Process for the recovery of antioxidant 702 from a 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether kettle residue

Abstract

The present application relates to the chemical industry field, especially to a method for recovering antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether still residue, the method comprising: dissolving the 3,5-benzyl ether still residue in a solvent, converting 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether in the still residue into antioxidant 702 through acid catalysis reaction, after the reaction is completed, neutralizing and washing with water, further carrying out desolventizing, purifying, temperature reducing crystallization, drying and the like to obtain antioxidant 702. The present application can recover by-product antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether still residue, which can not only reduce production cost, save resources, but also reduce waste discharge, protect the environment, and realize economic benefit and environmental benefit.

Description

Technical Field

[0001] This invention relates to the chemical industry, and in particular to a method for recovering antioxidant 702 from the residue of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor. Background Technology

[0002] Antioxidants are a general term for a large class of compounds that have antioxidant and anti-aging effects. The addition of antioxidants can delay or inhibit the thermal oxidative degradation of certain polymers during processing, thereby extending the service life of polymer materials.

[0003] 3,5-Di-tert-butyl-4-hydroxybenzyl methyl ether (antioxidant 762, referred to as "3,5-benzyl ether" in this article) is a hindered phenolic antioxidant with characteristics such as anti-discoloration and low volatility. It can be used in polymer materials such as rubber, ABS resin, polyester, and plastics, and can also be used in gasoline and lubricating oil. However, it is generally used as an intermediate of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (antioxidant 330).

[0004] In its industrial production, 3,5-benzyl ether is mainly produced from paraformaldehyde, 2,6-di-tert-butylphenol, and alcohol solvents. Under alkaline catalysts, a high-temperature reflux reaction is carried out for 6-8 hours to achieve alkaline condensation. After the reaction, solvent removal and crystallization purification (crystallization → solid-liquid separation (centrifugation / filtration)) are performed to obtain crystals and a mother liquor. The obtained crystals are dried to obtain the product (i.e., the target product, antioxidant 762). Additionally, the mother liquor obtained in the crystallization purification process is distilled to recover the alcohol solvent. The residue in the distillation vessel is the solvent-removed residue of the mother liquor (hereinafter referred to as "3,5-benzyl ether residue").

[0005] During the reaction, the antioxidant 3,5-benzyl ether undergoes an irreversible side reaction, generating a byproduct 4,4'-methylenebis(2,6-di-tert-butylphenol), also known as antioxidant 702. The residue of antioxidant 3,5-benzyl ether in the reactor is complex, mainly consisting of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, antioxidant 702, and impurities from incomplete reactions.

[0006] Patent SU-A-395351 and US Patent US4952736 both describe a method for synthesizing 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, but both inevitably involve side reactions, generating byproducts such as 4,4'-methylenebis(2,6-di-tert-butylphenol). However, current technologies address the issue of residual antioxidant 702 ( ) in the reactor residue after the synthesis of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether. Figure 2 There is very little research on recycling (as shown in the figure).

[0007] In current production processes, 3,5-benzyl ether reactor residue is treated as solid waste and disposed of by qualified companies, resulting in environmental pollution and resource waste. Currently, no relevant technology has been found to recycle this residue. However, in the industrial production of 3,5-benzyl ether, a targeted reactor residue recovery method could be developed to economically and efficiently convert the effective components in the residue into high-purity antioxidant 702, achieving resource utilization and high-value use of the residue, thus realizing significant environmental and economic benefits. Summary of the Invention

[0008] In view of this, the present invention provides a method for recovering antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor residue, which can efficiently recover antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor residue, realize the high-value utilization of 3,5-benzyl ether reactor residue, and achieve resource conservation and product economic maximization while protecting the environment.

[0009] This invention provides a method for recovering antioxidant 702 from reactor residues of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, comprising the following steps:

[0010] S1. Raw material pretreatment:

[0011] The residue from the 3,5-benzyl ether reactor was dissolved in the first organic solvent, and then the solid and liquid were separated to obtain the reactor residue solution.

