Method for separating high-boiling carboxylic acid vinyl ester/carboxylic acid mixtures

Abstract

The invention relates to a method for separating a mixture containing at least one carboxylic acid vinyl ester of general formula RC(O)OCHCH.sub.2 and at least one carboxylic acid of general formula RCOOH, wherein R in either case can be an aliphatic group having 12 to 22 C atoms or a cycloaliphatic group having 12 to 22 C atoms, or an aromatic group having 12 to 22 C atoms, and R can be identical or different, characterized in that the carboxylic acid is converted to its anhydride RC(O)OC(O)R and the carboxylic acid vinyl ester is subsequently separated.

Claims

1. A process for separating a mixture comprising at least one vinyl carboxylate ester of general formula RC(O)OCHCH.sub.2 and at least one carboxylic acid of general formula RCOOH, wherein in each case R may be an aliphatic radical having 12 to 22 carbon atoms or a cycloaliphatic radical having 12 to 22 carbon atoms or an aromatic radical having 12 to 22 carbon atoms and R may be identical or different, said process comprising the steps of converting the carboxylic acid into its anhydride RC(O)OC(O)R and subsequently removing the vinyl carboxylate ester.

2. The process as claimed in claim 1, wherein the conversion of the carboxylic acid RCOOH into the corresponding anhydride RC(O)OC(O)R is effected by reaction with an anhydride of general formula R*C(O)OC(O)R*, wherein R* is identical or different and represents an aliphatic radical having 1 to 10 carbon atoms or a cycloaliphatic radical having up to 10 carbon atoms or an aromatic radical having up to 10 carbon atoms.

3. The process as claimed in claim 2, wherein 0.1 to 5 molar equivalents of the anhydride R*C(O)OC(O)R* relative to the carboxylic acid RCOOH are employed and the reaction is effected at temperatures of 0 C. to 150 C., at a pressure of 0.001 to 10 bar abs., and with a reaction time of up to 5 hours.

4. The process as claimed in claim 2, wherein the anhydride of general formula R*C(O)OC(O)R* employed is an anhydride selected from the group consisting of anhydrides of acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, 2-methylbutyric acid, 3-methylbutyric acid, pivalic acid, caproic acid, cyclohexanecarboxylic acid, n-heptanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, isononanoic acid, neononanoic acid, n-decanoic acid, and neodecanoic acid.

5. The process as claimed in claim 1, wherein the conversion of the carboxylic acid RCOOH into the corresponding anhydride RC(O)OC(O)R is effected by transition-metal-catalyzed reactive distillation with a vinyl carboxylate ester of general formula RC(O)OCHCH.sub.2, wherein R may be an aliphatic radical having 1 to 10 carbon atoms or a cycloaliphatic radical having up to 10 carbon atoms or an aromatic radical having up to 10 carbon atoms.

6. The process as claimed in claim 5, wherein the reactive distillation is performed in the presence of Ru compounds or Pd compounds as catalyst, with a molar ratio of vinyl carboxylate ester RC(O)OCHCH.sub.2 to carboxylic acid RCOOH of 1:1 to 40:1 and at a temperature of 100 C. to 180 C.

7. The process as claimed in claim 5, wherein the vinyl carboxylate ester RC(O)OCHCH.sub.2 employed is a vinyl carboxylate ester having an alkyl radical having 1 to 6 carbon atoms as radical R.

8. The process as claimed in claim 1, wherein the vinyl carboxylate ester is removed by distillation.

9. The process as claimed in claim 1, wherein the conversion of the carboxylic acid into its anhydride is preceded by a transvinylation of a carboxylic acid of general formula RCOOH with a vinyl carboxylate ester of general formula RC(O)OCHCH.sub.2.

10. The process as claimed in claim 9, wherein the transvinylation comprises a transvinylation of vinyl acetate with stearic acid and/or palmitic acid which is catalyzed with a ruthenium or palladium catalyst.

11. The process as claimed in claim 7, wherein the vinyl carboxylate ester is vinyl acetate.

Description

DETAILED DESCRIPTION

(1) Carboxylic acids which may be present in the mixture with the vinyl carboxylate ester are carboxylic acids of general formula RCOOH, wherein R may be an aliphatic radical having 12 to 22 carbon atoms or a cycloaliphatic radical having 12 to 22 carbon atoms or an aromatic radical having 12 to 22 carbon atoms. Carboxylic acids with different radicals R may also be present in the mixture. Examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid, naphtalenecarboxylic acid or mixtures thereof. Particular preference is given to fatty acids having 15 to 22 carbon atoms, such as palmitic acid and stearic acid and mixtures thereof.

