WO2012085195A1

WO2012085195A1 - Environmental friendly purification of an organic solution of etfbo

Info

Publication number: WO2012085195A1
Application number: PCT/EP2011/073776
Authority: WO
Inventors: Max Josef Braun
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 2010-12-23
Filing date: 2011-12-22
Publication date: 2012-06-28
Anticipated expiration: 2013-06-23

Abstract

A process for the purification of an alkenone ether having the general formula (I): CF3-C(O)-C(H)=C(H)-OR wherein R is a C1-C4-alkyl group; or a C1-C4-alkyl group which is substituted by at least 1 halogen atom, aryl, substituted aryl,which comprises (a) subjecting a first fraction comprising said alkenone ether, water and optionally organic impurities to a liquid/vapour separation operation and (b) recovering from said liquid/vapour separation operation a fraction F containing purified alkenone ether, having reduced water content compared to the first fraction.

Description

Environmental friendly purification of an organic solution of ETFBO

The invention which claims priority to EP patent application

N° 10196814.7 filed on December 23, 2010 the whole content of which is incorporated herein by reference for all purposes relates to a process of purification of an organic solution of alkenone ethers, especially halogenated alkenone ethers.

Halogenated alkenone ethers, for example 4-ethoxy- l, l, l-trifluoro-3-buten-2-one ("ETFBO"), can be used as building blocks in chemical synthesis. They can be prepared for example by reacting an acid chloride with vinyl ether in the presence of a base.

In EP 0744400, the ETFBO is prepared by reacting an acid chloride with vinyl ether in the presence of a base, namely pyridine. According to the process described therein, the base can also be used in excess as solvent. This reference proposes that ETFBO can be isolated by distilling off other liquid components from the reaction solution ; however in the examples, said ethers are not isolated from the obtained organic solution but the said solution is immediately subjected to further reaction.

M.G. Gorbunova et al. (Synthesis 2000, No. 5, pages 738 - 742) disclose the preparation of a variety of halogenated alkenone ethers, having various fluoro-containing substituents of different length and branching, as well as a different number of fluorine atoms. Said ethers are isolated by distillation in yields varying from 40 to 83 %. However, there is no example describing either the preparation or the purification of ETFBO.

US 7,057,079 patent describes the synthesis of ETFBO in the presence of an "onium" salt of a carboxylic acid, in particular pyridinium-onium acetate. In some examples, the raw reaction mixture which contains dichloromethane added as a solvent was contacted with water. After phase separation, added

dichloromethane was distilled off and the remaining product was subjected to a fine distillation.

GB patent application 2305174 discloses an example wherein

(E)-4-ethoxy-l, 1, l-trifluoro-3buten-2-one is manufactured from trifluoroacetic anhydrided and ethyl vinyl ether. The resulting reaction mixture washed 3 times with water, and the organic layer was found to contain the butanone. It is further mentioned that ethyl vinyl ether was removed by atmospheric distillation. There is no indication about any potential presence of water in the reaction mixture or in view of any water content in the reaction mixture or the product after removal of ethyl vinyl ether.

It has been found a process whereby halogenated alkenone ethers in particular prepared from trifluoroacetic acid chloride can be isolated e.g. from reaction mixtures with high yield and purity.

It is thus an object of the invention to make available a process for the purification of an alkenone ether having the general formula (I) :

CF₃-C(0)-C(H)=C(H)-OR (I) wherein R is aryl ; substituted aryl ; a Ci-Cio-alkyl group ; or a Ci-Cio-alkyl group which is substituted by at least 1 halogen atom, aryl or substituted aryl, which comprises

(a) subjecting a first fraction comprising the said alkenone ether, water and optionally organic impurities to a liquid/vapour separation operation and

(b) recovering from said liquid/vapour separation operation a fraction Fl

containing purified alkenone ether, having reduced water content compared to the first fraction.

Brief description of the drawing

Figure 1 represents a plant which can be used for carrying out the purification process according to the invention. The plant includes two distillation columns (2) and (6).

Detailed description of the invention

A preferred process according to the invention concerns a process for the purification of an alkenone ether having the general formula (I) :

CF₃-C(0)-C(H)=C(H)-OR (I) wherein R is a Ci-Cio-alkyl group ; or a Ci-Cio-alkyl group which is substituted by at least 1 halogen atom, aryl, substituted aryl, which comprises

(b) recovering from said liquid/vapour separation operation a fraction Fl

Thus, to perform the process of the present invention, a first fraction is provided containing the said alkenone ether, water and optionally organic impurities, e.g. an intermediate product. In the process according to the invention, the alkenone ethers of formula (I) can be prepared by reacting an acid halide of the formula (II)

CF₃-C(0)X (Π), wherein X is F, CI or Br,

with a vinyl ether of the formula (III)

CH₂ = C(H)-OR (ΠΙ), wherein Ris as described above.

