A method for preparing aluminum isooctoate

Abstract

This invention belongs to the field of thickener preparation technology, specifically relating to a method for preparing aluminum isooctanoate. The method involves mixing and dissolving a catalyst-functionalized heteropolyacid ionic liquid and a boron tetrafluoride ionic liquid, adding isooctyl alcohol, and then refluxing at 100-110°C with pure oxygen while stirring. The reaction mixture is extracted three times with anhydrous diethyl ether, and the organic phases are combined, washed, dried, and distilled under reduced pressure to obtain isooctanoic acid. The isooctanoic acid is then heated to 60-70°C, and glacial acetic acid is added dropwise under stirring. The temperature is then further increased to 140-150°C, and aluminum hydroxide is added. The reaction is allowed to proceed for 6-8 hours. After the reaction is complete, the mixture is cooled, ground, washed, and dried to obtain aluminum isooctanoate. In the preparation of isooctanoic acid, this invention uses a functionalized heteropolyacid ionic liquid as a catalyst and pure oxygen as an oxidant to catalyze the oxidation of isooctyl alcohol to isooctanoic acid. The functionalized heteropolyacid ionic liquid has the advantages of good catalytic effect and low corrosivity to equipment.

Description

Technical Field

[0001] This invention belongs to the field of thickener preparation technology, specifically relating to a method for preparing aluminum isooctanoate. Background Technology

[0002] Aluminum isooctanoate (2-ethylhexanoate) is a thickener widely used in some industrial oils such as lubricating grease, thickened benzene, gasoline and turpentine. Currently, aluminum isooctanoate on the market is mainly obtained by metathesis reaction of isooctanoic acid and aluminum sulfate under alkaline conditions. Specifically, isooctanoic acid needs to be prepared first.

[0003] The main production methods of isooctanoic acid are isooctyl alcohol oxidation and butyraldehyde condensation plus hydroxide method. At present, the domestic research on isooctanoic acid synthesis mainly focuses on isooctyl alcohol oxidation, which includes potassium permanganate oxidation, nitric acid oxidation, ultrasonic radiation, dehydrogenation and oxidation, oxygen oxidation, etc. All of the above methods use strong acids and strong bases, which are highly corrosive to equipment, and some precious metal catalysts used are expensive. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing aluminum isooctanoate to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing aluminum isooctanoate includes the following steps:

[0007] S1. Imidazole salts were prepared using imidazole nitroxide radicals, 1,4-dibromobutane and N-methylimidazolium as raw materials;

[0008] Functionalized heteropolyacid ionic liquids were prepared using imidazole salts and phosphotungstic acid as raw materials.

[0009] S2. Mix and dissolve the catalyst-functionalized heteropolyacid ionic liquid and boron tetrafluoride ionic liquid, add isooctanol, reflux at 100~110℃ and pass pure oxygen through, stir the reaction, and after the reaction is completed, extract the reaction solution three times with anhydrous diethyl ether, and combine the organic phase and ionic liquid phase respectively.

[0010] S3. The organic phase was washed with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain isooctanoic acid; the ionic liquid phase was recovered by distillation under reduced pressure at 70°C.

[0011] S4. Heat isooctanoic acid to 60-70℃, add glacial acetic acid dropwise under stirring, then continue heating to 140-150℃, slowly add aluminum hydroxide, react for 6-8 hours, cool after the reaction is complete, grind, wash and dry the product to obtain aluminum isooctanoate.

[0012] As a further improvement, in step S1, the preparation method of the imidazole salt is as follows: imidazole nitric oxide free radicals, sodium hydride and anhydrous acetone are mixed and stirred at room temperature, then 1,4-dibromobutane is slowly added dropwise, and the mixture is stirred at room temperature for 3-5 hours. After the reaction is completed, the mixture is rotary evaporated, then dissolved in deionized water, extracted with dichloromethane, dried to remove water from the organic phase, concentrated under reduced pressure, and purified by column chromatography to obtain an oily substance.

