Process to prepare aluminium diacetate chloride

Abstract

The invention is directed to a process to prepare aluminium diacetate chloride starting by reacting aluminium trichloride with an acetate compound in a solvent, wherein the acetate compound is alkali acetate and wherein the solvent is a mixture comprising an alcohol and an organic acetate, wherein the molar ratio of aluminium trichloride and the alkali acetate compound is between 1:1.5 and 1:3 and wherein a corresponding alkali chloride salt is obtained as a by-product.

Description

[0001] PROCESS TO PREPARE ALUMINIUM DIACETATE CHLORIDE

[0002] The invention is directed to a process to prepare aluminium diacetate chloride by reacting aluminium trichloride with an acetate compound in a solvent.

[0003] Such a process is described in Mehrotra, R. C.; Misra, R. A. Canadian Journal of Chemistry (1964), 42(4), 717-23. This publication describes the preparation of an aluminium complex by reacting aluminium trichloride with tert, butyl acetate in a benzene solvent or in an excess of tert, butyl acetate which acts as a reagent and solvent. The experiments performed in benzene were highly exothermic and required active cooling. After evaporation of the solvent and the formed tert, butyl chloride, the aluminium complex was obtained as a white powder. The experiments performed in an excess of tert, butyl acetate resulted in the preparation of aluminium triacetate or mixtures of aluminium diacetate chloride and aluminium triacetate.

[0004] Processes to prepare aluminium diacetate chloride by reacting diethylaluminium chloride with acetic acid are known. It is however the object of the present invention to prepare aluminium diacetate chloride starting from the less pyrophoric aluminium trichloride.

[0005] A problem with the process described in Mehrotra, R. C.; Misra, R. A. Canadian Journal of Chemistry (1964), 42(4), 717-23 is the use of benzene as a solvent. Benzene is toxic and is not a preferred solvent.

[0006] The object of the present invention is to provide a process to prepare aluminium diacetate chloride by reacting aluminium trichloride with an acetate compound in a solvent which does not require the use of benzene as a solvent.

[0007] This object is achieved by the following process. Process to prepare aluminium diacetate chloride starting by reacting aluminium trichloride with an acetate compound in a solvent, wherein the acetate compound is alkali acetate and wherein the solvent is a mixture comprising an alcohol and an organic acetate, wherein the molar ratio of aluminium trichloride and the alkali acetate compound is between 1 :1.5 and 1 :3 and wherein a corresponding alkali chloride salt is obtained as a by-product. Applicants found that aluminium diacetate chloride can be prepared in a solvent mixture comprising an alcohol and an organic acetate which is considered considerably less toxic as benzene. This avoids the use of benzene as a solvent. Further it is found that the reaction is less exothermic when starting from an alkali acetate instead of a butyl acetate. A next advantage is that the aluminium diacetate chloride is soluble in the solvent mixture. No sticky product is obtained as in some of the prior art processes. A next advantage is that no organic chloride compounds are formed as a by-product. These compounds are normally considered a difficult to dispose chemical waste. Instead an alkali salt is obtained which is considered to be a easier to dispose compound. Further some of the alkali salts can be obtained as a solid enabling easy separation from the reaction mixture thereby avoiding having to evaporate the organic chloride by-product as in the prior art.

[0008] The solvent is suitably a mixture of an alcohol and an organic acetate. The alcohol may be methanol, ethanol, propanol, butanol or their mixtures. More preferably the alcohol is a primary alcohol selected from methanol or ethanol or a secondary alcohol having 3 to 5 carbon atoms. Examples of such secondary alcohols are 2-propanol, 2-butanol and 2-pentanol. A preferred alcohol is ethanol because potassium acetate and sodium acetate has a high solubility in ethanol and the formed sodium chloride salt and the formed potassium chloride salt has a low solubility in ethanol. The organic acetate is preferably a linear acetate and preferably selected from methyl acetate and ethyl acetate or their mixtures. Non-linear alkyl acetates, such as tert.-butyl acetate, are less preferred because they react with aluminium trichloride. A preferred acetate is ethyl acetate because aluminium trichloride has a good solubility in ethyl acetate. Preferably the alcohol and organic acetate in the solvent mixture correspond. For example a preferred combination is ethanol and ethyl acetate and methanol and methyl acetate.