[0012] S2, acid-catalyzed reaction:

[0013] The residue solution obtained in step S1 is mixed with an acidic catalyst and reacted to obtain a reaction solution;

[0014] S3, Neutralization Wash:

[0015] The reaction solution obtained in step S2 is subjected to deacidification treatment, and the resulting organic phase is neutralized with an alkaline regulator and then washed with water to obtain the washed organic phase.

[0016] S4. Post-processing:

[0017] The first organic solvent is removed from the organic phase obtained after washing with water in step S3, and then the second organic solvent is added. The mixture is cooled and crystallized, and the solid and liquid are separated. The obtained solid is washed and dried to obtain antioxidant 702.

[0018] Preferably, the first organic solvent is at least one selected from methanol, ethanol, dichloromethane, toluene, and xylene;

[0019] The amount of the first organic solvent used is 3 to 5 times the residual mass of the 3,5-benzyl ether in the reactor.

[0020] Preferably, the acidic catalyst is at least one of p-toluenesulfonic acid, sulfuric acid, and a strong acidic cation exchange resin;

[0021] The amount of sulfuric acid used is 10% to 15% of the residual mass of 3,5-benzyl ether used in step S1;

[0022] The amount of p-toluenesulfonic acid used is 15% to 20% of the residual mass of 3,5-benzyl ether used in step S1;

[0023] The amount of the strong acid cation exchange resin used is 50% to 80% of the residual mass of the 3,5-benzyl ether used in step S1.

[0024] Preferably, the concentration of the sulfuric acid is 40wt% to 98wt%.

[0025] Preferably, when the catalyst used in step S2 is a strongly acidic cation exchange resin, the deacidification treatment in step S3 is by filtration.

[0026] When sulfuric acid is used as the catalyst in step S2, the deacidification process in step S3 is as follows: allow the mixture to stand and separate into layers, and then separate the lower layer of waste acid liquid.

[0027] When the catalyst used in step S2 is p-toluenesulfonic acid, the deacidification process is as follows: wash with water, then allow to stand and separate into layers, separating and retaining the lower organic phase.

[0028] Preferably, in step S3:

[0029] The alkaline regulator is an aqueous solution of sodium bicarbonate;

[0030] The goal of neutralization is to bring the pH value to 6-8.

[0031] Preferably, the second solvent is at least one selected from methanol, ethanol, toluene, cyclohexane, n-heptane, and petroleum ether.

[0032] Preferably, in step S4:

[0033] The cooling is to reduce the temperature to 0~5℃;

[0034] The washing is performed with cold methanol; the temperature of the cold methanol is 0~5℃.

[0035] Preferably, in step S1, the residue of the 3,5-benzyl ether reactor is the residue of the mother liquor obtained from the crystallization and purification process during the production of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether after solvent removal.

[0036] Preferably, in step S1, the 3,5-benzyl ether residue includes: 55wt%~70wt% of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, 15wt%~20wt% of 4,4'-methylenebis(2,6-di-tert-butylphenol), and 10wt%~25wt% of other impurities.

[0037] The present invention provides a method for recovering antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor residue, comprising: dissolving the 3,5-benzyl ether reactor residue in a solvent; converting the 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether in the reactor residue into antioxidant 702 through an acid-catalyzed reaction; after the reaction, neutralizing and washing with water; and further performing solvent removal, purification, cooling crystallization, and drying to obtain antioxidant 702. The present invention can recover the byproduct antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor residue, which not only reduces production costs and saves resources, but also reduces waste emissions and protects the environment, achieving both economic and environmental benefits. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a process flow diagram of the present invention for recovering antioxidant 702 from the reactor residue of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether;

[0040] Figure 2 The liquid chromatogram of the residue from the 3,5-benzyl ether reactor in Example 1 is shown below.

[0041] Figure 3 This is a liquid chromatogram of the antioxidant 702 recovered in Example 3. Detailed Implementation

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0044] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0045] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 0~5℃ means that the units for the left endpoint "0" and the right endpoint "5" are both in degrees Celsius.

[0047] This invention provides a method for recovering antioxidant 702 from reactor residues of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, comprising the following steps:

[0048] S1. Raw material pretreatment:

[0049] The residue from the 3,5-benzyl ether reactor was dissolved in the first organic solvent, and then the solid and liquid were separated to obtain the reactor residue solution.

