Preparation method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldiol

Abstract

The present invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol. In the present invention, 2,6-di-tert-butylphenol is first used as a raw material to obtain an intermediate 3,3',5,5'-tetra-tert-butyl-4,4'-biphenoquinone through an oxidative coupling reaction, and then the obtained intermediate is reduced with Raney nickel as a catalyst and an alcohol reagent as a reducing agent to obtain 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol. The 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol product prepared by the production process of the present invention is a white powder, with a maximum yield of 79.2%, a purity as high as 99.5%, a chromaticity value of 73.5, and good color. This process not only solves the contradiction between high purity and poor color in the traditional method, but also has reaction conditions that are easy to control, which is conducive to industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a preparation method of an intermediate 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol for use as a raw material for liquid crystal materials. Background Art

[0002] 3,3',5,5'-Tetra-tert-butyl-4,4'-biphenol (TBB) is a very important synthetic intermediate, which can be used as a modified monomer for many products such as polyesters, polyurethanes, polycarbonates, polysulfones, and epoxy resins to manufacture excellent engineering plastics and composite materials; it can also be used as an antioxidant for rubbers, emulsions, and plastics, as well as a dye intermediate or a stabilizer for petroleum products, and has broad application prospects.

[0003] Currently, the main production method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol is to use 2,6-di-tert-butylphenol as a raw material, through oxidative coupling to generate an intermediate 3,3',5,5'-tetra-tert-butyl-4,4'-biphenoquinone, and then use a reducing agent to reduce the intermediate to tetra-tert-butylbiphenol. However, the control of reaction conditions in the reduction stage of this process route is relatively harsh, by-products are easily formed, the conversion rate of the reaction process is low, and the chromaticity of the obtained product is also poor.

[0004] For example, domestic patent CN102659525A reports a preparation method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol, that is, using 2,6-di-tert-butylphenol as a raw material, and using a self-made copper-amine complex as a catalyst for oxidative coupling reaction to obtain 3,3',5,5'-tetra-tert-butyl-4,4'-biphenoquinone, and then using the raw material itself as a reducing agent to carry out a reduction reaction at 135 - 160 °C to obtain 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol. This method uses the raw material itself as a reducing agent, resulting in a low product yield, and the product obtained by this method is a yellow solid powder with poor chromaticity.

[0005]

[0006] Patent CN114308028A also mentions a reduction method of biphenoquinone, that is, using Pd-C, Pt-C, Rh-C, Pd-Al 2 O 3 、Raney nickel, etc. as catalysts, and introducing hydrogen to carry out reduction under certain temperature and pressure conditions. However, this process requires strict control of reaction conditions, otherwise the double bond in benzoquinone may be completely reduced and the target product cannot be obtained.

[0007] In addition, US Patent US2018 / 185299 reported a method for preparing 3,3’,5,5’-tetraisopropyl-4,4’-biphenol. Using 2,6-diisopropylphenol as the raw material and inorganic salts (preferably silver carbonate and anhydrous magnesium sulfate) as the oxidant for oxidative coupling reaction to obtain 3,3’,5,5’-tetraisopropyl-4,4’-biphenoquinone, and then using sodium dithionite as the reducing agent for reduction reaction to obtain 3,3’,5,5’-tetraisopropyl-4,4’-biphenol. This method requires the use of a large amount of oxidant and reducing agent, and produces a large amount of waste liquid, which is not conducive to environmental protection.

[0008]

[0009] Therefore, it is extremely necessary to find suitable oxidants and reducing agents to achieve the oxidative coupling of 2,6-di-tert-butylphenol and the reduction of the intermediate 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, while improving the yield and purity of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol and improving the color of the product. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a method for preparing 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol.

[0011] The method for preparing 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol provided by the present invention is specifically as follows: First, using 2,6-di-tert-butylphenol as the raw material, through an oxidative coupling reaction to obtain the intermediate 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, and then using Raney nickel as the catalyst and an alcohol reagent as the reducing agent to reduce the obtained intermediate to produce 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol.

