Method for synthesizing 2, 5-dihydroxy terephthalic acid

Abstract

The invention relates to the technical field of synthesis of 2, 5-dihydroxy terephthalic acid, and discloses a method for synthesizing 2, 5-dihydroxy terephthalic acid, which comprises the following steps: by taking diethyl succinylsuccinate as a raw material and trichloroisocyanuric acid or supported trichloroisocyanuric acid as an oxidizing agent, reacting in a polar solvent at the temperature of 50-100 DEG C for 2-4 hours at the temperature of 50-100 DEG C to obtain 2, 5-dihydroxy terephthalic acid. The method comprises the following steps: oxidizing diethyl succinylsuccinate by using an oxidizing agent, hydrolyzing in the presence of an alkaline substance, and acidifying to obtain 2, 5-dihydroxy terephthalic acid; the dosage of trichloroisocyanuric acid serving as an oxidizing active component in the oxidizing agent is 1-2 times of the molar weight of the diethyl succinylsuccinate. The synthesis method provided by the invention is green and environment-friendly, mild in reaction condition, simple in process, easy to operate and high in product yield, and can be applied to actual industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of 2,5-dihydroxyterephthalic acid synthesis, in particular to a method for synthesizing 2,5-dihydroxyterephthalic acid. Background Art

[0002] 2,5-Dihydroxyterephthalic acid (DHTA) is an important pharmaceutical intermediate and organic synthesis intermediate. It can be used in the synthesis of polymer materials and is used in many fields such as medicine, fire protection, automobiles, aviation, and military.

[0003] The currently reported methods for preparing 2,5-dihydroxyterephthalic acid are mainly divided into the following categories:

[0004] Patent CN106380387A uses p-xylene as a raw material, reacts with hydrogen peroxide in the presence of a solid catalyst for 6 to 14 hours, and obtains 2,5-dihydroxyterephthalic acid by separation and purification by a chromatographic column. In this method, the solid catalyst uses magnesium aluminum hydrotalcite as a precursor and modified nano kaolin as a carrier. The catalyst preparation process is complicated and cumbersome, and the cost is high, and it has no practical application value.

[0005] In patent CN101508642B, sodium phenolate, potassium hydroxide and carbon dioxide are used as reactants, and 2,5-dihydroxyterephthalic acid potassium salt is first prepared by Pd(II) / C catalysis, and then recrystallization and acidification are performed to obtain 2,5-dihydroxyterephthalic acid.

[0006] Patent CN104829449A uses p-xylene as a raw material and produces 2,5-dihydroxyterephthalic acid by oxidation in one step in the presence of a copper-containing catalyst. This method not only requires the preparation of a catalyst separately, but also introduces copper ions into the product, affecting the product quality and limiting the scope of application.

[0007] Patent CN112624915A uses 1,4-cyclohexanedione-2,5-dicarboxylic acid dimethyl ester (DMSS) as a raw material, iodine or quinones as a catalyst, and hydrogen peroxide is used for oxidation under heating conditions to obtain 2,5-dihydroxyterephthalic acid. This method involves the high-temperature use of hydrogen peroxide, which poses a high safety hazard.

[0008] Patent CN114956985A uses dialkyl succinylsuccinate as a raw material and uses oxygen-containing gas to oxidize dialkyl succinylsuccinate under alkaline conditions to prepare 2,5-dihydroxyterephthalic acid. This method uses a gas oxidant and requires high temperature and high pressure conditions, which poses certain safety hazards. Summary of the invention

[0009] In order to solve the shortcomings of the existing technology for synthesizing 2,5-dihydroxyterephthalic acid, the present invention proposes a method for synthesizing 2,5-dihydroxyterephthalic acid, wherein diethyl succinylsuccinate is used as a raw material, reacts with trichloroisocyanuric acid (TCCA) in an organic solvent at a suitable temperature, then hydrolyzes in the presence of an alkaline substance, and then acidifies to obtain 2,5-dihydroxyterephthalic acid. The synthesis method is green and environmentally friendly, has mild reaction conditions, is simple and easy to operate, has a high product yield, and can be applied to actual industrial production.

[0010] A method for synthesizing 2,5-dihydroxyterephthalic acid comprises: using diethyl succinylsuccinate as a raw material and trichloroisocyanuric acid or supported trichloroisocyanuric acid as an oxidant, in a polar solvent at 50-100° C., the oxidant first oxidizes the diethyl succinylsuccinate, then hydrolyzes it in the presence of an alkaline substance, and then acidifies it to obtain 2,5-dihydroxyterephthalic acid;

[0011] The amount of trichloroisocyanuric acid, an oxidatively active component in the oxidant, is 1 to 2 times the molar amount of diethyl succinylsuccinate.

[0012] Preferably, the supported trichloroisocyanuric acid is one of non-magnetic oxidant I, non-magnetic oxidant II, magnetic oxidant I and magnetic oxidant II.