[0013] The oily substance, N-methylimidazole and acetonitrile were mixed and reacted at 60-65℃ for 6-8 hours. After the reaction was completed, diethyl ether was added to precipitate the precipitate. The precipitate was washed with diethyl ether to obtain imidazole salt.

[0014] As a further improvement, the molar ratio of the imidazole nitroxide radical to 1,4-dibromobutane is 3:4 to 4.2; the molar ratio of the oil to the N-methylimidazolium is 1:1 to 1.1.

[0015] As a further improvement, the method for preparing the imidazole nitroxide radical is as follows: 4-hydroxybenzaldehyde and N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine are mixed, anhydrous methanol is added, and the mixture is refluxed at 75~80℃ for 48h. After the reaction is completed, the mixture is filtered, and the filter cake is washed with methanol and diethyl ether to obtain the intermediate.

[0016] The intermediate was dissolved in dichloromethane, and sodium periodate aqueous solution was added dropwise at 0-5°C. After the addition was complete, the reaction was carried out. After the reaction was completed, the mixture was extracted with dichloromethane, the organic phase was dried and filtered, and the filtrate was distilled under reduced pressure to obtain imidazole nitroxide free radicals.

[0017] As a further improvement, the molar ratio of 4-hydroxybenzaldehyde and N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1:1.5.

[0018] As a further improvement, in step S1, the preparation method of the functionalized heteropolyacid ionic liquid is as follows: imidazole salt is added to deionized water, stirred evenly, and then added dropwise to phosphotungstic acid aqueous solution. The mixture is stirred at room temperature for 4-6 hours, filtered, and the filter cake is washed with deionized water and diethyl ether, and then vacuum dried to obtain the functionalized heteropolyacid ionic liquid.

[0019] As a further improvement, the phosphotungstic acid aqueous solution is obtained by dissolving phosphotungstic acid in deionized water; the molar ratio of the imidazole salt to the phosphotungstic acid is 3:1.

[0020] As a further improvement, in step S2, the ratio of the functionalized heteropolyacid ionic liquid to the boron tetrafluoride ionic liquid is 1g:200mL; the ratio of the functionalized heteropolyacid ionic liquid to isooctyl alcohol is 1g:25mL; and the rate of pure oxygen introduction is 25mL / min.

[0021] As a further improvement, in step S4, the amount of glacial acetic acid added is 11% of the mass of isooctanoic acid, and the molar ratio of isooctanoic acid to aluminum hydroxide is 1:0.32~0.35.

[0022] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0023] This invention provides a method for preparing aluminum isooctanoate. In the preparation process of isooctanoate, a functionalized heteropolyacid ionic liquid is used as a catalyst and pure oxygen is used as an oxidant to catalyze the oxidation of isooctyl alcohol to isooctanoate. The heteropolyacid in the functionalized heteropolyacid ionic liquid has strong acidity, but it has less corrosion to the equipment. It has the advantages of good catalytic effect and low corrosion to the equipment.

[0024] In this invention, a functionalized heteropolyacid ionic liquid is prepared by using heteropolyacids and imidazole salts. It has good compatibility with the solvent boron tetrafluoride ionic liquid. After the catalytic groups in the functionalized heteropolyacid ionic liquid have completed their catalytic effect, the catalyst can be recovered and reused by loading it with boron tetrafluoride ionic liquid. It can be recycled more than six times, reducing production costs.

[0025] In this invention, imidazole nitroxide radicals are loaded onto heteropolyacid ionic liquids. With the participation of imidazole nitroxide radicals, the catalytic effect is further improved. At the same time, the benzene ring in the imidazole nitroxide radicals improves the hydrophobicity of the imidazole nitroxide radicals, improves their compatibility with boron tetrafluoride ionic liquids, and further improves the separation effect of the catalyst and isooctanoic acid.

