A porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid

Abstract

The present invention belongs to the field of catalytic synthesis of azelaic acid, and provides a porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid. The metal-organic framework material is synthesized by a traditional solvothermal method, and based on its porous nature, Cr2O3 is loaded into the pores of the MOF to make it catalytically active. Due to the stability of the MOF structure, during the reaction of preparing azelaic acid by oxidizing oleic acid, it can maintain the structural stability whether in a heating environment or in an organic solvent. This catalyst is a heterogeneous catalyst, and has the advantages of high selectivity, no pollution in the reaction, easy separation from the solution, recyclability, and low cost in the preparation of azelaic acid.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic synthesis of azelaic acid, and particularly relates to a porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and is not necessarily to be regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Azelaic acid, also known as azelaic acid, is a medium-long chain dicarboxylic acid. It is one of the important fine chemical intermediates and has a very wide range of uses. For example, azelaic acid is commonly used in the synthesis of azelaic acid ester plasticizers, synthetic fragrances, lubricating oils, polyamides, and cosmetics; in addition, azelaic acid can also be used for the treatment of skin diseases and improving the service life of electrolytes in capacitors, etc.

[0004] Methods for preparing azelaic acid at home and abroad mainly adopt the oxidation method of unsaturated fatty acids such as oleic acid. According to different oxidants, it can be divided into ozonation method, hydrogen peroxide oxidation method, potassium permanganate oxidation method, nitric acid oxidation method, hypochlorite oxidation method, etc. The ozonation method is the main method for industrial preparation of azelaic acid at present, but this method has high energy consumption, high requirements for reaction equipment, and is a typical gas-liquid reaction process. The mass transfer problem is the key factor affecting the reaction; the disadvantage of the potassium permanganate oxidation method is low yield, high cost, generation of a large amount of manganese dioxide waste residue, troublesome post-treatment and easy to cause environmental pollution; the nitric acid oxidation method has low selectivity, serious corrosion to equipment, and is also easy to cause environmental pollution; the hypochlorite oxidation method has the advantages of mild reaction conditions and simple reaction process, but a large amount of solid waste will be generated after the reaction. Therefore, using hydrogen peroxide with high reaction selectivity, high product yield and no pollution as an oxidant to prepare azelaic acid is one of the currently recognized preferred methods. The catalysts reported for the oxidation of oleic acid to prepare azelaic acid are mainly tungsten-containing compounds such as tungstic acid, sodium tungstate, phosphotungstic acid, etc.; when using the above-mentioned tungsten-containing catalysts to prepare azelaic acid, there are disadvantages such as difficult catalyst recovery and high reaction costs. Since 1992, there have been reports on embedding transition metal compounds into porous molecular sieves for the preparation of new catalytic materials. Metal-Organic Framework (MOF) is a new type of porous material, which is a crystalline material with a periodic grid structure formed by the self-assembly of metal ions and organic ligands. It has the advantages of simple synthesis, high stability, large specific surface area, adjustable pore size and shape, and has a wide range of applications in the field of catalysis. For example: Patent CN108047027A discloses a system and method for preparing isononanoic acid and a preparation method of a metal-organic framework catalyst. However, since azelaic acid and isononanoic acid are two completely different chemical substances, and the metal-organic framework catalyst has strong specificity, the method of this patent cannot meet the requirements for catalyzing the oxidation of oleic acid to prepare azelaic acid.

[0005] At present, due to the wide variety and different performances of metal-organic framework catalysts, the industry has not found a metal-organic framework catalyst that can efficiently catalyze the oxidation of oleic acid to prepare azelaic acid. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid. Using a porous metal-organic framework material loaded with transition metal Cr as a catalyst to achieve multiple uses of the catalyst, and using hydrogen peroxide as an oxidant and oleic acid as a raw material to provide an experimental method for preparing azelaic acid with low production cost, simple process, mild conditions and no pollution to the environment.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, there is provided a porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid, comprising:

[0009] Mix 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand, zirconium salt and solvent evenly, and carry out a crystallization reaction at 130-150 °C for 48-72 hours, then cool down to obtain the MOF material;

[0010] Then mix the chromium salt solution with the MOF material and add 0.1-0.15 mol / L sodium hydroxide solution, and react at 100-125 °C for 24-48 h, then cool down to obtain the porous metal-organic framework material Cr2O3@MOF loaded with Cr2O3;

[0011] The dosage ratio of the zirconium salt to 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand is such that the molar ratio of metal ions to organic ligands is 1:2-2.5;

[0012] The mass ratio of the chromium salt to the MOF material is 1:0.5-1.5.