[0013] Preferably, the preparation method of the non-magnetic oxidant I is: forming a coordination bond between the carbonyl functional group of trichloroisocyanuric acid and the transition metal ion, and forming a coordination bond between the transition metal ion and the pyridine nitrogen on the ligand I, thereby obtaining the non-magnetic oxidant I;

[0014] The preparation method of the ligand I is:

[0015] Step S1-1, using the Suzuki coupling reaction mechanism, under the catalysis of a palladium catalyst, the boronic acid pinacol ester group of 2,6-bis(methoxycarbonyl)pyridine-4-boronic acid pinacol ester and the bromine functional group of N1,N1,N4,N4-tetrakis(4-bromophenyl)benzene-1,4-diamine undergo a coupling reaction to obtain a carboxylic acid methyl ester functional monomer;

[0016] Step S1-2: under alkaline conditions, the methyl carboxylate functional group of the methyl carboxylate functional monomer undergoes a hydrolysis reaction to generate ligand I.

[0017] Preferably, the preparation method of the non-magnetic oxidant II is: forming a coordination bond between the carbonyl functional group of trichloroisocyanuric acid and the transition metal ion, and forming a coordination bond between the transition metal ion and the pyridine nitrogen and pyrazole nitrogen on the ligand II, thereby obtaining the non-magnetic oxidant II;

[0018] The preparation method of the ligand II is:

[0019] Step S2-1, using the Claisen condensation reaction mechanism, condensing α-H-containing acetophenone with triethylpyridine-2,4,6-tricarboxylate to obtain a benzoylacetylpyridyl functional monomer;

[0020] Step S2-2, utilizing the nucleophilic addition reaction mechanism, the carbonyl functional group of the benzoylacetylpyridyl functional monomer undergoes a nucleophilic addition reaction with the hydrazine group of p-carboxyphenylhydrazine to close the ring and generate ligand II.

[0021] Preferably, the preparation method of the magnetic oxidant I is: the magnetic oxidant I is obtained by an esterification reaction between the carboxyl functional group of the ligand I in the non-magnetic oxidant I and the hydroxyl functional group on the surface of the hydroxylated ferrosoferric oxide nanoparticles.

[0022] Preferably, the preparation method of the magnetic oxidant II is: the carboxyl functional group of the ligand II in the non-magnetic oxidant II undergoes an esterification reaction with the hydroxyl functional group on the surface of the hydroxylated ferrosoferric oxide nanoparticles to obtain the magnetic oxidant II.

[0023] Preferably, the polar solvent is one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

[0024] Preferably, the alkaline substance is sodium hydroxide or potassium hydroxide, and the amount of sodium hydroxide or potassium hydroxide used is 2 to 5 times the molar amount of diethyl succinylsuccinate.

[0025] Preferably, the recycling method of the magnetic oxidant I is: using the trichloroisocyanuric acid synthesis method, the inactivated magnetic oxidant I recovered by magnetic separation is converted into an active magnetic oxidant I, and then it is used again in the experiment of oxidizing diethyl succinylsuccinate to synthesize 2,5-dihydroxyterephthalic acid;

[0026] The trichloroisocyanuric acid synthesis method is one of the sodium cyanurate chlorine method, the sodium hypochlorite method, the chlorine-solvent method, and the composite method.

[0027] Preferably, the transition metal is one of cadmium, nickel, palladium, platinum, cobalt, ruthenium, copper and manganese.

[0028] Beneficial Effects

[0029] The present invention uses trichloroisocyanuric acid as an oxidant and adopts a technical route of oxidizing diethyl succinylsuccinate with trichloroisocyanuric acid to synthesize 2,5-dihydroxyterephthalic acid.

[0030] Using trichloroisocyanuric acid as an oxidant has good selectivity and high yield, and trichloroisocyanuric acid is cheap, which can reduce the reaction cost;

[0031] Furthermore, the present invention prepares four types of supported trichloroisocyanuric acid oxidants by functionally modifying the trichloroisocyanuric acid oxidant, which are: non-magnetic oxidant I, non-magnetic oxidant II, magnetic oxidant I, and magnetic oxidant II;

[0032] The experiment found that: on the one hand, the above four supported trichloroisocyanuric acid oxidants can utilize the technical route of oxidizing diethyl succinylsuccinate to synthesize 2,5-dihydroxyterephthalic acid, and on the other hand, they all have better oxidation activity than trichloroisocyanuric acid. Thirdly, magnetic oxidant I and magnetic oxidant II also have excellent recycling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The chemical reaction formula for synthesizing 2,5-dihydroxyterephthalic acid;

[0034] Figure 2 is the chemical structural formula of non-magnetic oxidant I;

[0035] Figure 3 is the chemical reaction formula for synthesizing carboxylic acid methyl ester functional monomer;

[0036] Figure 4 is the chemical structural formula of ligand Ⅰ;

