Production process method of antioxidant BHT (butylated hydroxytoluene)
By replacing high-temperature distillation with a cooling crystallization process, the problems of high energy consumption and difficulty in utilizing by-products in the production of antioxidant BHT have been solved, achieving energy conservation, consumption reduction, and resource value enhancement, and producing high-efficiency, high-value-added antioxidant LK51.
Patent Information
- Application Number
- CN202511850432.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-02-17
AI Technical Summary
The traditional BHT antioxidant production process is difficult to process, has high energy consumption and high cost, and the by-products are difficult to utilize in a high-value manner.
A cooling crystallization process is adopted to replace high-temperature distillation. The recrystallization mother liquor is separated by cooling crystallization filtration and further alkylation to convert the by-product into high-value-added antioxidant LK51.
It significantly reduces production energy consumption and equipment investment, improves BHT purity and recovery efficiency, and converts by-products into high-performance liquid antioxidant LK51, achieving high-value utilization of resources and reducing costs.
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Figure CN121537259A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of antioxidant synthesis, in particular to a production process of antioxidant BHT. BACKGROUND
[0002] 2,6-di-tert-butyl-p-cresol, referred to as antioxidant BHT (or T501), as a high-efficiency and economical hindered phenolic antioxidant, is widely used in chemical industry, food and feed industries, and the market demand is continuously booming. The traditional production process is as follows: under the action of acid catalysts such as sulfuric acid, p-toluenesulfonic acid or sulfonic acid type ion exchange resin, p-cresol and isobutene undergo alkylation reaction. The typical reaction product composition is roughly as follows: 2,6-di-tert-butyl-p-cresol accounts for about 93%, and also contains about 2.0% of dimerized and trimerized isobutene, 0.1% of residual p-cresol, 3% of intermediate 2-tert-butyl-p-cresol (mono-tert-butyl phenol), 0.5% of 4(6)-tert-butyl-m-cresol and 1% of 4,6-di-tert-butyl-m-cresol. After neutralization and water washing, the reaction liquid is purified by alcohol recrystallization, and then dried to remove alcohol, and finally the qualified product with BHT content higher than 99.5% is obtained.
[0003] However, this process has significant defects in the recrystallization mother liquor treatment link, see Figure 2 The mother liquor is first recovered by rectification 1 to recycle solvent alcohol, and the remaining material composition is complex, containing p-cresol, mono-tert-butyl phenol, various di-tert-butyl phenol homologues and BHT, etc. Then, rectification 2 is used to obtain reusable components, including dimerized and trimerized isobutene (a fraction) as by-products, alkylation raw materials rich in p-cresol and mono-tert-butyl phenol (a fraction), and about 75% BHT crude product (a fraction). Due to the high and close boiling points of these alkyl phenolic substances, subsequent rectification 2 separation and purification is extremely difficult, and high reflux ratio batch rectification must be used, and high vacuum must be used. This process has huge energy consumption, and the heating medium temperature needs to be maintained at about 230°C, relying on medium-high pressure steam or special heat conducting oil system, resulting in high equipment investment and high operating cost. And long time high temperature operation aggravates material coking, increases the yield of by-product heavy alkyl phenol, and the color is dark brown, which can only be treated as a low value-added product. A large amount of BHT is repeatedly circulated among the alkylation, recrystallization and rectification units, not only reducing the production efficiency, but also increasing the overall production cost, which becomes the key bottleneck restricting the economy of the process. SUMMARY
[0004] In view of the above problems, the present application provides a production process of antioxidant BHT, which can conveniently solve the problems existing in the recrystallization mother liquor treatment process in the production process of antioxidant BHT.
[0005] The application provides a production process of antioxidant BHT. p-Cresol is subjected to alkylation reaction with isobutene in the presence of an acidic catalyst, and the reaction product is subjected to neutralization and water washing, and then is subjected to alcohol recrystallization and purification post. After the recrystallization mother liquor is subjected to rectification and separation to recover solvent alcohol and a fraction containing dimerized and trimerized isobutene, a rectification kettle liquid is obtained. Instead of being subjected to rectification 2, the rectification kettle liquid is directly sent to cooling and crystallization filtration 1 post, and is subjected to separation by using a cooling, crystallization and filtration process. The obtained first crude BHT is used in the recrystallization post, and the obtained first filtrate is sent to the alkylation reaction post, and the acidic catalyst is added to the first filtrate to further convert the enriched p-cresol and mono-tertiary phenol in the first filtrate into product BHT by alkylation reaction with isobutene. After the product BHT is subjected to neutralization and water washing, the product BHT is sent to cooling and crystallization filtration 2 post. The second crude BHT obtained by cooling and crystallization filtration is used in the recrystallization post, and the second filtrate is a mixed alkyl phenol liquid antioxidant LK51 which has antioxidant performance comparable to T501.
