Preparation method and application of branched chain polycarboxylic acid

Abstract

Formula (1) and formula (2)

Description

Technical Field

[0001] This invention relates to the field of fine chemistry, specifically to a method for preparing branched polycarboxylic acids and their applications. Background Technology

[0002] Branched polycarboxylic acids (BPCAs) are a class of organic acids whose molecular structure contains two or more carboxyl groups (-COOH) and whose carbon chains are branched. Their branched structure and carboxyl functional groups endow the molecules with unique spatial configurations, solubility, and reactivity, making them irreplaceable in various fields. For example, the multi-carboxyl group characteristics and branched structure of BPCAs allow them to be added as functional monomers to the preparation of polymer materials, effectively controlling the polymerization process and product performance. The low irritation, good water solubility, and metal ion chelating ability of BPCAs make them suitable for daily chemical products, food preservation, wastewater treatment, pharmaceuticals, and fertilizer enhancement. Furthermore, BPCAs and their salts (such as ammonium BPCAs) are key electrolytes in the working electrolytes of high-performance aluminum electrolytic capacitors, exhibiting good solubility and low crystallinity, high conductivity, high flash voltage, excellent high and low temperature performance, and chemical repair capabilities, showing significant performance advantages compared to traditional straight-chain polycarboxylic acids.

[0003] Currently, straight-chain polycarboxylic acids are mainly synthesized by the oxidation of cyclic alkanes, alkenes, alcohols, and ketones. For example, adipic acid, an important chemical raw material, is obtained by oxidizing cyclohexane, cyclohexene, cyclohexanol, or cyclohexanone with nitric acid or ozone. Kazuhiko Sato et al. first reported that straight-chain carboxylic acids could be obtained by oxidizing cyclic ketones with hydrogen peroxide, with the oxidation of cyclohexanone to adipic acid being the most representative example. However, the oxidation synthesis of branched polycarboxylic acids by substituting cyclic ketones and alcohols has not been reported (Science 1998, 281(5383), 1646-1647). The synthesis methods of branched polycarboxylic acids mainly include synthesis methods based on straight-chain carboxylic acids and substitution, hydrolysis, and oxidation of related carbonyl derivatives. For example, patent application CN104193612A discloses the oxidation of dicyclopentadiene as a raw material with sodium periodate and hydrogen peroxide under the catalysis of osmium tetroxide to obtain the branched polycarboxylic acid 2,3,5-tricarboxycyclopentylacetic acid. Chen Yao reported a method for synthesizing branched long-chain carboxylic acids using alkylcyclohexanone and isoprene as raw materials. Specifically, under the catalysis of Fenton's reagent, alkylcyclohexanone undergoes ring cleavage and low-temperature polymerization with isoprene (a branched conjugated diene) to generate a branched long-chain dicarboxylic acid ester. Under strongly alkaline conditions, the carboxylic acid ester is hydrolyzed to convert into the corresponding carboxylic acid (Journal of Guangzhou University (Natural Science Edition), 2014, 13(05), 23-28). Patent CN101206955A discloses a method for synthesizing branched polycarboxylic acids using cyclohexanone and methacrylate as raw materials. Cyclohexanone reacts with hydrogen peroxide in ethanol, and under acid catalysis, methyl methacrylate is added to generate a mixture of branched polycarboxylic acid esters. Further saponification and acidification treatment yield a mixture of branched polycarboxylic acids. Patent application CN114315563A discloses a method for obtaining branched carboxylic acids by addition reaction of alkyl olefins with specific structures as raw materials under the catalytic action of a catalytic system composed of palladium chloride, monophosphine ligands, formic acid, acetic anhydride, and lithium chloride. Patent application CN102969161A discloses a method for preparing 2-methyl-2-ethyl sebacate. This method first reacts with metallic sodium in the solvent ethanol, then sequentially adds ethyl 2-methylbutyrate and ethyl 8-bromooctanoate for further reaction. After reflux and treatment, the intermediate diethyl 2-methyl-2-ethyl sebacate is obtained, which is then hydrolyzed and acidified to obtain the target product. Patent application CN109192513A discloses a method for preparing a mixture of branched polycarboxylic acid ammonium salts. Cyclohexanone and hydrogen peroxide are reacted in an alcohol solvent in the presence of an acid catalyst and benzyltriethylammonium chloride, with the addition of potassium sorbate or methyl sorbate and a metal salt to generate a mixture of branched polycarboxylic acid esters. This mixture is then saponified and acidified to obtain the final mixture of branched polycarboxylic acids. Among these methods, the linear carboxylic acid synthesis method uses strong oxidants such as nitric acid, ozone, potassium permanganate, and periodate, which have problems such as strong corrosion to equipment, high safety hazards, and environmental pollution.The synthesis of branched polycarboxylic acids by means of carbonyl derivative substitution, hydrolysis, oxidation, etc. also has drawbacks such as complex synthesis process, limited source of raw materials, low overall yield, complex products, difficult purification, and use of highly toxic reagents and expensive catalysts.