[0037] Figure 5 is the chemical structural formula of non-magnetic oxidant II;

[0038] Figure 6 is the chemical reaction formula for synthesizing benzoylacetylpyridyl monomer;

[0039] Figure 7 is the chemical reaction formula for synthesizing ligand II;

[0040] Figure 8 These are the experimental results of the oxidation of magnetically supported trichloroisocyanuric acid to synthesize 2,5-dihydroxyterephthalic acid. DETAILED DESCRIPTION

[0041] The present invention provides a method for synthesizing 2,5-dihydroxyterephthalic acid, such as Figure 1 As shown, its preparation method is:

[0042] Using diethyl succinylsuccinate as a raw material and trichloroisocyanuric acid as an oxidant, in a polar solvent at 50-100° C., trichloroisocyanuric acid oxidizes diethyl succinylsuccinate to generate an intermediate product, diethyl 2,5-dihydroxyterephthalate; the diethyl 2,5-dihydroxyterephthalate is first hydrolyzed in the presence of sodium hydroxide or potassium hydroxide, and then acidified with a protonic acid to prepare 2,5-dihydroxyterephthalic acid;

[0043] The polar solvent is one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

[0044] In order to screen and obtain the optimal experimental conditions for synthesizing 2,5-dihydroxyterephthalic acid, the present invention implemented the following experiments, specifically including Examples I-1 to I-6.

[0045] Example I-1:

[0046] 2.56 g of diethyl succinylsuccinate and 50 mL of ethanol were added to a round-bottom flask. Under mechanical stirring, 2.32 g of trichloroisocyanuric acid oxidant was added in batches. The temperature was raised to 50° C. and stirred for reaction for 2 h. Then, sodium hydroxide solution (prepared with 0.8 g of sodium hydroxide and 30 mL of deionized water) was added to the flask. The temperature was raised to 80° C. and stirred for reaction for 5 h. Concentrated hydrochloric acid was used to adjust the solution pH to 1. The solution was cooled to room temperature, the mixture was filtered, the filter cake was washed with deionized water and dried to obtain 1.67 g of product.

[0047] The reaction products were qualitatively and quantitatively analyzed using a Varian Prostar high performance liquid chromatograph, which was equipped with a Chromspher 5C18 (4.6 mm × 150 mm) chromatographic column, the UV detector wavelength was set to 254 nm, the column temperature was set to 30°C, the mobile phase was methanol and 0.1% perchloric acid aqueous solution in a volume ratio of 3:2, and the analysis was performed at a flow rate of 1.0 mL / min. The yield of 2,5-dihydroxyterephthalic acid in the product was calculated, and the specific calculation method was as follows:

[0048] Yield of 2,5-dihydroxyterephthalic acid = n(2,5-dihydroxyterephthalic acid) / n(diethyl succinylsuccinate)

[0049] ={1.67g / [198.1(g / mol)]} / {2.56g / [256.3(g / mol)]}=84.3%;

[0050] The product was tested using a Vario EL IIICHNSO element analyzer, and the test results were as follows: the measured value of the C element was 48.54% (theoretical value 48.50%), and the measured value of the H element was 3.11% (theoretical value 3.05%);

[0051] The elemental analysis results show that the measured values ​​of C and H elements in the product are basically consistent with the theoretical values ​​in 2,5-dihydroxyterephthalic acid, further proving that the product is 2,5-dihydroxyterephthalic acid.

[0052] Example I-2:

[0053] 2.56 g of diethyl succinylsuccinate and 50 mL of isopropanol were added to a round-bottom flask, and 4.64 g of trichloroisocyanuric acid oxidant was added in batches under mechanical stirring, and the temperature was raised to 70° C. and stirred for reaction for 5 h. Then, sodium hydroxide solution (prepared with 1.6 g of sodium hydroxide and 30 mL of deionized water) was added to the flask, and the temperature was raised to 80° C. and stirred for reaction for 5 h. The solution was adjusted to pH=1 with concentrated hydrochloric acid, cooled to room temperature, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain 1.85 g of product.

[0054] The yield of 2,5-dihydroxyterephthalic acid in the product was measured by Varian Prostar high performance liquid chromatography and was 93.4%;

[0055] The elemental analysis results further proved that the product was 2,5-dihydroxyterephthalic acid (the measured value of the C element in this embodiment was 48.56% (theoretical value 48.50%), and the measured value of the H element was 3.09% (theoretical value 3.05%)).

[0056] Example I-3:

[0057] 2.56 g of diethyl succinylsuccinate and 50 mL of N,N-dimethylformamide were added to a round-bottom flask, and 3.48 g of trichloroisocyanuric acid oxidant was added in batches under mechanical stirring, and the temperature was raised to 100° C. and stirred for reaction for 10 h. Then, potassium hydroxide solution (prepared with 2.8 g of potassium hydroxide and 30 mL of deionized water) was added to the flask, and the temperature was raised to 80° C. and stirred for reaction for 5 h. The solution was adjusted to pH=1 with concentrated hydrochloric acid, cooled to room temperature, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain 1.80 g of product.