[0026] Aluminum isooctanoate can be prepared in one step using isooctanoic acid and aluminum hydroxide as raw materials. The process is simple, does not require the use of corrosive liquids such as strong alkalis, and the reaction products are pollution-free and more environmentally friendly. Attached Figure Description

[0027] Figure 1 This is the infrared spectrum of imidazole nitroxide free radicals in Example 1 of the present invention;

[0028] Figure 2 This is the infrared spectrum of the imidazole salt in Example 1 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0030] Example 1: A method for preparing aluminum isooctanoate, comprising the following steps:

[0031] S1. Mix 10 mmol of 4-hydroxybenzaldehyde and 15 mmol of N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine, add 40 mL of anhydrous methanol, and reflux at 75 °C for 48 h. After the reaction is complete, filter the mixture and wash the filter cake with methanol and diethyl ether to obtain a white solid intermediate.

[0032] The reaction equation is:

[0033] ;

[0034] Dissolve 1.6 mmol of sodium periodate in 6 mL of distilled water to obtain an aqueous solution of sodium periodate;

[0035] 1.6 mmol of the intermediate was mixed and dissolved with 10 mL of dichloromethane. Sodium periodate aqueous solution was added dropwise at 0 °C. After the addition was complete, the reaction was carried out for 20 min. After the reaction was completed, the mixture was extracted three times with 50 mL of dichloromethane. The organic phases were combined and dried overnight with anhydrous sodium sulfate. After filtration, the filtrate was distilled under reduced pressure to remove dichloromethane, yielding imidazole nitric oxide free radicals.

[0036] The reaction equation is:

[0037] ;

[0038] S2. Mix 15 mmol of imidazole nitroxide radicals, 25 mmol of sodium hydride and 25 mL of anhydrous acetone, stir at room temperature for 10 min, then slowly add 20 mmol of 1,4-dibromobutane dropwise, stir at room temperature for 3 h. After the reaction is complete, remove acetone by rotary evaporation, add 30 mL of deionized water to dissolve, then extract three times with 15 mL of dichloromethane, combine the organic phases and dry with anhydrous sodium sulfate, concentrate under reduced pressure at 40 °C and separate by column chromatography to obtain an oily substance, with the eluent being a mixture of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0039] The reaction equation is:

[0040] ;

[0041] Take 3 mmol of oil, 3 mmol of N-methylimidazole and 1 mL of acetonitrile and mix them. React at 60 °C for 6 h. After the reaction is complete, add 5 mL of diethyl ether to precipitate the precipitate. After filtration, wash the precipitate twice with 5 mL of diethyl ether to obtain the imidazole salt.

[0042] The reaction equation is:

[0043] ;

[0044] 0.02 mol of phosphotungstic acid was dissolved in deionized water to obtain a 5% (w / w) aqueous solution of phosphotungstic acid.

[0045] 0.06 mol of imidazole salt was added to deionized water to obtain a 5% (w / w) imidazole salt aqueous solution. The imidazole salt aqueous solution was added dropwise to a phosphotungstic acid aqueous solution and stirred at room temperature for 4 h. The mixture was then filtered, and the filter cake was washed with deionized water and ether, respectively. Finally, it was dried under vacuum at 50 °C for 24 h to obtain a functionalized heteropolyacid ionic liquid.

[0046] The reaction equation is:

[0047] ;

[0048] S3. Mix 0.15 mol of n-butane bromide and 0.1 mol of N-methylimidazole, heat to 70 °C under stirring and react for 24 h. After the reaction is complete, remove excess n-butane bromide by vacuum distillation at 70 °C. Then add 100 mL of acetone and 0.1 mol of sodium borate and stir at room temperature for 48 h. After the reaction is complete, freeze filter the reaction solution and remove acetone by vacuum distillation of the filtrate to obtain boron tetrafluoride ionic liquid.

[0049] S4. Mix and dissolve 2g of catalyst-functionalized heteropolyacid ionic liquid and 400mL of boron tetrafluoride ionic liquid, then add 50mL of isooctanol, reflux at 100℃, and introduce pure oxygen at a rate of 25mL / min. Stir the reaction for 5h. After the reaction is complete, add anhydrous diethyl ether to the reaction solution for extraction three times, and combine the organic phase and ionic liquid phase respectively.

[0050] S5. The organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, and distilled under reduced pressure to remove diethyl ether, yielding isooctanoic acid.

[0051] The ionic liquid phase was recovered by vacuum distillation at 70 °C.