Advantageously, the alkenone ethers are those wherein R is a linear or branched Ci-C4-alkyl group, a Ci-C4-alkyl group which is substituted by at least 1 halogen atom, aryl, substituted aryl, for example, halogen- substituted phenyl. Particularly preferred, are alkenone ethers wherein R is a linear or branched Ci-C4-alkyl. More particularly preferred, are alkenone ethers wherein R is methyl, ethyl, n-propyl or i-propyl. Most particularly preferred, are alkenone ethers wherein R is ethyl.

X preferably denotes CI ; thus, CF₃C(0)C1 is the preferred acid halide.

If desired, the reaction of the acid halide with the vinyl ether optionally may be carried out in the presence of a base. If a base is used, it is

advantageously an organic base. The base to be used may, for example, be a nitrogen-containing heterocyclic compound such as pyridine, quinoline or picoline ; or a tertiary base such as trialkylamines, especially triethylamine ; dimethylaniline, diethylaniline or 4-dimethylaminopyridine. Among them, pyridine, triethylamine, dimethylaniline, diethylaniline or

4-dimethylaminopyridine are preferred. Among them, pyridine is particularly preferred. These bases may be used alone or in combination by providing them in the form of a mixture of, preferably, at least to organic bases. If appropriate, the base is used usually in an amount of from 1.0 to 3.0 equivalents, preferably from 1.05 to 1.5 equivalents, per mol carboxylic acid halide.

The reaction of the acid halide with the vinyl ether can be carried out in the presence of a solvent. Aprotic solvents are preferred. The solvent to be used may, for example, be an aromatic hydrocarbon such as benzene, toluene or xylene, an aliphatic hydrocarbon such as pentane or hexane ; a halogenated hydrocarbon such as a chlorinated hydrocarbon selected in particular from methylene chloride, chloroform or ethylene dichloride or a fluorinated hydrocarbon selected in particular from 1,1, 1,3,3-pentafluoropropane or, preferably 1,1, 1,3,3-pentafluorobutane ; or an ether such as diethyl ether, dibutyl ether or tetrahydrofuran. Among them, an aromatic hydrocarbon or a halogenated hydrocarbon is preferred. Particularly preferred among them, is methylene chloride, benzene or toluene. These solvents may be used alone or in combination in the form of a mixture of at least two of them. If appropriate, the solvent is used usually in an amount of from 1 to 35 parts by weight, preferably from 3 to 16 parts by weight, per part by weight of the carboxylic acid halide.

If the reaction mixture is a liquid under the reaction conditions, a solvent is not needed. If desired, starting compounds, reaction products and a base could be used as solvent.

In the process according to the invention, the first fraction which is subjected to the liquid/vapour separation operation can be drawn off directly from a reactor containing the reaction mixture or can be recovered from the reaction mixture according to a operation such as for example filtration, decantation, centrifugation and/or extraction of the reaction solution.

For the purpose of the present invention, the term "reaction mixture" refers to the mass contained in the reactor and includes the reaction solution as well as any liquid- or solid-phase substances not in solution.

For the purpose of the present invention, "the reaction solution" refers to the solution formed by the reactants (e.g. vinyl ethers, acid halides), the solvent, optionally a base and possibly one or more reaction products of the reactants.

If the reaction of the acid halide with the vinyl ether is carried out in the presence of a base, it is especially advantageous to recover the first fraction from the reaction mixture. Said reaction mixture can for instance contain salt byproducts which may be formed by reaction of the hydrogen halide obtained with the base. If the salt by-products are in a solid form, they may, prior to extraction, for example, be separated from the reaction mixture by filtration, decantation, centrifugation or membrane separation processes. Preferably, the extraction is performed by adding water to the reaction mixture containing the alkenone ether of the formula (I). If desired, in addition to water, an organic solvent may be used in combination, whereby the alkenone ether of the formula (I) can efficiently be recovered in the organic layer. The organic solvent which can be used in combination for extraction, may, for example, be an aromatic

