Process for the preparation of solid acid catalysts and 4,4'-butylidenebis(6-tert-butyl-m-cresol) antioxidant

Abstract

The present application provides a kind of solid acid catalyst and the method for preparing 4,4'- butylidene bis (6-tert-butyl-m-cresol) antioxidant using the catalyst.The solid acid catalyst of the present application includes active component containing Lewis acid and catalyst carrier, the Lewis acid includes one or more of AlCl3, ZnCl2, SbCl3, the carrier includes pillared montmorillonite, the pillared montmorillonite is selected from one or more of titanium pillared montmorillonite, silicon pillared montmorillonite, aluminum pillared montmorillonite, zirconium pillared montmorillonite.The catalyst of the present application has high catalytic activity, good repeatability, simple separation and recovery process, high yield of antioxidant preparation method, green, economical and environmental preparation process.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a solid acid catalyst and a method for preparing 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant using the catalyst. Background Technology

[0002] Antioxidant 4,4′-Butylbis(6-tert-butyl-m-cresol) (i.e., antioxidant BBM), CAS No.: 85-60-9, Molecular formula C 26 H 38 O2 can be used as an excellent antioxidant in PE, PP, PVC, ABS, SBS resins, polyamides, and rubber products. It does not pollute or color the product, does not decompose during high-temperature processing, and can significantly improve the heat resistance and antioxidant properties of the product.

[0003]

[0004] The traditional synthesis method for the antioxidant 4,4′-butylenebis(6-tert-butyl-m-cresol) involves using phenol and aldehyde as raw materials and a common protic acid as a catalyst in a condensation reaction to obtain the final product. Most existing technologies use inorganic protic acids such as hydrochloric acid and sulfuric acid, or organic sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, or trifluoromethanesulfonic acid as catalysts to synthesize the antioxidant BBM.

[0005] Patent US2822404 uses 6-tert-butyl-m-cresol and trimetaldehyde as raw materials, with hydrochloric acid as a catalyst. After the reaction, a large amount of sodium carbonate solution is added for neutralization. The crude product is recrystallized in a benzene-alcohol mixture as a crystallization solvent, yielding a product with a yield of 84% and a melting point of 201-202℃. Patent US2970151 uses 6-tert-butyl-m-cresol as the phenol source and n-butyraldehyde as the aldehyde source, with hydrochloric acid as a catalyst for synthesis. After the reaction, vacuum distillation is performed to remove excess hydrochloric acid from the system. Then, benzene is added to dissolve the product, and a large amount of water is added to remove residual acid. The process is overly cumbersome. CN 108586206A describes a one-pot synthesis method for preparing 4,4′-butylenebis(6-tert-butyl-m-cresol) using 6-tert-butyl-m-cresol and n-butyraldehyde as raw materials, methanol as solvent, and hydrochloric acid as catalyst. After the condensation reaction, an aromatic hydrocarbon solvent is added. A mixed solvent consisting of methanol and aromatic hydrocarbon solvents completely dissolves the reaction mixture at the reflux temperature of methanol, causing it to separate into layers. The acidic aqueous layer is separated, and the remaining methanol is evaporated from the organic layer. Post-treatment yields the crystalline product. However, inorganic acid catalysts such as hydrochloric acid and sulfuric acid not only corrode production equipment, but also often require large amounts of water and alkali for washing and neutralization after the reaction to remove the catalyst. This is not only complex but also generates large amounts of saline wastewater, harming the environment. Furthermore, the complex process of recovering saline wastewater increases production costs.

[0006] CN110302845A synthesizes BBM using 6-tert-butyl-m-cresol and n-butyraldehyde as raw materials and p-toluenesulfonic acid as a catalyst, and demonstrates effective catalyst recovery. JP2007269711A uses organic sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, or trifluoromethanesulfonic acid as catalysts to react 6-tert-butyl-3-methylphenol with n-butyraldehyde in the presence of N-diethylhydroxylamine to synthesize BBM. However, using organic sulfonic acids as catalysts still requires post-treatment processes such as distillation and extraction to achieve effective catalyst recovery. Recovery requires the use of organic extractants such as toluene, causing environmental pollution and increasing costs. Summary of the Invention

[0007] To address the aforementioned technical problems in the prior art, this invention provides a solid acid catalyst and a method for synthesizing the antioxidant 4,4′-butylenebis(6-tert-butyl-m-cresol) using the catalyst. The solid acid catalyst of this invention is a modified acidic natural clay, which not only exhibits excellent catalytic activity in the synthesis of the antioxidant 4,4′-butylenebis(6-tert-butyl-m-cresol), but also features a simple catalyst recovery process and can be reused multiple times.