[0052] S6. Heat 1 mol of isooctanoic acid to 60℃, add 15.86 g of glacial acetic acid dropwise under stirring, then continue to heat to 140℃, slowly add 0.35 mol of aluminum hydroxide, react for 8 h, cool after the reaction is complete, grind and pulverize the product, wash with 75℃ hot water, then wash with anhydrous ethanol, filter and dry to obtain aluminum isooctanoate.

[0053] like Figure 1 The image shown is the infrared spectrum of the imidazole nitroxide radicals prepared in this embodiment, where the radical is located at 3258 cm⁻¹. -1 The characteristic peak of the phenolic hydroxyl group appears at 1370 cm⁻¹. -1 and 1358cm -1 The peak at this location is a characteristic peak for the NO group.

[0054] like Figure 2 The image shown is the infrared spectrum of the imidazole salt prepared in this embodiment, where the peak value is located at 1370 cm⁻¹. -1 and 1358cm -1 The characteristic peak of the NO group at 1570 cm⁻¹ remained unchanged. -1 and 1465cm -1 The peak at this location is a characteristic peak of the butyl-linked imidazole group.

[0055] Example 2 A method for preparing aluminum isooctanoate, comprising the following steps:

[0056] S1. Mix 10 mmol of 4-hydroxybenzaldehyde and 15 mmol of N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine, add 40 mL of anhydrous methanol, and reflux at 80 °C for 48 h. After the reaction is complete, filter the mixture and wash the filter cake with methanol and diethyl ether to obtain a white solid intermediate.

[0057] Dissolve 1.6 mmol of sodium periodate in 6 mL of distilled water to obtain an aqueous solution of sodium periodate;

[0058] 1.6 mmol of the intermediate was mixed and dissolved with 10 mL of dichloromethane. Sodium periodate aqueous solution was added dropwise at 5 °C. After the addition was complete, the reaction was carried out for 20 min. After the reaction was completed, the mixture was extracted three times with 50 mL of dichloromethane. The organic phases were combined and dried overnight with anhydrous sodium sulfate. After filtration, the filtrate was distilled under reduced pressure to remove dichloromethane, yielding imidazole nitric oxide free radicals.

[0059] S2. Mix 15 mmol of imidazole nitroxide radicals, 25 mmol of sodium hydride and 25 mL of anhydrous acetone, stir at room temperature for 10 min, then slowly add 21 mmol of 1,4-dibromobutane dropwise, stir at room temperature for 5 h. After the reaction is complete, remove acetone by rotary evaporation, add 30 mL of deionized water to dissolve, then extract three times with 15 mL of dichloromethane, combine the organic phases and dry with anhydrous sodium sulfate, concentrate under reduced pressure at 40 °C and separate by column chromatography to obtain an oily substance, with the eluent being a mixture of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0060] Take 3 mmol of oil, 3.3 mmol of N-methylimidazole and 1 mL of acetonitrile and mix them. React at 65 °C for 8 h. After the reaction is complete, add 5 mL of diethyl ether to precipitate. After filtration, wash the precipitate twice with 5 mL of diethyl ether to obtain imidazole salt.

[0061] 0.02 mol of phosphotungstic acid was dissolved in deionized water to obtain a 5% (w / w) aqueous solution of phosphotungstic acid.

[0062] 0.06 mol of imidazole salt was added to deionized water to obtain a 5% (w / w) imidazole salt aqueous solution. The imidazole salt aqueous solution was added dropwise to a phosphotungstic acid aqueous solution and stirred at room temperature for 6 h. The mixture was then filtered, and the filter cake was washed with deionized water and ether, respectively. Finally, it was dried under vacuum at 50 °C for 24 h to obtain a functionalized heteropolyacid ionic liquid.

[0063] S3. Mix 0.15 mol of n-butane bromide and 0.1 mol of N-methylimidazole, heat to 70 °C under stirring and react for 24 h. After the reaction is complete, remove excess n-butane bromide by vacuum distillation at 70 °C. Then add 100 mL of acetone and 0.1 mol of sodium borate and stir at room temperature for 48 h. After the reaction is complete, freeze filter the reaction solution and remove acetone by vacuum distillation of the filtrate to obtain boron tetrafluoride ionic liquid.