hydrocarbon such as benzene, toluene or xylene ; a halogenated hydrocarbon such as a chlorinated hydrocarbon selected in particular from methylene chloride, chloroform or ethylene dichloride or a fluorinated hydrocarbon, preferably a hydrofluorocarbon with 3 to 5 carbon atoms and 4 to 6 fluorine atoms, selected in particular from 1,1, 1,3,3-pentafluoropropane or, preferably 1, 1,1,3,3-pentafluorobutane ; an ether such as diethyl ether or dibutyl ether ; or an acetate such as methyl acetate or ethyl acetate. Among them, an aromatic hydrocarbon or a fluorinated hydrocarbon is preferred. Particularly preferred among them is benzene, toluene, or 1, 1,1,3,3-pentafluorobutane.

If desired, the organic layer containing the alkenone ether of the formula (I) may be washed with water, optionally followed by drying to remove water. The drying is preferably carried out by using a drying agent such as anhydrous magnesium sulfate, anhydrous sodium sulfate or anhydrous calcium sulfate.

It has been found surprisingly that the process according to the invention can be performed without drying the organic solution. In consequence, the process of the present invention can be realized on industrial scale thereby avoiding the use of drying agents at industrial scale. Accordingly, in a preferred embodiment of the present invention, the organic solution is not subjected to a drying step, and the organic solution containing water is subjected to the inventive process. The water may, for example, be washing water, originate as impurity from starting materials or solvents, from any inert gases applied, or may be incorporated into the solution from atmospheric moisture.

The water content of the first fraction which is drawn off directly from the reactor is advantageously at least 1 ppm by weight of water, preferably at least 5 ppm by weight of water, more preferably at least 10 ppm by weight of water, most preferably at least 15 ppm by weight of water relative to the total weight of the first fraction. The water content of the first fraction which is drawn off directly from the reactor is advantageously at most 55 ppm by weight of water, preferably at most 50 ppm by weight of water, more preferably at most 45 ppm by weight of water, most preferably at most 40 ppm by weight of water relative to the total weight of the first fraction. Thus, the first fraction is drawn off directly from a reactor and may preferably contain a water content from 1 to 55 ppm by weight of water relative to the total weight of the first fraction.

The water content of the first fraction which is recovered from the reaction mixture after extraction of said reaction mixture with water as described above is advantageously at least 20 ppm by weight of water, preferably at least 30 ppm by weight of water, more preferably at least 40 ppm by weight of water, most preferably at least 50 ppm by weight of water relative to the total weight of the first fraction. The water content of the first fraction which is recovered from the reaction mixture after extraction of said reaction mixture with water is advantageously at most 2500 ppm by weight of water of first fraction, preferably at most 2000 ppm by weight of water, more preferably at most 1500 ppm by weight of water, most preferably at most 1000 ppm by weight of water relative to the total weight of the first fraction. Thus, the first fraction is recovered from the reaction mixture after extraction of said reaction mixture with water and preferably may have a water content from 20 to 2500 ppm by weight of water relative to the total weight of the first fraction.

It is assumed that in a first step, an addition product of CF₃-C(0)X and CH₂ = C(H)-OR is formed having the formula CF₃-C(0)CH₂ - C(H)(X)-OR. This intermediate product is not stable towards heat and/or base and splits off hydrogen halide (HX) to form the alkenone ether of formula (I). Sometimes, the dehydrohalogenation reaction is not 100 % complete, and some intermediate product is present in the reaction mixture. Accordingly, in another embodiment, the first fraction further comprises a halogenated precursor of the alkenone ether, in particular CETFBO. The first fraction generally contains at least 0.5 % by weight, preferably at least 1 % by weight of the halogenated precursor of the alkenone ether to the total weight of the reaction medium. The first fraction generally contains less than 7 % by weight, preferably less than 4 % by weight of the halogenated precursor of the alkenone ether to the total weight of the reaction medium. Preferably, the first fraction contains 1 to 7 % by weight of the halogenated precursor of the alkenone ether to the total weight of the reaction medium.

For the purpose of the invention, the term "liquid/vapour separation operation" is intended to denote in particular an operation whereby a liquid phase is separated from a vapour phase.

The liquid/vapour separation operation can be performed by a variety of separation techniques comprising, for example, distillation techniques such as batch, continuous, vacuum, fractional, steam and azeotropic distillations, evaporations, and stripping.

The liquid/vapour separation operation is preferably performed by distillation.

The distillation is preferably a fractional distillation.