[0012] Since the oxidation product of 2,6-di-tert-butylphenol, 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, is brown to black, if the reduction is not complete, a small amount of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone will remain in the product, which will cause the final product to be yellow to brownish-yellow. This is also the main reason why the color of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol products in the prior art is brownish-yellow.

[0013] However, during the long-term experimental research process, the present inventor found that based on the oxidizing property of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldione, under the action of Raney nickel, using a specific alcohol reagent to reduce it, the reduction process is relatively thorough. Not only is the yield of the product significantly increased, but also the chromaticity of the product is good, and there will be no situation where it shows yellow or brownish-yellow due to incomplete reduction.

[0014] The Raney nickel used as the catalyst in the present invention is a solid heterogeneous catalyst with a porous structure and a large specific surface area. Its high catalytic activity comes from its porous structure. Of course, the good catalytic performance of nickel itself also directly determines whether this reduction reaction can be achieved. Research shows that substances containing trace amounts of nickel can accelerate the rate of addition of organic substances and hydrogen ions. Therefore, the reduction efficiency of Raney nickel is much higher than that of noble metal catalysts such as palladium and rhodium, and the reduction is more thorough, and this conclusion has also been confirmed in the experiments of the present invention.

[0015] Moreover, during the process of reducing 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldione with Raney nickel in an alcohol reagent in the present invention, it is not necessary to introduce hydrogen, but the hydrogen protons of the alcohol reagent are used for the reduction reaction. The whole reduction process is simple, efficient and avoids the risk of using hydrogen.

[0016] Furthermore, a method for preparing 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol provided by the present invention includes the following steps:

[0017] (1) Heat 2,6-di-tert-butylphenol to melt it, then mix it fully with the catalyst and heat it to 130-180 °C. Uniformly and smoothly introduce compressed air, observe the oxygen content detection result of the gas measuring device, and by controlling the flow rates of air and oxygen, stably control the oxygen content in the flask within the range of 18-26%, and carry out an oxidative coupling reaction to obtain the intermediate product 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldione;

[0018] The catalyst described above is selected from at least one of potassium hydroxide, calcium hydroxide, sodium hydroxide, sodium phenoxide, sodium acetate, etc.;

[0019] (2) Mix the intermediate product obtained in (1) fully with Raney nickel and an alcohol reagent, heat it to 50-100 °C, and carry out a reduction reaction. After the reaction is completed, obtain 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol through purification treatment.

[0020] In the above steps, preferably, the heating temperature of 2,6-di-tert-butylphenol in (1) is 40-50 °C.

[0021] Preferably, the dosage of the catalyst in (1) accounts for 0.1-2% of the weight of 2,6-di-tert-butylphenol.

[0022] During the oxidative coupling reaction process, if the dosage of the catalyst is too high, it will not only cause serious waste and result in a high output of waste liquid, but also there will be no significant improvement in the catalytic efficiency of the reaction. However, if the dosage of the catalyst is too low, the reaction time will be longer.

[0023] Preferably, the addition amount of Raney nickel in (2) is 1-10% of the weight of 2,6-di-tert-butylphenol, and the addition amount of the alcohol reagent accounts for 30-50% of the weight of 2,6-di-tert-butylphenol.

[0024] More preferably, the addition amount of Raney nickel in (2) is 5-10% of the weight of 2,6-di-tert-butylphenol, and the addition amount of the alcohol reagent accounts for 40-50% of the weight of 2,6-di-tert-butylphenol.

[0025] Preferably, the alcohol reagent in (2) has the following general formula: C n H 2n+1 OH, where 3 ≤ n ≤ 10.

[0026] Preferably, the alcohol reagent in (2) is selected from at least one of normal alcohols with 3-10 carbon atoms and their isomers.

[0027] Preferably, the operation of the purification treatment in (2) is specifically as follows: First, add a hydrochloric acid solution to acidify the reaction solution after the reaction ends, dissolve the product with dichloromethane, filter, add ethanol for pulping to the filtrate after rotary evaporation under reduced pressure, and then dry.

[0028] Preferably, the volume fraction of ethanol during pulping is 80-85%.