[0006] The application provides a production process of antioxidant BHT, and mainly relates to a treatment process of recrystallization mother liquor in the production process of BHT. Step 1: the recrystallization mother liquor is subjected to rectification and separation to recover solvent alcohol (which is used in the recrystallization post) and a fraction (water, dimerized isobutene, trimerized isobutene and other light components). Step 2: the material after the rectification is sent to cooling and crystallization filtration 1 post to be subjected to cooling and crystallization filtration treatment, the obtained first crude product is sent to the recrystallization post to recover product BHT, and the obtained first mother liquor is sent to the alkylation post. Step 3: a certain amount of acidic catalyst is added to the first mother liquor, and the first mother liquor is subjected to alkylation reaction with isobutene at a certain temperature to further convert the raw material p-cresol and the intermediate product mono-tertiary phenol into product BHT. Step 4: the reaction liquid in step 3 is subjected to neutralization and water washing, and then is sent to cooling and crystallization filtration 2 post to be subjected to cooling and crystallization filtration treatment. The obtained second crude product is sent to the recrystallization post to recover product BHT, and the obtained second mother liquor is antioxidant LK51, which is a mixture of 2-tert-butyl-p-cresol, 4(6)-tert-butyl-m-cresol, 2,6-di-tert-butyl-p-cresol (BHT) and 4,6-di-tert-butyl-m-cresol. Due to the antioxidant synergistic effect of different alkyl phenols, the second mother liquor is a liquid antioxidant with excellent antioxidant performance, and can be widely used as an antioxidant additive for lubricating oil, gasoline, biodiesel, aviation kerosene and the like.
[0007] Preferably, the rectification in step 1 requires that the content of alcohol and water and other light components in the kettle liquid is less than 0.1% or even less, otherwise the alkylation reaction speed and reaction conversion rate of the first crystallization mother liquor will be affected.
[0008] Preferably, the cooling crystallization filtering 1 of step 2 is operated at a temperature of 5-35°C, more preferably 10-20°C, and the filtering equipment used can be a suction filter, a centrifugal filter, a filter press, or other commonly used filters.
[0009] Preferably, the first crude product of step 2 has a BHT content of about 90%, and only one recrystallization is needed to reach the product quality index of a BHT content of greater than 99.5%. However, the crude product obtained by the old process of rectification 2 has a BHT content of only about 75%, and two recrystallizations are needed to reach the product quality index of a BHT content of greater than 99.5%.
[0010] Preferably, the first mother liquor of step 2 has a p-cresol content of 3-5% and a 2-tert-butyl-p-cresol content of 25-30%.
[0011] Preferably, the acid catalyst of step 3 can be sulfuric acid, p-toluene sulfonic acid, or any other acid, and the amount used is 0.5-1% of the weight of the first mother liquor.
[0012] Preferably, the alkylation reaction of step 3 is operated at a temperature of 60-110°C, more preferably 80-90°C, and the reaction is terminated when the p-cresol content in the reaction product is less than 0.1% and the 2-tert-butyl-p-cresol content is less than 5%.
[0013] Preferably, the neutralization and water washing of step 4 is operated at a temperature of 70-80°C using a sodium carbonate aqueous solution as the neutralizing agent.
[0014] Preferably, the cooling crystallization filtering 2 of step 4 is operated at a temperature of 5-35°C, more preferably 10-20°C, and the filtering equipment used can be a suction filter, a centrifugal filter, a filter press, or other commonly used filters.
[0015] Preferably, the second crude product of step 4 has a BHT content of about 88%, and only one recrystallization is needed to reach the product quality index of a BHT content of greater than 99.5%. However, the crude product obtained by the old process of rectification 2 has a BHT content of only about 75%, and two recrystallizations are needed to reach the product quality index of a BHT content of greater than 99.5%.
[0016] Preferably, the second mother liquor, i.e. LK51, of step 5 is a light yellow liquid antioxidant, which is a high value-added byproduct of the present application and has a price of about 5 times that of heavy alkyl phenol. The 2-tert-butyl-p-cresol content is 7-9%, the BHT content is about 35%, and the total alkyl phenol content is greater than 98%.
[0017] Preferably, the liquid antioxidant LK51 in step 4 is detected by a commissioned professional testing institution, and the antioxidant performance thereof in the application fields of lubricating oil, gasoline, biodiesel, aviation kerosene and the like can be comparable to that of the solid antioxidant T501 and the like, and the liquid is more convenient than the solid in conveying, metering and using, is free of dust, is easy to dissolve and mix, and is cheaper in price.