[0004] Therefore, establishing a simple, rapid, green, and economical synthetic method to obtain multi-branched carboxylic acids is of great significance for the development of applications in polymer material performance and polymerization process control, daily chemical products, food preservation, wastewater treatment, pharmaceuticals, fertilizer enhancement, and working electrolytes for high-performance aluminum electrolytic capacitors. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of complex synthesis process, low yield and difficult purification of branched polycarboxylic acids in the existing technology, and to provide a method for preparing branched polycarboxylic acids and their applications. The preparation method has mild reaction conditions, is easy to separate and purify, is green and environmentally friendly, is suitable for large-scale production, and has broad application prospects.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing branched polycarboxylic acids, the method comprising: In the presence of hydrogen peroxide, the cyclic alcohols represented by formula (1) and / or the cyclic ketones represented by formula (2) undergo oxidative ring-opening reactions under the action of a catalyst.

[0007] Equation (1) Equation (2) Among them, R1, R2, R3 and R4 are each hydrogen, C1~C18 alkyl groups, , , , or Furthermore, R1, R2, R3, and R4 are not all hydrogen at the same time; or any two of R1, R2, R3, and R4 that are not hydrogen are connected to form a ring structure; n is an integer from 0 to 10.

[0008] Preferably, the catalyst includes an oxidation reaction catalyst and a phase transfer catalyst.

[0009] Preferably, the molar ratio of the oxidation reaction catalyst to the phase transfer catalyst is 1:0.5~1.

[0010] Preferably, the oxidation reaction catalyst is at least one selected from tungstic acid, sodium tungstate, and phosphotungstic acid.

[0011] Preferably, the phase transfer catalyst is at least one selected from sodium dodecyl sulfate, sodium dodecyl sulfate, tetrabutylammonium bisulfate, tetrahexylammonium bisulfate, trioctylmethylammonium bisulfate, hexadecyltrimethylammonium bisulfate, and tetrabutylammonium bromide.

[0012] Preferably, the conditions for the oxidative ring-opening reaction include a temperature of 60°C to 100°C.

[0013] Preferably, the total amount of the cyclic alcohol and the cyclic ketone, the molar ratio of hydrogen peroxide in the hydrogen peroxide and the catalyst is 1:4~8:0.01~0.1.

[0014] Preferably, the cyclic alcohol can be at least one selected from 3-methylcyclobutanol, 3-methylcyclopentanol, 3-methylcyclohexanol, 4-methylcyclohexanol, 3-5-dimethylcyclohexanol, menthol, 3,3-dimethylcyclohexanol, 3-ethylcyclohexanol, 4-ethylcyclohexanol, 4-isopropylcyclohexanol, 4-tert-butylcyclohexanol, 4-pentylcyclohexanol, 4-cyclohexylcyclohexanol, 4,4'-bicyclohexanol, hydrogenated bisphenol A, and 3,3,5,5-tetramethylcyclohexanol.

