Method for preparing 2, 2 '-diphenyldicarboxylic acid through continuous oxidation of 9, 10-dihydrophenanthrene

Abstract

The invention belongs to the technical field of fine chemical engineering, and discloses a method for preparing 2, 3, 4-trimethyl-1, 3-dihydrophenanthrene through continuous oxidation of 9, 10- The invention discloses a method for preparing 9, 10-phenanthrenequinone, which is characterized in that 9, 10-dihydrophenanthrene is used as a raw material, t-BHP is used as an oxidant, under the action of a catalyst, a mild oxidation reaction is carried out at 60 DEG C and normal pressure to prepare 9, 10-phenanthrenequinone, the conversion rate of the dihydrophenanthrene is 99%, the yield of the 9, 10-phenanthrenequinone is 77%, H2O2 is added into an acetic acid solvent to oxidize the 9, 10-phenanthrenequinone, the conversion rate of the 9, 10-phenanthrenequinone is 99%, and the yield of the 2, 2 '-diphenyldicarboxylic acid is 96%. According to the method, the traditional process for producing 2, 2 '-diphenyldicarboxylic acid is replaced by a process for producing 2, 2'-diphenyldicarboxylic acid through continuous oxidation by taking 9, 10-dihydrophenanthrene as a raw material and an oxidizing agent, no strong alkaline substance is used, the cost is low, the condition is mild, the operation is easy, and meanwhile, the conversion rate of 9, 10-dihydrophenanthrene and the yield of 2, 2 '-diphenyldicarboxylic acid are high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal chemical industry and fine chemical industry, and relates to a method for preparing 2,2'-biphenyldicarboxylic acid, in particular to a method for preparing 2,2'-biphenyldicarboxylic acid by continuous oxidation of 9,10-dihydrophenanthrene. BACKGROUND

[0002] 2,2'-biphenyldicarboxylic acid is an aromatic dicarboxylic acid with a rigid conjugated structure, which is a white crystal at room temperature, difficult to dissolve in water but soluble in polar organic solvents. The two carboxyl groups in its molecule are distributed at the ortho position of biphenyl, giving it good coordination ability and structural regulation characteristics, so it is widely used in metal organic frameworks, coordination polymers and functional polymer materials. Due to its stable structure and adjustable electronic effect, 2,2'-biphenyldicarboxylic acid is not only an important intermediate for organic synthesis, but also shows important application potential in the fields of high-performance materials and green catalysis. Therefore, through the improvement of the industrial production technology of 2,2'-biphenyldicarboxylic acid, the yield of 2,2'-biphenyldicarboxylic acid is improved and the production cost is reduced, which has important significance for promoting the development of the entire chemical industry.

[0003] The commonly used synthesis method is to take phenanthrene as a starting material, and to add chemical reagents such as ozone, oxygen / air, sodium hypochlorite, peracetic acid, etc., but there are usually problems such as environmental pollution, poor selectivity, low yield, long reaction time, high energy consumption, etc. US3118934 and US344419 disclose a method for preparing 2,2'-biphenyldicarboxylic acid by one or two oxidations of phenanthrene using ozone as an oxidizing agent, and the yield of biphenyldicarboxylic acid is more than 90%, but multiple oxidations are not only high in cost but also complex in process, and are difficult to be industrialized. In the exploration process of phenanthrene oxidation products using oxygen / air as an oxidizing agent, Applied Catalysis A: General, 1997, 15(7): 311-334. discloses that phenanthrene is oxidized using air as an oxidizing agent and a V2O5 or V2O5 and alkali metal oxide, alkali metal sulfate composite catalytic system, and the oxidation products are mainly phenanthrenequinone and biphenyldicarboxylic acid. This method using oxygen / air as an oxidizing agent has a wide source and low price, but it usually needs to be carried out at high temperature and high pressure, and has high requirements for equipment, so that the industrialization is limited. CN1046326A discloses a method for preparing 2,2'-biphenyldicarboxylic acid by oxidizing phenanthrene with ruthenium tetroxide-sodium hypochlorite, and the yield of 2,2'-biphenyldicarboxylic acid is 85% in a strong alkaline medium. However, the method is sensitive to pH value, and phenanthrenequinone is generated in a dominant position at a low pH value, and only when the pH value is more than 13, a large amount of biphenyldicarboxylic acid can be generated. The use of strong alkaline medium will cause serious “three wastes” problem and bring serious pollution to the environment, and there is still a certain distance to realize industrialization. The peracetic acid oxidation method is a more moderate and green oxidation method, and has realized industrialization. CN101565368A, CN1735580A and other patents disclose a process in which phenanthrene is oxidized in an acetic acid medium with 30% H2O2 as an oxidizing agent, the reaction temperature is controlled at 80-110 ℃, and the product is obtained through reflux, concentration and recrystallization. However, the reaction is easy to generate phenanthrenequinone intermediate when the oxidation is incomplete, and is easy to generate phthalic acid when the oxidation is excessive, and the yield of biphenyldicarboxylic acid is greatly affected by the amount of oxidizing agent. Therefore, it is of great significance to develop a method for preparing 2,2'-biphenyldicarboxylic acid by catalytic selective oxidation of phenanthrene and its derivatives under moderate conditions. SUMMARY