[0050] S2, acid-catalyzed reaction:

[0051] The residue solution obtained in step S1 is mixed with an acidic catalyst and reacted to obtain a reaction solution;

[0052] S3, Neutralization Wash:

[0053] The reaction solution obtained in step S2 is subjected to deacidification treatment, and the resulting organic phase is neutralized with an alkaline regulator and then washed with water to obtain the washed organic phase.

[0054] S4. Post-processing:

[0055] The first organic solvent is removed from the organic phase obtained after washing with water in step S3, and then the second organic solvent is added. The mixture is cooled and crystallized, and the solid and liquid are separated. The obtained solid is washed and dried to obtain antioxidant 702.

[0056] The process flow of this invention is as follows: Figure 1 As shown.

[0057] Antioxidant 702, chemically named 4,4'-methylenebis(2,6-di-tert-butylphenol), is a white to light yellow crystalline powder with a melting point of 155–159°C. It is a high-performance bisphenol antioxidant, mainly used to improve the antioxidant properties of polymers and lubricating oils. The method provided in this invention converts 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether residue in the reactor into antioxidant 702, which is then recovered along with the original antioxidant 702 in the reactor residue, achieving high-value utilization of the 3,5-benzyl ether reactor residue.

[0058] Regarding step S1 :

[0059] S1. Raw material pretreatment: Dissolve the 3,5-benzyl ether residue in the reactor with the first organic solvent, and then separate the solid and liquid to obtain the reactor residue solution.

[0060] In this invention, the 3,5-benzyl ether residue refers to the residue after solvent removal from the mother liquor obtained in the crystallization and purification process during the production of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether (antioxidant 762). The production process of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether is not particularly limited and can be a conventional production process in the art; as follows: using paraformaldehyde, 2,6-di-tert-butylphenol, and alcohol solvents as raw materials, a high-temperature reflux aldol condensation reaction is carried out under the action of an alkaline catalyst. After the reaction, the residue is removed by solvent removal, crystallization purification, and drying to obtain 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether. The crystallization and purification process yields crystals and a mother liquor. The crystals are dried to obtain the 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether product. The mother liquor is distilled to remove the solvent and is recovered. The residue remaining in the reactor after solvent removal is the 3,5-benzyl ether residue described herein.

[0061] In this invention, the 3,5-benzyl ether residue includes: 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, 4,4'-methylenebis(2,6-di-tert-butylphenol), and other impurities. Specifically, the content of each component is as follows: 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether 55wt%~70wt%, 4,4'-methylenebis(2,6-di-tert-butylphenol) 15wt%~20wt%, and other impurities 10wt%~25wt%.

[0062] In this invention, the first organic solvent is preferably at least one selected from methanol, ethanol, dichloromethane, toluene, and xylene. The amount of the first organic solvent used is preferably 3 to 5 times the residual mass of the 3,5-benzyl ether in the reactor, specifically 3, 4, or 5 times.

[0063] In this invention, the residue of 3,5-benzyl ether in the reactor is dissolved in a first organic solvent. The preferred dissolution temperature is 30-70°C, specifically 30°C, 40°C, 60°C, or 70°C. The preferred dissolution time is 20-40 minutes, specifically 20 minutes, 30 minutes, or 40 minutes. Stirring is performed during the dissolution process to ensure complete dissolution of the material.

[0064] In this invention, after the above-described dissolution, solid-liquid separation is performed. The method of solid-liquid separation is not particularly limited and can be any conventional method in the art, such as filtration. After filtration, salt impurities and other unknown components insoluble in the first organic solvent are removed from the residue, yielding the residue solution.

[0065] Regarding step S2 :

[0066] S2, Acid-catalyzed reaction: The residue solution obtained in step S1 is mixed with an acidic catalyst to react and obtain a reaction solution.