The distillation columns which can be used in the process according to the invention are known per se. Use may be made, for example, of conventional plate columns or plate columns of dual-flow type or alternatively of columns with bulk or structured packing.

The distillation column is advantageously provided with associated auxiliary equipment such as for example at least one reboiler, at least one condenser and a device for returning a portion of the resultant condensate to the top of the column as reflux.

In a first preferred embodiment of the present invention, the liquid/vapour separation operation comprises at least two distillation steps wherein (a) the first fraction is subjected to a first distillation step (step Dl) wherein a low boiling fraction comprising water is separated and a fraction Fl containing purified alkenone ether having reduced water content compared to the first fraction is recovered (b) at least part of the fraction Fl from step (a) is supplied to a second distillation step (step D2) wherein high boiling impurities are separated from fraction Fl and a fraction F2 containing purified alkenone ether having a reduced content of high boiling impurities compared to fraction Fl is recovered (c) optionally, fraction F2 is further purified in a third distillation step (step D3).

For the purpose of the present invention, "a low boiling fraction" is understood to denote in particular a fraction exhibiting, at the pressure of the distillation in the presence of the alkenone ether, a boiling point lower than the boiling point of the alkenone ether. The term "high-boiling impurity" is understood to denote an impurity exhibiting, at the pressure of the distillation in the presence of the alkenone ether, a boiling point greater than the boiling point of the alkenone ether.

In the process according to the invention, at least one distillation step is a fractional distillation.

Each of the distillation steps can be carried out in one or more distillation columns. Use will preferably be made of a single distillation column per distillation step.

In a particular aspect of the first embodiment of the process according to the invention, (a) step Dl advantageously consists in the separation of the first fraction inside a first distillation column into two different fractions, namely a low boiling fraction comprising water which leaves at the top of the first distillation column and a fraction Fl containing purified alkenone ether having reduced water content compared to the first fraction which leaves at the bottom of first distillation column, (b) Step D2 advantageously consists in the separation of at least part of the fraction Fl (fraction Fla) drawn off from the bottom of the first distillation column inside a second distillation column into two different fractions, namely the fraction F2 containing purified alkenone ether having a reduced content of high boiling impurities compared to the fraction Fl which leaves at the top of the second distillation column and high boiling impurities which leave at the bottom of second distillation column, (c) Step D3 advantageously consists in a further purification of at least part of the fraction F2 drawn off from the top of the second distillation column by passing said fraction F2 through a third distillation column. The purified alkenone ether having higher purity compared to the fraction F2 leaves advantageously at the top of the third distillation column.

The abovementioned step Dl is advantageously performed at a pressure of at least 100 mbar preferably of at least 110 mbar and in a particularly preferred manner of at least 115 mbar at the top of the first distillation column. Step Dl is advantageously performed at a pressure of at most 135 mbar, preferably of at most 130 mbar and in a particularly preferred manner of at most 125 mbar at the top of the first distillation column. The pressure is most preferred at 120 mbar at the top of the first distillation column.

Step Dl is advantageously performed at a pressure of at least 125 mbar preferably of at least 130 mbar and in a particularly preferred manner of at least 135 mbar at the bottom of the first distillation column. Step Dl is advantageously performed at a pressure of at most 155 mbar, preferably of at most 150 mbar and in a particularly preferred manner of at most 145 mbar at the bottom of the first distillation column. The pressure is most preferred at 140 mbar at the bottom of the first distillation column.

Thus, preferably, the pressure is from 100 to 135 mbar at the top of the first distillation column and from 125 to 155 mbar at the bottom of the first distillation column

The abovementioned step D2 is advantageously performed at a pressure of at least 60 mbar preferably of at least 65 mbar and in a particularly preferred manner of at least 70 mbar at the top of the second distillation column. Step D2 is advantageously performed at a pressure of at most 90 mbar, preferably of at most 85 mbar and in a particularly preferred manner of at most 80 mbar at the top of the second distillation column. The pressure is most preferred at 75 mbar at the top of the second distillation column.

Step D2 is advantageously performed at a pressure of at least 80 mbar preferably of at least 85 mbar and in a particularly preferred manner of at least 90 mbar at the bottom of the second distillation column. Step D2 is advantageously performed at a pressure of at most 115 mbar, preferably of at most 110 mbar and in a particularly preferred manner of at most 105 mbar at the bottom of the second distillation column. The pressure is most preferred at 100 mbar at the bottom of the second distillation column.

Thus, preferably the pressure is from 60 to 90 mbar at the top of the second distillation column and from 80 to 115 mbar at the bottom of the second distillation column.