[0004] The purpose of the present application is to provide a continuous oxidation of 9,10-dihydrophenanthrene based on the prior art, so that 9,10-dihydrophenanthrene is oxidized with t-BHP under the action of a catalyst to obtain 9,10-phenanthrenequinone, and then H2O2 is added in acetic acid solvent to oxidize 9,10-phenanthrenequinone to obtain 2,2'-biphenyldicarboxylic acid with high yield, which has the characteristics of low cost, moderate conditions, simple process and environmental friendliness.

[0005] The technical scheme of the present application is:

[0006] A method for preparing 2,2'-biphenyldicarboxylic acid by continuous oxidation of 9,10-dihydrophenanthrene, the steps are as follows:

[0007] 1) After mixing and stirring 9,10-dihydrophenanthrene and catalyst in water, add dropwise oxidant t-BHP to perform oxidation reaction to obtain 9,10-phenanthrenequinone; the mass ratio of catalyst to 9,10-dihydrophenanthrene is 1:3-10, the molar ratio of oxidant t-BHP to 9,10-dihydrophenanthrene is 2-22:1, preferably 18:1; the reaction temperature is 40-80℃, preferably 60℃; the reaction time is 2-10h, preferably 6h;

[0008] 2) After mixing and stirring 9,10-phenanthrenequinone in acetic acid, add dropwise H2O2 to perform oxidation reaction to obtain 2,2'-biphenyldicarboxylic acid; the molar ratio of 9,10-phenanthrenequinone to acetic acid is 1:17.5-70, preferably 1:35, the molar ratio of 9,10-phenanthrenequinone to H2O2 is 1:10-40, preferably 1:20; the reaction temperature is 30-80℃, preferably 50℃; the reaction time is 3-9h, preferably 5h.

[0009] In step 1), the catalyst is RuO2 / TiO2, RuO2 / CeO2 or RuO2 / ZrO2, preferably RuO2 / TiO2, wherein the loading amount of RuO2 accounts for 7.8% of the mass percentage of the catalyst.

[0010] The beneficial effects of the present application are:

[0011] 1) The present application uses 9,10-dihydrophenanthrene as raw material, which is not affected by the pH of the solvent compared with the liquid phase oxidation method of phenanthrene, avoiding the use of strong alkali;

[0012] 2) The present application uses 9,10-dihydrophenanthrene as raw material, and the reaction conditions are mild during the oxidation process, avoiding the use of high temperature and high pressure conditions compared with the commonly used liquid phase oxidation of phenanthrene;

[0013] 3) The present application adopts continuous oxidation method, compared with the traditional oxidation directly using phenanthrene as raw material, the oxidation product 9,10-phenanthrenequinone of 9,10-dihydrophenanthrene is used as raw material to continue oxidation, the selectivity and yield of 2,2'-biphenyldicarboxylic acid can be improved, which is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the influence result graph of the amount of t-BHP on the preparation of 9,10-phenanthrenequinone by oxidation of 9,10-dihydrophenanthrene.

[0015] Figure 2 is the influence result graph of reaction temperature on the preparation of 2,2'-biphenyldicarboxylic acid by oxidation of 9,10-phenanthrenequinone. DETAILED DESCRIPTION

[0016] The specific embodiments of the present application are further described below with reference to the accompanying drawings and technical solutions.

[0017] Example 1:

[0018] 0.4 mmol 9,10-dihydrophenanthrene and 20 mg RuO2 / TiO2 were added to 2 mL water, heated to keep the temperature at 40℃, then 2.4 mmol t-BHP was added to the above reaction solution, and stirred for 4 h. After the reaction was completed, liquid chromatography was used for analysis, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 95.7% and 53.4%, respectively.

[0019] Example 2:

[0020] 0.4 mmol 9,10-dihydrophenanthrene and 20 mg RuO2 / CeO2 were added to 2 mL water, heated to keep the temperature at 40℃, then 2.4 mmol t-BHP was added to the above reaction solution, and stirred for 4 h. After the reaction was completed, liquid chromatography was used for analysis, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 24.1% and 56.6%, respectively.

[0021] Example 3:

[0022] 0.4 mmol 9,10-dihydrophenanthrene and 20 mg RuO2 / ZrO2 were added to 2 mL water, heated to keep the temperature at 40℃, then 2.4 mmol t-BHP was added to the above reaction solution, and stirred for 4 h. After the reaction was completed, liquid chromatography was used for analysis, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 34.9% and 53.2%, respectively.