[0008] In a first aspect, the present invention provides a solid acid catalyst comprising an active component containing a Lewis acid and a catalyst support, wherein the active component containing the Lewis acid is selected from one or more of AlCl3, ZnCl2, and SbCl3, and the support comprises pillared montmorillonite, wherein the pillared montmorillonite is selected from one or more of titanium pillared montmorillonite, silicon pillared montmorillonite, aluminum pillared montmorillonite, and zirconium pillared montmorillonite.

[0009] According to some embodiments of the present invention, the carrier comprises titanium-pillared montmorillonite, i.e., metal-modified montmorillonite.

[0010] Modification of montmorillonite with metals such as titanium provides spatial support, enabling it to form a well-developed mesoporous structure. This increases the specific surface area of ​​the pillared montmorillonite support, allowing active components such as Lewis acids to be uniformly loaded onto the modified montmorillonite and exert catalytic activity. The solid acid catalyst of this invention belongs to the broad category of Lewis acids. Its structure uses Lewis acids such as AlCl3, ZnCl2, and SbCl3 as electron donors, with a two-dimensional layered nanostructure of montmorillonite as the basic structural framework, and interlayer pillars of metal oxides such as titanium, aluminum, and zirconium to form a three-dimensional structure with a very high specific surface area and high catalytic activity.

[0011] According to some embodiments of the present invention, the mass ratio of the Lewis acid to the pillared montmorillonite is 1:(1-3), preferably 1:(1.2-2.5); for example, optional mass ratios are 1:1.2, 1:1.5, 1:2, 1:2.5, and 1:3.

[0012] Secondly, the present invention also provides a method for preparing the solid acid catalyst, comprising the following steps:

[0013] A first solution containing Lewis acid and organic acid is mixed with a second solution containing a columnarizing agent precursor and a ketone solvent to obtain a columnar liquid; then montmorillonite is mixed with the columnar liquid to obtain a wet gel; the wet gel is aged, dried and calcined to obtain the solid acid catalyst.

[0014] In some embodiments, the preparation method includes the following steps:

[0015] a. Mix the Lewis acid with an organic acid to obtain a first solution;

[0016] b. Mix the columnarizing agent precursor and the ketone solvent to obtain a second solution;

[0017] c. Add the second solution dropwise to the first solution to obtain the columnar liquid;

[0018] d. Dissolve montmorillonite to obtain a suspension, and mix the suspension with the columnar liquid obtained in step c to obtain a wet gel;

[0019] e. The wet gel obtained in step d is aged, dried, and calcined to obtain the solid acid catalyst.

[0020] In some embodiments, it is more advantageous for the first and second solutions to be dissolved in an alcohol solvent or water, wherein the alcohol solvent is ethanol.

[0021] In some embodiments, the organic acid includes at least one of monobasic fatty acids, dibasic fatty acids, and polybasic fatty acids, preferably at least one of formic acid, acetic acid, tartaric acid, oxalic acid, malic acid, and citric acid. In some embodiments, the organic acid is selected from oxalic acid. In some embodiments, the molar ratio of the Lewis acid to the organic acid in the first solution is (1-5):1, for example, 1:1, 1:2, 1:3, 1:4, 1:5, or any value between them, preferably (1-2):1.

[0022] In some embodiments, the columnarizing agent precursor is selected from at least one of titanium columnar precursors, silicon columnar precursors, aluminum columnar precursors, and zirconium columnar precursors. In some preferred embodiments, the columnarizing agent precursor is a titanium columnar precursor. In some more preferred embodiments, the titanium columnar precursor comprises tetrabutyl titanate, which decomposes in water to form Ti(OH)4, and then reacts with organic acids such as oxalic acid to generate an organotitanium salt. The organotitanium salt undergoes calcination, during which all carbon chains are carbonized, preserving the structure, and the titanium remains in the three-dimensional structure, thereby forming titanium columnar montmorillonite.

[0023] In this invention, the pillar proppant formed by titanium pillar precursor, silicon pillar precursor, aluminum pillar precursor and zirconium pillar precursor can effectively prop open the montmorillonite soil layer, form a good mesoporous structure, significantly increase the specific surface area of ​​the prepared pillar proppant montmorillonite carrier, and improve the activity of the catalyst.

[0024] In some embodiments, the molar ratio of the Lewis acid catalyst to the column precursor is (3-7):1, for example 4:1, 5:1, 6:1.

