by 25 times, and more preferably is greater by 30 times, to that of said dialkyl peroxide,

- Preferably following the step of evaporation of the methanolic composition, the latter undergoes a condensation step then step of passage through at least one hydrocarbon, so as to obtain an organic phase containing said hydrocarbon as well as all or part dialkyl peroxide R1-OO-R2 and an aqueous phase containing water and methanol;

the process can thus comprise, after the distillation step a), an extraction step b) carried out by bringing said hydrocarbon into contact with the condensate obtained in step a), so as to obtain an organic phase containing said hydrocarbon as well as all or part of the dialkyl peroxide and an aqueous phase containing the hydroperoxide, water and methanol; in other words, the process according to the invention is preferably an extractive distillation process,

- alternatively, the hydrocarbon can be present in the composition before stage a) of distillation, or introduced during the stage of distillation;

advantageously, steps a) and b) can be carried out concomitantly; very advantageously, the hydrocarbon is chosen from C ₆ to C 12 hydrocarbons, preferably C ₆ to C ₈ hydrocarbons; more preferably a hydrocarbon in

C ₇ ;

- Preferably, the hydrocarbon is saturated;

- Advantageously, the above-mentioned methanolic aqueous phase is recycled to the distillation boiler so as in particular to conserve the quantity of methanol necessary to maintain the purification;

- According to a possibility offered by the invention, the above organic phase is distilled in order to separate said hydrocarbon from dialkyl peroxide;

advantageously, the distillation of the mixture according to the invention (alkyl hydroperoxide R-OOH / methanol / dialkyl peroxide R-OO-R / water) is carried out at a temperature between 25 ° C and 60 ° C, preferably between 30 ° C fe45 ° C;

advantageously, the distillation of the mixture according to the invention (alkyl hydroperoxide R-OOH / methanol / dialkyl peroxide R-OO-R / water) is carried out at a pressure between 30 and 200 mbar (millibars), preferably between 40 and 180 mbar, and more preferably between 50 and 160 mbar,

advantageously still, the distillation of the mixture according to the invention (alkyl hydroperoxide R-OOH / alcohol / dialkyl peroxide R-OO-R / water) is carried out at a pressure of between 90 and 200 mbar (millibars), preferably between 100 and 180 mbar, and more preferably between 100 and 160 mbar.

The Applicant has thus discovered a selective and secure distillation process, avoiding the loss and / or thermal degradation of organic peroxides. Said process comprises a more selective distillation step in dialkyl peroxide, as well as, very advantageously, its recovery preferably carried out by selective extraction in a hydrocarbon.

Advantageously, the recovery of dialkyl peroxide is carried out by selective extraction in a hydrocarbon. In other words, the process can also comprise at least one step b) of extraction using a hydrocarbon of dialkyl peroxide.

This offers both the advantage of safely reducing the heating of the peroxide mixture and the advantage of easily recycling the water and methanol solvents, which have contributed to the purification.

The use of a composition comprising methanol allows the elimination of the dialkyl peroxide in the hydroperoxide to be purified, by generating a dilute solution of alkyl hydroperoxide with methanol and water which can be easily removed by direct distillation. then by settling known to those skilled in the art.

The description which follows is given only by way of illustration and without limitation. DETAILED DESCRIPTION OF THE INVENTION

Distillation, evaporation as well as extraction are per se methods well known to those skilled in the art.

The condensation of the distillation head comprising the dialkyl peroxide to be eliminated, that is to say the condensation step, preferably takes place between -30 ° C and 0 ° C, preferably between -20 ° C and -10 ° C. The distillation head is recovered by any means well known to those skilled in the art, such as a condenser.

Preferably, the method according to the invention comprises a step of selective recovery of the dialkyl peroxide using a hydrocarbon.

Thus during the passage of the composition comprising the dialkyl peroxide to be eliminated in a hydrocarbon, the hydrocarbon is maintained in liquid form by adjusting the temperature, the latter being preferably between -30 ° C and 0 ° C, very preferably between -20 ° C and -10 ° C, in order to reduce the risk of boiling of the methanol phase and maintain good separation of the phases during selective capture of the dialkyl peroxide by the hydrocarbon.

The hydrocarbon is preferably chosen from hydrocarbons comprising from 6 to 12 carbon atoms. Said hydrocarbons comprising from 6 to 12 carbon atoms remain liquid at the condensation temperature of the distillation head. Hydrocarbons in C _? are preferred for their ease of elimination when entrained with the methanolic solution in the boiler during its recycling.