[0067] In this invention, the acidic catalyst is preferably at least one of p-toluenesulfonic acid, sulfuric acid, and a strong acidic cation exchange resin. The sulfuric acid is preferably industrial sulfuric acid, with a concentration preferably between 40-98% (w / w), specifically 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 98%. The source of the strong acidic cation exchange resin is not particularly limited; it can be a conventionally available commercial product. The strong acidic cation exchange resin can be recycled after treatment.

[0068] In this invention, the amount of the acidic catalyst is as follows: the amount of sulfuric acid is 10% to 15% of the residual mass of 3,5-benzyl ether used in step S1, specifically 10%, 11%, 12%, 13%, 14%, or 15%. The amount of p-toluenesulfonic acid is 15% to 20% of the residual mass of 3,5-benzyl ether used in step S1, specifically 15%, 16%, 17%, 18%, 19%, or 20%. The amount of the strong acidic cation exchange resin is 50% to 80% of the residual mass of 3,5-benzyl ether used in step S1, specifically 50%, 55%, 60%, 65%, 67%, 70%, 75%, or 80%. When the catalyst is a strong acidic cation exchange resin, the catalyst needs to be removed by filtration after the reaction to obtain the reaction solution.

[0069] In this invention, the preferred reaction temperature is 10~70℃, specifically 30℃, 35℃, 45℃, 60-65℃, or 70℃; the preferred reaction time is 1~4 hours, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. Following an acid-catalyzed reaction, the 3,5-di-tert-butyl-4-hydroxybenzylmethyl ether in the 3,5-benzyl ether residue undergoes a self-condensation reaction to form 4,4'-methylenebis(2,6-di-tert-butylphenol), i.e., antioxidant 702; the reaction route is as follows:

[0070]

[0071] Regarding step S3 :

[0072] S3, Neutralization and Washing: The reaction solution obtained in step S2 is deacidified, and the resulting organic phase is neutralized with an alkaline regulator and then washed with water to obtain the washed organic phase.

[0073] In this invention, when the catalyst used in step S2 is a strongly acidic cation exchange resin, the deacidification process is filtration, i.e., removing the catalyst by filtration. When the catalyst used in step S2 is sulfuric acid, the deacidification process is as follows: allowing the mixture to stand and separate into layers, separating the lower waste acid liquid; specifically, the reaction solution is transferred to a separating funnel and allowed to stand and separate into layers. After the liquid in the funnel has separated into upper and lower layers and stabilized, the lower waste acid liquid is separated, and the upper organic phase is retained. When the catalyst used in step S2 is p-toluenesulfonic acid, the deacidification process is as follows: washing with water, then allowing the mixture to stand and separate into layers, separating and retaining the lower organic phase.

[0074] In this invention, after the above-mentioned deacidification treatment, an alkaline regulator is added for neutralization. The alkaline regulator is preferably an aqueous solution of sodium bicarbonate; the concentration of the sodium bicarbonate aqueous solution is preferably 5wt%~10wt%, specifically 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%. The goal of neutralization is to achieve a pH value of 6~8, specifically 6, 7, or 8.

[0075] In this invention, after the above neutralization, the organic phase is washed with water. The washing is preferably done with pure water. After washing with water, the organic phase is filtered into another container to obtain the washed organic phase.

[0076] Regarding step S4 :

[0077] S4. Post-processing: Remove the first organic solvent from the organic phase obtained after washing with water in step S3, then add the second organic solvent, cool down to crystallize, separate the solid and liquid, wash and dry the obtained solid to obtain antioxidant 702.

[0078] In this invention, the preferred method for removing the first organic solvent is distillation, i.e., evaporating the first solvent. Specifically, the organic phase after water washing is transferred to a distillation apparatus, and the first solvent is evaporated by heating. The distillation temperature is not particularly limited and can be controlled according to the boiling point of the first solvent.

[0079] In this invention, after removing the first solvent, a second organic solvent is added. Preferably, the second solvent is at least one selected from methanol, ethanol, toluene, cyclohexane, n-heptane, and petroleum ether. The volume ratio of the second solvent to the first solvent is preferably (160~100):100, specifically 100:100, 120:100, 130:100, 140:100, 150:100, or 160:100. In this invention, the addition of the second solvent dissolves the solid. The dissolution method varies depending on the type of second solvent used: if methanol is added, no additional treatment is required, and the next step can proceed directly; if other solvents are added, the solid is heated to dissolve, filtered, and then the next step can proceed.