[0025] In some embodiments, the ketone solvent, such as acetone or acetylacetone, serves as a solvent displacement agent. In some embodiments, the molar ratio of the tetrabutyl titanate to the ketone organic solvent is 1:(0.5 to 1.5), for example, 1:0.5, 1:1, 1:1.2, 1:1.5, or any value between them.

[0026] In some embodiments, the silanizing agent precursor includes at least one of aminopropyltrimethoxysilane and tetraethyl orthosilicate.

[0027] In some embodiments, the aluminum columnarizing agent precursor includes one or more of aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0028] In some embodiments, the zirconium pillaring agent precursor is zirconium oxychloride.

[0029] In some embodiments, the aging temperature is 10–90°C, and the aging time is 2–4 days. The drying is preferably natural air drying. The calcination temperature is 500–1000°C, and the calcination time is 1–5 hours. In specific embodiments, the aging temperature can be, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, or 90°C. The calcination temperature can be, for example, 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C.

[0030] The present invention also provides a method for preparing the solid acid catalyst, comprising the following steps:

[0031] a. Mix the Lewis acid with an organic acid and dissolve it in ethanol to obtain a first solution;

[0032] b. Mix tetrabutyl titanate and acetylacetone, dissolve them in ethanol to obtain a second solution;

[0033] c. Add the second solution dropwise to the first solution to obtain a titanium pillar liquid;

[0034] d. Mix montmorillonite with water to obtain a suspension, and mix the suspension with the titanium pillar liquid obtained in step c to obtain a wet gel;

[0035] e. The wet gel obtained in step d is aged, dried, and calcined to obtain the solid acid catalyst.

[0036] Thirdly, the present invention provides a method for preparing 4,4′-butylidene bis(6-tert-butyl-m-cresol) antioxidant, comprising: reacting 6-tert-butyl-m-cresol and n-butyraldehyde as raw materials in the presence of the solid acid catalyst described in the first aspect of the present invention to obtain 4,4′-butylidene bis(6-tert-butyl-m-cresol).

[0037] In some embodiments, the mass ratio of 6-tert-butyl-m-cresol to the solid acid catalyst is 1:(0.01-0.05), for example, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, or any value between them. In some preferred embodiments, the mass ratio of 6-tert-butyl-m-cresol to the solid acid catalyst is 1:(0.02-0.04).

[0038] In some embodiments, the molar ratio of n-butyraldehyde to 6-tert-butyl-m-cresol is 1:(4-5), for example 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, or any value between them. In some preferred embodiments, the molar ratio of n-butyraldehyde to 6-tert-butyl-m-cresol is 1:(4.3-4.7).

[0039] In some embodiments, the reaction is carried out in an organic solvent. The organic solvent is selected from alcohols having 1-6 carbon atoms, such as one or more of methanol, ethanol, and isopropanol. In some embodiments, the volume ratio of the organic solvent to the mass ratio of the 6-tert-butyl-m-cresol is (0.5-1.5):1 mL / g.

[0040] In some embodiments, the reaction temperature is a reflux temperature, preferably 60-95°C; for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C. In some embodiments, the reaction time is 2-10 hours.

[0041] In some embodiments, the reaction further includes a post-processing step, which includes: performing solid-liquid separation on the reaction solution, and then cooling and crystallizing the liquid phase to obtain 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant.

[0042] In some embodiments, the solvent used for the cooling crystallization includes alkane and / or aromatic solvents, preferably one or more of toluene, xylene, trimethylbenzene, and petroleum ether.

[0043] In some embodiments, the volume of the solvent used for cooling crystallization is 2-10 times the volume of the liquid phase obtained by solid-liquid separation.

[0044] In some embodiments, the cooling crystallization includes first cooling to room temperature, holding at that temperature for 1-3 hours, and then cooling to 5-10°C and holding at that temperature for 1-3 hours.

[0045] In some embodiments, after cooling and crystallization, the mixture is filtered, and the solid phase is washed and dried to obtain a 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant. Preferably, the drying temperature is 140-160°C.

[0046] According to some embodiments of the present invention, the preparation of the antioxidant includes the following steps:

[0047] (1) Mix 6-tert-butylm-cresol and the solid acid catalyst with a first organic solvent to obtain a mixture;

[0048] (2) The mixture is mixed with n-butyraldehyde and heated to react. After the reaction is completed, the reaction solution is subjected to a first solid-liquid separation to obtain a solid acid catalyst and a liquid phase.