[0029] Preferably, the duration of the oxidative coupling reaction in (1) is 5-10 h, and the duration of the reduction reaction in (2) is 2-5 h.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) By introducing Raney nickel as a catalyst and using an alcohol reagent as a reducing agent during the reduction process of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldione, the present invention significantly improves the yield, purity, and color of the product 3,3',5,5'-tetra-tert-butyl-4,4'-biphenol. The finally prepared product is a white powder, with a yield of 79.2%, a purity as high as 99.5%, and the chromaticity is 73.5 as measured by a whiteness meter, showing good color, thus solving the contradiction of high purity but poor color in the traditional method.

[0032] (2) The preparation method of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol of the present invention has a simple operation process during the whole reaction, requires relatively low equipment, and does not involve highly volatile and highly toxic substances during the oxidation and reduction processes, will not produce excessive waste liquid, is pollution-free, and is conducive to large-scale industrial production.

[0033] (3) An innovative ethanol pulping and purification process of 80-85% is adopted. After pulping and purification, the content of the intermediate 3,3’,5,5’-tetra-tert-butyl-4,4’-dihydroxybiphenyl is greater than 99.5%, and the single-pass yield is greater than 60%.

[0034] (4) In addition, the mother liquor containing a small amount of the raw material 2,6-di-tert-butylphenol and the product 3,3’,5,5’-tetra-tert-butyl-4,4’-dihydroxybiphenyl remaining after pulping can be directly used for the next oxidation reaction after concentration. The utilization rate of the raw material is high, the loss of the raw material is small, and the overall yield of the oxidation coupling-reduction in the whole process is greater than 98.5%. Description of the Drawings

[0035] Figure 1 It is the appearance diagram of the 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol product prepared in Example 2 of the present invention;

[0036] Figure 2 It is the high performance liquid chromatography diagram of the 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol product prepared in Example 2 of the present invention;

[0037] Figure 3 It is the appearance diagram of the 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol product prepared by the traditional process in Comparative Example 1 of the present invention;

[0038] Figure 4 It is the high performance liquid chromatography diagram of the 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol product prepared by the traditional process in Comparative Example 1 of the present invention. Detailed Embodiments

[0039] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0040] Example 1

[0041] A preparation method of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol is as follows:

[0042] (1) Add 50 g of 2,6 - di - tert - butylphenol to a round - bottom flask, heat it to 50 °C to completely melt it, then add 0.25 g of sodium hydroxide, stir well, continue to heat up to 160 °C. After the temperature of the reaction liquid material rises to 120 °C, start to evenly and steadily introduce compressed air. Observe the oxygen content detection result of the gas measuring device, and steadily control the oxygen content in the flask within the range of 20 - 24% by the flow rates of air and oxygen. Stop the oxygen introduction after reacting for 6 h to obtain the reaction liquid of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldiquinone, and the yield of the intermediate is 67.2%;

[0043] (2) Add 1.0 g of Raney nickel and 20 g of n - propanol to the above - mentioned reaction system, stir well, and react at 90 °C for 4 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, and then add 85% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldiol is obtained. After detection, the yield of the product is 70.6%, the purity is 99.0%, and the chromaticity is 72.1.

[0044] Example 2

[0045] A preparation method of 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldiol, the specific steps are as follows:

[0046] Add 50 g of 2,6 - di - tert - butylphenol to a round - bottom flask, heat it to 50 °C to completely melt it, then add 0.5 g of sodium hydroxide, stir well, continue to heat up to 160 °C. After the temperature of the reaction liquid material rises to 120 °C, start to evenly and steadily introduce compressed air. Observe the oxygen content detection result of the gas measuring device, and steadily control the oxygen content in the flask within the range of 20 - 24% by the flow rates of air and oxygen. Stop the oxygen introduction after reacting for 6 h to obtain the reaction liquid of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldiquinone, and the yield of the intermediate is 85.1%;

[0047] Add 3.0 g of Raney nickel and 20 g of n - propanol to the above - mentioned reaction system, stir well, react at 92 °C for 4 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, and then add 85% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldiol is obtained, and the color of the product is as shown in the appendix Figure 1 as shown.

