The method comprises the following steps: preparing high-purity 2, 2apos; 1, 2, 3, 3 apos; , 5, 5apos; process for the preparation of-hexamethylbiphenol

Abstract

The invention provides a solvent-free oxidative coupling method for preparing 2, 2 ', 3, 3', 5, 5 '-hexamethyl biphenyl (HMBP), the method comprises the following steps: in the presence of a metal salt catalyst and an amine auxiliary agent, trimethylphenol is subjected to oxidative coupling to obtain 2, 2', 3, 3, 5, 5 '-hexamethyl biphenyl, the catalyst is selected from one or more of the following groups: salts of iron, copper, cobalt, nickel and zinc; and / or the amine auxiliary agent is selected from one or more of the following groups: organic amine and ammonia water.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, specifically to a reaction process and post-processing process for the efficient preparation of high-purity 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP). Background Technology

[0002] 2,2',3,3',5,5'-Hexamethylbiphenyl (HMBP) is an important organic and fine chemical raw material, primarily used for the modification of polyphenylene oxide (PPO). PPO is one of the world's five major general-purpose engineering plastics, widely used in electronics, automotive, machinery, and chemical industries due to its excellent dielectric properties, good weather resistance, and halogen-free flame retardancy. However, PPO suffers from poor flowability and moderate mechanical strength, generally requiring modification before use. Because HMBP has reactive phenolic hydroxyl groups at both ends and significant rotational steric hindrance between the two benzene rings in the molecule, HMBP-modified PPO molecular chains exhibit greater rigidity, resulting in significant improvements in electrical properties, mechanical properties, and processability.

[0003] Currently, there is limited research on HMBP preparation methods. The synthesis of 3,3',5,5'-tetramethylbiphenylquinone (TMBP) with a similar structure can be referenced. Reported synthetic routes for TMBP are divided into two-step and one-step methods. The two-step method involves first oxidizing the starting material 2,6-dimethylphenol (DMP) to 3,3',5,5'-tetramethylbiphenylquinone (TMDQ), and then reducing it with a reducing agent to the product TMBP. Reduction methods include self-reduction of the starting material (CN102659525A), Pd / C metal-catalyzed hydrogen reduction (CN114308028A), and sodium hydrosulfite reduction (US2018185299), but these methods suffer from drawbacks such as low yield, poor selectivity, poor product color, and high catalyst consumption. CN119350130A reports a bifunctional ruthenium / maltodextrin catalyst that can catalyze the stepwise oxidation / reduction process of DMP; however, its catalyst preparation is difficult and requires a large amount of solvent. The one-step method, which involves the direct oxidative coupling of DMP to TMBP, requires sophisticated reaction equipment and is prone to producing byproducts such as biphenylquinone and polyphenylene ether, and is therefore rarely reported.

[0004] Therefore, it is of great significance to develop a solvent-free, one-step oxidative coupling method for the synthesis of high-purity 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP). Summary of the Invention

[0005] The purpose of this application is to provide a solvent-free, one-step oxidative coupling method for the synthesis of 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP). This method avoids introducing organic solvents into the oxidation reaction, effectively mitigating the safety risks associated with oxidation. The one-step preparation of 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP) offers significant advantages over the previously reported two-step methods. Through in-depth research, the inventors of this application discovered that amine auxiliaries form complexes with catalyst metal salts, regulating the electronic state and spatial configuration of the metal center, effectively improving conversion rate, suppressing side reactions, and solving the problem of numerous byproducts in traditional methods. The oxidative coupling preparation of 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP) using this invention exhibits high product selectivity, effectively improving product yield, and achieving a product purity >99.9%.

[0006] Therefore, this application provides a solvent-free oxidative coupling method for preparing 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP), the method comprising:

[0007] In the presence of a metal salt catalyst and an amine auxiliary, trimethylphenol is oxidatively coupled to yield 2,2',3,3',5,5'-hexamethylbiphenyl, wherein:

[0008] The catalyst is selected from one or more salts of iron, copper, cobalt, nickel, and zinc; and / or

[0009] Amine auxiliaries are selected from one or more of the following groups: organic amines and ammonia.

[0010] In a preferred embodiment, the amount of catalyst, in molar terms, is 0.001-1% of the amount of trimethylphenol, preferably 0.001-0.1%; and the amount of auxiliary agent, in molar terms, is 0.002-1% of the amount of trimethylphenol, preferably 0.002-0.1%. In a preferred embodiment, the molar ratio of catalyst to auxiliary agent is 0.01-5, preferably 0.5-2.5.