[0018] All the equipment involved in steps 1-4, such as recrystallization, rectification, cooling crystallization filtration, alkylation reaction, neutralization and water washing, can be reused without the need of adding new equipment, and only part of the material pipelines need to be changed.
[0019] The beneficial effects of the present application are: The present application realizes multiple breakthroughs in energy saving and consumption reduction, quality improvement and efficiency increase, and resource high value through process innovation. First, the cooling crystallization process successfully replaces the traditional high-temperature rectification unit, greatly reduces the production energy consumption and equipment investment, and effectively solves the problems of high energy consumption and high cost in the traditional process. Moreover, higher purity BHT crude is obtained through the cooling crystallization process than through the rectification process, which significantly improves the recovery efficiency and production benefit of the main product. More importantly, the by-product that is difficult to handle in the traditional process is innovatively converted into the liquid antioxidant LK51 with excellent antioxidant performance, which can replace the traditional antioxidant T501 and perform excellently in biodiesel, lubricating oil, gasoline and aviation kerosene, thereby not only solving the problem of by-product treatment, but also realizing the high value utilization of resources and creating significant economic benefits. BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, which together with the embodiments of the present application, serve to explain the present application, and do not constitute a limitation of the present application. In the drawings,
[0021] Figure 1 The recrystallization mother liquor treatment process of the present application is shown in the following table: Figure 2 The recrystallization mother liquor treatment process of the present application is shown in the following table: DETAILED DESCRIPTION
[0022] The embodiments of the present application are described in detail as follows: The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and processes are given, but the protection scope of the present application is not limited to the following embodiments. The experimental methods not specified in the following embodiments are usually performed under conventional conditions. EMBODIMENT
[0023] Take 1000g of rectification 1 pot liquid (its composition is shown in Table 1), add it into a 2000mL four-necked flask, and rectify it at ~150℃ and 0.095MPa vacuum degree. The compositions of the distillate and the pot liquid after distillation are analyzed, and the results are shown in Table 1. Example
[0024] The four-neck flask of the post-distillation kettle liquid of Example 1 was placed in a magnetic stirring constant-temperature water bath, and was cooled to crystallize at 15℃ for 2 hours. The 1st crude product and the 1st mother liquor were analyzed, and the results are shown in Table 1 (Note: the water content was analyzed by Karl Fischer method). Example
[0025] 300g of the 1st filtrate was taken into a 500mL four-neck flask, 1.5g of sulfuric acid was added, and isobutene was introduced at 80~90℃ for 2 hours. The composition of the reaction was analyzed, and the results are shown in Table 1. Example
[0026] The four-neck flask containing the reaction liquid after neutralization and water washing of Example 3 was placed in a magnetic stirring constant-temperature water bath, and was cooled to crystallize at 15℃ for 2 hours. The 2nd crude product and the 2nd mother liquor were analyzed, and the results are shown in Table 1.
[0027] The three fractions of the rectification 2 unit before the improvement of the production workshop (the crude product BHT used for recrystallization) tank were mixed and analyzed, and the 2-tert-butyl-p-cresol content was 9.42%, the BHT content was 80.29%, and the other alkyl phenols (4(6)-tert-butyl-m-cresol, 4,6-di-tert-butyl-m-cresol, etc.) were 10.29%. The crude product BHT obtained by rectification 2 was obviously lower than the 1st crude product and the 2nd crude product obtained by cooling crystallization and filtration. Table 1 Product composition of each process
[0028] Note: The 2nd filtrate in Table 1 is the liquid antioxidant LK51 obtained by the present application. The excellent antioxidant performance of LK51 is illustrated by Examples 5-8 below. Example
[0029] The oxidation stability detection results of LK51 applied in biodiesel and the comparison results with T501 are shown in Table 2. The oxidation stability was tested by X1 company (using the method of petrochemical standard NB / SH / T 0825-2010), and the antioxidant addition amount in the biodiesel base oil was 0.2%, and the results all met the quality technical indicators of biodiesel specified in the national standard GB / T 20828-2015, and the oxidation stability index was not less than 6 hours.
[0030] Table 2 Oxidation stability detection results of antioxidants in biodiesel Description: The liquid antioxidant LK51 is more convenient to use than the solid antioxidant T501, is easy to transport, measure, and dissolve and mix uniformly, and has no dust; under the same addition amount, the antioxidant effects are equivalent, and the price is cheaper. Example
[0031] The results of the oxidation stability detection of LK51 applied in lubricating oil and the comparison results with T501 are shown in Table 3. The oxidation stability is detected by X1 and X2 companies respectively. The 150# lubricating oil base oil used for testing is produced by Nanjing Refinery and Dalian Lubricating Oil Company respectively, the additive amount of antioxidant in the lubricating oil base oil is 0.8%, and the detection method is carried out according to SH / T 0913.