The temperature at which step Dl is performed is advantageously at least 30°C, preferably at least 35°C and in a particularly preferred manner at least 38°C at the top of the first distillation column. It is advantageously at most 50°C, preferably at most 45°C and in a particularly preferred manner at most 42°C at the top of the first distillation column. The temperature is most preferred at 40°C at the top of the first distillation column.

The temperature at which step Dl is performed is advantageously at least 85°C, preferably at least 90°C and in a particularly preferred manner at least 95°C at the bottom of the first distillation column. It is advantageously at most 110°C, preferably at most 105°C and in a particularly preferred manner at most 102°C at the bottom of the first distillation column. The temperature is most preferred at 99°C at the bottom of the first distillation column.

Thus, preferably, the temperature is from 30 to 50°C at the top of the first distillation column and from 85 to 110°C at the bottom of the first distillation column.

The temperature at which step D2 is performed is advantageously at least 35°C, preferably at least 40°C and in a particularly preferred manner at least 43°C at the top of the second distillation column. It is advantageously at most 55°C, preferably at most 50°C and in a particularly preferred manner at most 47°C at the top of the second distillation column. The temperature is most preferred at 45°C at the top of the second distillation column.

The temperature at which step D2 is performed is advantageously at least 100°C, preferably at least 105°C and in a particularly preferred manner at least 110°C at the bottom of the second distillation column. It is advantageously at most 125°C, preferably at most 120°C and in a particularly preferred manner at most 115°C at the bottom of the second distillation column. The temperature is most preferred at 112°C at the bottom of the second distillation column. Thus, preferably, the temperature is from 35 to 55°C at the top of the second distillation column and from 100 to 125°C at the bottom of the second distillation column.

The number of theoretical plates in step Dl is generally at least 4. It is often at least 8. A number of at least 12 gives good results.

The number of theoretical plates in step D2 is generally at least 4. It is often at least 8. A number of at least 12 gives good results.

The first fraction is advantageously fed to the first distillation column at a feed point intermediate between the bottom and the top of the distillation column. At least part of the fraction Fl (fraction Fla) is advantageously fed to the second distillation column at a feed point two third of the bottom of the distillation column. The fraction F2 is advantageously fed to the third distillation column at the bottom of the distillation column.

If desired, fraction Fla can be subjected to a thermolysis treatment selected from a flash thermolysis, a vacuum thermolysis and a thermolysis under stripping with an inert gas prior to being fed to the second distillation column.

For the purpose of the present invention, the term "flash thermolysis" refers to a process wherein the liquid reaction medium is heated up in a short time. Typical heating times for flash thermolysis are less than 1 hour, in particular less than 30 min, preferably about 15 minutes. Generally, the heating time is greater than Is, often greater than 15s.

In particular aspects of the process according to this embodiment, the flash thermolysis is conducted at a temperature ranging from -20°C to 140°C and a period of time ranging from 30 seconds to 1 hour, preferably at a temperature ranging from 0°C to 130°C and a period of time ranging from 30 seconds to 30 min, more preferably at a temperature ranging from 20°C to 120°C and a period of time ranging from 30 seconds to 20 min.

The thermolysis or flash thermolysis can be optionally carried out under stripping with an inert gas stream such as nitrogen gas, argon gas.

For the purpose of the present invention, the term "stripping" denotes in particular a physical separation process where in one or more components, in particular HC1, are removed from the liquid reaction medium by a gas stream. The liquid and gas streams can have concurrent or countercurrent flow directions. If appropriate, the stripping is advantageously carried out with a nitrogen stream. The nitrogen stream preferably is passed through the liquid to be stripped.

The process according to this embodiment, generally comprises carrying out the thermolysis at a temperature of -20°C to 140°C, preferably from 60 to 130°C, for example at equal to or about 80°C and more preferably at equal to or about 120°C.

The thermolysis or flash thermolysis may be carried out under vacuum. In that case, the vacuum is preferably from 100 to 600 mbar.

This embodiment is particular suitable when fraction Fla contains the halogenated precursor of the alkenone ether. The thermolysis or flash thermolysis allows the conversion of said precursor into the alkenone ether.

The low boiling fraction which leaves at the top of the first distillation column comprises, besides water, organic compounds such as, for example, solvent, ethanol, diethylether, trifluorobutyrate, trifluoroacetic halides, trifluoroacetic acids, vinyl ethers, chloroethers ; gaseous compounds such as hydrogen halides, oxygen and nitrogen.