[0049] (3) The liquid phase is mixed with the second organic solvent, cooled and crystallized, and a second solid-liquid separation is performed. The solid phase is washed and dried to obtain 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant.

[0050] In the above method, the first organic solvent in step (1) is selected from alcohols with 1-6 carbon atoms, preferably one or more of methanol, ethanol and isopropanol.

[0051] In the above method, the second organic solvent in step (3) includes alkane and / or aromatic solvents, preferably one or more of toluene, xylene, trimethylbenzene, and petroleum ether.

[0052] The method of the present invention can effectively recover solid acid catalyst by performing the first solid-liquid separation in step (2) above. The operation is simple and efficient, and the recovered catalyst can be directly reused. After multiple reuses, the catalytic performance does not decrease significantly.

[0053] Fourthly, the present invention provides the use of the solid acid catalyst described in the first aspect in the preparation of 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant.

[0054] The solid acid catalyst described in the first aspect of this invention exhibits good catalytic activity, high reaction yield, good catalyst repeatability, and is recyclable in the reaction of preparing 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant from 6-tert-butyl-m-cresol and n-butyraldehyde, and does not put pressure on the environment.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. This invention uses pillared montmorillonite with a high specific surface area as a support to load Lewis acid and other catalytically active components to obtain a solid acid catalyst, which can efficiently prepare 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant with high reaction yield.

[0057] 2. The solid acid catalyst of the present invention enables the preparation process of 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant to avoid the problems of using conventional inorganic acids, which require a large amount of alkaline solution for neutralization and the treatment of large amounts of saline wastewater.

[0058] 3. The method for preparing 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant of the present invention allows for efficient recovery of the catalyst through simple solid-liquid separation after the reaction. At the same time, this solid acid catalyst can be reused multiple times while maintaining high catalytic activity, exhibiting good repeatability. The separation and reuse method is simple, environmentally friendly, and reduces production costs. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0060] Unless otherwise stated, the terms used in this invention generally have the meanings commonly understood by those skilled in the art.

[0061] The term "solid acid catalyst" used in this article refers to an important class of acid-base catalysts. Their catalytic function originates from catalytically active acidic sites, called acid centers, on the surface of the solid. These catalysts are widely used in ionic catalytic reactions. Types of solid acid catalysts include natural clay catalysts, mixed oxide catalysts, molecular sieve catalysts, and supported solid acid catalysts.

[0062] The term "pillared montmorillonite" used in this article refers to a three-dimensional structure formed by inserting pillar materials between the layers of montmorillonite, which has a two-dimensional layered nanostructure as its basic structural framework. Commonly used pillar materials include titanium pillar materials, aluminum pillar materials, silicon pillar materials, and zirconium pillar materials.

[0063] According to a specific embodiment of the present invention, the preparation method of the solid acid catalyst includes the following steps:

[0064] (a) Dissolve AlCl3 or ZnCl2 or SbCl3 with oxalic acid in ethanol or water at a molar ratio of (1-5):1 to obtain solution A;

[0065] (b) Add tetrabutyl titanate and acetylacetone to ethanol in a molar ratio of 1:(0.5-1.5), stir, and obtain solution B;

[0066] (c) Add liquid B dropwise to liquid A under stirring to obtain titanium pillar liquid;

[0067] (d) Add montmorillonite to deionized water to obtain a montmorillonite suspension. Add the titanium pillar liquid obtained in step (c) dropwise to the montmorillonite suspension and stir to obtain a wet gel.

[0068] (e) The wet gel is aged at 30-80°C for 2-3 days and then air-dried to obtain a dry gel;

[0069] (f) The dry gel obtained in step (e) is ground and then calcined at 500-1000℃ for 1-5 hours under a protective atmosphere to obtain a solid acid catalyst.

[0070] According to a specific embodiment of the present invention, the preparation method of the 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant includes the following steps:

[0071] (1) Mix 6-tert-butyl-m-cresol, the above-mentioned solid acid catalyst and an alcohol organic solvent having 1-6 carbon atoms in a mass ratio of 1:(0.01-0.05):(0.5-1.5) to obtain a mixture;

[0072] (2) Add n-butyraldehyde dropwise to the mixture and react at 75-95℃ for 2-10h, wherein the molar ratio of n-butyraldehyde to 6-tert-butyl-m-cresol in step (1) is 1.0:(4.3-4.7);

[0073] (3) After the reaction is completed, the reaction solution is hot filtered at 75-95℃ to obtain a solid acid catalyst and filtrate;

[0074] (4) Add alkane and / or aromatic solvents to the filtrate after filtration in step (3), cool to 30-35℃ and stir for 1-3 hours, then continue to cool to 5-10℃ with ice water and keep warm for 1-3 hours to crystallize, filter, wash and dry to obtain product 4,4′-butylidene bis(6-tert-butyl-m-cresol), wherein the volume of alkane and / or aromatic solvent is 2-10 times the volume of filtrate in step (3).