[0011] In some embodiments, the catalyst is selected from: ferric chloride, ferric acetate, copper chloride, copper nitrate, copper acetate, and metal salts of cobalt, nickel, and zinc and their hydrates.

[0012] In some embodiments, the amine auxiliaries are selected from: diethylamine, triethylamine, diethanolamine, triethanolamine, and ammonia.

[0013] In some embodiments, the oxidant is selected from oxygen, air, hydrogen peroxide, or one or more of the above-mentioned oxidants.

[0014] In a preferred embodiment, the solvent-free oxidative coupling method for preparing 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP) includes the following steps:

[0015] (1) Add the raw material trimethylphenol to the reactor and heat it to melt it;

[0016] (2) Add amine auxiliaries to the metal salt catalyst to prepare a catalyst solution;

[0017] (3) Pump the catalyst solution from step (2) into the reactor, add the oxidant, and obtain the reaction solution;

[0018] (4) The reaction solution from step (3) is subjected to hot filtration to maintain the temperature of the reaction solution and the insulation jacket, thereby obtaining a hot filter cake and a hot filtrate.

[0019] (5) Apply the hot filtrate from step (4) to step (1);

[0020] (6) Wash and filter the hot filter cake from step (4) with a washing solvent to obtain washing liquid and washing cake;

[0021] (7) Place the washed cake from step (6) into a vacuum drying oven and dry it under vacuum to obtain high-purity 2,2',3,3',5,5'-hexamethylbiphenyl.

[0022] In some implementations, step (1) further includes a nitrogen purging step.

[0023] In some implementations, the material temperature in step (1) is 60-90°C.

[0024] In some embodiments, in step (1), the reactor also contains the hot filtrate from step (4).

[0025] In some embodiments, step (1) includes a stirring step, with a stirring speed range of 200-800 rpm, preferably 400-600 rpm.

[0026] In some embodiments, in step (2), the catalyst solution is prepared at a temperature of 10-50°C, preferably 20-40°C.

[0027] In some embodiments, in step (3), the oxidant is a solid oxidant and the reaction pressure is provided by nitrogen.

[0028] In some implementations, in step (3), the oxidant is one or both of air and oxygen, and the oxygen or air pipeline is kept open to replenish the consumed gas.

[0029] In some embodiments, the reaction pressure in step (3) is 0-1.2 MPa, preferably 0.2-0.4 MPa.

[0030] In some embodiments, the reaction temperature in step (3) is 60-90°C.

[0031] In some implementations, the reaction time in step (3) is 30 minutes to 3 hours.

[0032] In some embodiments, in step (4), the heat filtration temperature is 60-90°C, preferably 70-80°C.

[0033] In some embodiments, in step (6), the hot filter cake from step (4) is added to a four-necked flask, a solvent is added to the four-necked flask, and the mixture is washed and filtered to obtain a washing solution and a washing cake. The washing and filtration are repeated to obtain a washing solution and a washing cake.

[0034] In some embodiments, in step (6), the HMBP product is washed using a washing solvent-based washing method, with the washing solvent being applied sequentially without adding fresh solvent in between.

[0035] In some embodiments, in step (6), the washing solvent is selected from one or more of the following: n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, methanol, ethanol, propanol, isopropanol, dioxane, methyl acetate, ethyl acetate, toluene, and xylene.

[0036] In some implementations, the washing temperature in step (6) is 60-90°C.

[0037] In some embodiments, in step (6), the filtration temperature is 20-50°C, preferably 30-40°C.

[0038] In some implementations, the number of washes in step (6) is 2-6 times, preferably 3-5 times.

[0039] In some embodiments, in step (7), the drying temperature is 40-90°C, the vacuum degree is 1-5 kPa, and the drying time is 2-8 h. Detailed Implementation

[0040] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0042] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0043] In this application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0044] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0045] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0046] In this description, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0047] Unless otherwise specified, percentages (%) or parts refer to weight percentages or parts by weight of the composition.

[0048] Unless otherwise stated herein, the sum of the contents of the components in the composition is 100%.

[0049] Unless otherwise stated herein, the sum of the parts of each component in the composition may be 100 parts by weight.