[0080] In this invention, after the above treatment, cooling crystallization is performed. The cooling is preferably to 0-5°C, specifically 0°C, 1°C, 2°C, 3°C, 4°C, or 5°C. Crystals precipitate after cooling, followed by solid-liquid separation. The solid-liquid separation is preferably performed by vacuum filtration. The obtained solid is then washed. The washing is preferably done with cold methanol. The temperature of the cold methanol is preferably 0-5°C, specifically 0°C, 1°C, 2°C, 3°C, 4°C, or 5°C. After washing, the solid is dried to obtain white to slightly yellow crystals, which is antioxidant 702.

[0081] This invention provides a method for recovering antioxidant 702 from 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor residue. Through further catalytic reaction of the 3,5-benzyl ether reactor residue, the 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether in the residue is converted into antioxidant 702. The residue is then purified through a crystallization process, achieving a recovery rate of over 70% and a purity of over 97%. This method realizes the high-value utilization of 3,5-benzyl ether reactor residue. This invention not only achieves excellent recovery results under laboratory conditions but is also suitable for large-scale industrial production, reducing production costs and waste emissions, thus protecting the environment. It improves economic efficiency while reducing environmental pollution. In summary, this invention rationally recovers and utilizes reactor residue generated during the production of 3,5-benzyl ether, improving economic efficiency, reducing hazardous waste emissions, lowering production costs, and achieving environmental protection.

[0082] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0083] Example 1

[0084] 1. Obtaining 3,5-benzyl ether residue from the reactor:

[0085] In a 1L high-pressure reactor equipped with an electric stirrer, thermometer, and built-in condenser coil, 400mL of methanol, 15.6g of paraformaldehyde, and 80g of 2,6-di-tert-butylphenol were added sequentially. After nitrogen purging, 15mL of dimethylamine methanol solution (dimethylamine to methanol volume ratio of 1:1.5) was added. The high-pressure reactor was heated to 100-120℃, and the pressure inside the reactor was maintained at 0.3MPa. After the reaction was maintained for 5 hours, a reaction solution was obtained. The reaction solution was then cooled and crystallized inside the reactor. After the temperature dropped below 15℃, the solution was filtered to obtain a crystalline solid and a mother liquor. The crystalline solid was dried to obtain 3,5-benzyl ether product. The residue obtained after distilling the mother liquor at 60-80℃ to remove the solvent is the 3,5-benzyl ether reactor residue.

[0086] The reaction route for synthesizing 3,5-benzyl ether is shown below:

[0087]

[0088] High-performance liquid chromatography (HPLC) analysis revealed the following composition of the 3,5-benzyl ether residue: 60.02% 3,5-benzyl ether, 17.92% antioxidant 702, and the remaining 22% consisting of solvent methanol and other byproduct impurities. The HPLC chromatogram is shown below. Figure 2 As shown.

[0089] 2. Recovery of antioxidant 702 from 3,5-benzyl ether reactor residue:

[0090] S1. Raw material pretreatment:

[0091] In a 500mL four-necked flask equipped with an electric stirrer, thermometer, and condenser, add 30g of 3,5-benzyl ether residue and 100mL of dichloromethane. Start the stirrer and heat to 40℃. After stirring for 30min, filter the mixture into a reaction flask to obtain the residue solution.

[0092] S2, acid-catalyzed reaction:

[0093] Concentrated sulfuric acid (86% concentration, 15% of the residual mass of 3,5-benzyl ether) was added dropwise to the reaction flask. After the addition was completed, the reaction was maintained at 30°C for 2 hours to obtain the reaction solution.

[0094] S3, Neutralization Wash:

[0095] The resulting reaction solution was transferred to a separatory funnel and allowed to stand to separate into layers. The lower layer of waste acid was separated, and the upper organic phase was retained. Then, the solution was neutralized and washed with sodium bicarbonate aqueous solution (6wt%) until pH=7. After that, it was washed with 100mL of pure water. The organic phase was filtered into another 500mL reaction flask to obtain the washed organic phase.