[0075] The solid acid catalyst provided by this invention exhibits good reproducibility and a simple separation and reuse method in the preparation of 4,4′-butylenebis(6-tert-butyl-m-cresol) antioxidant. On the one hand, it reduces raw material costs, and on the other hand, it greatly reduces the generation of saline wastewater, making a significant contribution to reducing the cost of waste treatment and protecting the environment.

[0076] Example 1: Preparation of Solid Acid Catalyst A

[0077] A method for preparing a solid acid catalyst, comprising the following steps:

[0078] a. Dissolve 10g of AlCl3 (75mmol) and 5g of oxalic acid (15.7mmol) in 50mL of ethanol to form a colorless and transparent solution, which is called solution A.

[0079] b. Add 5g of tetrabutyl titanate (14.7mol) and 1.5g of acetylacetone to 10mL of ethanol to form a colorless and transparent solution, called solution B.

[0080] c. Under continuous stirring, add solution B to solution A at a rate of 1 drop / s and continue stirring for 5 hours to form a titanium columnarizing agent;

[0081] d. Weigh 12g of montmorillonite and add it to 50mL of deionized water. Stir vigorously for 5h to form a suspension. Slowly add the titanium columnarizing agent described in step c to the montmorillonite suspension and stir thoroughly for 10h. Then age the obtained wet gel in a 50℃ water bath for 3 days and then air dry it to obtain a dry gel.

[0082] e. Grind the dry gel obtained in step d into powder in a mortar, and then calcine the powder at 700°C for 3 hours under a nitrogen atmosphere to obtain solid acid catalyst A. XRD pattern analysis confirmed that AlCl3 was successfully loaded onto montmorillonite.

[0083] Example 2: Preparation of Solid Acid Catalyst B

[0084] A method for preparing a solid acid catalyst, comprising the following steps:

[0085] a. Dissolve 10g of ZnCl2 and 5g of oxalic acid in 50mL of water to form a colorless and transparent solution, which is called solution A.

[0086] b. Add 5g of tetrabutyl titanate and 1.5g of acetylacetone to 10mL of ethanol to form a colorless and transparent solution, which is called solution B.

[0087] c. Under continuous stirring, add solution B to solution A at a rate of 1 drop / s and continue stirring for 5 hours to form a titanium columnarizing agent;

[0088] d. Weigh 12g of montmorillonite and add it to 50mL of deionized water. Stir vigorously for 5h to form a suspension. Slowly add the titanium columnarizing agent described in step c to the montmorillonite suspension and stir thoroughly for 10h. Then age the obtained wet gel in a 50℃ water bath for 3 days and then air dry it to obtain a dry gel.

[0089] e. Grind the dry gel obtained in step d into powder in a mortar, and then calcine the powder at 700°C for 3 hours under a nitrogen atmosphere to obtain solid acid catalyst B. XRD pattern analysis confirmed that ZnCl2 was successfully loaded onto montmorillonite.

[0090] Example 3: Preparation of antioxidant 4,4′-butylenebis(6-tert-butylm-cresol)

[0091] A method for preparing 4,4′-butylidene bis(6-tert-butyl-m-cresol) is carried out according to the following steps:

[0092] a. Add 50.0g (0.3mol) 6-tert-butyl-m-cresol, 1.6g solid acid catalyst A and 70mL methanol to a 250mL straight four-necked flask, connect a stirrer, a condenser and nitrogen protection, and stir until a mixture is formed.

[0093] b. Using a constant pressure dropping funnel, slowly add 6.2 mL (0.067 mol) of n-butyraldehyde to the reaction solution over 1.5 h. After the addition is complete, keep the reaction at reflux temperature for 5 h.

[0094] c. After the reaction is completed, the reaction solution is hot filtered and the filter cake is collected and used directly as a catalyst. The filtrate is put into a four-necked flask, 300 mL of xylene is added to the filtrate, and then the temperature of the reaction solution is slowly lowered to room temperature and kept warm for 2 hours. Then, it is cooled to 6-8℃ with ice water and kept warm for 1 hour.