[0023] The examples 1-3 are listed as follows:

[0024]

[0025] Example 4:

[0026] 0.4 mmol 9,10-dihydrophenanthrene and 20 mg RuO2 / TiO2 were added to 2 mL water, heated to keep the temperature at 40℃, then 2.4 mmol t-BHP was added to the above reaction solution, and stirred for 2 h. After the reaction was completed, liquid chromatography was used for analysis, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 87.7% and 42.7%, respectively.

[0027] Example 5:

[0028] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 40 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 95.7% and 56.5%, respectively.

[0029] Example 6:

[0030] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 40 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 8 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 97.0% and 54.6%, respectively.

[0031] Example 7:

[0032] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 40 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 10 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 95.2% and 54.7%, respectively.

[0033] Examples 4 through 7 are listed below:

[0034]

[0035] Example 8:

[0036] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 50 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 94.7% and 52.9%, respectively.

[0037] Example 9:

[0038] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 96.3% and 64.8%, respectively.

[0039] Example 10:

[0040] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 70 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 96.1% and 49.3%, respectively.

[0041] Example 11:

[0042] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of RuO2 / TiO2 were added to 2 mL of water, and the mixture was heated to 80 °C. Then, 2.4 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion rate of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 97.7% and 50.7%, respectively.

[0043] Examples 8 through 11 are listed below:

[0044]

[0045] Example 12:

[0046] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of catalyst were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 0.8 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 69.8% and 40.0%, respectively.

[0047] Example 13:

[0048] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of catalyst were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 4 mmol of t-BHP was added to the reaction solution, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 98.2% and 69.2%, respectively.

[0049] Example 14:

[0050] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of catalyst were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 5.6 mmol of t-BHP was added to the reaction mixture, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 98.4% and 77.0%, respectively.

[0051] Example 15:

[0052] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of catalyst were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 7.2 mmol of t-BHP was added to the reaction solution, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 99.5% and 77.7%, respectively.

[0053] Example 16:

[0054] 0.4 mmol of 9,10-dihydrophenanthrene and 20 mg of catalyst were added to 2 mL of water, and the mixture was heated to 60 °C. Then, 8.8 mmol of t-BHP was added to the reaction solution, and the mixture was stirred for 6 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the conversion of 9,10-dihydrophenanthrene and the selectivity of 9,10-phenanthrenequinone were calculated to be 99.3% and 73.9%, respectively.

[0055] Examples 12-16 are listed below:

[0056]

[0057] Example 17:

[0058] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 30 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 98.7% and 89.7%, respectively.

[0059] Example 18:

[0060] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 40 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the mixture was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.4% and 90.8%, respectively.

[0061] Example 19:

[0062] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 50 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.7% and 96.2%, respectively.

[0063] Example 20:

[0064] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 60 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the calculated conversion rates of phenanthrenequinone and the yields of 2,2'-biphenyl dicarboxylic acid were 99.7% and 72.3%, respectively.

[0065] Example 21:

[0066] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 70 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the mixture was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.5% and 65.9%, respectively.

[0067] Example 22:

[0068] Example 1 : 0.5 mmol of 9, 10-phenanthrenequinone was added to 17.5 mmol of acetic acid, heated to maintain the temperature at 80 °C, then 9.8 mmol of H2O2 was added to the above reaction solution, and stirred for 5 h. After the reaction was completed, it was analyzed by liquid chromatography, and the calculated conversion of phenanthrenequinone and the yield of 2,2'-biphenyldicarboxylic acid were 99.4% and 46.9%, respectively.

[0069] Examples 17-22 are listed as follows:

[0070]

[0071] Example 23:

[0072] Example 23: 0.5 mmol of 9, 10-phenanthrenequinone was added to 8.75 mmol of acetic acid, heated to maintain the temperature at 50 °C, then 9.8 mmol of H2O2 was added to the above reaction solution, and stirred for 5 h. After the reaction was completed, it was analyzed by liquid chromatography, and the calculated conversion of 9, 10-phenanthrenequinone and the yield of 2,2'-biphenyldicarboxylic acid were 99.9% and 90.8%, respectively.

[0073] Example 24:

[0074] Example 24: 0.5 mmol of 9, 10-phenanthrenequinone was added to 26.25 mmol of acetic acid, heated to maintain the temperature at 50 °C, then 9.8 mmol of H2O2 was added to the above reaction solution, and stirred for 5 h. After the reaction was completed, it was analyzed by liquid chromatography, and the calculated conversion of 9, 10-phenanthrenequinone and the yield of 2,2'-biphenyldicarboxylic acid were 99.7% and 84.1%, respectively.