[0050] In this document, unless otherwise stated, “combination of” means a multi-component mixture of the elements, such as two, three, four, and up to the maximum possible multi-component mixture.

[0051] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0052] In this paper, unless otherwise stated, all reactions were carried out at room temperature and pressure.

[0053] Therefore, this application provides a method for preparing 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP), comprising the following steps:

[0054] (1) Add a certain mass of trimethylphenol or a certain mass of trimethylphenol and hot filtrate to a stainless steel reactor at normal pressure and room temperature. After the system melts, start stirring; replace with nitrogen and heat to a certain temperature.

[0055] (2) Add a certain amount of additive to a certain amount of catalyst, maintain a certain temperature, and mix evenly to prepare a catalyst solution;

[0056] (3) Pump the catalyst solution from step (2) into the reaction raw materials in the reactor. After the catalyst solution is added, close the vent valve. Add a certain amount of oxidant and keep the reaction under a certain pressure for a certain time to obtain the reaction solution.

[0057] (4) The reaction solution in step (3) is subjected to hot filtration, and the reaction solution and the heat insulation jacket are kept at a certain temperature to obtain hot filter cake and hot filtrate;

[0058] (5) Apply the hot filtrate from step (4) to step (1) and add a certain amount of trimethylphenol to keep the molar amount of trimethylphenol consistent;

[0059] (6) Add the hot filter cake to the four-necked flask, add a certain mass of solvent to the four-necked flask, wash at a certain temperature to obtain a washing solution and a washing cake, and then filter at a certain temperature; repeat washing and filtration a certain number of times to obtain a washing solution and a washing cake.

[0060] (7) Place the cake washed for the last time in a vacuum drying oven and dry it under vacuum at a certain temperature for a certain time to obtain a high-purity HMBP product.

[0061] In step (1), the amount of trimethylphenol used is 1-10 mol, preferably 1-5 mol, and more preferably 1-3 mol.

[0062] In step (1), the temperature is raised to 60-90°C, preferably 60-80°C.

[0063] In step (1), the stirring speed ranges from 200 to 800 rpm, preferably from 400 to 600 rpm.

[0064] In step (2), the amount of catalyst used, in molar terms, can be 0.001-1% of the amount of trimethylphenol used, preferably 0.001-0.1%, more preferably 0.001-0.01%, for example 0.001-0.005%, 0.001-0.0045%, 0.001-0.003%.

[0065] In step (2), the amount of the additive, in molar terms, can be 0.002-1% of the amount of trimethylphenol, preferably 0.002-0.1%, more preferably 0.002-0.06%, for example 0.002-0.01%, 0.002-0.005%, 0.002-0.004%.

[0066] In step (2), the catalyst is selected from: ferric chloride, ferric acetate, copper chloride, copper nitrate, copper acetate, and transition metal salts such as cobalt, nickel, and zinc and their hydrates (e.g., chlorides, acetates, etc.), or one or more of the above catalysts.

[0067] In step (2), the additive is selected from: diethylamine, triethylamine, diethanolamine, triethanolamine, ammonia and other amino-containing substances, or one or more of the above additives.

[0068] In step (2), the catalyst solution is prepared at a temperature of 10-50°C, preferably 20-40°C.

[0069] In step (2), the molar ratio of catalyst to auxiliary agent is 0.01-5, preferably 0.08-5, more preferably 0.25-5, for example 0.25-2.5 or 0.5-2.5.

[0070] In step (3), the oxidant is selected from oxygen, air, hydrogen peroxide, or one or more of the above oxidants. If the oxidant is a solid oxidant, the reaction pressure is provided by nitrogen. If the oxidant is one or both of air and oxygen, the oxygen or air pipeline is kept open to replenish the consumed gas. The reaction pressure is 0-1.2 MPa, preferably 0.2-0.4 MPa. The reaction temperature is 60-90℃, preferably 60-80℃. The reaction time is 30 minutes to 3 hours.

[0071] In step (4), the heat filtration temperature is 60-90℃, preferably 60-85℃, and more preferably 70-80℃.

[0072] In step (6), the solvent is selected from one or more of the following: n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, methanol, ethanol, propanol, isopropanol, dioxane, methyl acetate, ethyl acetate, toluene, and xylene. The washing temperature is 60-90℃. The filtration temperature is 20-50℃, preferably 30-40℃. The number of washing cycles is 2-6, preferably 3-5.