[0015] Preferably, the cyclic ketone is at least one selected from 3-methylcyclobutanone, 3-methylcyclopentanone, 3-ethylcyclopentanone, 3-methylcyclohexanone, 4-methylcyclohexanone, menthone, 3,5-dimethylcyclohexanone, 4,4-dimethylcyclohexanone, 3,3-dimethylcyclohexanone, 4-ethyl-4-methylcyclohexanone, 3,3,5-trimethylcyclohexanone, 3,3,5,5-tetramethylcyclohexanone, 4-tert-butylcyclohexanone, 4-cyclohexylcyclohexanone, 2,2-di(4-carbonylcyclohexane)propane, camphor, bicyclo[2.2.1]heptanone, and 4-(4'-propylcyclohexyl)-cyclohexanone.

[0016] A second aspect of the present invention provides a branched polycarboxylic acid obtained by the above preparation method.

[0017] Preferably, the branched polycarboxylic acid has at least one of the structures shown in formula (1-1), formula (1-2), formula (1-3), formula (1-4), formula (1-5), formula (1-6), formula (1-7), and formula (1-8):

[0018] Equation (1-1) Equation (1-2) Equation (1-3)

[0019] Equation (1-4) Equation (1-5) Equation (1-6)

[0020] Equation (1-7) Equation (1-8).

[0021] A third aspect of the present invention provides an electrolyte comprising an ammonium salt of the aforementioned branched polycarboxylic acid and a solvent.

[0022] Preferably, the concentration of the ammonium salt of the branched polycarboxylic acid in the electrolyte is 5-30 wt%.

[0023] Preferably, the pH value of the electrolyte is 7-8.

[0024] Preferably, the solvent is at least one of ethylene glycol, propylene glycol, and γ-butyrolactone.

[0025] The fourth aspect of the present invention provides the application of the above-mentioned electrolyte in aluminum electrolytic capacitors.

[0026] Compared with the prior art, the present invention has the following advantages: 1. This invention utilizes cyclic alcohols or cyclic ketones as raw materials, and in the presence of hydrogen peroxide and a catalyst, sequentially carries out an oxidation-hydrolysis-oxidation reaction process to obtain the target product, branched polycarboxylic acid.

[0027] 2. The synthesis method provided by this invention has the advantages of mild reaction conditions, easy separation and purification, green and environmentally friendly, and suitable for large-scale production compared with the traditional synthesis method of branched polycarboxylic acids. The synthesized multi-substituted alkylated dicarboxylic acid side chain structure is rich and has broad application prospects in the fields of electrolytes, pharmaceuticals, and polymer materials. Attached Figure Description

[0028] Figure 1 This is the 1H NMR spectrum of BPCA-1 prepared in Example 1 of this invention; Figure 2 This is the carbon NMR spectrum of BPCA-1 prepared in Example 1 of this invention; Figure 3 This is the infrared spectrum of BPCA-1 prepared in Example 1 of this invention; Figure 4 This is the mass spectrum of BPCA-1 prepared in Example 1 of this invention; Figure 5 This is the 1H NMR spectrum of BPCA-2 prepared in Example 2 of this invention; Figure 6 This is the infrared spectrum of BPCA-2 prepared in Example 2 of this invention; Figure 7 This is the 1H NMR spectrum of BPCA-3 prepared in Example 3 of this invention; Figure 8 This is the carbon NMR spectrum of BPCA-3 prepared in Example 3 of this invention. Detailed Implementation

[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of technical features indicated. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0032] The method for preparing branched polycarboxylic acids according to the present invention includes: in the presence of hydrogen peroxide, oxidative ring-opening reaction of cyclic alcohols represented by formula (1) and / or cyclic ketones represented by formula (2) under the action of a catalyst;

[0033] Equation (1) Equation (2) Among them, R1, R2, R3 and R4 are each hydrogen, C1~C18 alkyl groups, , , , or Furthermore, R1, R2, R3, and R4 are not all hydrogen at the same time; or any two of R1, R2, R3, and R4 that are not hydrogen are connected to form a ring structure; n is an integer from 0 to 10.

