A process for the synthesis of 2,5-dihydroxyterephthalic acid

Abstract

The present application relates to the technical fields of 2,5-dihydroxyterephthalic acid synthesis, and discloses a method for synthesizing 2,5-dihydroxyterephthalic acid, comprising: using succinic acid diethyl ester as a raw material, using trichloroisocyanuric acid or supported trichloroisocyanuric acid as an oxidizing agent, oxidizing the succinic acid diethyl ester in a polar solvent at 50-100 DEG C, then hydrolyzing in the presence of a basic substance, and then acidifying to obtain 2,5-dihydroxyterephthalic acid; the amount of the oxidizing active component trichloroisocyanuric acid in the oxidizing agent is 1-2 times the molar amount of the succinic acid diethyl ester. The synthesis method is green and environmentally friendly, the reaction conditions are mild, the process is simple and easy to operate, the product yield is high, and the method 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 applied 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 separates and purifies 2,5-dihydroxyterephthalic acid via a chromatographic column. The solid catalyst in this method uses magnesium aluminum hydrotalcite as a precursor and modified nano-kaolin as a carrier. The catalyst preparation process is complex and tedious, and the cost is high, which 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 through a one-step oxidation process in the presence of a copper-containing catalyst. This method not only requires the preparation of a separate catalyst but also introduces copper ions into the product, affecting product quality and limiting its scope of application.

[0007] Patent CN112624915A uses dimethyl 1,4-cyclohexanedione-2,5-dicarboxylate (DMSS) as a raw material, iodine or quinones as catalysts, and hydrogen peroxide is used to oxidize 2,5-dihydroxyterephthalic acid under heating conditions. 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 risks. Summary of the Invention

[0009] To address the shortcomings of existing technologies for synthesizing 2,5-dihydroxyterephthalic acid, the present invention proposes a method for synthesizing 2,5-dihydroxyterephthalic acid. The method involves reacting diethyl succinylsuccinate with trichloroisocyanuric acid (TCCA) in an organic solvent at a suitable temperature, followed by hydrolysis in the presence of an alkaline substance, and acidification to obtain 2,5-dihydroxyterephthalic acid. This method is environmentally friendly, features mild reaction conditions, is simple and easy to operate, and offers high product yields, making it suitable for practical 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 the succinylsuccinate in the presence of an alkaline substance, and then acidifies the oxidant to obtain 2,5-dihydroxyterephthalic acid;

[0011] The amount of trichloroisocyanuric acid, an oxidizing 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 a 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 pinacol borate 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 methyl carboxylate functional monomer;

[0016] Step S1-2: Under alkaline conditions, the carboxylate functional group of the 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 a 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] In step S2-2, a nucleophilic addition reaction mechanism is used to generate ligand II by a nucleophilic addition reaction between the carbonyl functional group of the benzoylacetylpyridyl functional monomer and the hydrazine group of p-carboxyphenylhydrazine to close the ring.

[0021] Preferably, 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.

[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 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 to oxidize diethyl succinylsuccinate to synthesize 2,5-dihydroxyterephthalic acid;

[0026] The trichloroisocyanuric acid synthesis method is one of the sodium cyanurate chlorination 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 the 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 reaction costs;

[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 the above four supported trichloroisocyanuric acid oxidants can, on the one hand, 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 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 produce 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 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 5 h. The pH of the solution was adjusted to 1 with concentrated hydrochloric acid. The mixture was cooled to room temperature, and 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 equipped with a Chromspher 5C18 (4.6 mm × 150 mm) column. The UV detector wavelength was set to 254 nm, the column temperature was set to 30° C., and the mobile phase was methanol and 0.1% perchloric acid aqueous solution in a volume ratio of 3:2. 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 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 III CHNSO elemental 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 results of elemental analysis 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. Under mechanical stirring, 4.64 g of trichloroisocyanuric acid oxidant was added in batches. The temperature was raised to 70° C. and stirred 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. 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 mixture was 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] Elemental analysis results further confirmed that the product was 2,5-dihydroxyterephthalic acid (the measured value of element C in this example was 48.56% (theoretical value 48.50%), and the measured value of element H was 3.09% (theoretical value 3.05%)).