[0064] S4. Mix and dissolve 2g of catalyst-functionalized heteropolyacid ionic liquid and 400mL of boron tetrafluoride ionic liquid, then add 50mL of isooctanol, reflux at 110℃, and introduce pure oxygen at a rate of 25mL / min. Stir the reaction for 5h. After the reaction is complete, add anhydrous diethyl ether to the reaction solution for extraction three times, and combine the organic phase and ionic liquid phase respectively.

[0065] S5. The organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, and distilled under reduced pressure to remove diethyl ether, yielding isooctanoic acid.

[0066] The ionic liquid phase was recovered by vacuum distillation at 70 °C.

[0067] S6. Heat 1 mol of isooctanoic acid to 70℃, add 15.86 g of glacial acetic acid dropwise under stirring, then continue to heat to 150℃, slowly add 0.32 mol of aluminum hydroxide, react for 6 h, cool after the reaction is complete, grind and pulverize the product, wash with 75℃ hot water, then wash with anhydrous ethanol, filter and dry to obtain aluminum isooctanoate.

[0068] Example 3 A method for preparing aluminum isooctanoate, comprising the following steps:

[0069] S1. Mix 10 mmol of 4-hydroxybenzaldehyde and 15 mmol of N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine, add 40 mL of anhydrous methanol, and reflux at 78 °C for 48 h. After the reaction is complete, filter the mixture and wash the filter cake with methanol and diethyl ether to obtain a white solid intermediate.

[0070] Dissolve 1.6 mmol of sodium periodate in 6 mL of distilled water to obtain an aqueous solution of sodium periodate;

[0071] 1.6 mmol of the intermediate was mixed and dissolved with 10 mL of dichloromethane. Sodium periodate aqueous solution was added dropwise at 3 °C. After the addition was complete, the reaction was carried out for 20 min. After the reaction was completed, the mixture was extracted three times with 50 mL of dichloromethane. The organic phases were combined and dried overnight with anhydrous sodium sulfate. After filtration, the filtrate was distilled under reduced pressure to remove dichloromethane, yielding imidazole nitric oxide free radicals.

[0072] S2. Mix 15 mmol of imidazole nitroxide radicals, 25 mmol of sodium hydride and 25 mL of anhydrous acetone, stir at room temperature for 10 min, then slowly add 20.5 mmol of 1,4-dibromobutane dropwise, stir at room temperature for 4 h. After the reaction is complete, remove acetone by rotary evaporation, add 30 mL of deionized water to dissolve, then extract three times with 15 mL of dichloromethane, combine the organic phases and dry with anhydrous sodium sulfate, concentrate under reduced pressure at 40 °C and separate by column chromatography to obtain an oily substance, with the eluent being a mixture of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0073] Take 3 mmol of oil, 3.15 mmol of N-methylimidazole and 1 mL of acetonitrile and mix them. React at 63 °C for 7 h. After the reaction is complete, add 5 mL of diethyl ether to precipitate. After filtration, wash the precipitate twice with 5 mL of diethyl ether to obtain imidazole salt.

[0074] 0.02 mol of phosphotungstic acid was dissolved in deionized water to obtain a 5% (w / w) aqueous solution of phosphotungstic acid.

[0075] 0.06 mol of imidazole salt was added to deionized water to obtain a 5% (w / w) imidazole salt aqueous solution. The imidazole salt aqueous solution was added dropwise to a phosphotungstic acid aqueous solution and stirred at room temperature for 5 h. The mixture was then filtered, and the filter cake was washed with deionized water and ether, respectively. Finally, it was dried under vacuum at 50 °C for 24 h to obtain a functionalized heteropolyacid ionic liquid.

[0076] S3. Mix 0.15 mol of n-butane bromide and 0.1 mol of N-methylimidazole, heat to 70 °C under stirring and react for 24 h. After the reaction is complete, remove excess n-butane bromide by vacuum distillation at 70 °C. Then add 100 mL of acetone and 0.1 mol of sodium borate and stir at room temperature for 48 h. After the reaction is complete, freeze filter the reaction solution and remove acetone by vacuum distillation of the filtrate to obtain boron tetrafluoride ionic liquid.