[0095] d. After the heat preservation period, the crystallization solution from step c was filtered. The filter cake was washed three times with 100 mL of xylene and then dried in an oven at 150 °C for 2 hours to obtain 23.20 g of the product 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product was 90.53%, the purity was 98.87%, and the melting point was 201-204 °C.

[0096] Example 4: Preparation of antioxidant 4,4′-butylenebis(6-tert-butylm-cresol)

[0097] A method for preparing 4,4′-butylidene bis(6-tert-butyl-m-cresol) is carried out according to the following steps:

[0098] a. Add 50.0g (0.3mol) 6-tert-butyl-m-cresol, 1.6g solid acid catalyst B and 70mL methanol to a 250mL straight four-necked flask, connect a stirrer, a condenser and nitrogen protection, and stir until a mixture is formed.

[0099] b. Using a constant pressure dropping funnel, slowly add 6.2 mL (0.067 mol) of n-butyraldehyde to the reaction solution over 1.5 h. After the addition is complete, keep the reaction at 70 °C for 5 h.

[0100] c. After the reaction is completed, the reaction solution is hot filtered and the filter cake is collected and used directly as a catalyst. The filtrate is put into a four-necked flask, 300 mL of xylene is added to the filtrate, and then the temperature of the reaction solution is slowly lowered to room temperature and kept warm for 2 hours. Then, it is cooled to 6-8℃ with ice water and kept warm for 1 hour.

[0101] d. After the heat preservation period, the crystallization solution from step c was filtered. The filter cake was washed three times with 100 mL of xylene and then dried in an oven at 150 °C for 2 hours to obtain 23.05 g of the product 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product was 89.93%, the purity was 96.94%, and the melting point was 197-201 °C.

[0102] Example 5: Experiment on the application of solid acid catalysts

[0103] 50.0 g (0.3 mol) of 6-tert-butyl-m-cresol, the filter cake recovered in step c of Example 3 (recovered solid acid catalyst A), and 70 mL of methanol were added to a 250 mL straight four-necked flask. A stirrer, a condenser, and nitrogen protection were connected, and the mixture was stirred until homogeneous. 6.2 mL of n-butyraldehyde was added dropwise over 1.5 h. After the addition was completed, the reaction was kept at 70 °C for 5 h. After the reaction was completed, the reaction solution was hot filtered. The filter cake was recovered and reused as a catalyst. The filtrate was used for crystallization and drying to obtain the final product. This process was repeated 5 times. The final product, 4,4′-butylenebis(6-tert-butyl-m-cresol), had a yield of 88.31%, a purity of 95.35%, and a melting point of 195-199 °C.

[0104] Comparative Example 1 used AlCl3 as a catalyst to synthesize the antioxidant 4,4′-butylenebis(6-tert-butylm-cresol).

[0105] a. Add 50.0g (0.3mol) 6-tert-butyl-m-cresol, 0.6g AlCl3 and 70mL methanol to a 250mL straight four-necked flask, connect a stirrer, a condenser and nitrogen protection, and stir until a mixture is formed.

[0106] b. Using a constant pressure dropping funnel, slowly add 6.2 mL (0.067 mol) of n-butyraldehyde to the reaction solution over 1.5 h. After the addition is complete, keep the reaction at reflux temperature for 5 h.

[0107] c. After the reaction is completed, the reaction solution is hot filtered and the filter cake is collected and used directly as a catalyst. The filtrate is put into a four-necked flask, 300 mL of xylene is added to the filtrate, and then the temperature of the reaction solution is slowly lowered to room temperature and kept at that temperature for 2 hours. Then, it is cooled to 6-8℃ with ice water and kept at that temperature for 1 hour.

[0108] d. After the heat preservation period, the crystallization solution from step c was filtered. The filter cake was washed three times with 100 mL of xylene and then dried in an oven at 150 °C for 2 hours to obtain 22.18 g of the product 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product was 86.55%, the purity was 91.23%, and the melting point was 185-191 °C.

[0109] Comparative Example 2: Montmorillonite was modified with H2SO4 and then used as a catalyst for the synthesis of 4,4′-butylenebis(6-tert-butyl-m-cresol).

[0110] a. Add 12g of montmorillonite to 50ml of 30% H2SO4 solution, stir to form a suspension, heat to 80℃ and keep warm and stir for 10h, filter after stirring, and dry the filter cake in an oven at 105℃ for 5h to obtain H2SO4 modified montmorillonite.