[0056] Example 1-3:

[0057] 2.56 g of diethyl succinylsuccinate and 50 mL of N,N-dimethylformamide were added to a round-bottom flask. Under mechanical stirring, 3.48 g of trichloroisocyanuric acid oxidant was added in batches. The temperature was raised to 100°C and stirred 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. 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 mixture was 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 the 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] Elemental analysis results further confirmed that the product was 2,5-dihydroxyterephthalic acid (the measured value of element C in this example was 48.59% (theoretical value 48.50%), and the measured value of element H was 3.14% (theoretical value 3.05%)).

[0060] Example 1-4:

[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 2 h. Potassium hydroxide solution (prepared with 2.8 g of potassium hydroxide and 30 mL of deionized water) was then 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 mixture was cooled to room temperature, and the mixture was filtered. The filter cake was washed with deionized water and 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] Elemental analysis results further confirmed that the product was 2,5-dihydroxyterephthalic acid (the measured value of element C in this example was 48.53% (theoretical value 48.50%), and the measured value of element H was 3.08% (theoretical value 3.05%)).

[0064] Example 1-5:

[0065] 2.56 g of diethyl succinylsuccinate and 50 mL of isopropanol 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 50° C. and stirred 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. 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 mixture was 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] Elemental analysis results further confirmed that the product was 2,5-dihydroxyterephthalic acid (the measured value of element C in this example was 48.54% (theoretical value 48.50%), and the measured value of element H 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 mixture was cooled to room temperature, and the mixture was filtered. The filter cake was washed with deionized water and 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] Elemental analysis results further confirmed that the product was 2,5-dihydroxyterephthalic acid (the measured value of element C in this example was 48.57% (theoretical value 48.50%), and the measured value of element H was 3.08% (theoretical value 3.05%)).

[0072] Example I-7:

[0073] The results of the synthesis experiments of Examples I-1 to I-6 are summarized, and the specific results are shown in Table 1 below.

[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 Examples I-1 to 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 the raw material diethyl succinylsuccinate, isopropanol as the reaction solvent, sodium hydroxide (the amount is 4 times the molar amount of the raw material diethyl succinylsuccinate) as the alkaline substance, the reaction temperature is 70°C, and the reaction time is 5 hours.

[0078] In order to improve the reactivity 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. The modification method is as follows: 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. Further research and development experiments are carried out using the above preferred experimental conditions. 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 the 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 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 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 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 the cadmium ion, and on the other hand, the pyridine nitrogen and pyrazole nitrogen on ligand II form a coordination bond with the cadmium ion 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: 8.7 g of ligand II, 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 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: 30 g of non-magnetic oxidant I and 5 g of hydroxylated ferrosoferric oxide nanoparticles are added to 200 mL of N,N-dimethylformamide, ultrasonically shaken for 10 minutes, 0.1 g of concentrated sulfuric acid is added dropwise, and then stirred in a 65°C water bath for 5 hours. The reaction product is centrifuged and placed in a 60°C oven to dry for 12 hours 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: 30 g of non-magnetic oxidant II and 5 g of hydroxylated ferrosoferric oxide nanoparticles are added to 200 mL of N,N-dimethylformamide, ultrasonically shaken for 10 minutes, 0.1 g of concentrated sulfuric acid is added dropwise, and then stirred in a 65°C water bath for 5 hours. The reaction product is centrifuged and placed in a 60°C oven to dry for 12 hours 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, and the yields were 95.4%, 94.9%, 95.2%, and 94.6%, respectively.

[0098] The molar content of the oxidizing 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 oxidizing agent trichloroisocyanuric acid.

[0099] Example II-6:

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

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

[0102] Example II-7:

[0103] Magnetic oxidant II was used to replace magnetic oxidant I in Example II-6. The same experimental steps and conditions were followed to recycle magnetic oxidant II for the synthesis of 2,5-dihydroxyterephthalic acid. 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, the Figure 8 ;

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

[0107] Compared with trichloroisocyanuric acid, trichloroisocyanuric acid oxidants (non-magnetic oxidant I and non-magnetic oxidant II) supported on metal-organic frameworks (MOFs) exhibited superior oxidation activity. The possible mechanism is that the large surface area of ​​the MOFs facilitated the uniform dispersion of trichloroisocyanuric acid oxidants.