[0096] S4. Post-processing:

[0097] After washing with water, the organic phase was heated to 40°C to distill off the dichloromethane solvent. Then, 100 mL of methanol was added, and the temperature was lowered to 0-5°C to crystallize. After filtration, the resulting crystalline solid was washed with fresh cold methanol (4°C) and dried to obtain a slightly yellow crystalline powder, namely antioxidant 702.

[0098] Qualitative and quantitative analysis was performed using high performance liquid chromatography. The results showed that the main content of antioxidant 702 in the product was 97.1%, and the yield was 73.5%. The melting point of antioxidant 702 was determined to be 154.5-156.0℃ by a melting point apparatus.

[0099] Example 2

[0100] 1. Obtaining 3,5-benzyl ether residue: Same as in Example 1.

[0101] 2. Recovery of antioxidant 702 from 3,5-benzyl ether reactor residue:

[0102] S1. Raw material pretreatment:

[0103] In a 500mL four-necked flask equipped with an electric stirrer, thermometer, and condenser, add 30g of 3,5-benzyl ether residue and 100mL of dichloromethane. Start the stirrer and heat to 40℃. After stirring for 30min, filter the mixture into a reaction flask to obtain the residue solution.

[0104] S2, acid-catalyzed reaction:

[0105] Concentrated sulfuric acid (86% concentration, 15% of the residual mass of 3,5-benzyl ether) was added dropwise to the reaction flask. After the addition was completed, the reaction was maintained at 30°C for 2 hours to obtain the reaction solution.

[0106] S3, Neutralization Wash:

[0107] The resulting reaction solution was transferred to a separatory funnel and allowed to stand to separate into layers. The lower layer of waste acid was separated, and the upper organic phase was retained. Then, the solution was neutralized and washed with sodium bicarbonate aqueous solution (6wt%) until pH=7. After that, it was washed with 100mL of pure water. The organic phase was filtered into another 500mL reaction flask to obtain the washed organic phase.

[0108] S4. Post-processing:

[0109] After washing with water, the organic phase was heated to 40°C to distill off the dichloromethane solvent, resulting in the precipitation of a yellow solid. Then, 120 mL of n-heptane was added, and the mixture was heated to 85°C until the solid was completely dissolved. After hot filtration, the mixture was cooled to 0-5°C to crystallize. After filtration, the resulting crystalline solid was washed with fresh, cold methanol (5°C) and dried to obtain a white to slightly yellow crystalline powder, which is antioxidant 702.

[0110] Qualitative and quantitative analysis was performed using high performance liquid chromatography. The results showed that the main content of antioxidant 702 in the product was 97.3%, and the yield was 72.8%. The melting point of antioxidant 702 was determined to be 155.1-156℃ by a melting point apparatus.

[0111] Example 3

[0112] 1. Obtaining 3,5-benzyl ether residue: Same as in Example 1.

[0113] 2. Recovery of antioxidant 702 from 3,5-benzyl ether reactor residue:

[0114] S1. Raw material pretreatment:

[0115] In a 500mL four-necked flask equipped with an electric stirrer, thermometer, and condenser, add 30g of 3,5-benzyl ether residue and 100mL of methanol, start stirring and heat to 60℃, stir for 30min, then filter into a reaction flask to obtain the residue solution.

[0116] S2, acid-catalyzed reaction:

[0117] A strong acidic cation exchange resin (source: Kehaisi Technology Co., Ltd., model T-62MP; the amount added is 67% of the residual mass of 3,5-benzyl ether in the reactor) was added to the reaction flask, and the reaction was maintained at 60-65℃ for 3 hours to obtain the reaction solution.

[0118] S3, Neutralization Wash:

[0119] The resulting reaction solution was filtered to remove the catalyst, then neutralized and washed with sodium bicarbonate aqueous solution (6wt%) until pH=7. After that, it was washed with 100mL of pure water, and the organic phase was filtered into another 500mL reaction flask to obtain the washed organic phase.