[0111] b. Add 50.0g (0.3mol) 6-tert-butyl-m-cresol, 1.0g of the catalyst prepared in step a and 70mL of methanol to a 250mL straight four-necked flask, connect a stirrer, a condenser and nitrogen protection, and stir until a mixture is formed.

[0112] c. Using a constant pressure dropping funnel, slowly add 6.2 mL (0.067 mol) of n-butyraldehyde to the reaction solution over 1.5 h. After the addition is complete, keep the reaction at reflux temperature for 5 h.

[0113] d. After the reaction is completed, the reaction solution is hot filtered and the filter cake is collected and used directly as a catalyst. The filtrate is put into a four-necked flask, 300 mL of xylene is added to the filtrate, and then the temperature of the reaction solution is slowly lowered to room temperature and kept warm for 2 hours. Then, it is cooled to 6-8℃ with ice water and kept warm for 1 hour.

[0114] e. After the heat preservation is completed, the crystallization solution from step c is filtered. The filter cake is washed three times with 100 mL of xylene and then dried in an oven at 150 °C for 2 h to obtain 21.13 g of product 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product is 82.45%, the purity is 88.78%, and the melting point is 181-186 °C.

[0115] Comparative Example 3

[0116] The difference from Example 3 lies in the type of catalyst: the catalyst support is activated carbon. Specifically, the catalyst is prepared according to the following steps:

[0117] a. Dissolve 10g of AlCl3 and 5g of oxalic acid in 50mL of ethanol to form a colorless and transparent solution, which is called solution A.

[0118] b. Add 5g of tetrabutyl titanate and 1.5g of acetylacetone to 10mL of ethanol to form a colorless and transparent solution, which is called solution B.

[0119] c. Under continuous stirring, add solution B to solution A at a rate of 1 drop / s and continue stirring for 5 hours to form a titanium columnarizing agent;

[0120] d. Weigh 12g of activated carbon and add it to 50mL of deionized water. Stir vigorously for 5h to form a suspension. Slowly add the titanium columnarizing agent described in step c to the suspension of activated carbon and stir thoroughly for 10h. Then age the obtained wet gel in a 50℃ water bath for 3 days and then air dry it to obtain a dry gel.

[0121] e. Grind the dry gel obtained in step d into powder in a mortar, and then calcine the powder at 700°C for 3 hours under a nitrogen atmosphere to obtain solid acid catalyst C.

[0122] The final product obtained was 21.39 g of 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product was 83.47%, the purity was 89.34%, and the melting point was 183-189 °C.

[0123] Comparative Example 4

[0124] The difference from Example 3 lies in the type of catalyst: the catalyst support is diatomaceous earth. Specifically, the catalyst is prepared according to the following steps:

[0125] a. Dissolve 10g of AlCl3 and 5g of oxalic acid in 50mL of ethanol to form a colorless and transparent solution, which is called solution A.

[0126] b. Add 5g of tetrabutyl titanate and 1.5g of acetylacetone to 10mL of ethanol to form a colorless and transparent solution, which is called solution B.

[0127] c. Under continuous stirring, add solution B to solution A at a rate of 1 drop / s and continue stirring for 5 hours to form a titanium columnarizing agent;

[0128] d. Weigh 12g of diatomaceous earth and add it to 50mL of deionized water. Stir vigorously for 5h to form a suspension. Slowly add the titanium columnarizing agent described in step c to the diatomaceous earth suspension and stir thoroughly for 10h. Then age the obtained wet gel in a 50℃ water bath for 3 days and then air dry it to obtain a dry gel.

[0129] e. Grind the dry gel obtained in step d into powder in a mortar, and then calcine the powder at 700°C for 3 hours under a nitrogen atmosphere to obtain solid acid catalyst D.

[0130] The final product obtained was 20.84 g of 4,4′-butylenebis(6-tert-butyl-m-cresol). The yield of the product was 81.33%, the purity was 88.17%, and the melting point was 182-187℃.

[0131] A comparison of the results of Examples 3-5 and Comparative Examples 1-4 shows that the solid acid catalyst provided in this application can be directly separated from the reaction liquid system by filtration. The post-processing operation is simple, there is no generation of saline wastewater, the content and yield of the final product are high, and the recovered solid acid catalyst can be directly reused. After multiple reuses, the catalytic performance does not decrease significantly.