[0058] The yield of 2,5-dihydroxyterephthalic acid in the product was measured by Varian Prostar high performance liquid chromatography and was 90.9%;

[0059] The elemental analysis results further proved that the product was 2,5-dihydroxyterephthalic acid (the measured value of the C element in this embodiment was 48.59% (theoretical value 48.50%), and the measured value of the H element was 3.14% (theoretical value 3.05%)).

[0060] Example I-4:

[0061] 2.56 g of diethyl succinylsuccinate and 50 mL of methanol were added to a round-bottom flask. Under mechanical stirring, 2.32 g of trichloroisocyanuric acid oxidant was added in batches. The temperature was raised to 80° C. and stirred for reaction for 2 h. Then, potassium hydroxide solution (prepared with 2.8 g of potassium hydroxide and 30 mL of deionized water) was added to the flask. The temperature was raised to 80° C. and stirred for reaction for 5 h. Concentrated hydrochloric acid was used to adjust the solution pH to 1. The solution was cooled to room temperature, the mixture was filtered, the filter cake was washed with deionized water, and then dried to obtain 1.73 g of product.

[0062] The yield of 2,5-dihydroxyterephthalic acid in the product was measured by Varian Prostar high performance liquid chromatography and was 87.3%;

[0063] The elemental analysis results further proved that the product was 2,5-dihydroxyterephthalic acid (the measured value of the C element in this example was 48.53% (theoretical value 48.50%), and the measured value of the H element was 3.08% (theoretical value 3.05%)).

[0064] Example I-5:

[0065] 2.56 g of diethyl succinylsuccinate and 50 mL of isopropanol were added to a round-bottom flask, and 4.64 g of trichloroisocyanuric acid oxidant was added in batches under mechanical stirring, and the temperature was raised to 50° C. and stirred for reaction for 8 h. Then, sodium hydroxide solution (prepared with 0.8 g of sodium hydroxide and 30 mL of deionized water) was added to the flask, and the temperature was raised to 80° C. and stirred for reaction for 5 h. The solution was adjusted to pH=1 with concentrated hydrochloric acid, cooled to room temperature, and the mixture was filtered. The filter cake was washed with deionized water and dried to obtain 1.71 g of product.

[0066] The yield of 2,5-dihydroxyterephthalic acid in the product was measured by Varian Prostar high performance liquid chromatography and was 86.3%;

[0067] The elemental analysis results further proved that the product was 2,5-dihydroxyterephthalic acid (the measured value of the C element in this embodiment was 48.54% (theoretical value 48.50%), and the measured value of the H element was 3.13% (theoretical value 3.05%)).

[0068] Example I-6:

[0069] 2.56 g of diethyl succinylsuccinate and 50 mL of ethanol were added to a round-bottom flask. Under mechanical stirring, 4.64 g of trichloroisocyanuric acid oxidant was added in batches. The temperature was raised to 70° C. and stirred for 10 h. Then, potassium hydroxide solution (prepared with 2.3 g of potassium hydroxide and 30 mL of deionized water) was added to the flask. The temperature was raised to 80° C. and stirred for 5 h. The pH of the solution was adjusted to 1 with concentrated hydrochloric acid. The solution was cooled to room temperature, the mixture was filtered, the filter cake was washed with deionized water, and then dried to obtain 1.84 g of product.

[0070] The yield of 2,5-dihydroxyterephthalic acid in the product was measured by Varian Prostar high performance liquid chromatography and was 92.9%;

[0071] The elemental analysis results further proved that the product was 2,5-dihydroxyterephthalic acid (the measured value of the C element in this embodiment was 48.57% (theoretical value 48.50%), and the measured value of the H element was 3.08% (theoretical value 3.05%)).

[0072] Example I-7:

[0073] The synthetic experimental results of Example I-1 to Example I-6 are summarized, and the specific results are shown in the following Table 1;

[0074] Table 1 Synthesis experimental results of Example I-1 to Example I-6 (the amount of raw material diethyl succinylsuccinate is 2.56g)

[0075]

[0076]

[0077] By analyzing the experimental results in Example I-1 to Example I-6 (or analyzing the summary results in Table 1), it is concluded that the preferred experimental conditions for synthesizing 2,5-dihydroxyterephthalic acid from diethyl succinylsuccinate are: the amount of trichloroisocyanuric acid as the oxidant is twice the molar amount of diethyl succinylsuccinate as the raw material, isopropanol as the reaction solvent, sodium hydroxide as the alkaline substance (the amount is 4 times the molar amount of diethyl succinylsuccinate as the raw material), the reaction temperature is 70°C, and the reaction time is 5h;

[0078] In order to improve the reaction activity of trichloroisocyanuric acid oxidant and to make the trichloroisocyanuric acid oxidant have recycling performance, the present invention conducts functional modification research on trichloroisocyanuric acid oxidant, and the modification method is: the trichloroisocyanuric acid oxidant is loaded on a metal organic framework formed by assembling a transition metal and an organic ligand, and is grafted with magnetic ferrosoferric oxide, and further research and development experiments are carried out using the above preferred experimental conditions, and the specific experiments include Examples II-1 to II-8;

[0079] Among them, the transition metal is one of nickel, palladium, platinum, cadmium, cobalt, ruthenium, copper, and manganese. In Examples II-1 to II-8, transition metal cadmium is selected to construct a metal organic framework and participate in research and development experiments.

