Process for preparing a carboxylic acid

Abstract

A process for preparing a carboxylic acid, including a step of bringing at least one vicinal diol or at least one vicinal polyol into contact with an atmosphere including oxygen, and a catalyst, and in the absence of additional solvent.

Claims

1. A process for preparing carboxylic acid comprising a step of placing at least one vicinal diol or at least one vicinal polyol in contact with an atmosphere comprising oxygen, a catalyst and in the absence of additional solvent, the catalyst having the formula I below:
[Al.sub.nSi.sub.mO.sub.pM.sub.q][A].sub.r  (I) wherein: n, m and q are natural integers (), which may be identical or different, chosen, independently of each other, such that n, m and q may simultaneously be equal to 0; p is a nonzero natural integer (*); r is zero or 1; M corresponds to at least one chemical element chosen from zirconium, tungsten, titanium and rare-earth metals, and A corresponds to at least one chemical element chosen from alkaline-earth metals, alkali metals, rare-earth metals and titanium; wherein the catalyst is one of the following catalysts: Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, and ZrO.sub.2.

2. The process according to claim 1, wherein the catalyst has a specific surface area of from 50 to 200 m.sup.2/g.

3. The process according to claim 1, comprising a prior step of hydroxylation of an olefin or of hydrolysis of an epoxide.

4. The process according to claim 1, wherein the at least vicinal diol or the at least vicinal polyol is derived from a plant oil.

5. The process according to claim 3, wherein the olefin is a fatty acid or a fatty acid ester bearing a carbon-based chain of 10 to 30 carbon atoms.

6. The process according to claim 5, wherein the fatty acid or the fatty acid ester is chosen from the group consisting of myristoleic acid, palmitoleic acid, oleic acid, ricinoleic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, di-homo-γ-linolenic acid, arachidonic acid, timnodonic acid, and cervonic acid.

7. The process according to claim 1, wherein the at least vicinal diol is methyl 9,10-dihydroxystearate.

8. The process according to claim 1, wherein the carboxylic acid is a monocarboxylic acid or a dicarboxylic acid, or a mixture thereof.

9. The process according to claim 1, wherein the carboxylic acid obtained from the process is a mixture of pelargonic acid and azelaic acid.

10. The process according to claim 1, wherein the reaction step is performed at a pressure from 1 to 40 bar.

11. The process according to claim 1, wherein a mole ratio between dioxygen and said at least one vicinal diol or said at least one vicinal polyol is from 0.6 to 3.5 equivalents.

12. The process according to claim 2, wherein the catalyst has a specific surface area of 150 m.sup.2/g.

13. The process according to claim 3, wherein the olefin is derived from a plant oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention will be understood more clearly on reading the examples, which do not have any limiting nature.

EXAMPLES

Example 1: Preparation of an Alumina or Silica Catalyst According to the Invention: Example of Calcined Catalyst

(2) Alumina or silica (20 g), in powder form, is calcined for 3 hours up to 550° C., with a temperature increase of the order of 2° C. per minute. The calcined alumina or silica is then stored in a desiccator so as to protect it from moisture.

Example 2: Process for Esterifying and Purifying Methyl 9,10-Dihydroxystearate

(3) The starting methyl 9,10-dihydroxystearate has a purity ranging from 60%-70%.

(4) An amount of 30 g of methyl 9,10-dihydroxystearate, i.e. 90 mM, is placed in contact with 400 mL of pentane. The mixture is stirred for 2 hours at room temperature.

(5) The solvent is then removed by filtration and the precipitate is dried under vacuum. 25 g of a precipitate are recovered, i.e. 83% by weight of the mixture.

(6) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(7) To this end, the precipitate is placed in contact with methanol (200 mL) and Amberlyst 15 (10% by weight) and refluxed overnight at 80° C.

(8) The resin thus obtained is removed by filtration and the filtrate is evaporated under vacuum.

(9) The precipitate is finally recrystallized from hot in the methanol.

(10) 17 g of 9,10DHSM are obtained (57% yield) in a purity of greater than 98% (analysis by NMR and GC).

Example 3: Reactivity of Methyl 9,10-Dihydroxystearate in Oxidizing Medium in the Absence of Catalyst: Control

(11) An amount of 9.5 g (equivalent to 28.8 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with mechanical stirring.

(12) The reaction is performed at 140° C. for 15 hours under 8 bar of air according to the following reaction scheme:

(13) ##STR00001##

(14) After cooling to room temperature, an orange oil is obtained corresponding to 95% by weight of the initial mixture.

(15) The reaction medium is analyzed by gas chromatography after dissolution in methanol.

(16) A mixture of methyl 9 and/or 10-oxostearate is obtained after identification by mass spectrometry and proton and carbon nuclear magnetic resonance.

(17) In the absence of catalyst, no oxidative cleavage is observed, but transformation (rearrangement) of the diol into ketone is observed: this is an isophysical reaction without any change in the degree of oxidation.