[0034] In this invention, C1-C18 alkyl groups include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, neopentyl, n-hexyl, isohexyl, or cyclohexyl.

[0035] n is an integer from 0 to 10, specifically 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0036] In the above formulas (1) and (2), the substituents R1, R2, R3, and R4 can be the same or different, but they cannot all be hydrogen. The substitution positions of R1, R2, R3, and R4 can be arbitrary. When at least two of R1, R2, R3, and R4 are not hydrogen, any two of R1, R2, R3, and R4 that are not hydrogen form a ring structure. Preferably, any two of R1, R2, R3, and R4 that are not hydrogen form a ring structure, that is, R1 and R2 form a ring structure, or R1 and R3 form a ring structure, or R1 and R4 form a ring structure, or R2 and R3 form a ring structure, or R2 and R4 form a ring structure, or R3 and R4 form a ring structure.

[0037] In this invention, the hydrogen peroxide is an aqueous solution of hydrogen peroxide with a mass concentration of 10-70%, preferably 25-35%, and more preferably 30%.

[0038] In this invention, the cyclic alcohol represented by formula (2) can be at least one of 3-methylcyclobutanol, 3-methylcyclopentanol, 3-methylcyclohexanol, 4-methylcyclohexanol, 3-5-dimethylcyclohexanol, menthol, 3,3-dimethylcyclohexanol, 3-ethylcyclohexanol, 4-ethylcyclohexanol, 4-isopropylcyclohexanol, 4-tert-butylcyclohexanol, 4-pentylcyclohexanol, 4-cyclohexylcyclohexanol, 4,4'-bicyclohexanol, hydrogenated bisphenol A, and 3,3,5,5-tetramethylcyclohexanol, preferably at least one of 3-methylcyclohexanol, 4-ethylcyclohexanol, 4-tert-butylcyclohexanol, 3,3,5,5-tetramethylcyclohexanol, and hydrogenated bisphenol A, which can yield a higher product yield.

[0039] In this invention, the cyclic ketone represented by formula (3) can be at least one of 3-methylcyclobutanone, 3-methylcyclopentanone, 3-ethylcyclopentanone, 3-methylcyclohexanone, 4-methylcyclohexanone, menthone, 3,5-dimethylcyclohexanone, 4,4-dimethylcyclohexanone, 3,3-dimethylcyclohexanone, 4-ethyl-4-methylcyclohexanone, 3,3,5-trimethylcyclohexanone, 3,3,5,5-tetramethylcyclohexanone, 4-tert-butylcyclohexanone, 4-cyclohexylcyclohexanone, 2,2-di(4-carbonylcyclohexyl)propane, camphor, bicyclo[2.2.1]heptanone, and 4-(4'-propylcyclohexyl)-cyclohexanone, preferably camphor and / or 4-(4'-propylcyclohexyl)-cyclohexanone, which can yield a higher product yield.

[0040] The catalyst of the present invention includes an oxidation reaction catalyst and a phase transfer catalyst, wherein the molar ratio of the oxidation reaction catalyst to the phase transfer catalyst is preferably 1:0.5~1, and more preferably 1:0.9~1.

[0041] The oxidation reaction catalyst of the present invention can be at least one of tungstic acid, sodium tungstate and phosphotungstic acid, preferably tungstic acid.

[0042] The phase transfer catalyst of the present invention may be at least one of sodium dodecyl sulfate, sodium dodecyl sulfate, tetrabutylammonium hydrogen sulfate, tetrahexylammonium hydrogen sulfate, trioctylmethylammonium hydrogen sulfate, hexadecyltrimethylammonium hydrogen sulfate and tetrabutylammonium bromide, preferably at least one of sodium dodecyl sulfonate, hexadecyltrimethylammonium hydrogen sulfate and tetrabutylammonium hydrogen sulfate.