[0080] Example II-1:

[0081] Preparation of non-magnetic oxidant I: On the one hand, the carbonyl functional group of trichloroisocyanuric acid forms a coordination bond with the cadmium ion, and on the other hand, the pyridine nitrogen on the ligand I forms a coordination bond with the cadmium ion to obtain a non-magnetic oxidant I, whose chemical structure is as follows Figure 2 As shown;

[0082] Among them, the chemical reaction formula of ligand I is as follows Figure 3 and Figure 4 As shown, a preparation process of ligand Ⅰ is as in Experimental Example Ⅰ;

[0083] The specific synthesis steps for synthesizing the non-magnetic oxidant I are as follows: 10.7 g of ligand I, 11.6 g of trichloroisocyanuric acid and 30.2 g of cadmium nitrate tetrahydrate are added to 500 mL of ethanol, the temperature is raised to 100° C. and stirred for reaction for 12 h, and the solvent is removed by rotary evaporation to obtain the non-magnetic oxidant I.

[0084] Example II-2:

[0085] Preparation of non-magnetic oxidant II: On the one hand, the carbonyl functional group of trichloroisocyanuric acid forms a coordination bond with cadmium ions, and on the other hand, the pyridine nitrogen and pyrazole nitrogen on ligand II form a coordination bond with cadmium ions to obtain non-magnetic oxidant II, whose chemical structure is as follows Figure 5 As shown;

[0086] Among them, the chemical reaction formula of ligand II is as follows Figure 6 and Figure 7 As shown, a preparation process of ligand II is as shown in Experimental Example II;

[0087] The specific synthesis steps for synthesizing non-magnetic oxidant II are as follows: add 8.7 g of ligand II, 11.6 g of trichloroisocyanuric acid and 30.2 g of cadmium nitrate tetrahydrate into 500 mL of ethanol, heat to 100° C. and stir to react for 12 h, and remove the solvent by rotary evaporation to obtain non-magnetic oxidant II.

[0088] Example II-3:

[0089] Preparation of magnetic oxidant I: the carboxyl functional group of ligand I in non-magnetic oxidant I undergoes esterification reaction with the hydroxyl functional group on the surface of hydroxylated ferrosoferric oxide nanoparticles to obtain magnetic oxidant I;

[0090] Among them, a preparation process of hydroxylated ferroferric oxide nanoparticles is as shown in Experimental Example III;

[0091] The specific synthesis steps for synthesizing magnetic oxidant I are as follows: add 30g of non-magnetic oxidant I and 5g of hydroxylated ferrosoferric oxide nanoparticles into 200mL of N,N-dimethylformamide, ultrasonically vibrate for 10min, add 0.1g of concentrated sulfuric acid dropwise, and then stir and react in a 65°C water bath for 5h. After centrifuging the reaction product, place it in a 60°C oven and dry it for 12h to obtain magnetic oxidant I.

[0092] Example II-4:

[0093] Preparation of magnetic oxidant II: the carboxyl functional group of ligand II in non-magnetic oxidant II undergoes esterification reaction with the hydroxyl functional group on the surface of hydroxylated ferrosoferric oxide nanoparticles to obtain magnetic oxidant II;

[0094] Among them, a preparation process of hydroxylated ferroferric oxide nanoparticles is as shown in Experimental Example III;

[0095] The specific synthesis steps for synthesizing magnetic oxidant II are as follows: add 30g of non-magnetic oxidant II and 5g of hydroxylated ferrosoferric oxide nanoparticles into 200mL of N,N-dimethylformamide, ultrasonically shake for 10min, add 0.1g of concentrated sulfuric acid, and then stir the reaction in a 65°C water bath for 5h. After centrifuging the reaction product, place it in a 60°C oven and dry it for 12h to obtain magnetic oxidant II.

[0096] Example II-5:

[0097] 2,5-dihydroxyterephthalic acid was synthesized using the preferred experimental conditions obtained by the above screening, and non-magnetic oxidant I, non-magnetic oxidant II, magnetic oxidant I, and magnetic oxidant II were used to replace the oxidant trichloroisocyanuric acid in sequence, and the yields were 95.4%, 94.9%, 95.2%, and 94.6%, respectively.