Example 4: Oxidative Cleavage of Methyl 9,10-Dihydroxystearate According to the Process of the Invention

(18) The oxidative cleavage reaction of the process according to the invention was performed, according to the following reaction scheme, under various conditions of amount of substrate, of calcined or non-calcined catalyst and of reaction times:

(19) ##STR00002##

(20) a) In the presence of calcined basic alumina: 2 g of DHSM

(21) a1) Oxidative cleavage

(22) An amount of 2 g (equivalent to 6.06 mmol) of methyl 9,10-dihydroxystearate (DHSM) is placed in a 300 mL autoclave with magnetic stirring, in the presence of calcined alumina oxide (i.e. 5% by weight of the mixture). The mixture is maintained at 140° C. for 16 hours under 8 bar of air (mole O.sub.2=20 mmol), the reaction takes place according to step 1) of the above reaction scheme.

(23) The mixture is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(24) a2) Esterification

(25) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(26) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered, step 2) of the above reaction scheme. Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(27) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(28) The crude product is analyzed by gas chromatography and by NMR.

(29) A mixture of methyl pelargonate (PM) and dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 64/36.

(30) The DHSM conversion is 100%.

(31) b) In the presence of calcined basic alumina: 12 g of DHSM

(32) b1) Oxidative cleavage

(33) An amount of 12 g (equivalent to 36.4 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with mechanical stirring, in the presence of calcined alumina oxide (5% by weight).

(34) The mixture is maintained at 140° C. for 16 hours under 8 bar of air (mole O.sub.2=20 mmol), the reaction takes place according to step 1) of the above reaction scheme.

(35) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(36) b2) Esterification

(37) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(38) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered, step 2) of the preceding reaction scheme. Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(39) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(40) The crude product is analyzed by gas chromatography and by NMR.

(41) A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 65/35.

(42) The DHSM conversion is 64%.

(43) c2) In the presence of non-calcined basic alumina—24 h

(44) c1) Oxidative cleavage

(45) An amount of 2 g (equivalent to 6.06 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with magnetic stirring, in the presence of non-calcined alumina oxide (5% by weight). The mixture is maintained at 140° C. for 24 hours under 8 bar of air (mole O.sub.2=20 mmol), the reaction takes place according to step 1) of the above reaction scheme.

(46) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (93% by weight).

(47) c2) Esterification

(48) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(49) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered (step 2) of the preceding reaction process). Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(50) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(51) The crude product is analyzed by gas chromatography and by NMR.

(52) A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 63/37.

(53) The DHSM conversion is 100%.

(54) d) In the presence of calcined basic alumina—5 h

(55) d1) Oxidative cleavage

(56) An amount of 2 g (equivalent to 6.06 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with magnetic stirring, in the presence of calcined alumina oxide (5% by weight).

(57) The mixture is maintained at 140° C. for 5 hours under 8 bar of air (mole O.sub.2=20 mmol), and the reaction takes place according to step 1) of the above reaction scheme.

(58) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (92% by weight).

(59) d2) Esterification

(60) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(61) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered (step 2) of the preceding reaction scheme). Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(62) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(63) The crude product is analyzed by gas chromatography and by NMR.

(64) A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 50/50.

(65) The DHSM conversion is 100%.

(66) e) In the presence of non-calcined neutral alumina—5 h

(67) e1) Oxidative cleavage

(68) An amount of 2 g (equivalent to 6.06 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with mechanical stirring, in the presence of non-calcined neutral alumina oxide (5% by weight).

(69) The mixture is maintained at 140° C. for 5 hours under 8 bar of air (mole O.sub.2=20 mmol), and the reaction takes place according to step 1) of the above reaction scheme.

(70) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(71) e2) Esterification

(72) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(73) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered, step 2) of the preceding reaction scheme. Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(74) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(75) The crude product is analyzed by gas chromatography and by NMR.

(76) A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 65/35.

(77) The DHSM conversion is 64%.

(78) f) In the presence of calcined basic alumina—5 h

(79) f1) Oxidative cleavage

(80) An amount of 15 g (equivalent to 45.5 mmol) of methyl 9,10-dihydroxystearate is placed in a 300 mL autoclave with magnetic stirring, in the presence of calcined alumina oxide (5% by weight).

(81) The mixture is maintained at 140° C. for 5 hours under 30 bar of air (mole O.sub.2=20 mmol), and the reaction takes place according to step 1) of the above reaction scheme.

(82) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (corresponding to 88% by weight of the mixture).

(83) f2) Esterification

(84) The products obtained on conclusion of the reaction (oxidation products) are esterified for the purposes of the analysis techniques.

(85) To this end, the reaction medium is diluted in 50 mL of methanol and is then filtered, step 2) of the preceding reaction scheme. Next, 10% by weight of Amberlyst® is added to the filtrate, which is refluxed for 5 hours.

(86) The resin is removed by filtration and the filtrate is then evaporated under reduced pressure.

(87) The crude product is analyzed by gas chromatography and by NMR.

(88) A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 65/35.

(89) The DHSM conversion is 60%.

(90) The isolated yield after distillation is 23% and 21% for methyl pelargonate and dimethyl azelate, respectively.