(2) The mixture of carboxylic acid RCOOH and vinyl carboxylate ester RC(O)OCHCH.sub.2 may comprise further components, for example from a transvinylation reaction, such as catalysts, anhydrides, acids and polymeric constituents.

(3) The molar fraction x of the carboxylic acid RCOOH relative to the mixture of vinyl carboxylate ester RC(O)OCHCH.sub.2 and carboxylic acid RCOOH may be 0 mol %<x<100%, preference being given to a proportion of 0.01 mol %x50 mol %, particular preference being given to a ratio of 0.1 mol %x30 mol %.

(4) In a first preferred embodiment the conversion of the carboxylic acid RCOOH into the corresponding anhydride RC(O)OC(O)R is effected by reaction with an anhydride of general formula R*C(O)OC(O)R*, wherein R* is identical or different and represents an aliphatic radical having 1 to 10 carbon atoms or a cycloaliphatic radical having up to 10 carbon atoms or an aromatic radical having up to 10 carbon atoms. Examples thereof include the anhydrides of the acids: acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, 2-methylbutyric acid, 3-methylbutyric acid, pivalic acid, caproic acid, cyclohexanecarboxylic acid, n-heptanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, isononanoic acid, neononanoic acid, n-decanoic acid, neodecanoic acid. Preference is given to employing the anhydride of acetic acid (acetic anhydride).

(5) 0.1 to 5 molar equivalents of the anhydride R*C(O)OC(O)R* relative to the carboxylic acid RCOOH are employed. It is preferable when 0.25 to 3 molar equivalents of the anhydride are employed, particularly preferably 0.5 to 2 molar equivalents, in each case relative to the carboxylic acid RCOOH.

(6) The reaction of the mixture comprising a vinyl carboxylate ester RC(O)OCHCH.sub.2 and a carboxylic acid RCOOH with the anhydride R*C(O)OC(O)R* is generally effected at temperatures of 0 C. to 150 C., preferably at 30 C. to 120 C., particularly preferably at 50 C. to 100 C. The reaction time is generally up to 5 hours, preferably up to 2 hours, particularly preferably 5 to 60 minutes. The pressure at which the reaction is effected is generally 0.001 to 10 bar abs., preferably 0.1 to 2 bar, particular preference being given to operation at standard pressure (1 bar abs.).

(7) In a second preferred embodiment the conversion of the carboxylic acid RCOOH into its anhydride RC(O)OC(O)R may be effected by transition-metal-catalyzed reactive distillation with a vinyl carboxylate ester of general formula RC(O)OCHCH.sub.2, wherein R may be an aliphatic radical having 1 to 10 carbon atoms or a cycloaliphatic radical having up to 10 carbon atoms or an aromatic radical having up to 10 carbon atoms. Preference is given to using low molecular weight vinyl carboxylate esters, wherein R is an alkyl radical having 1 to 6 carbon atoms. Particular preference is given to using vinyl acetate.

(8) Preferred catalysts are Ru compounds or Pd compounds typically employed for transvinylation reactions. Suitable catalysts are known to a person skilled in the art, for example from WO 2011/139360 A1, WO 2011/139361 A1 and U.S. Pat. No. 4,981,973, the disclosure of which in this regard is hereby incorporated by reference. Preference is given to employing Ru compounds. Particular preference is given to using Ru acetate or an active Ru catalyst solution of the type known to a person skilled in the art from laid-open patent applications DE 102014206915 and DE 102014206916.

(9) The molar ratio of vinyl carboxylate ester RC(O)OCHCH.sub.2 to carboxylic acid RCOOH may be 1:1 to 40:1.

(10) Preference is given to a ratio of vinyl carboxylate ester to the carboxylic acid of 10:1 to 30:1, particular preference being given to a ratio of 15:1 to 25:1.

(11) The reactive distillation is generally performed at a temperature of 100 C. to 180 C., preferably at a temperature of 120 C. to 160 C. The pressure at which the reactive distillation is effected is generally 1 bar abs. The reaction is preferably performed in a protective gas atmosphere, for example nitrogen, in a manner known per se.

(12) The residence time in the reactor is generally 1 to 10 hours, preferably 3 to 8 hours.

(13) The reactor employed may be a bubble column or a continuous stirred tank. Preference is given to employing a continuous stirred tank.