[0009] The volume ratio of the alcohol and the organic acetate in the solvent is preferably between 0.5 : 1 and 5 : 1.

[0010] The alkali acetate may suitably be lithium acetate, sodium acetate or potassium acetate, and more preferably sodium acetate and potassium acetate. It has been found that the formed potassium chloride or the formed sodium chloride are in their solid form enabling easy separation from the reaction mixture. Thus when sodium acetate or potassium acetate is used the corresponding sodium or potassium chloride salts are obtained as a solid by-product and the solid by-product and any non-reacted solid alkali acetate is suitably separated from the aluminium diacetate chloride as present in the solvent by a solid-liquid separation method. Suitable solidliquid separation methods are for example centrifugal processes. Possible centrifugal processes make use of a centrifuge and / or make use of a hydrocyclone. Preferably the solid alkaline salt is separated by filtration. In the filtration, the filtrate is suitably washed with an alcohol and preferably with the same alcohol as present in the solvent.

[0011] The reaction between aluminium trichloride and the alkali acetate compound is exothermic. The temperature is suitably kept below the boiling temperature of the solvent mixture at the operating pressure. Preferably the temperature at which the reaction is performed is between 10 °C and the boiling point of the solvent mixture. The operating pressure is suitably ambient pressure.

[0012] The molar ratio of aluminium trichloride and the alkali acetate compound is suitably between 1 :1.9 and 1 :2.5 and preferably between 1 :2 and 1 :2.4.

[0013] Preferably the aluminium trichloride is first dissolved in the organic acetate to obtain an aluminium trichloride-organic acetate mixture. Dissolving aluminium trichloride in the organic acetate is exothermic and the temperature is preferably kept below 60 °C by cooling. The addition is preferably performed gradually to avoid excessive temperature rise. The concentration of the aluminium trichloride in the obtained aluminium trichloride-organic acetate mixture is preferably between 0.5 and 3 mol / l.

[0014] This aluminium trichloride-organic acetate mixture is subsequently added to a mixture of the alkali acetate and the alcohol. The concentration of the alkali acetate in the mixture of the alkali acetate and the alcohol is preferably between 0.5 and 3 mol / l. This addition is also exothermic and the temperature is preferably kept below 80 °C by cooling and more preferably between 20 and 60 °C. The aluminium trichloride-organic acetate mixture is preferably added gradually to the mixture of the alkali acetate and alcohol to avoid excessive temperature rise. The alkali acetate and alcohol mixture may be a slurry wherein the alkali acetate is the solid phase.

[0015] After adding the aluminium trichloride-organic acetate mixture to the mixture of the alkali acetate and the alcohol the resulting mixture is stirred to allow the reaction to aluminium diacetate chloride. This phase may continue for between 2 and 18 hours. The temperature is preferably maintained between 25 and 50 °C. Preferably this phase is continued until all or substantially all of the aluminium trichloride has reacted.

[0016] After separation of the alkali salt the remaining solvent can be separated by evaporation wherein the aluminium diacetate chloride product is obtained as a white powder. The separated solvent may be advantageously used in the process of this invention. In a continuous process they may be recycled to the continuously operated reactor in which the process is performed. In the batch or semi-batch process the evaporated solvents may be condensed and added to the batch reactor to be used in a next run of the process.

[0017] The solid aluminium diacetate chloride may be further used as such. It is found that the aluminium diacetate chloride as present in the solvent mixture, optionally diluted with washing fluid of the preferred filtration, can be directly used as starting compound in a reaction as performed in the same solvent mixture.

[0018] The invention will be illustrated by the following non-limiting examples.