The high boiling fraction which leaves at the bottom of the second distillation column comprises organic compounds such as, for example, dimers, oligomers, all reactions with reactive intermediate for instance reaction of trifluorobutyrate with ethanol and many more reactions.

The low boiling fraction generally contains at least 20 ppm by weight of water, preferably at least 30 ppm by weight of water, more preferably at least 40 ppm by weight of water, most preferably at least 50 ppm by weight of water relative to the total weight of the low boiling fraction. The low boiling fraction generally contains at most 5000 ppm by weight of water, preferably at most 4000 ppm by weight of water, more preferably at most 2500 ppm by weight of water, most preferably at most 1500 ppm by weight of water relative to the total weight of the low boiling fraction. Thus, preferably, the water content of the low boiling fraction is from 20 to 5000 ppm by weight of water relative to the total weight of the low boiling fraction.

Fraction Fl generally contains at least 1 ppm by weight of water, preferably at least 5 ppm by weight of water, more preferably at least 10 ppm by weight of water, most preferably at least 15 ppm by weight of water relative to the total weight of Fraction Fl . Fraction Fl generally contains at most 1500 ppm by weight of water, preferably at most 1000 ppm by weight of water, more preferably at most 800 ppm by weight of water, most preferably at most 500 ppm by weight of water relative to the total weight of Fraction F 1. Thus, preferably, the water content of fraction Fl is from 1 to 1500 ppm by weight of water relative to the total weight of the low boiling fraction.

The purity of the purified alkenone ether in fraction Fl obtained according to the process of the invention is generally equal to or greater than 90 % wt.

Often this purity is equal to or greater than 93 % wt. Preferably, it is equal to or greater than 96 % wt.

The purity of the purified alkenone ether in fraction F2 obtained according to the process of the invention is generally equal to or greater than 97 % wt.

Often this purity is equal to or greater than 98 % wt. Preferably, it is equal to or greater than 99.5 % wt.

In a second less preferred embodiment of the present invention, the liquid/vapour separation operation comprises at least three distillation steps wherein (a) the first fraction is subjected to a first distillation step (step Dl ') wherein a fraction FT comprising purified alkenone ether and water is recovered and high boiling impurities are separated from the first fraction (b) at least part of fraction Fl '(fraction F' la) from step (a) is supplied to a second distillation step (step D2') wherein a low boiling fraction comprising water is separated and a fraction F2' containing purified alkenone ether having reduced water content compared to the fraction FT is recovered (c) fraction F2' is further purified in a third distillation step (step D3').

It is understood that the different processes and embodiments disclosed herein apply in most preferred way to the purification of

trifluoroalkoxybutenones wherein first chlorotrifluoroalkoxybutanone is formed from alkyl-vinylether and trifluoroacetic acid halide, in particular from ethyl vinyl ether and trifluoroacetyl chloride, followed by elimination of hydrogen halide to form trifluoroalkoxybutenone, in particular ETFBO.

It has been found, surprisingly, that the process according to the invention makes it possible to isolate ETFBO with very high yield and very pure from reaction mixtures comprising water and high boiling impurities.

FIG. 1 represents a diagram of a plant which can be used for carrying out the process for the purification of an alkenone ether according to the invention.

The numbers refer to FIG. 1. The first fraction comprising the said alkenone ether, water and optionally organic impurities is introduced via route (1) into a first distillation column (2). At the top (3) of this column (2), a low boiling fraction comprising water is obtained. At the bottom (4) of this column (2), a fraction Fl is obtained comprising purified alkenone ether having reduced water content compared to the first fraction, which fraction is introduced via route (5) into the second distillation column (6). At the bottom (7) of the second column (6), a fraction is recovered which is enriched in high boiling impurities. At the top (8) of the second column (6), purified alkenone ether having a reduced content of high boiling impurities compared to the fraction Fl is obtained.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

EXAMPLES

The following examples are intended to illustrate the invention in further detail without limiting its scope.