[0075] Example 25:

[0076] Example 25: 0.5 mmol of 9, 10-phenanthrenequinone was added to 35 mmol of acetic acid, heated to maintain the temperature at 50 °C, then 9.8 mmol of H2O2 was added to the above reaction solution, and stirred for 5 h. After the reaction was completed, it was analyzed by liquid chromatography, and the calculated conversion of 9, 10-phenanthrenequinone and the yield of 2,2'-biphenyldicarboxylic acid were 99.7% and 83.1%, respectively.

[0077] Examples 23-25 are listed as follows:

[0078]

[0079] Example 26:

[0080] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 50 °C. Then, 4.9 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography. The calculated conversion rates of 9,10-phenanthrenequinone and the yields of 2,2'-biphenyl dicarboxylic acid were 99.1% and 88.0%, respectively.

[0081] Example 27:

[0082] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 50 °C. Then, 14.7 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography. The calculated conversion rates of 9,10-phenanthrenequinone and the yields of 2,2'-biphenyl dicarboxylic acid were 99.9% and 85.3%, respectively.

[0083] Example 28:

[0084] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the mixture was heated to 50 °C. Then, 19.6 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 5 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the calculated conversion rates of 9,10-phenanthrenequinone and the yields of 2,2'-biphenyl dicarboxylic acid were 99.9% and 85.5%, respectively.

[0085] Examples 26-28 are listed below:

[0086]

[0087] Example 29:

[0088] 0.5 mmol of 9,10-phenanthrenequinone was mixed with 17.5 mmol of acetic acid and heated to 50 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 3 h. After the reaction was completed, the mixture was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.6% and 87.8%, respectively.

[0089] Example 30:

[0090] 0.5 mmol of 9,10-phenanthrenequinone was mixed with 17.5 mmol of acetic acid and heated to 50 °C. Then, 9.8 mmol of H₂O₂ was added to the reaction mixture, and the mixture was stirred for 7 h. After the reaction was completed, the reaction was analyzed by liquid chromatography, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.7% and 90.4%, respectively.

[0091] Example 31:

[0092] 0.5 mmol of 9,10-phenanthrenequinone was added to 17.5 mmol of acetic acid, and the temperature was kept at 50 °C. Then 9.8 mmol of H2O2 was added to the above reaction solution, and the reaction was stirred for 9 h. After the reaction was completed, liquid chromatography was used for analysis, and the calculated conversion rate of phenanthrenequinone and the yield of 2,2'-biphenyl dicarboxylic acid were 99.7% and 80.4%, respectively.

[0093] Examples 29-31 are listed as follows:

[0094]

[0095] The above examples are only used to help understand the method of the present application and its core idea. It should be pointed out that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made to the present application, and these improvements and modifications should all belong to the protection scope of the claims of the present application.

Claims

1. A process for the continuous oxidation of 9, 10-dihydrophenanthrene to 2,2'-diphenic acid, characterized in that, The steps are as follows: 1) After mixing and stirring 9,10-dihydrophenanthrene and a catalyst in water, an oxidant t-BHP is added dropwise to perform an oxidation reaction, to obtain 9,10-phenanthrenequinone; 2) After mixing and stirring 9,10-phenanthrenequinone in acetic acid, H2O2 is added dropwise to perform an oxidation reaction, to obtain 2,2'-biphenyldicarboxylic acid.

2. The process for the continuous oxidation of 9,10-dihydrophenanthrene to 2,2'-diphenic acid according to claim 1, characterized in that, In step 1), the catalyst is RuO2 / TiO2, RuO2 / CeO2 or RuO2 / ZrO2, wherein the loading amount of RuO2 accounts for 7.8% of the mass percentage of the catalyst.

3. The process for the continuous oxidation of 9,10-dihydrophenanthrene to 2,2'-diphenic acid according to claim 1, characterized in that, In step 1), the mass ratio of the catalyst to 9,10-dihydrophenanthrene is 1:3-10, and the molar ratio of the oxidant t-BHP to 9,10-dihydrophenanthrene is 2-22:

1.

4. The process for the continuous oxidation of 9,10-dihydrophenanthrene to 2,2'-diphenic acid according to claim 1, characterized in that, In step 1), the reaction temperature is 40-80℃, and the reaction time is 2-10h.

5. The process for the continuous oxidation of 9,10-dihydrophenanthrene to 2,2'-diphenoic acid according to claim 1, characterized in that, In step 2), the molar ratio of 9,10-phenanthrenequinone to acetic acid is 1:17.5-70, and the molar ratio of 9,10-phenanthrenequinone to H2O2 is 1:10-40.

6. The process for the continuous oxidation of 9,10-dihydrophenanthrene to 2,2'-diphenoic acid according to claim 1, characterized in that, In step 2), the reaction temperature is 30-80℃, and the reaction time is 3-9h.

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