[0073] In step (7), the drying temperature is 40-90℃, the vacuum degree is 1-5kPa, and the drying time is 2-8h.

[0074] Compared with the prior art, the method for preparing 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP) in this application has at least the following beneficial effects:

[0075] (1) The present invention develops a solvent-free oxidative coupling preparation method, which avoids the introduction of organic solvents in the oxidation reaction and effectively avoids the safety risks of the oxidation reaction;

[0076] (2) This invention provides a one-step method for preparing HMBP, which has significant advantages over the two-step method reported in the literature;

[0077] (3) The present invention forms a complex between amine auxiliaries and metal salts, regulates the electronic state and spatial configuration of the metal center, effectively improves the conversion rate, inhibits the occurrence of side reactions, and solves the problem of many by-products in traditional methods;

[0078] (4) The product selectivity of HMBP prepared by oxidative coupling of the present invention is high, the washing process effectively improves the product yield, and the product purity is >99.9%.

[0079] Unless otherwise specified, all raw materials used in this application are commercially available or prepared according to conventional methods in the art. Unless otherwise defined or stated, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this disclosure. Other aspects of this disclosure will be apparent to those skilled in the art from the content of this disclosure. Experimental methods in the following examples, where specific conditions are not specified, are performed according to conventional methods and conditions or as selected in the product specification.

[0080] Example

[0081] The present invention will be further described below with reference to specific embodiments.

[0082] Raw material sources and preparation

[0083] 2,3,5-Trimethylphenol, TMP, purchased from Lianyungang Guanxin Pharmaceutical Technology Co., Ltd.

[0084] Copper acetate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0085] Copper chloride was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0086] Ferric chloride, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0087] Zinc acetate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0088] Diethanolamine was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0089] Ammonia solution was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0090] Diethanolamine was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0091] Diethylamine was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0092] Methanol was purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0093] Equipment source

[0094] Reactor: Purchased from Beijing Century Senlang.

[0095] Calculation formula:

[0096] TMP conversion rate = (1 - m1 / m2) * 100;

[0097] HMBP selectivity = (m3 / 270) / ((m2-m1) / 272)*100;

[0098] m1 is the mass of TMP remaining after the reaction, m2 is the mass of TMP added, and m3 is the mass of HMBP after the reaction.

[0099] Example 1

[0100] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor and heated to prepare the catalyst solution. 0.816 g (0.006 mol) of 12.5% ​​ammonia solution was added to 0.556 g (0.003 mol) of copper acetate, the reactor was sealed, and the liquid temperature was maintained at no less than 40°C. The mixture was stirred for 10 min to prepare the catalyst solution. After the catalyst solution was prepared, nitrogen was used to purge the reactor, and the temperature inside the reactor was controlled at 65°C. The catalyst solution was added to the reactor through the catalyst pipeline, and 0.2 MPa of oxygen was introduced. All other valves were closed, but the oxygen pipeline was opened, maintaining the pressure inside the reactor at 0.2 MPa and the temperature at 65°C for 1 h. The oxygen pipeline was then closed, and the pressure was released to atmospheric pressure. Samples were taken for testing. The TMP conversion rate was 40.2%, and the HMBP selectivity was 97.3%.

[0101] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a 65°C heat-insulating jacket with a vacuum degree of 2 kPa, yielding 250.53 g of hot filter cake and 160.18 g of hot filtrate.

[0102] The hot filter cake was transferred to a 2L four-necked glass flask. 501.21g of methanol was added to the hot filter cake, and the temperature was raised to 60℃ for a first wash. The mixture was kept at this temperature and stirred for 1 hour. Then, hot filtration was performed to obtain a first wash cake and a first wash solution. The same amount of methanol was added to the first wash cake for a second wash, resulting in a second wash cake and a second wash solution. This washing process was repeated three times to obtain a fourth wash cake and a fourth wash solution. The fourth wash cake was placed in a vacuum drying oven at 60℃ and a vacuum of 1 kPa for 6 hours. After drying, 70.36g of high-purity HMBP (GC content 99.93%) was obtained, appearing as a white, lumpy to powdery solid.