[0077] S4. Mix and dissolve 2g of catalyst-functionalized heteropolyacid ionic liquid and 400mL of boron tetrafluoride ionic liquid, then add 50mL of isooctanol, reflux at 105℃, and introduce pure oxygen at a rate of 25mL / min. Stir the reaction for 5h. After the reaction is complete, add anhydrous diethyl ether to the reaction solution for extraction three times, and combine the organic phase and ionic liquid phase respectively.

[0078] S5. The organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, and distilled under reduced pressure to remove diethyl ether, yielding isooctanoic acid.

[0079] The ionic liquid phase was recovered by vacuum distillation at 70 °C.

[0080] S6. Heat 1 mol of isooctanoic acid to 65℃, add 15.86 g of glacial acetic acid dropwise under stirring, then continue to heat to 145℃, slowly add 0.33 mol of aluminum hydroxide, react for 7 h, cool after the reaction is complete, grind and pulverize the product, wash with 75℃ hot water, then wash with anhydrous ethanol, filter and dry to obtain aluminum isooctanoate.

[0081] Comparative Example 1: A method for preparing aluminum isooctanoate, with the same specific steps as in Example 1, except that imidazole nitroxide radicals are not used in the preparation of the catalyst. The specific preparation method of the catalyst is as follows:

[0082] S1. Mix 3 mmol of n-butane bromide, 3 mmol of N-methylimidazol and 1 mL of acetonitrile, and react at 60 °C for 6 h. After the reaction is complete, add 5 mL of diethyl ether to precipitate the precipitate. After filtration, wash the precipitate twice with 5 mL of diethyl ether to obtain imidazolium salt.

[0083] S2. Dissolve 0.02 mol of phosphotungstic acid in deionized water to obtain a 5% (w / w) aqueous solution of phosphotungstic acid.

[0084] 0.06 mol of imidazole salt was added to deionized water to obtain a 5% (w / w) imidazole salt aqueous solution. The imidazole salt aqueous solution was added dropwise to a phosphotungstic acid aqueous solution and stirred at room temperature for 4 h. The mixture was then filtered, and the filter cake was washed with deionized water and ether, respectively. Finally, it was dried under vacuum at 50 °C for 24 h to obtain a heteropolyacid ionic liquid.

[0085] Comparative Example 2: A method for preparing aluminum isooctanoate, the specific steps of which are the same as those in Example 1, except that: the catalyst is a mixture of heteropolyacid ionic liquid and imidazole nitroxide free radicals in a ratio of 1g:1mL, wherein the heteropolyacid ionic liquid is prepared by the preparation method described in Comparative Example 1, and the imidazole nitroxide free radicals are prepared by the preparation method described in Example 1.

[0086] Comparative Example 3: A method for preparing aluminum isooctanoate, with the same specific steps as in Example 1, except that in the preparation method of catalyst-functionalized heteropolyacid ionic liquid, TEMPO is used instead of imidazole nitroxide radicals in Example 1.

[0087] The specific preparation method is as follows:

[0088] 15 mmol TEMPO, 25 mmol sodium hydride and 25 mL anhydrous acetone were mixed and stirred at room temperature for 10 min. Then 20 mmol 1,4-dibromobutane was slowly added dropwise and the mixture was stirred at room temperature for 3 h. After the reaction was completed, the acetone was removed by rotary evaporation, and the mixture was dissolved in 30 mL deionized water. The mixture was then extracted three times with 15 mL dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate and concentrated under reduced pressure at 40 °C. The mixture was then separated by column chromatography to obtain an oily substance. The eluent was a mixture of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0089] Take 3 mmol of oil, 3 mmol of N-methylimidazole and 1 mL of acetonitrile and mix them. React at 60 °C for 6 h. After the reaction is complete, add 5 mL of diethyl ether to precipitate the precipitate. After filtration, wash the precipitate twice with 5 mL of diethyl ether to obtain the imidazole salt.