Upon contact of the top composition with the hydrocarbon, two phases are formed, an upper organic phase consisting of dialkyl peroxide and the hydrocarbon and a lower aqueous phase comprising the mixture of water and methanol.

Advantageously, the choice of hydrocarbon allows selective retention of dialkyl peroxide such as DTA or DI.

The aqueous phase can thus be recycled in the mixture to be purified so as to allow the exhaustion of dialkyl peroxide by distillation. Recycling can be done continuously, or discontinuously.

The purification process according to the invention, that is to say including the evaporation of the methanolic composition, its condensation, and according to a preferred mode, its extraction with the hydrocarbon and the recycling of the aqueous phase generated, can be carried out in batch, semi-continuous or continuous mode, depending on the mode of supply of the peroxide to be purified, methanol, water, and hydrocarbon.

During distillation, the hydrocarbon is concentrated in dialkyl peroxide. This hydrocarbon solution can be drawn off and renewed continuously. This hydrocarbon solution comprising dialkyl peroxide can be distilled so as to recycle the hydrocarbon to the purification process according to the invention, and to enhance the dialkyl peroxide thus isolated.

At the end of the batch distillation according to the invention, the purified mixture generally comprises alkyl hydroperoxide, water and methanol. A majority amount of water and methanol can be removed by any means well known to those skilled in the art, such as for example evaporation, for example by heating the mixture to a temperature between 30 and 50 ° C, under pressure reduced included between 60 and 200 mbar.

During the distillation process, the degradation of the alkyl hydroperoxide is between 0 and 1% by weight relative to the organic peroxide initially present in the solution to be purified.

The separation process according to the invention may comprise a step a ’), prior to step a), of synthesis of said alkyl hydroperoxide.

Step a ’) of synthesis of the alkyl hydroperoxide can be carried out by any method known by a person skilled in the art leading to the formation of dialkyl peroxide, as an impurity. In particular, step a ’) can be carried out by the reaction of at least one alcohol or at least one alkene with hydrogen peroxide in the presence of an acid, preferably sulfuric acid. Such a process results in particular in the synthesis of dialkyl peroxide as impurities.

Preferably, the alkyl hydroperoxide can be prepared in an acid medium.

In this case, the synthetic step a ’) notably consists in reacting hydrogen peroxide (hydrogen peroxide) in the presence of at least one alcohol or at least one alkene in an acid medium.

Preferably, step a ’) of synthesis consists in particular of reacting hydrogen peroxide (hydrogen peroxide) in the presence of at least one alcohol or an unsaturated compound in an acid medium.

Synthesis step a ’) can be carried out at a temperature which can range from 10 ° C to 80 ° C, preferably from 20 ° C to 40 ° C.

Preferably, stage a ’) of synthesis is carried out in the presence of one or more mineral or organic acids, in particular one or more mineral acids.

More preferably, the mineral acid is sulfuric acid.

The composition comprising at least one alkyl hydroperoxide and at least one dialkyl peroxide (before step a)) may comprise at least 50% by weight of alkyl hydroperoxide, preferably at least 60% by weight of alkyl hydroperoxide, more preferably at least 68% by weight of alkyl hydroperoxide, even more preferably at least 70% by weight of alkyl hydroperoxide relative to the total weight of organic peroxides.

According to embodiments, the composition comprising an alkyl hydroperoxide and a dialkyl peroxide (before step a)) comprises from 0.1% to 40% by weight of dialkyl peroxide, preferably from 1 to 30% by weight of dialkyl peroxide, more preferably from 2 to 22% by weight of dialkyl peroxide, even more preferably from 3 to 20% by weight of dialkyl peroxide relative to the total weight of alkyl hydroperoxide and dialkyl peroxide.

The present invention also relates to an alkyl hydroperoxide composition capable of being obtained by the process according to the invention.

Preferably, the composition thus obtained comprises less than 1% by weight of methanol, preferably less than 1000 ppm, and even more preferably less than 100 ppm relative to the total weight of the composition.

Advantageously, the composition thus obtained comprises less than 1000 ppm of hydrocarbon, relative to the total weight of said composition, preferably less than 100 ppm.

Another subject of the present invention relates to a purified alkyl hydroperoxide composition comprising less than 1000 ppm of dialkyl peroxide, preferably less than 500 ppm, preferably less than 250 ppm, and more preferably less than 100 ppm of dialkyl peroxide .

Preferably, said composition is an aqueous composition containing at least 60% by weight of alkyl hydroperoxide, as defined above, and less than 1000 ppm by weight of dialkyl peroxide as defined above, the proportions being calculated by weight relative to the total weight of the composition.