[0103] Example 2:

[0104] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor, and the mixture was heated to prepare the catalyst solution. 0.816 g (0.012 mol) of 25.0% ammonia solution was added to 0.556 g (0.003 mol) of copper acetate, the reactor was sealed, and the liquid temperature was maintained at no less than 30°C. The mixture was stirred for 20 min to prepare the catalyst solution. After the catalyst solution was prepared, nitrogen was used to purge the reactor, and the temperature inside the reactor was controlled at 75°C. The catalyst solution was added to the reactor through the catalyst pipeline, and 0.3 MPa of oxygen was introduced. All other valves were closed, but the oxygen pipeline was opened. The pressure inside the reactor was maintained at 0.3 MPa, and the temperature was maintained at 75°C for 40 min. The oxygen pipeline was then closed, and the pressure was released to atmospheric pressure. Samples were taken for testing. The TMP conversion rate was 37.2%, and the HMBP selectivity was 96.1%.

[0105] The reaction solution was heated to 85°C and then subjected to negative pressure filtration in a heat-insulating jacket at 85°C to obtain 234.10g of hot filter cake and 176.61g of hot filtrate.

[0106] The hot filter cake was transferred to a 2L four-necked glass flask. 459.21g of ethanol was added to the hot filter cake, and the temperature was raised to 70°C for a first wash. The mixture was kept at this temperature and stirred for 40 minutes. Then, hot filtration was performed to obtain a first-wash cake and a first-wash solution. This washing operation was repeated three times to obtain a fourth-wash cake and a fourth-wash solution. The fourth-wash cake was then placed in a vacuum drying oven at 60°C and a vacuum of 1 kPa for 7 hours. After drying, 66.34g of high-purity HMBP (GC content 99.94%) was obtained, appearing as a white, lumpy to powdery solid.

[0107] Example 3:

[0108] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor and heated to prepare the catalyst solution. 0.816 g (0.012 mol) of 25.0% ammonia solution was added to 5.560 g (0.030 mol) of copper acetate, the reactor was sealed, and the liquid temperature was maintained at no less than 40°C. The mixture was stirred for 10 min to prepare the catalyst solution. After the catalyst solution was prepared, nitrogen was used to purge the reactor, and the temperature inside the reactor was controlled at 85°C. The catalyst solution was then added to the reactor through the catalyst pipeline, and 0.2 MPa of oxygen was introduced. All other valves were closed, but the oxygen pipeline was opened, maintaining the pressure inside the reactor at 0.2 MPa and the temperature at 65°C for 0.5 h. The oxygen pipeline was then closed, and the pressure was released to atmospheric pressure. Samples were taken for testing. The TMP conversion rate was 48.3%, and the HMBP selectivity was 96.1%.

[0109] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a heating jacket at 65°C to obtain 250.53g of hot filter cake and 160.18g of hot filtrate.

[0110] The hot filter cake was transferred to a 2L four-necked glass flask. 501.07g of n-hexane was added to the hot filter cake, and the temperature was raised to 69°C for a first wash. The mixture was kept at this temperature and stirred for 1 hour. Hot filtration was then performed to obtain a first-wash cake and a first-wash solution. This washing process was repeated twice to obtain a third-wash cake and a third-wash solution. The third-wash cake was then placed in a vacuum drying oven at 60°C and a vacuum of 1 kPa for 6 hours. After drying, 147.63g of high-purity HMBP (GC content 99.73%) was obtained, which was a light white, powdery solid.

[0111] Example 4:

[0112] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor and heated to prepare the catalyst solution. 12.242 g (0.180 mol) of 25.0% ammonia solution was added to 2.037 g (0.015 mol) of copper chloride, the reactor was sealed, and the liquid temperature was maintained at no less than 30°C. The mixture was stirred for 10 min to prepare the catalyst solution. After the catalyst solution was prepared, nitrogen was used to purge the reactor, and the temperature inside the reactor was controlled at 65°C. The catalyst solution was added to the reactor through the catalyst pipeline, and 0.3 MPa of oxygen was introduced. All other valves were closed, but the oxygen pipeline was opened. The pressure inside the reactor was maintained at 0.3 MPa, and the temperature was maintained at 65°C for 1.2 h. The oxygen pipeline was then closed, and the pressure was released to atmospheric pressure. Samples were taken for testing. The TMP conversion rate was 46.4%, and the HMBP selectivity was 94.8%.

[0113] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a 65°C heat-insulating jacket to obtain 266.96g of hot filter cake and 143.75g of hot filtrate.