[0043] The oxidative ring-opening reaction described in this invention does not use a solvent or only adds an appropriate amount of water as a solvent. The reaction conditions are mild, with a temperature of 60℃~100℃, preferably 85℃~95℃.

[0044] In the oxidative ring-opening reaction of the present invention, the amounts of each raw material are as follows: the total amount of the cyclic alcohol and the cyclic ketone, the molar ratio of hydrogen peroxide in the hydrogen peroxide and the catalyst is 1:4~10:0.01~0.1, preferably 1:4.5~6.5:0.02~0.04.

[0045] In some specific implementations, the molar ratio of the cyclic alcohol, the hydrogen peroxide in the hydrogen peroxide solution, and the catalyst is 1:4~10:0.01~0.1.

[0046] In some specific implementations, the molar ratio of the cyclic ketone, the hydrogen peroxide in the hydrogen peroxide, and the catalyst is 1:4~10:0.01~0.1.

[0047] The preparation method of branched polycarboxylic acids of the present invention may further include post-processing, which includes: cooling the product of the oxidative ring-opening reaction to room temperature, adjusting the pH of the system to 9-10, adding an isopolar solvent (ethyl acetate or diethyl ether) for extraction, removing unreacted raw materials and reaction byproducts, adjusting the pH of the aqueous phase to 1-3, concentrating under reduced pressure to remove most of the solvent water, and then crystallizing to obtain the high-purity target product.

[0048] The branched polycarboxylic acid of the present invention is obtained by cyclic oxidative ring-opening of the cyclic alcohol represented by formula (2) or the cyclic ketone represented by formula (3).

[0049] In this invention, the branched polycarboxylic acid has at least one of the structures shown in formulas (1-1), (1-2), (1-3), (1-4), (1-5), (1-6), (1-7), and (1-8):

[0050] Equation (1-1) Equation (1-2) Equation (1-3)

[0051] Equation (1-4) Equation (1-5) Equation (1-6)

[0052] Equation (1-7) Equation (1-8).

[0053] In this invention, branched polycarboxylic acids with the above-mentioned structures can be prepared by changing the raw materials. The raw materials and the corresponding branched polycarboxylic acids are shown in Table 1.

[0054] Table 1

[0055]

[0056] The electrolyte of this invention comprises an ammonium salt of the aforementioned branched polycarboxylic acid and a solvent. In the electrolyte, the concentration of the ammonium salt of the branched polycarboxylic acid is preferably 5-30 wt%.

[0057] The pH value of the electrolyte is 7-8. The solvent used to prepare the electrolyte can be at least one of ethylene glycol, propylene glycol, and γ-butyrolactone.

[0058] The electrolyte described in this invention can be used in aluminum electrolytic capacitors.

[0059] The following examples further illustrate the preparation method and application of the branched polycarboxylic acids of the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0060] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0061] Example 1 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (10.94g, 43.79mmol), hydrogen peroxide (100.00g, 30wt%), and sodium dodecyl sulfonate (11.93g, 43.79mmol) were added. The temperature was raised to 55°C. After the reaction solution became a transparent solution, 3-methylcyclohexanol (100.00g, 875.75mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (350.00g, 30wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped after the reactants had completely reacted.

[0062] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was added for extraction to remove unreacted starting materials and byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-1. The 1H NMR spectrum of BPCA-1 is shown below. Figure 1 As shown, the carbon NMR spectrum is as follows: Figure 2 As shown, the infrared spectrum is as follows Figure 3 As shown, the mass spectrum is as follows Figure 4 As shown. The structural formula of BPCA-1 is shown in equation (1-1):

[0063] Equation (1-1).

[0064] Example 2 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (9.74g, 39.00mmol), water (50mL), hydrogen peroxide (100.00g, 30wt%), and sodium dodecyl sulfonate (10.62g, 39.00mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, 4-ethylcyclohexanol (100.00g, 779.94mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (300.00g, 30wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the reactants had completely reacted.