Abbreviations :

ETFBO = 4-ethoxy- 1, 1, 1 -trifluoro-3-buten-2-one

Example 1 : 31.7 g (0.44 mol) of ethyl vinyl ether and 52.2 g (0.66 mol) of pyridine were dissolved in 300 ml of methylene chloride. 87.6 g (0.66 mol) of trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 30°C. The mixture was further stirred at room

temperature for 1.5 hours. Then, 200 ml of ice water was added to the reaction solution. The organic layer was washed with water and a saturated sodium chloride aqueous solution and then dried with of sodium sulfate. The collected organic layer was then rotary evaporated at atmospheric pressure at 60°C to remove volatile methylene chloride. The residue obtained was further distilled in rotavap under vacuum (10 mbar) at 85°C to give 60.1 g of a clear solution containing 98.8 % trans-ETFBO and 1.2 % cis-ETFBO. Yield : 81 %

Example 2 : 31.7 g (0.44 mol) of ethyl vinyl ether and 52.2 g (0.66 mol) of pyridine were dissolved in 300 ml of methylene chloride. 87.6 g (0.66 mol) of trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 30°C. The mixture was further stirred at room

temperature for 1.5 hours. The water content of the reaction mixture was determined by the Karl Fischer method (17 ± 5 ppm). Then, 200 ml of ice water was added to the reaction solution. The organic layer was washed with water and a saturated sodium chloride aqueous solution. The water content of the organic layer was determined by the Karl Fischer method (825 ± 5 ppm). The organic layer was then dried with sodium sulfate and the water content was determined by the Karl Fischer method (294 ± 5 ppm).

Example 3 : 31.7 g (0.44 mol) of ethyl vinyl ether and 52.2 g (0.66 mol) of pyridine were dissolved in 300 ml of methylene chloride. 87.6 g (0.66 mol) of trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 30°C. The mixture was further stirred at room

temperature for 1.5 hours. The reaction mixture was then rotary evaporated at atmospheric pressure at 60°C to remove volatile methylene chloride. The residue obtained was further distilled in rotavap under vacuum (10 mbar) at 85°C to give an orange colored solution containing 88 % ETFBO and 9.6 % pyridine (GC analysis). The latter solution was further distilled over a fractional distillation column under vacuum (10 mbar). 49.2 g of a strong yellow colored solution was collected having a boiling temperature of 44°C at the top of the column. This solution was containing 98.5 % trans-ETFBO and 1.1 % cis-ETFBO (GC Analysis). Yield : 66 %.

Example 4 : 31.7 g (0.44 mol) of ethyl vinyl ether and 52.2 g (0.66 mol) of pyridine were dissolved in 300 ml of methylene chloride. 87.6 g (0.66 mol) of trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 30°C. The mixture was further stirred at room

temperature for 1.5 hours. Then, 200 m 1 of ice water was added to the reaction solution. The organic layer was washed with water and a saturated sodium chloride aqueous solution and then dried with of sodium sulfate. The water content of the organic layer was determined by GC measurements (surface area of the water peak relative to the total surface area is 0.26 %). The organic layer was then rotary evaporated at atmospheric pressure at 60°C to remove volatile methylene chloride. The water content of the volatile fraction was determined by GC measurements (surface area of the water peak relative to the total surface area is 0.31 %). The residue obtained was further distilled in rotavap under vacuum (10 mbar) at 85°C to give 58.0 g of a clear solution containing 98.7 % trans-ETFBO and 0.9 % cis-ETFBO (yield : 78.4 %). The water content of the clear solution was determined by GC measurements (surface area of the water peak relative to the total surface area is 0.05 %).

Example 5 : 30.3 g (0.42 mol) of ethyl vinyl ether and 36.4 g (0.46 mol) of pyridine were dissolved in 300 ml of toluene. 60.9 g (0.46 mol) of

trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 11°C by ice cooling. The mixture was further stirred at room temperature for 2.5 hours. Then, 200 ml of ice water was added to the reaction solution. The organic layer was washed with water and a saturated sodium chloride aqueous solution and then dried with sodium sulfate. The collected organic layer was then subjected to a fractional distillation. The different fractions were analysed by GC analysis. The experimental data are summarized in Table 1.

Table 1

Example 6 : 15.1 g (0.21 mol) of ethyl vinyl ether and 18.2 g (0.23 mol) of pyridine were dissolved in 150 ml of toluene. 30.4 g (0.23 mol) of

trifluoroacetyl chloride was blown under stirring into this solution while keeping the temperature under 11°C by ice cooling. The mixture was further stirred at room temperature for 2.5 hours. The water content of the reaction mixture was determined by the Karl Fischer method (22 ± 5 ppm). Then, 200 m 1 of ice water was added to the reaction solution. The organic layer was washed with water and a saturated sodium chloride aqueous solution. The water content of the organic layer was determined by the Karl Fischer method (60 ± 5 ppm). The organic layer was then dried with sodium sulfate and the water content was determined by the Karl Fischer method (41 ± 5 ppm).