[0032] Table 3 Oxidation stability detection results of antioxidants in lubricating oil Note: Under the same additive amount, the antioxidant performance of liquid antioxidant LK51 is similar or better than that of solid antioxidant T501; the liquid antioxidant LK51 is more convenient to use than the solid antioxidant T501, easy to transport, measure, dissolve and mix uniformly, no dust, and cheaper in price. Example
[0033] The results of the oxidation stability detection of LK51 applied in gasoline and the comparison results with antioxidant 44PD are shown in Table 4. The oxidation stability is tested by X1 company (using GB / T8018-2015 method), and GB 17930-2016 stipulates that the oxidation stability (induction period) of gasoline is ≥480 min. The additive amount of antioxidant 44PD (liquid antioxidant) in gasoline is 50 ppm, and the additive amount of antioxidant LK51 in gasoline is 100 ppm. The results are much better than the quality technical indicators of gasoline oxidation stability stipulated in GB / T 20828-2015.
[0034] Table 4 Oxidation stability detection results of antioxidants in gasoline Note: Under the same conditions of being liquid antioxidants, having equivalent antioxidant effects and being much better than the national standard, the price is cheaper, and the price of antioxidant 44PD is 3 times that of LK51. Example
[0035] The results of the oxidation stability detection of LK51 applied in aviation coal and the comparison results with T501 are shown in Table 5. The oxidation stability is tested by X1 company (using GB / T9169-2023 method). The additive amount of antioxidant T501 in aviation coal is 20 ppm, and the additive amount of antioxidant LK51 in aviation coal is 25 ppm. The antioxidant effects meet the quality technical indicators of aviation coal oxidation stability stipulated in GB6537-2018.
[0036] Table 5 Oxidation stability detection results of antioxidants in aviation coal Comparative advantage: liquid antioxidant LK51 is more convenient than solid antioxidant T501, easy to transport, measure, dissolve and mix uniformly, and has no dust; in the case of the same antioxidant effect, the cost of consuming antioxidant by aviation coal is lower.
[0037] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and the inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.
Claims
1. A process for the production of antioxidant BHT, characterized in that, The method comprises the following steps: Step 1, p-cresol is subjected to alkylation reaction with isobutene in the presence of an acid catalyst, and the reaction product is washed with a sodium carbonate aqueous solution at 70-80 DEG C to obtain an alkylation liquid; the alkylation liquid is subjected to alcohol recrystallization and filtration to obtain a recrystallization mother liquor; Step 2, the recrystallization mother liquor is subjected to rectification to recover solvent alcohol and a fraction containing dimeric and trimeric isobutene, and to obtain a rectification kettle liquid; Step 3, the rectification kettle liquid is subjected to first cooling crystallization and filtration to obtain a first crude product and a first mother liquor, and the first crude product is returned to the recrystallization procedure of Step 1 for recovery and purification; Step 4, the first mother liquor, an acid catalyst and isobutene are mixed to perform alkylation reaction until the content of p-cresol in the reaction product is less than 0.1% and the content of 2-tert-butyl-p-cresol is less than 5%, and a reaction liquid is obtained; Step 5, the reaction liquid is washed with a sodium carbonate aqueous solution at 70-80 DEG C, and then subjected to second cooling crystallization and filtration to obtain a second crude product and a second mother liquor; the second crude product is returned to the recrystallization procedure of Step 1 for recovery and purification; and the second mother liquor is liquid antioxidant LK51.
2. The process for the production of antioxidant BHT according to claim 1, characterized in that, In Step 2, the content of alcohol and water in the rectification kettle liquid is controlled to be less than 0.1% or below.
3. The process as claimed in claim 1, wherein the process is characterized by, The cooling crystallization filtration separation method is used to replace the high-temperature high-vacuum high-energy-consumption rectification separation method.
4. The process as claimed in claim 1, wherein the process is characterized by, The cooling crystallization temperature is 10-20 DEG C.
5. The production process of the antioxidant BHT according to claim 1, characterized in that, The acid catalyst is sulfuric acid or p-toluene sulfonic acid, and the alkylation reaction temperature is 80-90 DEG C.
6. The process as claimed in claim 1, wherein the process is carried out at a temperature in the range of 60-70°C. In Step 5, the liquid antioxidant LK51 is a mixture of 2-tert-butyl-p-cresol, 4(6)-tert-butyl-m-cresol, 2,6-di-tert-butyl-p-cresol, 4,6-di-tert-butyl-m-cresol and other alkyl phenols, and has superior antioxidant performance.