Preferably, the aqueous composition contains at least 70% by weight of alkyl hydroperoxide, as defined above, more preferably at least 80% by weight.

Preferably, the group R of the alkyl hydroperoxide as defined above represents a branched alkyl group, optionally substituted, of C -C ₈ , preferably of C ₅ - C ₈ , more preferably of C ₅ -C ₆ , even more preferably in C ₅ .

The alkyl hydroperoxide is preferably chosen from the group consisting of tert-amyl hydroperoxide, hexylene glycol hydroperoxide, tert-octyl hydroperoxide and tert-hexyl hydroperoxide.

More preferably, the alkyl hydroperoxide is tert-amyl hydroperoxide (TAHP). Advantageously, the aqueous composition contains less than 800 ppm by weight, preferably less than 700 ppm by weight of dialkyl peroxide, preferably less than 500 ppm by weight of dialkyl peroxide, preferably less than 250 ppm by weight of dialkyl peroxide, even more preferably less than 100 ppm by weight of dialkyl peroxide relative to the total weight of the composition.

Preferably, the dialkyl peroxide chosen from the group consisting of di-tertio-amyl peroxide, di-3-hydroxy-1, 1-dimethylbutyl peroxide, di-tert-octyl peroxide and di peroxide -tert-hexyle.

More preferably, the dialkyl peroxide is di-tertio-amyl peroxide.

Advantageously, the composition is a tert-amyl hydroperoxide composition and comprises less than 1000 ppm of dialkyl peroxide, preferably less than 1000 ppm of tert-amyl peroxide (DTA).

Advantageously, the aqueous composition contains at least 60% by weight of tert-amyl hydroperoxide (TAHP) and less than 1 000 ppm by weight of di-tertio-amyl peroxide (DTA), the proportions being calculated by weight relative to the total weight of the composition.

The present invention also relates to the use of the composition as defined above for the preparation of crosslinking agent (s) or of polymerization initiator (s).

Preferably, the initiator or initiators is or are initiators for radical polymerization, in particular ethylene under high pressure.

By "high pressure" is meant in the sense of the present invention, a pressure greater than 50 MPa. Preferably, the pressure varies from 500 bar (50 MPa) to 3000 bar (300 MPa), preferably from 1200 bar (120 MPa) to 3000 bar (300 MPa), better from 1200 bar (120 MPa) to 2600 bar (260 MPa).

Preferably, the crosslinking agents or the polymerization initiators are chosen from the group consisting of organic peroxides, in particular peroxyesters, hemi-peroxyacetals and peroxyacetals.

The term “hemi-peroxyacetal” means a compound of general formula (R ₃ ) (R ₄ ) C (- ORI) (- OOR ₂ ), in which:

- Ri represents an alkyl group, linear or branched, preferably in C1 -C12, preferably in C1 -C4, more preferably in C1, or a cycloalkyl group with R ₂ ,

R ₂ represents a linear or branched alkyl group, preferably of CrCi ₂ , preferably of C ₄ -Ci ₂ , more preferably of C ₅ , or a cyclo alkyl group with FL,

- R ₃ represents a hydrogen or an alkyl group, linear or branched, preferably C1-C12, more preferably C4-C12, or a cycloalkyl group with FL,

- FL represents a hydrogen or an alkyl group, linear or branched, preferably in C1-C12, more preferably in C4-C12, or a cyclo-alkyl group with FL.

Preferably FL forms a cycloalkyl group with FL.

Preferably, when R3 is hydrogen, FL is an alkyl group, linear or branched, preferably C1-C12, more preferably C4-C12.

In the description of the present invention, the percentages are indicated by weight, “ppm” means part per million by weight.

The following examples illustrate the invention without limiting it.

EXAMPLES

Example 1 Purification by Extractive Distillation of a TAHP Solution

Assembly:

The assembly consists of a flask surmounted by a distillation column equipped with temperature measurement at the bottom and at the top. A refrigerant is attached to the head of the column to condense the vapors.

The overhead vapor recovery / separation system (Dean Stark type) is connected to the refrigerant and has a cooled jacket. This system contains the hydrocarbon allowing the recovery of DTA and the methanolic aqueous phase.

This system is fitted with a bottom valve for recycling the methanolic aqueous phase below the column boiler.

The boiler is stirred and heated. The distillation is carried out under a vacuum of approximately 1 10 mbar. At equilibrium, the temperature of the boiler is around 31 ° C and around 28 ° C at the top of the column.