[0065] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted reactants and byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-2. The 1H NMR spectrum of BPCA-2 is shown below. Figure 5 As shown, the infrared spectrum is as follows Figure 6 As shown. The structural formula of BPCA-2 is shown in equation (1-2):

[0066] Equation (1-2).

[0067] Example 3 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (7.99g, 32.00mmol), water (50mL), hydrogen peroxide (80.00g, 30wt%), and sodium dodecyl sulfonate (8.72g, 32.00mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, 4-tert-butylcyclohexanol (100.00g, 639.92mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (250.00g, 30wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the reactants had completely reacted.

[0068] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted starting materials and byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-3. The 1H NMR spectrum of BPCA-3 is shown below. Figure 7 As shown, the carbon NMR spectrum is as follows: Figure 8 As shown. The structural formula of BPCA-3 is shown in equation (1-3):

[0069] Equation (1-3).

[0070] Example 4 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (7.99g, 32.00mmol), water (50mL), hydrogen peroxide (80.00g, 30wt%), and sodium dodecyl sulfonate (8.72g, 32.00mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, 3,3,5,5-tetramethylcyclohexanol (100.00g, 639.92mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (250.00g, 30wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the reactants had completely reacted.

[0071] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-4. The structural formula of BPCA-4 is shown in formula (1-4).

[0072] Equation (1-4) Example 5 Add tungstic acid (6.56 g, 26.27 mmol), hydrogen peroxide (50.00 g, 30 wt%), and sodium dodecyl sulfonate (7.16 g, 26.27 mmol) to a 1 L three-necked round-bottom flask equipped with a spherical condenser and a thermometer. Heat to 55 °C. After the reaction solution becomes a transparent solution, add the starting material 1,7,7-trimethylbicyclo[2.2.1]heptane-2-one (camphor, 80.00 g, 525.50 mmol). Stir and heat to 90 °C to react. Add the remaining hydrogen peroxide (250.00 g, 30 wt%) in batches. Monitor the reaction progress by TLC. Stop the reaction after the starting material has reacted completely.

[0073] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-5. The structural formula of BPCA-5 is shown in formula (1-5).

[0074] Equation (1-5) Example 6 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (7.99g, 32.00mmol), hydrogen peroxide (50.00g, 30wt%), and hexadecyltrimethylammonium hydrogen sulfate (12.21g, 32.00mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, the starting material 2-isopropyl-5-methylcyclohexanol (menthol, 100.00g, 639.92mmol) was added. The mixture was stirred and heated to 95°C. The remaining hydrogen peroxide (320.00g, 30wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the starting material had completely reacted.

[0075] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-6. The structural formula of BPCA-6 is shown in formula (1-6).

[0076] Equation (1-6) Example 7 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (8.10 g, 32.41 mmol), hydrogen peroxide (50.00 g, 30 wt%), and hexadecyltrimethylammonium hydrogen sulfate (12.37 g, 32.00 mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, the starting material 2-isopropyl-5-methylcyclohexanone (menthol, 100.00 g, 648.29 mmol) was added. The mixture was stirred and heated to 95°C. The remaining hydrogen peroxide (250.00 g, 30 wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the starting material had completely reacted.

[0077] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-6. The structural formula of BPCA-6 is shown in formula (1-6).

[0078] Equation (1-6) Example 8 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (2.81 g, 11.24 mmol), hydrogen peroxide (20.00 g, 30 wt%), and tetrabutylammonium hydrogen sulfate (3.82 g, 11.24 mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, 4-(4'-propylcyclohexyl)-cyclohexanone (50.00 g, 224.85 mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (85.00 g, 30 wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the reactants had completely reacted.

[0079] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-7. The structural formula of BPCA-7 is shown in formula (1-7):

[0080] Equation (1-7).