[0114] The hot filter cake was transferred to a 2L four-necked glass flask. 533.92g of cyclohexane was added to the hot filter cake, and the temperature was raised to 79°C for a first wash. The mixture was kept at this temperature and stirred for 1 hour. Hot filtration was then performed to obtain a first-wash cake and a first-wash solution. This washing process was repeated twice to obtain a third-wash cake and a third-wash solution. The third-wash cake was then placed in a vacuum drying oven at 60°C and a vacuum of 1 kPa for 8 hours. After drying, 157.36g of high-purity HMBP (GC content 99.81%) was obtained, which was a light white, powdery solid.

[0115] Example 5:

[0116] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor and heated to prepare the catalyst solution. 4.08 g (0.030 mol) of 12.5% ​​ammonia solution was added to 2.78 g (0.015 mol) of copper acetate, the reactor was sealed, and the liquid temperature was maintained at no less than 30°C. The mixture was stirred for 10 minutes to prepare the catalyst solution. After the catalyst solution was prepared, nitrogen was used to purge the reactor, and the temperature inside the reactor was controlled at 65°C. The catalyst solution was added to the reactor through the catalyst pipeline, and 0.6 MPa of oxygen was introduced. All other valves were closed, but the oxygen pipeline was opened, maintaining the pressure inside the reactor at 0.6 MPa and the temperature at 65°C for 3 hours. The oxygen pipeline was then closed, and the pressure was released to atmospheric pressure. Samples were taken for testing. The TMP conversion rate was 65.3%, and the HMBP selectivity was 95.7%. Due to the high conversion rate, washing could be performed directly inside the reactor.

[0117] 533.92g of methanol was added to the reactor and heated to 60℃ for a first wash. The mixture was kept at this temperature and stirred for 0.5h. The material was then discharged and hot-filtered to obtain a first wash cake and a first wash liquid. The first wash cake was transferred to a 2L four-necked flask for further washing, which was repeated three times to obtain a fourth wash cake and a fourth wash liquid. The fourth wash cake was placed in a vacuum drying oven at 70℃ and a vacuum of 2kPa for 8h. After drying, 182.32g of high-purity HMBP (GC content 99.90%) was obtained, which appeared as a white lumpy to powdery solid.

[0118] Example 6:

[0119] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor, and the mixture was heated to react. After reacting, nitrogen was used to purge the reactor, and the temperature was controlled at 75 °C. Then, 0.492 g (0.003 mol) of ferric chloride and 0.637 g (0.006 mol) of diethanolamine were added sequentially through the feeding valve. Oxygen was introduced at 0.2 MPa, all other valves were closed, the oxygen line was opened, and the reactor pressure was maintained at 0.2 MPa. The temperature was maintained at 75 °C for 1 hour. The oxygen line was then closed, the pressure was released to atmospheric pressure, and samples were taken for testing. The TMP conversion rate was 34.2%, and the HMBP selectivity was 97.3%.

[0120] The reaction solution was kept at 75°C and subjected to negative pressure filtration in a heating jacket at 75°C to obtain 221.78g of hot filter cake and 188.93g of hot filtrate.

[0121] The hot filter cake was transferred to a 2L four-necked glass flask. 443.57g of methanol was added to the hot filter cake, and the temperature was raised to 60°C for a first wash. The mixture was kept at this temperature and stirred for 1 hour. Hot filtration was then performed to obtain a first-wash cake and a first-wash solution. This washing process was repeated three times to obtain a fourth-wash cake and a fourth-wash solution. The fourth-wash cake was then placed in a vacuum drying oven at 60°C and a vacuum of 1 kPa for 6 hours. After drying, 60.24g of high-purity HMBP (GC content 99.93%) was obtained, appearing as a white, lumpy to powdery solid.

[0122] Example 7:

[0123] 410.71 g (3.000 mol) of TMP was added to a 1 L stainless steel reactor, and the mixture was heated to react. After reacting, nitrogen was used to purge the reactor, and the temperature was controlled at 65 °C. Then, 0.553 g (0.003 mol) of zinc acetate and 0.441 g (0.006 mol) of diethylamine were added sequentially through the feeding valve. Oxygen was introduced at 0.4 MPa, all other valves were closed, the oxygen line was opened, and the pressure inside the reactor was maintained at 0.4 MPa. The temperature was maintained at 65 °C for 1 hour. The oxygen line was then closed, the pressure was released to atmospheric pressure, and samples were taken for testing. The TMP conversion rate was 48.7%, and the HMBP selectivity was 95.5%.