(14) The reactive distillation to convert the carboxylic acid RCOOH into the corresponding anhydride RC(O)OC(O)R may be performed separately or in combination with a transvinylation reaction implemented in the form of a reactive distillation. In this case once the transvinylation reaction has been effected the reactive distillation is continued, and the carboxylic acid RCOOH thus converted into the corresponding anhydride RC(O)OC(O)R, until the content of residual carboxylic acid RCOOH in the reaction mixture is preferably not more than 5 wt %.

(15) In both preferred embodiments conversion of the carboxylic acid RCOOH into its anhydride RC(O)OC(O)R is followed by fractionation of the reaction mixture composed of vinyl carboxylate ester RC(O)OCHCH.sub.2 and the anhydride RC(O)OC(O)R.

(16) The mixture may optionally comprise further components such as catalysts, anhydrides, acids and polymeric constituents. The fractionation of the mixture is preferably effected by distillation. The pressure and temperature of the distillation and the configuration of the distillation columns depend on the components present in the product mixture and may be determined for example by means of routine tests performed by a person skilled in the art.

(17) The process according to the invention for separating a mixture comprising at least one vinyl carboxylate ester of general formula RC(O)OCHCH.sub.2 and at least one carboxylic acid of general formula RCOOH may be performed following a transvinylation of a carboxylic acid of general formula RCOOH with a vinyl ester of general formula RC(O)OCHCH.sub.2 and employed for fractionating the thus obtained reaction mixture. For example following a transvinylation of vinyl acetate with stearic acid and/or palmitic acid which is catalyzed with a ruthenium or palladium catalyst. The process conditions of a transvinylation are known to a person skilled in the art, for example from WO 92/09554 A1, WO 2011/139360 A1, WO 2011/139361 A1, WO 2013/117294 A1, WO 2013/117294 A1, DE 102013224491 and DE 102013224496, the disclosure of which in this regard is hereby incorporated by reference.

(18) The process according to the invention makes it possible to separate any desired mixtures of high-boiling vinyl carboxylate esters and high-boiling carboxylic acids. Conversion of the high-boiling carboxylic acid into the corresponding higher boiling carboxylic anhydride allows the vinyl carboxylate ester to be removed.

(19) It has been found that, surprisingly, the conversion of the high boiling carboxylic acid into the higher boiling carboxylic anhydride by reaction with a lower boiling anhydride can be achieved in simple fashion and with high selectivity.

(20) Surprisingly, conversion of the carboxylic acid into the higher boiling carboxylic anhydride by reactive distillation with a lower boiling vinyl carboxylate ester in the presence of a catalyst is also successful. A solid-liquid separation step which entails a great deal of process engineering complexity is not required. When the fractionation of the high-boiling vinyl carboxylate ester/carboxylic acid mixtures is performed in combination with a transvinylation reaction the obtained anhydride RC(O)OC(O)R of the carboxylic acid RCOOH can be directly reemployed in a transvinylation reaction without a further chemical process step being necessary beforehand.

(21) The process according to the invention makes high-boiling vinyl carboxylate esters and any desired mixtures thereof easily obtainable on a large-industrial scale.

EXAMPLES

(22) The examples which follow serve to more particularly elucidate the invention.

(23) The reported compositions of the reaction mixtures were determined by means of quantitative NMR spectroscopy.

Example 1

(24) Separation of a Vinyl Stearate/Stearic Acid Mixture by Addition of Acetic Anhydride

(25) A mixture of 35 g (113 mmol) of vinyl stearate (ABCR #AB123736) and 15 g (53 mmol) of stearic acid (Merck # 800673) was admixed with 8.1 g (79 mmol) of acetic anhydride (Aldrich # 110043) and stirred for 1 hour at 80 C. before excess acetic anhydride and the acetic acid formed were removed on a rotary evaporator. The mixture obtained thereafter was composed of 96.2 wt % vinyl stearate, 3.2 wt % stearic anhydride and 0.6 wt % stearic acid. Vacuum distillation at 100 C.-120 C. (0.02 mbar abs.) afforded the vinyl stearate in 99% purity.

(26) The example shows that addition of acetic anhydride converts the stearic acid into stearic anhydride and that vinyl stearate can be obtained in high purity via a subsequent vacuum distillation.