[0081] Example 9 In a 1L three-necked round-bottom flask equipped with a spherical condenser and a thermometer, tungstic acid (2.60 g, 10.04 mmol), hydrogen peroxide (30.00 g, 30 wt%), and tetrabutylammonium hydrogen sulfate (3.53 g, 10.40 mmol) were added. The mixture was then heated to 55°C. Once the reaction solution became transparent, the starting material 4,4'-(1-methylethylidene)bicyclohexanol (hydrogenated bisphenol A, 50.00 g, 208.00 mmol) was added. The mixture was stirred and heated to 90°C. The remaining hydrogen peroxide (200.00 g, 30 wt%) was added in batches. The reaction progress was monitored by TLC. The reaction was stopped once the starting material had completely reacted.

[0082] After the reaction was complete, the mixture was cooled to room temperature, filtered to recover the tungstic acid catalyst, and the pH of the filtrate was adjusted to 10 using an alkaline solution. Ethyl acetate was then added for extraction to remove unreacted raw materials and reaction byproducts. The pH of the aqueous phase was adjusted to 1 using dilute sulfuric acid, and then concentrated under reduced pressure to remove most of the solvent water. Crystallization yielded the product BPCA-8. The structural formula of BPCA-8 is shown in formula (1-8).

[0083] Equation (1-8) Example 10 The difference from Example 1 is that the amount of tungstic acid was adjusted to 21.90 mmol, and the product BPCA-1 was obtained.

[0084] Example 11 The difference from Example 1 is that the amount of 3-methylcyclohexanol was adjusted to 437.88 mmol, resulting in product BPCA-1.

[0085] The products of Examples 1-9 were structurally characterized, and the results are shown in Table 2.

[0086] Table 2

[0087] The yields of the products obtained in Examples 1-11 are shown in Table 3: Table 3

[0088] Example 12 The BPCA-1 prepared in Example 1 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-1-NH4. + .

[0089] Example 13 The BPCA-2 prepared in Example 2 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-2-NH4. + .

[0090] Example 14 The BPCA-3 prepared in Example 3 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-3-NH4. + .

[0091] Example 15 The BPCA-4 prepared in Example 4 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-4-NH4. + .

[0092] Example 16 The BPCA-5 prepared in Example 5 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-5-NH4. + .

[0093] Example 17 The BPCA-6 prepared in Example 6 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-6-NH4. + .

[0094] Example 18 The BPCA-7 prepared in Example 8 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-7-NH4. + .

[0095] Example 19 The BPCA-8 prepared in Example 9 was added to ethylene glycol to prepare a 10 wt% ethylene glycol solution. Ammonia gas was then introduced for ammoniation, and the endpoint was monitored until the pH of the solution reached 7.5, thus obtaining the ammonium carboxylate electrolyte BPCA-8-NH4. + .

[0096] Test Example 1: Flashover Voltage of Electrolyte Without adding any other additives, the ammonium carboxylate salt electrolyte prepared above was used as the working electrolyte for aluminum electrolytic capacitors. The relevant properties of each working electrolyte were tested and compared with those of electrolytes prepared with existing diammonium salts. The results are shown in Table 4.

[0097] Table 4

[0098] As can be seen from the data in Table 4, when the solute prepared by the multi-substituted alkylated dicarboxylic acid of the present invention is used as the electrolyte, its flash voltage is significantly improved compared with the existing representative straight-chain ammonium carboxylate and branched-chain ammonium carboxylate.

[0099] Test Example 2: Temperature resistance of the electrolyte The ammonium carboxylate electrolyte prepared above was subjected to constant temperature at 105℃, and the conductivity changes at different times were measured. The results are shown in Table 5.

[0100] Table 5

[0101] As can be seen from the data in Table 5, when the branched carboxylic acids obtained by the branched polycarboxylic acid synthesis method provided by the present invention are ammonified and used as electrolyte solutes, their temperature resistance is significantly improved compared with the existing representative straight-chain carboxylic acid ammonium salts and branched carboxylic acid ammonium salts.