[0048] Use high - performance liquid chromatography to detect the product. The high - performance liquid chromatogram of the product prepared in this example is as shown in the appendix Figure 2As shown, the specific parameters such as the retention time of each peak are shown in Table 1.

[0049] Table 1 Parameters of Each Peak in the High-Performance Liquid Chromatogram

[0050]

[0051] After calculation, the yield of the product is 79.2%, and the purity is 99.5%. The whiteness of the product was measured using a whiteness meter, and the chromaticity of the product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol was measured to be 73.5.

[0052] Example 3

[0053] A preparation method of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol, the specific steps are as follows:

[0054] Add 50 g of 2,6-di-tert-butylphenol to a round-bottom flask, heat it to 40 °C to completely melt it, then add 0.75 g of sodium hydroxide, stir well, continue to heat up to 160 °C, and start to evenly and steadily introduce compressed air when the temperature of the reaction liquid material rises to 120 °C. Observe the oxygen content detection result of the gas measuring device, and stably control the oxygen content in the flask within the range of 20-24% by the flow rates of air and oxygen. After reacting for 6 h, stop introducing oxygen to obtain the reaction liquid of the intermediate 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldione, and the yield of the intermediate is 85.0%;

[0055] Add 5 g of Raney nickel and 20 g of n-propanol to the above reaction system, stir well, react at 88 °C for 4 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, and then add a small amount of 85% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol is obtained. After detection, its yield is 79.3%, the purity is 99.5%, and the chromaticity is 73.4.

[0056] Example 4

[0057] A preparation method of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol, the specific steps are as follows:

[0058] Add 50 g of 2,6 - di - tert - butylphenol to a round - bottom flask, heat it to 50 °C to completely melt it, then add 0.5 g of sodium hydroxide, stir well, continue to heat up to 160 °C. After the temperature of the reaction liquid material rises to 120 °C, start to evenly and steadily introduce compressed air. Observe the oxygen content detection result of the gas measuring device, and steadily control the oxygen content in the flask within the range of 18 - 22% by the flow rates of air and oxygen. After reacting for 6 h, stop introducing oxygen to obtain the reaction liquid of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldione. The yield of the intermediate is 80.8%;

[0059] Add 3 g of Raney nickel and 15 g of n - propanol to the above - mentioned reaction system, stir well, react at 90 °C for 4 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, then add a small amount of 85% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyl diol is obtained. After detection, the yield of the product is 80.1%, the purity is 99.2%, and the chromaticity is 72.5.

[0060] Example 5

[0061] A preparation method of 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyl diol, the specific steps are as follows:

[0062] Add 50 g of 2,6 - di - tert - butylphenol to a round - bottom flask, heat it to 50 °C to completely melt it, then add 0.5 g of sodium hydroxide, stir well, continue to heat up to 160 °C. After the temperature of the reaction liquid material rises to 120 °C, start to evenly and steadily introduce compressed air. Observe the oxygen content detection result of the gas measuring device, and steadily control the oxygen content in the flask within the range of 24 - 26% by the flow rates of air and oxygen. After reacting for 6 h, stop introducing oxygen to obtain the reaction liquid of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldione. The yield of the intermediate is 84.9%;

[0063] Add 3 g of Raney nickel and 25 g of n - propanol to the above - mentioned reaction system, stir well, react at 90 °C for 3 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, then add 85% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyl diol is obtained. After detection, its yield is 78.2%, the purity is 99.6%, and the chromaticity is 73.5.

[0064] Example 6

[0065] A preparation method of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol is as follows:

[0066] Add 50 g of 2,6-di-tert-butylphenol into a round-bottom flask, heat it to 50 °C to completely melt 2,6-di-tert-butylphenol, then add 0.5 g of sodium hydroxide, stir well, continue to heat up to 160 °C. After the temperature of the reaction liquid material rises to 120 °C, start to evenly and steadily introduce compressed air, observe the oxygen content detection result of the gas measuring device, and stably control the oxygen content in the flask within the range of 20-24% through the flow rates of air and oxygen. After reacting for 5 h, stop introducing oxygen to obtain the reaction liquid of the intermediate 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, and the yield of the intermediate is 80.0%;

[0067] Add 3 g of Raney nickel and 20 g of n-propanol into the above reaction system, stir well, react at 92 °C for 5 h. After the reaction is completed, add 20 mL of 10% hydrochloric acid solution for acidification, dissolve the product with dichloromethane, filter to remove inorganic salts, rotary evaporate the filtrate under reduced pressure, then add 80% ethanol for pulping. After the product is washed and dried, white solid 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol is obtained. After detection, its yield is 79.5%, purity is 99.5%, and chromaticity is 74.0.