Example 2

(27) Separation of a Vinyl Stearate/Stearic Acid Mixture from a Transvinylation Reaction by Addition of Acetic Anhydride (in the Absence of Catalyst)

(28) In a 100 ml Berghoff autoclave 20.0 g (70 mmol) of stearic acid (Merck # 800673), 48.4 g (562 mmol) of vinyl acetate (Wacker Chemie AG), 0.068 g (0.3 mmol) of phenothiazine and 0.086 g (0.3 mmol) of [Ru.sub.3O(OAc).sub.6(H.sub.2O).sub.3]OAc (in the form of an acetic acid solution comprising 4.5 wt % Ru from Umicore) were heated to 140 C. for 4 hours at not more than 10.0 bar abs. Once cooled, acetic acid and vinyl acetate were removed on a rotary evaporator. Vinyl stearate and stearic acid were then distilled off at 154 C.-173 C. (1 mbar abs.).

(29) The obtained 18.5 g of a mixture of 94 wt % (17.4 g, 56 mmol) vinyl stearate and 6 wt % (1.1 g, 4 mmol) stearic acid were admixed with 0.59 g (6 mmol) of acetic anhydride (Aldrich # 110043) and stirred for 1 hour at 80 C. before excess acetic anhydride and the acetic acid formed were removed on a rotary evaporator. Renewed vacuum distillation at 173 C. (1 mbar abs.) afforded the vinyl stearate in 99.8% purity.

Example 3

(30) Separation of a Vinyl Stearate/Stearic Acid Mixture from a Transvinylation Reaction by Addition of Acetic Anhydride (in the Presence of Catalyst)

(31) In a 100 ml Berghoff autoclave 20.0 g (70 mmol) of stearic acid (Merck # 800673), 48.4 g (562 mmol) of vinyl acetate (Wacker Chemie AG), 0.068 g (0.3 mmol) of phenothiazine and 0.086 g (0.3 mmol) of [Ru.sub.3O(OAc).sub.6(H.sub.2O).sub.3]OAc (in the form of an acetic acid solution comprising 4.5 wt % Ru from Umicore) were heated to 140 C. for 4 hours at not more than 10.0 bar abs. Once cooled, acetic acid and vinyl acetate were removed on a rotary evaporator.

(32) The reaction mixture which comprised 19.2 g (62 mmol) of vinyl stearate and 1.56 g (5.5 mmol) of stearic acid was then admixed with 1.12 g (11 mmol) of acetic anhydride (Aldrich # 110043) and stirred for 1 hour at 80 C. before excess acetic anhydride and the acetic acid formed were removed on a rotary evaporator. Vacuum distillation at 105 C.-130 C. (0.07 mbar abs.) afforded the vinyl stearate in 99% purity.

Example 4

(33) Separation of a Vinyl Palmitate/Palmitic Acid Mixture from a Transvinylation Reaction by Reactive Distillation with Vinyl Acetate

(34) 220 g/h of a mixture of palmitic acid (Carl Roth #5907.2) and catalyst (active Ru catalyst solution based on RuCl.sub.3, as disclosed in DE 102014206915, 1000 ppm Ru relative to palmitic acid) and 27.7 l/min of gaseous vinyl acetate were introduced into a 2 l glass reactor equipped with a dip tube. Vinyl acetate and the acetic acid formed were discharged in gaseous form and condensed outside the reactor. The reaction was performed with a constant reactor fill volume of 1750 ml, an average residence time of 6.7 hours and at an internal reactor temperature of 140 C. A mixture composed of 76 wt % vinyl palmitate, 20 wt % palmitic anhydride and 4 wt % palmitic acid was obtained. Removal of the vinyl palmitate was effected via a vacuum distillation at 150 C. (1 mbar abs.).

Example 5

(35) Separation of a Vinyl Stearate/Stearic Acid Mixture from a Transvinylation Reaction by Reactive Distillation with Vinyl Acetate

(36) 225 g/h of a mixture of stearic acid (Carl Roth #9459.2) and catalyst (active Ru catalyst solution based on RuCl.sub.3, as disclosed in DE 102014206915, 1000 ppm Ru relative to stearic acid) and 25.5 l/min of gaseous vinyl acetate were introduced into a 2 l glass reactor equipped with a dip tube. Vinyl acetate and the acetic acid formed were discharged in gaseous form and condensed outside the reactor. The reaction was performed with a constant reactor fill volume of 1750 ml, an average residence time of 6.5 hours and at an internal reactor temperature of 140 C. A mixture composed of 79 wt % vinyl stearate, 18 wt % stearic anhydride and 3 wt % stearic acid was obtained. Removal of the vinyl stearate was effected via a vacuum distillation at 175 C. (1 mbar abs.).