[0098] The molar content of the oxidative active component trichloroisocyanuric acid in the non-magnetic oxidant I, the non-magnetic oxidant II, the magnetic oxidant I and the magnetic oxidant II is the same as the molar amount of the oxidant trichloroisocyanuric acid.

[0099] Example II-6:

[0100] The magnetic oxidant I without oxidation activity after the reaction in Example II-5 is separated and recovered by the action of a magnetic field, and the magnetic oxidant I without oxidation activity is used to prepare a magnetic oxidant I with oxidation activity by a composite method, which is directly used in the next round of reaction after drying, and the recovered magnetic oxidant I is used to synthesize 2,5-dihydroxyterephthalic acid again under the preferred experimental conditions obtained by the above screening, and the yield is 94.8%. The magnetic oxidant I is recycled three times for the synthesis reaction, and the yields are: 95.1%, 94.3%, and 94.1% respectively;

[0101] Among them, the specific experimental steps of preparing the magnetic oxidant I with oxidative activity by a composite method from the magnetic oxidant I without oxidative activity are as follows: 2.64g of sodium hydroxide and 20g of the magnetic oxidant I without oxidative activity are dissolved in 50mL of deionized water to prepare a trisodium cyanurate suspension of the magnetic oxidant I without oxidative activity, then chlorine gas is passed into 50mL of deionized water to prepare chlorine water, and the trisodium cyanurate suspension of the magnetic oxidant I without oxidative activity is slowly added into the chlorine water at 5°C, the pH is controlled to be 3, and the magnetic oxidant I with oxidative activity is filtered, washed and dried to obtain the magnetic oxidant I with oxidative activity.

[0102] Example II-7:

[0103] Magnetic oxidant II was used to replace magnetic oxidant I in Example II-6, and magnetic oxidant II was recycled and used to synthesize 2,5-dihydroxyterephthalic acid according to the same experimental steps and conditions. The yields were 94.3%, 94.5%, 94.2%, and 94.0% respectively;

[0104] Example II-8:

[0105] According to the experimental results of Ⅱ-6 and Ⅱ-7, Figure 8 ;

[0106] By analyzing the experimental results of Example I-2 and Example II-5, the following conclusions can be obtained:

[0107] Compared with trichloroisocyanuric acid oxidant, trichloroisocyanuric acid oxidants (non-magnetic oxidant I and non-magnetic oxidant II) loaded on metal organic frameworks have better oxidation activity. The possible mechanism is as follows: the large specific surface area of ​​the metal organic framework promotes the uniform dispersion of trichloroisocyanuric acid oxidant;

[0108] According to the experimental results of Example II-6 and Example II-7 (or analysis Figure 8 The following conclusions were drawn from the summary results: when the trichloroisocyanuric acid oxidant supported on the metal organic framework was grafted onto ferroferric oxide (magnetic oxidant I, magnetic oxidant II), it had excellent recycling performance.

[0109] Experimental Example I:

[0110] The synthesis of ligand I includes two synthesis processes, as follows:

[0111] Synthesis of carboxylic acid methyl ester functional monomer: Using the Suzuki coupling reaction mechanism, under the catalysis of palladium catalyst, the boric acid pinacol ester group of 2,6-bis(methoxycarbonyl)pyridine-4-boric acid pinacol ester and the bromine functional group of N1,N1,N4,N4-tetra(4-bromophenyl)benzene-1,4-diamine undergo coupling reaction to generate a carboxylic acid methyl ester functional monomer. The chemical reaction formula is as follows: Figure 3 As shown;

[0112] The specific experimental steps for synthesizing the carboxylic acid methyl ester functional monomer are as follows: 7.3 g of N1, N1, N4, N4-tetrakis (4-bromophenyl) benzene-1, 4-diamine, 12.84 g of 2, 6-bis (methoxycarbonyl) pyridine-4-boric acid pinacol ester, 6 g of tetrakis triphenylphosphine palladium and 15 g of anhydrous potassium carbonate are added to a round-bottom flask, and the flask is evacuated and nitrogen is passed through. Under a nitrogen atmosphere, 300 mL of 1, 4-dioxane and 50 mL of deionized water are added to the flask, the temperature is raised to 100 ° C, stirred and refluxed for 10 h, extracted with dichloromethane, dried over anhydrous magnesium sulfate, filtered and then rotary evaporated to obtain a carboxylic acid methyl ester functional monomer;

[0113] The nuclear magnetic resonance hydrogen spectrum of the carboxylic acid methyl ester functional monomer is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 3.98 (s, 24H), 7.09 (s, 4H), 7.21-7.23 (d, 8H), 7.63-7.65 (d, 8H), 8.22 (s, 8H);

[0114] Synthesis of ligand I: Under alkaline conditions, the carboxylic acid methyl ester functional group of the carboxylic acid methyl ester functional monomer undergoes hydrolysis reaction to generate ligand I, whose chemical structure is as follows: Figure 4 As shown;