[0124] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a heating jacket at 65°C to obtain 262.85g of hot filter cake and 147.86g of hot filtrate.

[0125] The hot filter cake was transferred to a 2L four-necked glass flask. 525.71g of ethanol was added to the hot filter cake, and the temperature was raised to 60°C for a first wash. The mixture was kept at this temperature and stirred for 1 hour. Hot filtration was then performed to obtain a first-wash cake and a first-wash solution. This washing process was repeated three times to obtain a fourth-wash cake and a fourth-wash solution. The fourth-wash cake was then placed in a vacuum drying oven at 60°C and a vacuum of 1 kPa for 6 hours. After drying, 67.61g of high-purity HMBP (GC content 99.93%) was obtained, appearing as a white, lumpy to powdery solid.

[0126] Example 8:

[0127] The oxidative coupling reaction and hot filtration were exactly the same as in Example 1, yielding 246.14 g of hot filter cake and 162.71 g of hot filtrate.

[0128] Transfer the hot filter cake to a 2L four-necked glass flask. Wash the HMBP product using a washing solution looping method, with each washing solution looped sequentially without adding fresh solvent. Add 483.32g of the second washing solution from the previous batch to the hot filter cake, heat to 60°C for a first wash, maintain the temperature and stir for 1 hour, then hot filter to obtain a first wash cake and a first wash solution. Add 476.65g of the third washing solution from the previous batch to the first wash cake for a second wash to obtain a second wash cake and a second wash solution. Add 476.65g of the third washing solution from the previous batch to the first wash cake for a second wash to obtain a second wash cake and a second wash solution. Add 484.63g of the fourth washing solution from the previous batch to the second wash cake for a third wash to obtain a third wash cake and a third wash solution. Finally, add 492.24g of methanol to the third wash cake to obtain a fourth wash cake and a fourth wash solution.

[0129] The washed cake was placed in a vacuum drying oven at 60℃ and 1 kPa for 6 hours. After drying, 121.67 g of high-purity HMBP (GC content 99.91%) was obtained, appearing as a white, blocky to powdery solid.

[0130] Example 9:

[0131] All other conditions were the same as in Example 1, except that oxygen was replaced with air and the pressure inside the reactor was maintained at 1.0 MPa. The TMP conversion rate was 36.4%, and the HMBP selectivity was 98.3%.

[0132] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a heating jacket at 65°C to obtain 221.78g of hot filter cake and 188.93g of hot filtrate.

[0133] Transfer the hot filter cake to a 2L glass four-necked flask, add 443.57g of methanol to the hot filter cake, heat to 60℃ for a first wash, keep warm and stir for 1 hour, and then perform hot filtration to obtain a first wash cake and a first wash solution; repeat the above washing operation twice to obtain a third wash cake and a third wash solution.

[0134] The washed cake was placed in a vacuum drying oven at 60℃ and 1 kPa for 6 hours. After drying, 78.33 g of high-purity HMBP (GC content 99.90%) was obtained, appearing as a white, blocky to powdery solid.

[0135] Example 10:

[0136] All other conditions were the same as in Example 1. The gas supply method was as follows: after adding the catalyst, 0.8 MPa air was introduced into the reactor, then the air supply was closed, and the system was quickly switched to 0.8 MPa oxygen. Similarly, the oxygen supply was kept open during the reaction. The TMP conversion rate was 44.3%, and the HMBP selectivity was 98.5%.

[0137] The reaction solution was kept at 65°C and subjected to negative pressure filtration in a heating jacket at 65°C to obtain 266.96g of hot filter cake and 143.75g of hot filtrate.

[0138] The hot filter cake was transferred to a 2L four-necked glass flask. 533.92g of methanol was added to the hot filter cake, and the temperature was raised to 60℃ for a first wash. The mixture was kept at this temperature and stirred for 1 hour, followed by hot filtration to obtain a first wash cake and a first wash solution. The same amount of methanol was added to the first wash cake for a second wash, yielding a second wash cake and a second wash solution. This washing process was repeated to obtain a third wash cake and a third wash solution. The third wash cake was placed in a vacuum drying oven at 60℃ and a vacuum of 1 kPa for 6 hours. After drying, 96.41g of high-purity HMBP (GC content 99.91%) was obtained, appearing as a white, lumpy to powdery solid.