(91) g) In the presence of calcined silica

(92) g1) Oxidative cleavage

(93) An amount of 15 g (equivalent to 45.5 mmol) of methyl 9,10-dihydroxystearate (DHSM) with a purity of about 97% is placed in a 300 mL autoclave with mechanical stirring, in the presence of calcined silica (5% by weight).

(94) The mixture is maintained at 140° C. for 5 hours under 30 bar of air (68 mmol of O2), and the reaction takes place according to step 1 (described previously).

(95) The mixture thus obtained is cooled to room temperature, and an orange oil is obtained (corresponding to 89% by weight of the mixture).

(96) g2) Esterification

(97) The products obtained on conclusion of the reaction (oxidation products) are then 100% esterified for the purposes of the analysis techniques. To this end, the reaction medium is diluted in 300 mL of methanol and is then filtered, step 2) of the preceding reaction scheme. Next, 10% by weight of Amberlyst® are added to the filtrate, which is refluxed for 16 hours. The resin is removed by filtration and the filtrate is then evaporated under reduced pressure. An orange oil is obtained (corresponding to 88% by weight of the mixture).

(98) The crude reaction product is analyzed by gas chromatography and by proton NMR. The inventors obtained a mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) with a PM/ADM ratio of 46/54.

(99) The DHSM conversion is greater than 95%.

(100) The summary of the results obtained is given in the table below:

(101) TABLE-US-00001 TABLE 1 Conv. Ex Time Ratio (%) Ratio (%) Sel. (%) No. Cat. (H) O.sub.2/DHSM DHSM PM/ADM C9/C8 a Calcined basic 16 3.3 100 64/36  84/16 Al.sub.2O.sub.3 b Calcined basic 16 0.6 64 65/35  80/20 Al.sub.2O.sub.3 c Non-calcined 24 3.3 100 63/37  83/17 basic Al.sub.2O.sub.3 d Calcined basic 5 3.3 100 50/50 95/5 Al.sub.2O.sub.3 e Non-calcined 5 3.3 100 65/35 97/3 neutral Al.sub.2O.sub.3 f Calcined basic 5 1.5 60 45/55 95/5 Al.sub.2O.sub.3 g Calcined silica 5 1.5 >95 46/54 97/3

Example 5: Preparation of a Silica Catalyst According to the Invention: Example of a Calcined Catalyst

(102) Silica (5 g), in powder form, is calcined for 3 hours up to 550° C., with a temperature increment of about 2° C. per minute. The calcined silica is then stored in a desiccator in order to protect it from moisture.

Example 6: Oxidative Cleavage of 9,10-Dihydroxystearic Acid According to the Process of the Invention—Catalysis with Alumina or Silica

(103) The 9,10-dihydroxystearic acid (DHSA) has a purity of 80.8%.

(104) The oxidative cleavage reaction of the process according to the invention was performed, according to the following reaction scheme, in the presence of various natures of calcined substrate:

(105) ##STR00003##

(106) a) In the presence of calcined basic alumina:

(107) An amount of 60 g (equivalent to 153 mmol) of 9,10-dihydroxystearic acid (DHSA) is placed in a 600 mL autoclave with magnetic stirring, in the presence of calcined basic alumina oxide (i.e. 5% by weight of the mixture; prepared under the conditions of example 1). The mixture is maintained at 140° C. for 5 hours under 30 bar of air (mole O.sub.2=107 mmol), and the reaction takes place according to the above reaction scheme.

(108) The mixture is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(109) The crude product is analyzed after esterification by gas chromatography. A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 15/85. The DHSA conversion is 94%.

(110) b) In the presence of calcined neutral alumina:

(111) An amount of 60 g (equivalent to 153 mmol) of 9,10-dihydroxystearic acid (DHSA) is placed in a 600 mL autoclave with magnetic stirring, in the presence of calcined neutral alumina oxide (i.e. 5% by weight of the mixture; prepared under the conditions of example 1). The mixture is maintained at 140° C. for 5 hours under 30 bar of air (mole O.sub.2=524 mmol), and the reaction takes place according to the above reaction scheme.

(112) The mixture is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(113) The crude product is analyzed after esterification by gas chromatography. A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 55/45. The DHSA conversion is 90%.

(114) c) In the presence of calcined silica:

(115) An amount of 60 g (equivalent to 153 mmol) of 9,10-dihydroxystearic acid (DHSA) is placed in a 600 mL autoclave with magnetic stirring, in the presence of calcined silica (i.e. 5% by weight of the mixture; prepared under the conditions of example 1). The mixture is maintained at 140° C. for 5 hours under 30 bar of air (mole O.sub.2=524 mmol), and the reaction proceeds according to the above reaction scheme.

(116) The mixture is cooled to room temperature, and an orange oil is obtained (corresponding to 90% by weight of the mixture).

(117) The crude product is analyzed after esterification by gas chromatography. A mixture of methyl pelargonate (PM) and of dimethyl azelate (ADM) is obtained with a PM/ADM ratio of 35/65. The DHSA conversion is 86%.