[0115] The specific experimental steps for synthesizing ligand I are as follows: 5.9 g of carboxylic acid methyl ester functional monomer, 1.6 g of sodium hydroxide and 100 mL of deionized water are added to a two-necked bottle, the temperature is raised to 70° C. and stirred for reaction for 2 h, concentrated hydrochloric acid is used to adjust the solution pH to 1, the solution is cooled and filtered, washed with deionized water, and dried with anhydrous magnesium sulfate to obtain ligand I;

[0116] The nuclear magnetic resonance hydrogen spectrum of ligand I is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 7.09 (s, 4H), 7.21-7.23 (d, 8H), 7.64-7.66 (d, 8H), 8.20 (s, 8H); the active hydrogen in the carboxyl functional group of ligand I has no peak in CDCl3 solvent;

[0117] Compared with the hydrogen spectrum of the carboxylic acid methyl ester functional monomer, there is no single peak attributed to -COOCH3 in the hydrogen spectrum of ligand Ⅰ, indicating that ligand Ⅰ was successfully synthesized;

[0118] The product was tested using a Vario EL IIICHNSO element analyzer, and the test results were as follows: the measured value of the C element was 65.01% (theoretical value 64.93%), the measured value of the H element was 3.43% (theoretical value 3.38%), and the measured value of the N element was 7.80% (theoretical value 7.83%);

[0119] The elemental analysis results show that the measured values ​​of C, H and N are basically consistent with the theoretical values. Combined with the hydrogen spectrum characterization results, it further proves that ligand Ⅰ was successfully synthesized.

[0120] Experimental Example II:

[0121] Synthesis of ligand II: includes two synthesis processes, as follows:

[0122] Synthesis of benzoyl acetyl pyridyl functional monomer: Using the Claisen condensation reaction mechanism, acetophenone containing α-H is condensed with triethylpyridine-2,4,6-tricarboxylate to generate benzoyl acetyl pyridyl functional monomer. The chemical reaction formula is as follows: Figure 6 As shown;

[0123] The specific experimental steps for synthesizing the benzoylacetylpyridyl functional monomer are as follows: 2.1 g of sodium ethoxide, 80 mL of anhydrous tetrahydrofuran and 5.9 g of triethylpyridine-2,4,6-tricarboxylate are added to a round-bottom flask in sequence, and 7.0 mL of acetophenone is added dropwise to the flask under mechanical stirring. After the addition is completed, the mixture is stirred and reacted at 45° C. for 2 h, cooled to room temperature, 40 mL of 2 mol / L hydrochloric acid is added, extracted with dichloromethane, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to obtain the benzoylacetylpyridyl functional monomer;

[0124] The nuclear magnetic resonance hydrogen spectrum of the benzoylacetylpyridyl functional monomer is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 3.79 (s, 4H), 3.94 (s, 2H), 7.45-7.48 (t, 6H), 7.56-7.59 (t, 3H), 7.92-7.96 (d, 6H), 8.98 (s, 2H);

[0125] Synthesis of ligand II: Using the nucleophilic addition reaction mechanism, the carbonyl functional group of the benzoyl acetyl pyridyl functional monomer undergoes a nucleophilic addition reaction with the hydrazine group of p-carboxylphenylhydrazine to close the ring and generate ligand II. The chemical reaction formula is as follows: Figure 7 As shown;

[0126] The specific experimental steps for synthesizing ligand II are as follows: under nitrogen protection and mechanical stirring, 5.2 g of benzoyl acetyl pyridyl functional monomer and 100 mL of glacial acetic acid are added to a two-necked flask, and after dissolution, 3.3 mL of p-carboxylphenylhydrazine is added dropwise to the flask, the temperature is raised to 60°C and stirred for reaction for 4 h, cooled to room temperature, filtered, washed with anhydrous ethanol, and dried to obtain ligand II;

[0127] The nuclear magnetic resonance hydrogen spectrum of ligand II is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 7.00 (s, 2H), 7.22 (s, 1H), 7.38-7.44 (m, 15H), 7.65 (s, 2H), 7.75-7.81 (m, 6H), 8.05-8.08 (m, 6H); The active hydrogen in the carboxyl functional group of ligand II did not emit a peak in CDCl3 solvent;

[0128] The product was tested using a Vario EL IIICHNSO element analyzer, and the test results were as follows: the measured value of the C element was 73.55% (theoretical value 73.52%), the measured value of the H element was 4.11% (theoretical value 4.07%), and the measured value of the N element was 11.25% (theoretical value 11.32%);

[0129] The elemental analysis results show that the measured values ​​of C, H and N are basically consistent with the theoretical values. Combined with the hydrogen spectrum results, it can be proved that ligand II was successfully synthesized.