Example 7 : Manufacture of ETFBO using two distillation columns for fractionation

Example 6 is repeated. After washing the organic layer with water, the organic layer was distilled in an apparatus comprising two columns. The pressure at the top of the first column is approximately 120 mbar, the pressure at the bottom of the first column is approximately 140 mbar. The bottoms of the first column are fed into the second column. In the second column, the pressure at the top is approximately 75 mbar and approximately 100 mbar at the top of the column. Highly purified product with reduced water content is obtained on the top of the second column.

Claims

C L A I M S

1. A process for the purification of an alkenone ether having the general formula (I) :

CF₃-C(0)-C(H)=C(H)-OR I) wherein R is aryl ; substituted aryl ; a Cl-C4-alkyl group ; or a Cl-C4-alkyl group which is substituted by at least 1 halogen atom, aryl or substituted aryl, which comprises

(a) subjecting a first fraction comprising said alkenone ether, water and

optionally organic impurities to a liquid/vapour separation operation and

(b) recovering from said liquid/vapour separation operation a fraction F

2. The process according to Claim 1, wherein R is methyl, ethyl, n- propyl or isopropyl, preferably ethyl.

3. The process according to Claim 1 or 2 wherein the first fraction is drawn off directly from a reactor and has a water content from 1 to 55 ppm by weight of water relative to the total weight of the first fraction.

4. The process according to Claim 1 or 2 wherein the first fraction is recovered from the reaction mixture after extraction of said reaction mixture with water and has a water content from 20 to 2500 ppm by weight of water relative to the total weight of the first fraction.

5. The process according to Claim 1 or 2, wherein the liquid/vapour separation operation comprises at least two distillation steps wherein (a) the first fraction is subjected to a first distillation step (Dl) wherein a low boiling fraction enriched in water is separated and a fraction Fl containing purified alkenone ether having reduced water content compared to the first fraction is recovered (b) at least part of the fraction Fl (fraction F la) from step (a) is supplied to a second distillation step (D2) wherein high boiling impurities are separated from the fraction F la and a fraction F2 containing purified alkenone ether having a reduced content of high boiling impurities compared to the fraction Fl is recovered (c) optionally, at least part of the fraction F2 is further purified in a third distillation step (D3).

6. The process according to Claim 5, wherein the water content of the low boiling fraction is from 20 to 5000 ppm by weight of water relative to the total weight of the low boiling fraction.

7. The process according to Claim 5, wherein the water content of fraction Fl is from 1 to 1500 ppm by weight of water relative to the total weight of the low boiling fraction.

8. The process according to Claim 5, wherein at least one distillation step is a fractional distillation.

9. The process according to Claim 5, wherein each distillation step is carried out in one or more distillation columns.

10. The process according to Claim 9, wherein each distillation step is carried out in one distillation column.

11. The process according to claim 10, wherein

(a) Step Dl consists in the separation of the first fraction inside a first

distillation column into two different fractions, a low boiling fraction comprising water which leaves at the top of the first distillation column and a fraction Fl containing purified alkenone ether having reduced water content compared to the first fraction which leaves at the bottom of first distillation column, and

(b) Step D2 consists in the separation of at least part of the fraction Fl

(fraction F la) inside a second distillation column into two different fractions, the fraction F2 containing purified alkenone ether having a reduced content of high boiling impurities compared to the fraction Fl which leaves at the top of the second distillation column and high boiling impurities which leave at the bottom of second distillation column.

12. The process according to claim 11, wherein the pressure is from 100 to 135 mbar at the top of the first distillation column and from 125 to 155 mbar at the bottom of the first distillation column.

13. The process according to claim 11, wherein the pressure is from 60 to 90 mbar at the top of the second distillation column and from 80 to 115 mbar at the bottom of the second distillation column.

14. The process according to claim 11 or 12, wherein the temperature is from 30 to 50°C at the top of the first distillation column and from 85 to 110°C at the bottom of the first distillation column.

15. The process according to claim 11 or 12, wherein the temperature is from 35 to 55 °C at the top of the second distillation column and from 100 to 125°C at the bottom of the second distillation column.

16. The process according to any one of claims 5 to 15, wherein the purity of the purified alkenone ether in fraction Fl is greater than 90 % wt.

17. The process according to any one of claims 5 to 15, wherein the purity of the purified alkenone ether in fraction F2 is greater than 97 % wt.