[0120] S4. Post-processing:

[0121] After washing with water, the organic phase was heated to distill off the methanol aqueous solvent, and a yellow solid precipitated out. Then, 120 mL of cyclohexane was added, and the mixture was heated to 80 °C until the solid was completely dissolved. After hot filtration, the mixture was cooled to 0-5 °C to crystallize. After filtration, the resulting crystalline solid was washed with fresh cold methanol (5 °C) and dried to obtain a white to slightly yellow crystalline powder, which is antioxidant 702.

[0122] Qualitative and quantitative analysis was performed using high-performance liquid chromatography (HPLC). The results showed that the main content of antioxidant 702 in the product was 97.2%, with a yield of 71.6%. The melting point of antioxidant 702 was determined to be 154.8-155.6℃. The HPLC chromatogram of this product is shown below. Figure 3 As shown.

[0123] Example 4

[0124] 1. Obtaining 3,5-benzyl ether residue: Same as in Example 1.

[0125] 2. Recovery of antioxidant 702 from 3,5-benzyl ether reactor residue:

[0126] S1. Raw material pretreatment:

[0127] In a 500mL four-necked flask equipped with an electric stirrer, thermometer, and condenser, add 30g of 3,5-benzyl ether residue and 100mL of dichloromethane. Start the stirrer and heat to 40℃. After stirring for 30min, filter the mixture into a reaction flask to obtain the residue solution.

[0128] S2, acid-catalyzed reaction:

[0129] Concentrated sulfuric acid (80% concentration, 13% of the residual mass of 3,5-benzyl ether in the reactor) was added dropwise to the reaction flask. After the addition was completed, the reaction was maintained at 35°C for 2.5 h to obtain the reaction solution.

[0130] S3, Neutralization Wash:

[0131] The resulting reaction solution was transferred to a separatory funnel and allowed to stand to separate into layers. The lower layer of waste acid was separated, and the upper organic phase was retained. Then, it was neutralized and washed with sodium bicarbonate aqueous solution (6wt%) until pH=8. After that, it was washed with 100mL of pure water and filtered into another 500mL reaction flask to obtain the washed organic phase.

[0132] S4. Post-processing:

[0133] After washing with water, the organic phase was heated to distill off 40 mL of dichloromethane solvent. Then, 120 mL of n-heptane was slowly added, and the temperature was raised and stirred to ensure that the material was in a solution state. The temperature was raised further to distill off dichloromethane until there was no more absorption at 60°C. After that, the temperature was lowered to 0-5°C to crystallize. After filtration, the obtained crystalline solid was washed with fresh cold methanol (4°C) and dried to obtain a white to slightly yellow crystalline powder, which is antioxidant 702.

[0134] Qualitative and quantitative analysis was performed using high performance liquid chromatography. The results showed that the main content of antioxidant 702 in the product was 97.3%, and the yield was 72.1%. The melting point of antioxidant 702 was determined to be 155.3-156.2℃ by a melting point apparatus.

[0135] Example 5

[0136] 1. Obtaining 3,5-benzyl ether residue: Same as in Example 1.

[0137] 2. Recovery of antioxidant 702 from 3,5-benzyl ether reactor residue:

[0138] S1. Raw material pretreatment:

[0139] In a 500mL four-necked flask equipped with an electric stirrer, thermometer, and condenser, add 30g of 3,5-benzyl ether residue and 100mL of dichloromethane. Start the stirrer and heat to 40℃. After stirring for 30min, filter the mixture into a reaction flask to obtain the residue solution.

[0140] S2, acid-catalyzed reaction:

[0141] 6g of p-toluenesulfonic acid was added to the reaction flask and the reaction was maintained at 45℃ for 4.0h to obtain the reaction solution.

[0142] S3, Neutralization Wash:

[0143] Add 20 mL of pure water to the reaction solution and stir at 40 °C for 20 min. Then, transfer the solution to a separatory funnel, allow it to stand and separate into layers, separate and retain the lower organic phase, then neutralize and wash it with sodium bicarbonate aqueous solution (6 wt%) until pH=8, then wash it with 100 mL of pure water, filter the organic phase into another 500 mL reaction flask, and obtain the water-washed organic phase.