[0102] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing branched polycarboxylic acids, characterized in that, The preparation method includes: In the presence of hydrogen peroxide, the cyclic alcohols represented by formula (1) and / or the cyclic ketones represented by formula (2) undergo oxidative ring-opening reactions under the action of a catalyst. Equation (1) Equation (2) Among them, R1, R2, R3 and R4 are each hydrogen, C1~C18 alkyl groups, , , , or Furthermore, R1, R2, R3, and R4 are not all hydrogen at the same time; or any two of R1, R2, R3, and R4 that are not hydrogen are connected to form a ring structure; n is an integer from 0 to 10.

2. The preparation method according to claim 1, characterized in that, The catalyst includes an oxidation reaction catalyst and a phase transfer catalyst; Preferably, the molar ratio of the oxidation reaction catalyst to the phase transfer catalyst is 1:0.5~1; Preferably, the oxidation reaction catalyst is at least one selected from tungstic acid, sodium tungstate, and phosphotungstic acid; Preferably, the phase transfer catalyst is at least one selected from sodium dodecyl sulfate, sodium dodecyl sulfate, tetrabutylammonium bisulfate, tetrahexylammonium bisulfate, trioctylmethylammonium bisulfate, hexadecyltrimethylammonium bisulfate, and tetrabutylammonium bromide.

3. The preparation method according to claim 1 or 2, characterized in that, The conditions for the oxidative ring-opening reaction include: a temperature of 60℃~100℃; and / or The total amount of the cyclic alcohol and the cyclic ketone, the molar ratio of hydrogen peroxide in the hydrogen peroxide and the catalyst is 1:4~10:0.01~0.

1.

4. The preparation method according to any one of claims 1-3, characterized in that, The cyclic alcohol may be at least one selected from 3-methylcyclobutanol, 3-methylcyclopentanol, 3-methylcyclohexanol, 4-methylcyclohexanol, 3-5-dimethylcyclohexanol, menthol, 3,3-dimethylcyclohexanol, 3-ethylcyclohexanol, 4-ethylcyclohexanol, 4-isopropylcyclohexanol, 4-tert-butylcyclohexanol, 4-pentylcyclohexanol, 4-cyclohexylcyclohexanol, 4,4'-bicyclohexanol, hydrogenated bisphenol A, and 3,3,5,5-tetramethylcyclohexanol; and / or The cyclic ketone is at least one selected from 3-methylcyclobutanone, 3-methylcyclopentanone, 3-ethylcyclopentanone, 3-methylcyclohexanone, 4-methylcyclohexanone, menthone, 3,5-dimethylcyclohexanone, 4,4-dimethylcyclohexanone, 3,3-dimethylcyclohexanone, 4-ethyl-4-methylcyclohexanone, 3,3,5-trimethylcyclohexanone, 3,3,5,5-tetramethylcyclohexanone, 4-tert-butylcyclohexanone, 4-cyclohexylcyclohexanone, 2,2-di(4-carbonylcyclohexane)propane, camphor, bicyclo[2.2.1]heptanone, and 4-(4'-propylcyclohexyl)cyclohexanone.

5. The branched polycarboxylic acid obtained by the preparation method according to any one of claims 1-4.

6. The branched polycarboxylic acid according to claim 5, characterized in that, The branched polycarboxylic acid has at least one of the structures shown in formula (1-1), formula (1-2), formula (1-3), formula (1-4), formula (1-5), formula (1-6), formula (1-7), and formula (1-8): Equation (1-1) Equation (1-2) Equation (1-3) Equation (1-4) Equation (1-5) Equation (1-6) Equation (1-7) Equation (1-8).

7. An electrolyte, characterized in that, The electrolyte comprises an ammonium salt of the branched polycarboxylic acid as described in claim 5 or 6 and a solvent.

8. The electrolyte according to claim 7, characterized in that, In the electrolyte, the concentration of the ammonium salt of the branched polycarboxylic acid is 5-30 wt%.

9. The electrolyte according to claim 7 or 8, characterized in that, The electrolyte has a pH of 7-8; and / or The solvent is at least one of ethylene glycol, propylene glycol, and γ-butyrolactone.

10. The application of the electrolyte according to any one of claims 7-9 in aluminum electrolytic capacitors.

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