Vapors condense in the refrigerant and the condensate falls into the hydrocarbon. In contact with the hydrocarbon, two phases are formed. DTA is selectively retained in the upper organic phase and methanol forms with water the lower methanolic aqueous phase, which is recycled to the boiler.

The distillation is continued by operating as described until almost all of the DTA is removed from the boiler. Starting mixture:

The mixture to be distilled is produced by mixing commercial TAHP comprising DTA, with methanol and water so as to obtain the following composition of: 58.7 g of TAHP, 3.1 g of DTA, 74.5 g of methanol and 79.8 g of 'water.

2.1 g of water, 3.9 g of methanol and 15.7 g of isododecane hydrocarbon are introduced into the recovery / separation system (Dean Stark).

At the end of the extractive distillation, 200.8 g of solution are recovered in the boiler containing 0.02 g of DTA, 57.5 g of TAHP, 65.6 g of methanol.

At the head of the distillation, 18.5 g of hydrocarbon phase containing 3 g of DTA and 15.5 g of hydrocarbon are recovered.

After removing the DTA, the contents of the boiler are distilled to remove the methanol in the same experimental system. The procedure is similar to the previous one except that nothing is recycled to the boiler during this second distillation. Thus, 102.0 g of the above mixture (consisting of 28.3 g of TAHP, 33.8 g of MeOH and 39.9 g of water) are introduced into the boiler. Then the distillation is carried out with a bath temperature of 32 to 35 ° C and a partial vacuum of 120 to 80 mbar. After distillation, the solution of the boiler phase in 2, the upper organic phase (27.6g) consists of 23.3 g of TAHP, 0.25 g of methanol and 4 g of water. DTA is no longer detected by gas chromatography within the detection limit of <100 ppm. The lower aqueous phase (27.2 g) consists of 1.5 g of TAHP, 0.4 g of methanol and 25.3 g of water. At the top of the column, 3.2 g of TAHP are recovered with condensed methanol.

This example shows the possibility of reducing the amount of DTA present in the commercial TAHP, to a content of around one hundred ppm (0.01%) thanks to the process according to the invention, and in complete safety.

Example 2:

Example 2a: Extractive Distillation of TAHP Using Alcohols Different from Methanol

Extractive distillation as described in Example 1 was carried out with alcohols other than methanol, such as tert-amyl alcohol and ethanol. The distillation of these mixtures was carried out under total reflux for a hundred minutes at 40 ° C. The DTA / alcohol / water mixtures subjected to distillation were mixed in a 1: 1: 1 mass ratio.

The products obtained at the top of the distillation are presented below. [Table 1]

These experiments indicate that, unlike methanol, a significant entrainment of TAHP at the top of the distillation is obtained for alcohols other than methanol as well as a lower entrainment rate of DTA to be eliminated than that allowed by methanol.

These experiments clearly show that the elimination of DTA with a reduced loss of TAHP is more effective with methanol than with the other alcohols tested above.

Example 3: Elimination of di-tert-butyl peroxide (DI) in tert-butyl hydroperoxide (TBH)

The assembly carried out corresponds to the assembly of Example 1. The starting mixture is composed of 34.7 g of tert-butyl hydroperoxide (TBH), 2.7 g of di-tert-butyl peroxide (DI), 49.4 g of methanol and 62, 4 g of water. This mixture is placed in the distillation bottom flask.

The Dean Stark is initially charged with a methanolic aqueous phase composed of 2.4 g of water, 1.7 g of methanol, and an upper phase of 6.9 g of isododecane. The quantity of DI present in the distillation bottom in the initial TBH thus diluted is 1.8% by weight of the methanolic composition.

The flask is heated using a water bath, set at 35 ° C, and is stirred with a magnetic bar at 500 rpm. The distillation is carried out under a vacuum of between 1 12 mbar (millibar) and 106 mbar, to maintain a head temperature of between 28 ° C and 30 ° C.

The condensates are recovered in the Dean Stark containing the isododecane. Thus 2 phases appear, the upper hydrocarbon phase containing the DI and a lower water-methanol phase. The latter is recycled at the bottom. The method makes it possible to reduce the quantity of DI to 0.17% by weight of the foot composition by selective elimination permitted by the capture of DI in the hydrocarbon, according to the invention. If the distillation is further pushed, the amount of DI is further reduced to 0.07% in the base composition. Example 4 Simple distillation of the mixture as in Example 3, without hydrocarbon in the Dean Stark

A mixture comprising TBH, DI, MeOH and water, with the following mass composition DI / Methanol / water / TBH 3.5% / 32.6% / 64.0% / 27.9% respectively, was distilled but without hydrocarbon in the Dean Stark. The condensed vapors were not recycled to the boiler. GC analysis of the distillation head at equilibrium indicates a composition DI / MeOH / water / TBH 48.2% / 36.5% / 10.7% / 4.6% (head temperature between 30, 4 ° C and 31 ° C and a pressure between 1 15 mbar and 1 19 miar). After 180 minutes, the analysis of the distillation bottom indicates a depletion in DI because it represents 2.1% for 28.9% of TBHP and 31.6% of methanol.