[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-boronic acid pinacol ester and the bromine functional group of N1,N1,N4,N4-tetrakis(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-boronic acid pinacol ester, 6 g of tetrakistriphenylphosphine palladium, and 15 g of anhydrous potassium carbonate are added to a round-bottom flask, and the mixture is evacuated and purged with nitrogen. Under a nitrogen atmosphere, 300 mL of 1,4-dioxane and 50 mL of deionized water are added to the flask, and the mixture is heated to 100° C. and stirred under reflux for 10 h. The mixture is extracted with dichloromethane, dried over anhydrous magnesium sulfate, filtered, and then the solvent is rotary evaporated to obtain the 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 carboxylate functional group of the carboxylate functional monomer undergoes hydrolysis 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 methyl carboxylate functional monomer, 1.6 g of sodium hydroxide, and 100 mL of deionized water were added to a two-necked flask, the temperature was raised to 70°C, and the mixture was stirred for 2 h. The pH of the solution was adjusted to 1 with concentrated hydrochloric acid. After cooling, the solution was filtered, washed with deionized water, and dried over anhydrous magnesium sulfate to obtain ligand I.

[0116] The H NMR spectrum of ligand I is characterized as follows: 1 H NMR (CDCl3, 400 MHz) 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 did not emit a 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 III CHNSO elemental 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 elements 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: It 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 a 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 sequentially to a round-bottom flask; 7.0 mL of acetophenone is added dropwise to the flask under mechanical stirring; after the addition is complete, the mixture is stirred at 45° C. for 2 h, cooled to room temperature, and 40 mL of 2 mol / L hydrochloric acid is added; the mixture is extracted with dichloromethane, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain a 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 reacts with the hydrazine group of the carboxylphenylhydrazine to form ligand II through ring closure. 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 benzoylacetylpyridyl functional monomer and 100 mL of glacial acetic acid were added to a two-necked flask. After dissolution, 3.3 mL of p-carboxyphenylhydrazine was added dropwise to the flask. The temperature was raised to 60°C and stirred for 4 h. The reaction was then 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, 400 MHz) 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 III CHNSO elemental 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 elements 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, 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℃ and react for 8h, cool to room temperature and take out, centrifuge and wash with ethanol and water, and finally place it in a 60℃ oven to dry 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, the oxidizing active component in the oxidant, is 1-2 times the molar amount of diethyl succinylsuccinate; The supported trichloroisocyanuric acid is one of the non-magnetic oxidant I, non-magnetic oxidant II, magnetic oxidant I and magnetic oxidant II; The non-magnetic oxidant I is prepared by forming a coordination bond between the carbonyl functional group of trichloroisocyanuric acid and a transition metal ion, and the transition metal ion forms a coordination bond with the pyridine nitrogen on the ligand I; The non-magnetic oxidant II is prepared by forming a coordination bond between the carbonyl functional group of trichloroisocyanuric acid and a transition metal ion, and the transition metal ion forms a coordination bond with the pyridine nitrogen and pyrazole nitrogen on the ligand II. The transition metal ion is a cadmium ion; The magnetic oxidant I is prepared by esterification reaction between the carboxyl functional group of ligand I in the non-magnetic oxidant I and the hydroxyl functional group on the surface of hydroxylated ferrosoferric oxide nanoparticles; The magnetic oxidant II is prepared by esterification reaction between the carboxyl functional group of ligand II in the non-magnetic oxidant II and the hydroxyl functional group on the surface of hydroxylated ferrosoferric oxide nanoparticles. The chemical structure of ligand I is: ； The chemical structure of ligand II is: 。 2. The method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 1, wherein The polar solvent is one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

3. The method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 1, wherein: The alkaline substance is sodium hydroxide or potassium hydroxide, and the amount of sodium hydroxide or potassium hydroxide used is 2-5 times the molar amount of diethyl succinylsuccinate.

4. The method for synthesizing 2,5-dihydroxyterephthalic acid according to claim 1, wherein: The recycling method of the magnetic oxidant I is as follows: 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 chlorination method, the sodium hypochlorite method, the chlorine-solvent method, and the composite method.

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