[0130] Experimental Example III:

[0131] Preparation of hydroxylated ferroferric oxide nanoparticles: Add 10g of sodium citrate, 3g of sodium acetate and 100mL of ethylene glycol to a beaker, stir and dissolve, then add 5g of ferric chloride hexahydrate to the beaker, and ultrasonicate for 30min to obtain a reaction precursor solution; pour it into the polyvinyl fluoride lining of a high-temperature and high-pressure reactor, place it in a muffle furnace, heat to 200°C and react for 8h, cool to room temperature and take it out, wash it by centrifugation with ethanol and water, and finally dry it in a 60°C oven for 2h to obtain hydroxylated ferroferric oxide nanoparticles.

Claims

1. A method for synthesizing 2,5-dihydroxyterephthalic acid, characterized in that: include: Using diethyl succinylsuccinate as a raw material and trichloroisocyanuric acid or supported trichloroisocyanuric acid as an oxidant, in a polar solvent at 50-100° C., the oxidant first oxidizes diethyl succinylsuccinate, then hydrolyzes it in the presence of an alkaline substance, and then acidifies it to obtain 2,5-dihydroxyterephthalic acid; The amount of trichloroisocyanuric acid, an oxidatively active component in the oxidant, is 1 to 2 times the molar amount of diethyl succinylsuccinate.

2. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 1, characterized in that: The supported trichloroisocyanuric acid is one of non-magnetic oxidant I, non-magnetic oxidant II, magnetic oxidant I and magnetic oxidant II.

3. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 2, characterized in that: The preparation method of the non-magnetic oxidant I is as follows: the carbonyl functional group of trichloroisocyanuric acid forms a coordination bond with a transition metal ion, and the transition metal ion forms a coordination bond with the pyridine nitrogen on the ligand I, thereby obtaining the non-magnetic oxidant I; The preparation method of the ligand I is: Step S3-1, using the Suzuki coupling reaction mechanism, under the catalysis of a palladium catalyst, the boronic acid pinacol ester group of 2,6-bis(methoxycarbonyl)pyridine-4-boronic acid pinacol ester and the bromine functional group of N1,N1,N4,N4-tetra(4-bromophenyl)benzene-1,4-diamine undergo a coupling reaction to obtain a carboxylic acid methyl ester functional monomer; Step S3-2: under alkaline conditions, the methyl carboxylate functional group of the methyl carboxylate functional monomer undergoes a hydrolysis reaction to generate ligand I.

4. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 2, characterized in that: The preparation method of the non-magnetic oxidant II is as follows: the carbonyl functional group of trichloroisocyanuric acid forms a coordination bond with a transition metal ion, and the transition metal ion forms a coordination bond with the pyridine nitrogen and pyrazole nitrogen on the ligand II, thereby obtaining the non-magnetic oxidant II; The preparation method of the ligand II is: Step S4-1, using the Claisen condensation reaction mechanism, condensing α-H-containing acetophenone with triethylpyridine-2,4,6-tricarboxylate to obtain a benzoylacetylpyridyl functional monomer; Step S4-2, utilizing the nucleophilic addition reaction mechanism, the carbonyl functional group of the benzoylacetylpyridyl functional monomer undergoes a nucleophilic addition reaction with the hydrazine group of p-carboxyphenylhydrazine to close the ring and generate ligand II.

5. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 3, characterized in that: The preparation method of the magnetic oxidant I is: the carboxyl functional group of the ligand I in the non-magnetic oxidant I undergoes an esterification reaction with the hydroxyl functional group on the surface of the hydroxylated ferrosoferric oxide nanoparticles to obtain the magnetic oxidant I.

6. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 4, characterized in that: The preparation method of the magnetic oxidant II is as follows: the carboxyl functional group of the ligand II in the non-magnetic oxidant II undergoes an esterification reaction with the hydroxyl functional group on the surface of the hydroxylated ferrosoferric oxide nanoparticles to obtain the magnetic oxidant II.

7. A method for synthesizing 2,5-dihydroxyterephthalic acid according to any one of claims 1 to 6, characterized in that: The polar solvent is one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

8. A method for synthesizing 2,5-dihydroxyterephthalic acid according to any one of claims 1 to 6, characterized in that: The alkaline substance is sodium hydroxide or potassium hydroxide, and the amount of sodium hydroxide or potassium hydroxide used is 2 to 5 times the molar amount of diethyl succinylsuccinate.

9. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 2, characterized in that: The recycling method of the magnetic oxidant I is: using a trichloroisocyanuric acid synthesis method, the inactivated magnetic oxidant I recovered by magnetic separation is converted into an active magnetic oxidant I, which is then used again in an experiment of oxidizing diethyl succinylsuccinate to synthesize 2,5-dihydroxyterephthalic acid; The trichloroisocyanuric acid synthesis method is one of the sodium cyanurate chlorine method, the sodium hypochlorite method, the chlorine-solvent method, and the composite method.

10. A method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 3 or 4, characterized in that: The transition metal is one of cadmium, nickel, palladium, platinum, cobalt, ruthenium, copper and manganese.

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