[0068] Example 7

[0069] Different from Example 2, n-butanol is used as the reducing agent for the reduction reaction of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, and the other conditions are the same as those in Example 2.

[0070] The obtained product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol is a white solid, with a yield of 78.2%, purity of 99.4%, and chromaticity of 72.0.

[0071] Example 8

[0072] Different from Example 2, tert-butanol is used as the reducing agent for the reduction reaction of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, and the other conditions are the same as those in Example 2.

[0073] The obtained product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenol is a white solid, with a yield of 78.5%, purity of 99.3%, and chromaticity of 71.0.

[0074] Example 9

[0075] Different from Example 2, n-pentanol is used as the reducing agent for the reduction reaction of 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenoquinone, and the other conditions are the same as those in Example 2.

[0076] The obtained product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol is a white solid, with a yield of 78.0%, a purity of 99.3%, and a chromaticity of 71.2.

[0077] To more clearly describe the effects of conditions such as the catalyst, reducing agent, and reaction time on the reduction reaction, the reaction conditions in Examples 1 to 9 above were integrated, as shown in Table 2 below.

[0078] Table 2 Conditions of the reduction reaction and product quality in Examples 1 to 9

[0079]

[0080] As shown in Table 2, in Examples 1 to 3, as the amount of Raney nickel gradually increased, the overall yield, purity, etc. of the product showed an upward trend. However, when the addition amount of Raney nickel changed from 3 g to 5 g, that is, during the change from 6% to 10%, the yield change of the reduction product was not significant, and the purity and whiteness hardly changed. It can be seen that when the amount of Raney nickel is 6%, the product yield and chromaticity are the best, with a yield of 79.2%, a purity as high as 99.5%, and the chromaticity of the product is 73.5.

[0081] Moreover, in Examples 2 and 7 to 9, only the type of alcohol reagent in the reduction process was changed. Under the condition that the remaining conditions were exactly the same, the experimental results showed that when using n-propanol as the reducing agent, the yield and purity of the prepared product were the best. When using other types of alcohol preparations as the reducing agent, the chromaticity of the product decreased compared with the whiteness value when n-propanol was used as the reducing agent in Example 2. It can be seen that n-propanol as the reducing agent is more thorough in reducing 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldione.

[0082] In addition, in Example 6, the reduction reaction time was extended based on Example 2. Although the final product yield, purity, chromaticity and other parameters were all improved compared with those in Example 2, the improvement was not significant. Instead, the extension of the reaction time caused a great increase in production costs to a certain extent. Therefore, for industrial production, it is not suitable to use the method of extending the time to improve product quality. Therefore, the optimal reaction conditions for the reduction reaction are set as follows: 6% Raney nickel, 40% n-propanol, and the reaction time is 4 h for the reduction reaction.

[0083] Example 10

[0084] Recycling the raw materials for reuse to prepare 3,3’,5,5’-tetra-tert-butyl-4,4’-dihydroxybiphenyl.

[0085] Different from Example 2, the mother liquor containing 2,6 - di - tert - butylphenol and 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - dihydroxybiphenyl after reduction pulping in each experimental process was rotary evaporated under reduced pressure. After recovery, it was used as the initial raw material for the oxidation reaction, and the other conditions were the same as those in Example 2.

[0086] Although most of the product 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - dihydroxybiphenyl can be separated after pulping with 85% ethanol, since the mother liquor after pulping is still a saturated solution of 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - dihydroxybiphenyl and also contains a small amount of unreacted raw materials, therefore, after concentrating and recovering the mother liquor, it can be directly used as the raw material for the next oxidation reaction, which is beneficial to improving the utilization rate of raw materials.