[0144] S4. Post-processing:

[0145] After washing with water, the organic phase was heated to distill off 60 mL of dichloromethane solvent. Then, 100 mL of n-heptane was slowly added, and the temperature was raised and stirred to ensure that the material was in a solution state. The temperature was raised further to distill off dichloromethane until there was no more absorption at 60°C. After that, the temperature was lowered to 0-5°C to crystallize. After filtration, the obtained crystalline solid was washed with fresh cold methanol (4°C) and dried to obtain a white to slightly yellow crystalline powder, which is antioxidant 702.

[0146] Qualitative and quantitative analysis was performed using high performance liquid chromatography. The results showed that the main content of antioxidant 702 in the product was 97.1%, and the yield was 71.8%. The melting point of antioxidant 702 was determined to be 155.6-156.7℃ by a melting point apparatus.

[0147] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for recovering antioxidant 702 from the residue of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether reactor, characterized in that, Includes the following steps: S1. Raw material pretreatment: The residue from the 3,5-benzyl ether reactor was dissolved in a first organic solvent, followed by solid-liquid separation to obtain the reactor residue solution. S2, acid-catalyzed reaction: The residue solution obtained in step S1 is mixed with an acidic catalyst and reacted to obtain a reaction solution; S3, Neutralization Wash: The reaction solution obtained in step S2 is subjected to deacidification treatment, and the resulting organic phase is neutralized with an alkaline regulator and then washed with water to obtain the washed organic phase. S4. Post-processing: The first organic solvent is removed from the organic phase obtained after washing with water in step S3, and then the second organic solvent is added. The mixture is cooled and crystallized, and the solid and liquid are separated. The obtained solid is washed and dried to obtain antioxidant 702.

2. The method according to claim 1, characterized in that, The first organic solvent is at least one selected from methanol, ethanol, dichloromethane, toluene, and xylene; The amount of the first organic solvent used is 3 to 5 times the residual mass of the 3,5-benzyl ether in the reactor.

3. The method according to claim 1, characterized in that, The acidic catalyst is at least one of p-toluenesulfonic acid, sulfuric acid, and a strong acidic cation exchange resin; The amount of sulfuric acid used is 10% to 15% of the residual mass of 3,5-benzyl ether used in step S1; The amount of p-toluenesulfonic acid used is 15% to 20% of the residual mass of 3,5-benzyl ether used in step S1; The amount of the strong acid cation exchange resin used is 50% to 80% of the residual mass of the 3,5-benzyl ether used in step S1.

4. The method according to claim 3, characterized in that, The concentration of the sulfuric acid is 40wt%~98wt%.

5. The method according to claim 1 or 3, characterized in that, When the catalyst used in step S2 is a strongly acidic cation exchange resin, the deacidification treatment in step S3 is filtration. When sulfuric acid is used as the catalyst in step S2, the deacidification process in step S3 is as follows: allow the mixture to stand and separate into layers, and then separate the lower layer of waste acid liquid. When the catalyst used in step S2 is p-toluenesulfonic acid, the deacidification process is as follows: wash with water, then allow to stand and separate into layers, separating and retaining the lower organic phase.

6. The method according to claim 1, characterized in that, In step S3: The alkaline regulator is an aqueous solution of sodium bicarbonate; The goal of neutralization is to bring the pH value to 6-8.

7. The method according to claim 1, characterized in that, The second solvent is at least one of methanol, ethanol, toluene, cyclohexane, n-heptane, and petroleum ether.

8. The method according to claim 1, characterized in that, In step S4: The cooling is to reduce the temperature to 0~5℃; The washing is performed with cold methanol; the temperature of the cold methanol is 0~5℃.

9. The method according to claim 1, characterized in that, In step S1, the 3,5-benzyl ether residue is the residue of the mother liquor obtained from the crystallization and purification process during the production of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether after solvent removal.

10. The method according to claim 1 or 9, characterized in that, In step S1, the 3,5-benzyl ether residue includes: 55wt%~70wt% of 3,5-di-tert-butyl-4-hydroxybenzyl methyl ether, 15wt%~20wt% of 4,4'-methylenebis(2,6-di-tert-butylphenol), and 10wt%~25wt% of other impurities.

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