This experience shows that the process according to the invention implementing the distillation step a) makes it possible to recover DI with a satisfactory yield.

Claims

1. Process for the separation of an alkyl hydroperoxide from a dialkyl peroxide comprising at least one step a) of distillation of the composition comprising the alkyl hydroperoxide and said dialkyl peroxide in the presence of methanol and water .

2. Method according to claim 1, characterized in that the alkyl hydroperoxide is chosen from the group consisting of tert-butyl hydroperoxide, tert-amyl hydroperoxide, hexylene glycol hydroperoxide, l tert-octyl hydroperoxide, tert-hexyl hydroperoxide, 1-methyl-cyclopentyl hydroperoxide and 1-methyl-cyclohexyl hydroperoxide, preferably is chosen from the group consisting of tert-hydroperoxide butyl and tert-amyl hydroperoxide, still more preferably is tert-amyl hydroperoxide.

3. Method according to claim 1 or 2, characterized in that the dialkyl peroxide is chosen from the group consisting of ditertiobutyl, ditertioamyl peroxide, di-3-hydroxy-1, 1 -dimethylbutyl peroxide, peroxide di-tert-octyl, di-tert-hexyl peroxide, di (1-methyl-cyclopentyl) peroxide and di (1-methyl-cyclohexyl) peroxide, preferably is selected from the group consisting of ditertiobutyle and ditertioamyl peroxide, more preferably is ditertioamyl peroxide.

4. Method according to any one of the preceding claims, characterized in that the content by weight of methanol is greater by 5 times, preferably is greater by 10 times, preferably is greater by 25 times, and more preferably is greater by 30 times, to that of said dialkyl peroxide.

5. Method according to any one of the preceding claims, characterized in that the method also comprises at least one step b) of extraction using a dialkyl peroxide hydrocarbon.

6. Method according to claim 5, characterized in that step b) of extraction is carried out by bringing said hydrocarbon into contact with the condensate obtained in step a), so as to obtain an organic phase containing said hydrocarbon thus that all or part of the dialkyl peroxide and an aqueous phase containing the hydroperoxide, water and methanol.

7. Method according to claim 5 or 6, characterized in that the hydrocarbon is chosen from the group consisting of C ₆ to C 12 hydrocarbons, preferably C ₆ to C ₈ hydrocarbons _, preferably is a C hydrocarbon ₇ .

8. Method according to any one of the preceding claims, characterized in that the aqueous phase obtained in the distillation step is recycled to the distillation boiler.

9. Method according to any one of claims 5 to 8, characterized in that the organic phase of the condenser is distilled in order to separate the hydrocarbon (s) from the dialkyl peroxide.

10. Method according to any one of the preceding claims, characterized in that the distillation step a) is carried out at a temperature between 25 ° C and 60 ° C, preferably between 30 ° C and 45 ° C.

11. Method according to any one of the preceding claims, characterized in that the distillation step a) is carried out at a pressure of between 30 and 200 mbar (millibars), preferably between 40 and 180 mbar, and more preferably between 50 and 160 mbar.

12. Method according to any one of the preceding claims, characterized in that it comprises a step a ’), prior to step a), of synthesis of said alkyl hydroperoxide in an acid medium.

13. An alkyl hydroperoxide composition capable of being obtained by the process according to any one of the preceding claims.

14. Composition according to claim 13, comprising less than 1% by weight of methanol, preferably less than 1000 ppm, and even more preferably less than 100 ppm relative to the total weight of the composition.

15. Composition according to any one of claims 13 to 14, characterized in that the alkyl hydroperoxide comprises from 5 to 8 carbon atoms, preferably from 5 to 7, more preferably still is tert-amyl hydroperoxide.

16. Composition according to any one of claims 13 to 15, comprising less than 1000 ppm of dialkyl peroxide relative to the total weight of said composition, preferably less than 500 ppm of dialkyl peroxide, preferably less than 250 ppm, and more preferably less than 100 ppm of dialkyl peroxide.