[0087] Comparative Example 1

[0088] Different from Example 1, during the reduction of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldione, Raney nickel and other alcohol reagents were not added, but 2,6 - di - tert - butylphenol was used as the reducing agent for this reduction reaction. The color of the prepared product is as shown in the appendix Figure 3 as follows.

[0089] After the prepared product was detected by high - performance liquid chromatography, its high - performance liquid chromatography chart is as shown in the appendix Figure 4 as follows, and the specific parameters such as the retention time of each peak are shown in Table 3.

[0090] Table 3 Parameters of each peak in the high - performance liquid chromatography chart

[0091]

[0092] After detection and calculation, the yield of the product is 53%, the purity is 98.2%, and the chromaticity is 25.5.

[0093] As can be seen from the appendix Figure 3 the color of the product prepared in this comparative example shows an obvious brown - yellow color. It can be seen that only using 2,6 - di - tert - butylphenol as the reducing agent for the self - reduction reaction can realize the reduction of the intermediate 3,3’,5,5’ - tetra - tert - butyl - 4,4’ - biphenyldione, but the impurity content is relatively high and the reduction reaction is not complete, resulting in the brown - yellow color of the final product, which seriously restricts the use of the product.

[0094] Comparative Example 2

[0095] Different from Example 2, palladium-carbon was used as the catalyst for the reduction reaction, and the rest was the same as in Example 2. The obtained product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol was a brown solid, with a yield of 55% and a purity of 97.5%.

[0096] Comparative Example 3

[0097] Different from Example 2, rhodium-carbon was used as the catalyst for the reduction reaction, and the rest was the same as in Example 2. The obtained product 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol was a brown solid, with a yield of 54% and a purity of 97.8%.

[0098] From the results of Comparative Examples 2 to 3, using noble metals such as palladium and rhodium as catalysts and alcohol reagents as reducing agents to reduce the intermediate product without introducing hydrogen, although 3,3’,5,5’-tetra-tert-butyl-4,4’-biphenyldiol can be formed, the yield and purity of the product are much lower than the catalytic effect of using Raney nickel as the catalyst, and the effect of the catalytic reduction reaction is poor.

Claims

1. A preparation method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldiol, characterized in that, it comprises the following steps: (1) Heat 2,6-di-tert-butylphenol to 40-50 °C to melt it, then mix it fully with a catalyst and heat it to 130-180 °C. After that, start to evenly and steadily introduce compressed air. Observe the oxygen content detection result of the gas measuring device, and control the oxygen content in the flask within the range of 18-26% through the flow rates of air and oxygen, and carry out an oxidative coupling reaction to obtain the intermediate 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldione; The catalyst selected from at least one of potassium hydroxide, calcium hydroxide, sodium hydroxide, sodium phenoxide, sodium acetate, etc., and the dosage of the catalyst accounts for 0.1-2% of the weight of 2,6-di-tert-butylphenol; (2) Mix the intermediate obtained in (1) fully with Raney nickel and an alcohol reagent, heat it to 50-100 °C, and carry out a reduction reaction. After the reaction is completed, 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldiol is obtained through purification treatment. Among them, the addition amount of Raney nickel is 1-10% of the weight of 2,6-di-tert-butylphenol, and the addition amount of the alcohol reagent accounts for 30-50% of the weight of 2,6-di-tert-butylphenol. The alcohol reagent selected from any one of n-propanol, n-butanol, tert-butanol, and n-pentanol; The specific operation of the purification treatment is as follows: First, add a hydrochloric acid solution to acidify the reaction solution after the reaction, dissolve the product with dichloromethane, filter, and after the filtrate is rotary evaporated under reduced pressure, add ethanol with a volume fraction of 80-85% for pulping and drying.

2. According to the preparation method of 3,3',5,5'-tetra-tert-butyl-4,4'-biphenyldiol described in claim 1, characterized in that, the duration of the oxidative coupling reaction in (1) is 5-10 h, and the duration of the reduction reaction in (2) is 2-5 h.

Images