[0132] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant, comprising: Using 6-tert-butyl-m-cresol and n-butyraldehyde as raw materials, a reaction is carried out in the presence of a solid acid catalyst to obtain 4,4′-butylidene bis(6-tert-butyl-m-cresol); wherein, the solid acid catalyst comprises an active component containing a Lewis acid and a catalyst support, the Lewis acid comprising one or more of AlCl3, ZnCl2, and SbCl3, and the catalyst support comprising pillared montmorillonite; the pillared montmorillonite is selected from one or more of titanium pillared montmorillonite, silicon pillared montmorillonite, aluminum pillared montmorillonite, and zirconium pillared montmorillonite.

2. The method according to claim 1, characterized in that, The mass ratio of 6-tert-butyl-m-cresol to the solid acid catalyst is 1:(0.01-0.05); and / or, The molar ratio of n-butyraldehyde to 6-tert-butyl-m-cresol is 1:(4-5).

3. The method according to claim 2, characterized in that, The mass ratio of 6-tert-butyl-m-cresol to the solid acid catalyst is 1:(0.02-0.04).

4. The method according to claim 2, characterized in that, The molar ratio of n-butyraldehyde to 6-tert-butyl-m-cresol is 1:(4.3-4.7).

5. The method according to claim 1, characterized in that, The reaction is carried out in an organic solvent selected from alcohols having 1-6 carbon atoms; and / or, The reaction temperature is the reflux temperature, and / or the reaction time is 2-10 h.

6. The method according to claim 5, characterized in that, The organic solvent is selected from one or more of methanol, ethanol and isopropanol.

7. The method according to any one of claims 1-6, characterized in that, The reaction also includes a post-processing step, which includes: after the reaction is completed, the reaction solution is subjected to solid-liquid separation, and the liquid phase is cooled and crystallized to obtain 4,4′-butylenebis(6-tert-butylm-cresol) antioxidant.

8. The method according to claim 7, characterized in that, The crystallization solvent used for cooling crystallization includes alkane and / or aromatic solvents.

9. The method according to claim 8, characterized in that, The crystallization solvent used for cooling crystallization is selected from one or more of toluene, xylene, trimethylbenzene, and petroleum ether.

10. The method according to claim 7, characterized in that, The cooling crystallization process involves first cooling to room temperature and holding at that temperature for 1-3 hours, then cooling to 5-10°C and holding at that temperature for 1-3 hours.

11. The method according to claim 1, characterized in that, The catalyst support comprises titanium-pillared montmorillonite.

12. The method according to claim 11, characterized in that, The mass ratio of the Lewis acid to the catalyst support is 1:(1~3).

13. The method according to claim 12, characterized in that, The mass ratio of the Lewis acid to the catalyst support is 1:(1.2~2.5).

14. The method according to claim 1, characterized in that, The preparation method of the solid acid catalyst includes the following steps: A first solution containing Lewis acids and organic acids is mixed with a second solution containing a columnarizing agent precursor and a ketone solvent to obtain a columnar liquid; then montmorillonite is mixed with the columnar liquid to obtain a wet gel. The wet gel was aged, dried, and calcined to obtain the solid acid catalyst.

15. The method according to claim 14, characterized in that, The preparation method of the solid acid catalyst includes the following steps: a. Mix the Lewis acid and the organic acid to obtain a first solution; b. Mix the columnarizing agent precursor and the ketone solvent to obtain a second solution; c. Add the second solution dropwise to the first solution to obtain the columnar liquid; d. Dissolve montmorillonite to obtain a suspension, and mix the suspension with the columnar liquid obtained in step c to obtain a wet gel; e. The wet gel obtained in step d is aged, dried, and calcined to obtain the solid acid catalyst.

16. The method according to claim 14 or 15, characterized in that, The organic acid includes at least one of monobasic fatty acids, dibasic fatty acids, and polybasic fatty acids; and / or, The columnarizing agent precursor is selected from at least one of titanium columnar precursors, silicon columnar precursors, aluminum columnar precursors, and zirconium columnar precursors; and / or, The ketone solvent is selected from acetone and / or acetylacetone.

17. The method according to claim 16, characterized in that, The organic acid includes at least one of formic acid, acetic acid, tartaric acid, oxalic acid, malic acid, and citric acid.

18. The method according to claim 16, characterized in that, In the first solution, the molar ratio of the Lewis acid to the organic acid is (1~5):

1.

19. The method according to claim 16, characterized in that, The columnarizing agent precursor is selected from titanium column precursors, including titanium tetrabutyl titanate.

20. The method according to claim 19, characterized in that, The molar ratio of tetrabutyl titanate to ketone solvent is 1:(0.5~1.5).

Images