[0090] 0.02 mol of phosphotungstic acid was dissolved in deionized water to obtain a 5% (w / w) aqueous solution of phosphotungstic acid.

[0091] 0.06 mol of imidazole salt was added to deionized water to obtain a 5% (w / w) imidazole salt aqueous solution. The imidazole salt aqueous solution was added dropwise to a phosphotungstic acid aqueous solution and stirred at room temperature for 4 h. The mixture was then filtered, and the filter cake was washed with deionized water and ether, respectively. Finally, it was dried under vacuum at 50 °C for 24 h to obtain a functionalized heteropolyacid ionic liquid.

[0092] The conversion rate of raw materials and the yield of products in the preparation process of isooctanoic acid in Examples 1-3 and Comparative Examples 1-3 were determined by gas chromatography, and the results are shown in Table 1.

[0093] Table 1. Results of raw material conversion rate and product yield in the preparation of isooctanoic acid.

[0094]

[0095] As can be seen from Table 1, compared with Examples 1-3, the conversion rate of isooctyl alcohol and the yield of isooctanoic acid in Comparative Example 1 are both lower, indicating that the presence of imidazole nitroxide radicals is beneficial to improving the conversion rate of the reaction. The conversion rate of isooctyl alcohol and the yield of isooctanoic acid in Comparative Examples 2 and 3 are similar to those in Examples 1-3, indicating that the imidazole nitroxide radicals prepared in this invention have a similar catalytic effect on the reaction as existing nitroxide radicals.

[0096] The catalysts in Example 1 and Comparative Examples 1-3 were tested for their recycling performance.

[0097] 50 mL of isooctyl alcohol was added to the ionic liquid phase recovered after vacuum distillation. The mixture was refluxed at 100 °C, and pure oxygen was introduced at a rate of 25 mL / min. The mixture was stirred for 5 h. After the reaction was completed, anhydrous diethyl ether was added to the reaction solution for extraction three times. The organic phase and the ionic liquid phase were combined. The organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine, dried over anhydrous sodium sulfate, and the diethyl ether was removed by vacuum distillation to obtain isooctyl acid. The ionic liquid phase was recovered by vacuum distillation at 70 °C.

[0098] The above steps were repeated 6 times until the ionic liquid phase was used. The conversion rate of isooctyl alcohol and the yield of isooctanoic acid were measured after each reaction. The results are shown in Table 2.

[0099] Table 2. Test results of the recycling effect of ionic liquid phase

[0100]

[0101] As can be seen from Tables 1 and 2, the ionic liquid phase of Example 1 of the present invention is recycled 6 times, and the catalytic effect of converting isooctyl alcohol to isooctanoic acid does not decrease significantly.

[0102] The ionic liquid phase in Comparative Example 1 was recycled 6 times, and its catalytic effect on the conversion of isooctyl alcohol to isooctanoic acid did not decrease significantly, but its catalytic effect was not as good as that in Example 1.

[0103] The ionic liquid phase in Comparative Example 2 was recycled 6 times, and its catalytic effect on the conversion of isooctyl alcohol to isooctanoic acid gradually decreased. This is because the imidazole nitroxide radicals in Example 2 were not loaded on the heteropolyacid ionic liquid and some could not be recovered, resulting in a decrease in catalytic performance.

[0104] The ionic liquid phase in Comparative Example 3 was recycled 6 times, and its catalytic effect on the conversion of isooctyl alcohol to isooctanoic acid gradually decreased. This is because the compatibility between TEMPO and boron tetrafluoride ionic liquid is relatively weak, which leads to a decrease in its catalytic performance.