[0139] Comparative Example 1:

[0140] All other conditions were the same as in Example 1, but no catalyst or additives were added. At the end of the reaction, TMP was essentially not converted, with a conversion rate of approximately 0%.

[0141] Comparative Example 2:

[0142] All other conditions were the same as in Example 1, but no catalyst was added. At the end of the reaction, the TMP conversion was only 4%.

[0143] Comparative Example 3:

[0144] All other conditions were the same as in Example 1, but no additives were added. At the end of the reaction, TMP was essentially not converted, with a conversion rate of approximately 0%.

[0145] The above description is merely a preferred embodiment of this disclosure and is not intended to limit the scope of the substantive technical content of this disclosure. The substantive technical content of this disclosure is broadly defined within the scope of the claims of this application. Any technical entity or method completed by others that is completely identical to or an equivalent modification of the claims of this application shall be deemed to be covered within the scope of the claims.

[0146] All documents mentioned in this disclosure are incorporated herein by reference as if each document were individually incorporated herein by reference. Furthermore, it should be understood that after reading the foregoing contents of this disclosure, those skilled in the art can make various alterations or modifications to this disclosure, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A solvent-free oxidative coupling method for preparing 2,2',3,3',5,5'-hexamethylbiphenyl (HMBP), the method comprising: In the presence of a metal salt catalyst and an amine auxiliary, trimethylphenol is oxidatively coupled to yield 2,2',3,3',5,5'-hexamethylbiphenyl, wherein: The catalyst is selected from one or more salts of iron, copper, cobalt, nickel, and zinc; and / or Amine auxiliaries are selected from one or more of the following groups: organic amines and ammonia.

2. The method as described in claim 1, characterized in that: The amount of catalyst used, on a molar basis, is 0.001-1% of the amount of trimethylphenol, preferably 0.001-0.1%; The amount of the additive, in molar terms, is 0.002-1% of the amount of trimethylphenol, preferably 0.002-0.1%.

3. The method as described in claim 1, characterized in that: The molar ratio of catalyst to additive is 0.01-5, preferably 0.5-2.

5.

4. The method as described in claim 1, characterized in that, The method includes the following steps: (1) Add the raw material trimethylphenol to the reactor and heat it to melt it; (2) Add amine auxiliaries to the metal salt catalyst to prepare a catalyst solution; (3) Pump the catalyst solution from step (2) into the reactor, add the oxidant, and obtain the reaction solution; (4) The reaction solution from step (3) is subjected to hot filtration to maintain the temperature of the reaction solution and the insulation jacket, thereby obtaining a hot filter cake and a hot filtrate. (5) Apply the hot filtrate from step (4) to step (1); (6) Wash and filter the hot filter cake from step (4) with a washing solvent to obtain washing liquid and washing cake; (7) Place the washed cake from step (6) into a vacuum drying oven and dry it under vacuum to obtain high-purity 2,2',3,3',5,5'-hexamethylbiphenyl.

5. The method as described in claim 4, characterized in that, Step (1) also includes a nitrogen replacement step.

6. The method as described in claim 4, characterized in that, In step (1): The material processing temperature is 60-90℃; and / or The reactor also contains the hot filtrate from step (4); and / or It also includes a stirring step, with a stirring speed range of 200-800 rpm.

7. The method as described in claim 4, characterized in that, In step (3): The oxidizing agent is selected from one or more of the following groups: oxygen, air, hydrogen peroxide; and / or The reaction pressure is 0-1.2 MPa, preferably 0.2-0.4 MPa; and / or The reaction temperature is 60-90℃; and / or The reaction time is 30 minutes to 3 hours.

8. The method as described in claim 4, characterized in that, In step (4), the heat filtration temperature is 60-90℃, preferably 70-80℃.

9. The method as described in claim 4, characterized in that, In step (6): The washing solvent is selected from one or more of the following groups: n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, methanol, ethanol, propanol, isopropanol, dioxane, methyl acetate, ethyl acetate, toluene, xylene; and / or The washing temperature is 60-90℃; and / or The filtration temperature is 20-50℃, preferably 30-40℃; and / or Wash 2-6 times, preferably 3-5 times.

10. The method as described in claim 4, characterized in that, In step (7), the drying temperature is 40-90℃, the vacuum degree is 1-5kPa, and the drying time is 2-8h.