[0019] Example 1

[0020] 232.78 g of aluminium trichloride (AICI3) is added portion wise to a thermostated 5L reactor containing 0.67 L of Ethyl acetate. The reactor temperature is kept below 30°C during the addition. The AICI3 is then transferred to another thermostated reactor containing a slurry of 376.78 g of potassium acetate (KOAc) in 1 .5 L of ethanol (EtOH). The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.2. The reaction mixture is kept below 30 °C during the addition and stirred for an extra 12 hours after the end of the addition. The reactor is drained and filtered over paper filter, washed with 2 x 500 mL ethanol (EtOH) to separate solid potassium chloride and any unreacted potassium acetate. Analysis of the resulting filtrate showed that aluminium diacetate chloride was obtained:

[0021] 1 H-NMR (D2O): 5 1 .92 ppm (s),27AI-NMR(DMSO) ): 5 65.96 ppm (br. S)

[0022] Example 2

[0023] 20 g of AICI3 is added portion wise to a round bottom flask containing 115 mL of ethyl acetate. The reaction temperature is kept below 30°C during the addition. The AICI3 is then transferred to a round bottom flask containing a slurry of 29.3 g of KOAc in 230 mL of EtOH. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.0. The reaction mixture is kept below 30°C during the addition and stirred for an extra 12 hours after the end of the addition. The reactor is drained and filter over paper filter, washed with 2 x 20 mL EtOH to remove solid potassium chloride and any unreacted potassium acetate. The filtrate is concentrated under vacuum using a rotavapor apparatus. The obtained residue is stripped 3 times with toluene (30 mL) to obtain a free flowing aluminium diacetate chloride white powder. 24.76 g, 63% yield.

[0024] Example 3

[0025] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of methanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 72 mg of a white powder (95% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(0Ac)2 Cl) was prepared. Elemental analysis of the solid was determined by the Mikroanalytisches Laboratorium Kolbe, Oberhausen, Germany. Specifically, the content of chlorine was determined on a Metrohm Model 930 Compact IC Flex Oven / SeS / PP / Deg ion chromatograph after combustion digestion on a Mitsubishi AQF-21 OOH. The elemental analysis indicated a molar ratio between aluminium and chloride which confirms the formation of aluminium diacetate chloride.

[0026] Example 4

[0027] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of 2-propanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 62 mg of a white powder (82% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared. The elemental analysis indicated a molar ratio between aluminium and chloride which confirms the formation of aluminium diacetate chloride.

[0028] Example 5

[0029] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of 2-butanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 58 mg of a white powder (76% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared. The elemental analysis indicated a molar ratio between aluminium and chloride which confirms the formation of aluminium diacetate chloride.

[0030] Comparative experiment A

[0031] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AICI3 and 1.0 mL isobutyl acetate and subsequently added to the centrifuge tube. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 64 mg of a white powder (84% yield). Elemental analysis did not indicate that the majority of the formed aluminium compounds would be aluminium diacetate chloride (AI(OAc)2CI).

[0032] Comparative experiment B

[0033] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AICI3 and 1.0 mL isopropyl acetate and subsequently added to the centrifuge tube. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 66 mg of a white powder (87% yield). Elemental analysis did not indicate that the majority of the formed aluminium compounds would be aluminium diacetate chloride (AI(OAc)2CI).

[0034] Comparative experiment C

[0035] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AICI3 and 1 .0 mL n- propyl acetate and subsequently added to the centrifuge tube. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 75 mg of a white powder (99% yield). Elemental analysis did not indicate that the majority of the formed aluminium compounds would be aluminium diacetate chloride (AI(OAc)2CI).

[0036] Example 6

[0037] A 15 mL centrifuge tube was loaded with 98.14 mg of KOAc (potassium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1 .0:2.0. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 64 mg of a white powder (85% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared. The elemental analysis indicated a molar ratio between aluminium and chloride which confirms the formation of aluminium diacetate chloride.

[0038] Comparative experiment D

[0039] A 15 mL centrifuge tube was loaded with 49.07 mg of KOAc (potassium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0: 1.0. The reaction mixture was shaken for 16h at room temperature.27AI NMR confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared and unreacted AICI3 was present too. Comparative experiment E

[0040] A 15 mL centrifuge tube was loaded with 147.21 mg of KOAc (potassium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0: 3.0. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid potassium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 74 mg of a white powder (97% yield). Elemental analysis did not indicate that the majority of the formed aluminium compounds would be aluminium diacetate chloride (AI(OAc)2CI).

[0041] Example 7

[0042] A 15 mL centrifuge tube was loaded with 86.14 mg of NaOAc (sodium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the sodium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm to remove solid sodium chloride. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 64 mg of a white powder (85% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared.