[0105] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing aluminum isooctanoate, characterized in that, Includes the following steps: S1. Imidazole salts were prepared using imidazole nitroxide radicals, 1,4-dibromobutane and N-methylimidazolium as raw materials; Functionalized heteropolyacid ionic liquids were prepared using imidazole salts and phosphotungstic acid as raw materials. S2. Mix and dissolve the catalyst-functionalized heteropolyacid ionic liquid and boron tetrafluoride ionic liquid, add isooctanol, reflux at 100~110℃ and pass pure oxygen through, stir the reaction, and after the reaction is completed, extract the reaction solution three times with anhydrous diethyl ether, and combine the organic phase and ionic liquid phase respectively. S3. The organic phase was washed with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain isooctanoic acid; the ionic liquid phase was recovered by distillation under reduced pressure at 70°C. S4. Heat isooctanoic acid to 60-70℃, add glacial acetic acid dropwise under stirring, then continue heating to 140-150℃, slowly add aluminum hydroxide, react for 6-8 hours, cool after the reaction is complete, grind, wash and dry the product to obtain aluminum isooctanoate.

2. The method for preparing aluminum isooctanoate according to claim 1, characterized in that, In step S1, the preparation method of the imidazole salt is as follows: imidazole nitric oxide free radicals, sodium hydride and anhydrous acetone are mixed and stirred at room temperature, then 1,4-dibromobutane is slowly added dropwise, and the mixture is stirred at room temperature for 3-5 hours. After the reaction is completed, the mixture is rotary evaporated, then dissolved in deionized water, extracted with dichloromethane, dried to remove water from the organic phase, concentrated under reduced pressure, and purified by column chromatography to obtain an oily substance. The oily substance, N-methylimidazole and acetonitrile were mixed and reacted at 60-65℃ for 6-8 hours. After the reaction was completed, diethyl ether was added to precipitate the precipitate. The precipitate was washed with diethyl ether to obtain imidazole salt.

3. The method for preparing aluminum isooctanoate according to claim 2, characterized in that, The molar ratio of the imidazole nitroxide radical to 1,4-dibromobutane is 3:4 to 4.2; the molar ratio of the oil to the N-methylimidazolium is 1:1 to 1.

1.

4. The method for preparing aluminum isooctanoate according to claim 2, characterized in that, The method for preparing the imidazole nitroxide free radical is as follows: 4-hydroxybenzaldehyde and N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine are mixed, anhydrous methanol is added, and the mixture is refluxed at 75~80℃ for 48h. After the reaction is completed, the mixture is filtered, and the filter cake is washed with methanol and diethyl ether to obtain the intermediate. The intermediate was dissolved in dichloromethane, and sodium periodate aqueous solution was added dropwise at 0-5°C. After the addition was complete, the reaction was carried out. After the reaction was completed, the mixture was extracted with dichloromethane, the organic phase was dried and filtered, and the filtrate was distilled under reduced pressure to obtain imidazole nitroxide free radicals.

5. The method for preparing aluminum isooctanoate according to claim 4, characterized in that, The molar ratio of 4-hydroxybenzaldehyde and N,N-dihydroxy-2,3-dimethyl-2,3-butanediamine is 1:1.

5.

6. The method for preparing aluminum isooctanoate according to claim 1, characterized in that, In step S1, the preparation method of the functionalized heteropolyacid ionic liquid is as follows: imidazole salt is added to deionized water, stirred evenly, and then added dropwise to phosphotungstic acid aqueous solution. The mixture is stirred at room temperature for 4-6 hours, filtered, and the filter cake is washed with deionized water and diethyl ether, and then vacuum dried to obtain the functionalized heteropolyacid ionic liquid.

7. The method for preparing aluminum isooctanoate according to claim 6, characterized in that, The phosphotungstic acid aqueous solution is obtained by dissolving phosphotungstic acid in deionized water; the molar ratio of the imidazole salt to the phosphotungstic acid is 3:

1.

8. The method for preparing aluminum isooctanoate according to claim 1, characterized in that, In step S2, the ratio of the functionalized heteropolyacid ionic liquid to the boron tetrafluoride ionic liquid is 1 g: 200 mL; the ratio of the functionalized heteropolyacid ionic liquid to isooctanol is 1 g: 25 mL; and the oxygen inlet rate is 25 mL / min.

9. The method for preparing aluminum isooctanoate according to claim 1, characterized in that, In step S4, the amount of glacial acetic acid added is 11% of the mass of isooctanoic acid, and the molar ratio of isooctanoic acid to aluminum hydroxide is 1:0.32~0.35.

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