[0043] Example 8

[0044] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the potassium acetate compound was 1.0:2.1. The reaction mixture was shaken for 16h at room temperature. The reaction mixture was centrifuged for 5 minutes at 4000 rpm. The supernatant was dried under reduced pressure until dryness followed by the addition of 3 mL of toluene and drying the sample under reduced pressure until dryness again. Then, the resulting solid was dried under vacuum (70 °C, 8 mbar) for 64 hours to yield 62 mg of a white powder (82% yield).27AI NMR and elemental analysis confirmed that the desired aluminium complex (AI(0AC)2CI) was prepared.

[0045] Example 9

[0046] A 15 mL centrifuge tube was loaded with 69.28 mg of LiOAc (lithium acetate), 2.1 mL of ethanol and 1 mL of a 0.5 M stock solution of AICI3 in ethyl acetate. The molar ratio of aluminium trichloride and the lithium acetate compound was 1 .0:2.1 . The reaction mixture was shaken for 16h at room temperature.27AI NMR confirmed that the desired aluminium complex (AI(OAc)2CI) was prepared. No isolation and elemental analysis was performed because there was no precipitation of the expected LiCI after 16h at room temperature. Therefore no easy separation of the AI(OAC)2CI from LiCI by filtration / centrifugation as in the other examples. LiCI precipitation may be possible by using a different solvent (combination) I concentration I temperature.

[0047] Example 10

[0048] A 15 mL centrifuge tube was loaded with 103.05 mg of KOAc (potassium acetate) and 2.1 mL of ethanol. A 4 mL vial was loaded with 66.67 mg AICI3 and 1 .0 mL methyl acetate and subsequently added to the centrifuge tube. The reaction mixture was shaken for 16 hours at room temperature. The centrifuge tube was centrifuged for 3 minutes at 4000 rpm. The supernatant was removed and analysed and the formation of AI(OAc)2CI was confirmed.

Claims

CLAIMS1. Process to prepare aluminium diacetate chloride starting by reacting aluminium trichloride with an acetate compound in a solvent, wherein the acetate compound is alkali acetate and wherein the solvent is a mixture comprising an alcohol and an organic acetate, wherein the molar ratio of aluminium trichloride and the alkali acetate compound is between 1 :1.5 and 1 :3 and wherein a corresponding alkali chloride salt is obtained as a by-product.

2. Process according to claim 1 , wherein the alcohol is methanol, ethanol, propanol, butanol or their mixtures.

3. Process according to any one of claims 1 -2, wherein the organic acetate is ethyl acetate or methyl acetate.

4. Process according to any one of claims 1-3, wherein the alkali acetate is sodium acetate.

5. Process according to any one of claims 1-3, wherein the alkali acetate is potassium acetate.

6. Process according to any one of claims 4-5, wherein the sodium chloride salt or the potassium chloride is obtained as a solid by-product and wherein the solid by-product is separated from the aluminium diacetate chloride as present in the solvent by a solid-liquid separation method.

7. Process according to any one of claims 1 -6, wherein the temperature at which the reaction is performed is between 10 °C and the boiling point of the solvent mixture.

8. Process according to any one of claims 1 -7, wherein the molar ratio of aluminium trichloride and the alkali acetate compound is between 1 :1.9 and 1 :2.5.

9. Process according to any one of claims 5-8, wherein the acetate compound is potassium acetate, the solvent is ethanol, and the organic acetate is ethyl acetate.

10. Process according to any one of claims 1-9, wherein first the aluminium trichloride is dissolved in the organic acetate to obtain an aluminium trichloride- organic acetate mixture and wherein the aluminium trichloride-organic acetate mixture is subsequently added to a mixture of the alkali acetate and the alcohol.

11. Process according to claim 10, wherein aluminium trichloride is added gradually to the organic acetate.

12. Process according to any one of claims 10-11 , wherein the concentration of the aluminium trichloride in the obtained aluminium trichloride-organic acetate mixture is between 0.5 and 3 mol / L.

13. Process according to any one of claims 10-12, wherein the concentration of the alkali acetate in the mixture of the alkali acetate and the alcohol is between 0.5 and 3 mol / L.

14. Process according to any one of claims 10-13, wherein the aluminium trichloride-organic acetate mixture is added gradually to the mixture of the alkali acetate and alcohol.