[0013] Through systematic research and long-term experimental exploration, it is found in this application that further loading chromium salt on the metal-organic framework material synthesized with 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid as the ligand and zirconium salt as the metal center, the prepared porous metal-organic framework material Cr2O3@MOF loaded with Cr2O3 has high selectivity and yield for catalytic oxidation of oleic acid to prepare azelaic acid. At the same time, Cr2O3@MOF has good solvothermal stability and can still maintain structural integrity in a tert-butanol solution at 80 °C, and the catalyst is easy to recycle.

[0014] In the second aspect of the present invention, there is provided the porous metal-organic framework material Cr2O3@MOF prepared by the above method.

[0015] In the third aspect of the present invention, there is provided a method for catalytic synthesis of azelaic acid based on a functionalized porous metal-organic framework material, comprising:

[0016] Mix oleic acid, the above-mentioned Cr2O3@MOF and tert-butanol evenly, introduce O2 at room temperature, and gradually add dropwise H2O2, and carry out a constant temperature reaction at 60-80 °C for 2-3 d;

[0017] Filter the reaction solution while it is hot to remove the catalyst; wash the filter cake with hot methanol, collect the filtrate; concentrate the washing methanol and the solvent tert-butanol by rotary evaporation; then extract the concentrated filtrate with hot water; further concentrate the extract and freeze out crystals, filter, wash and dry to obtain azelaic acid.

[0018] Beneficial effects of the present invention

[0019] (1) The Cr2O3@MOF synthesized in the present invention can be used as a catalyst to catalyze the oxidation of oleic acid to prepare azelaic acid with high selectivity, high yield and high safety, and the catalyst is easy to recover, thereby reducing the production cost. In addition, the preparation method of the porous metal organic framework material loaded with Cr2O3 in the present invention is simple, high in purity, good in activity, and has good solvent stability, and still maintains structural stability in a tert-butanol solution at 80°C.

[0020] (2) The present invention realizes the recycling of the catalyst and saves the reaction cost by loading Cr2O3 on MOF as a catalyst for the redox reaction.

[0021] (3) The present invention uses hydrogen peroxide as an oxidant, and the reaction product is water, which is environmentally friendly.

[0022] (4) The present invention is significantly different from patent CN108047027A:

[0023] 1) Different raw materials. The raw material used in the present invention is oleic acid, while the patent CN108047027A uses isononanal. Compared with isononanal, oleic acid mainly comes from nature and exists in animal and vegetable oils in the form of glyceride. The raw material source is wider and cheaper.

[0024] 2) The products are different. The product of the present invention is azelaic acid, while the product of patent CN108047027A is isononanoic acid. Azelaic acid and isononanoic acid are two completely different chemical substances, and therefore, the products of the two are completely different.

[0025] 3) Different catalysts. The catalyst used in the present invention is a metal Zr-organic framework material loaded with Cr2O3, which has strong specificity, while the catalyst used in patent CN108047027A is a metal organic framework catalyst containing one or more transition elements of Fe, Co, V, Cr, Mn, and Cu. Since metal elements play a key role in metal organic framework materials, these are two completely different types of catalysts.

[0026] 4) Different synthesis devices. The present invention uses conventional temperature-controlled reflux devices with stirring functions, rotary evaporators, extraction devices, etc. to synthesize azelaic acid, while patent CN108047027A needs to use a series of complex devices such as oxidation reactors, coolers, metal ion separation devices, peroxide decomposition reactors, and distillation devices to synthesize isononanoic acid, and the discharge port of the metal ion separation device needs to be connected to the feed port of the oxidation reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings of the specification, which form a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0028] Figure 1 Flow chart for synthesizing metal-organic framework material loaded with Cr2O3 in Example 1.

[0029] Figure 2 Scanning electron micrograph of the metal-organic framework material synthesized in Example 1.

[0030] Figure 3 Thermogravimetric analysis chart of the metal-organic framework material synthesized in Example 1.

[0031] Figure 4 XRD chart of the metal-organic framework material synthesized in Example 1 after soaking in aqueous solution and tert-butanol solution. Detailed Description of the Invention

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0033] A porous metal-organic framework material loaded with Cr2O3 for catalytic synthesis of azelaic acid, comprising:

[0034] Mix 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid, zirconium salt and a solvent evenly, and carry out a crystallization reaction at 130 - 150 °C for 48 - 72 hours, then cool down to obtain the MOF material;

[0035] Then mix the chromium salt solution with the MOF material evenly and add a 0.1 - 0.15 mol / L sodium hydroxide solution, and carry out a reaction at 100 - 125 °C for 24 - 48 h, then cool down to obtain the porous metal-organic framework material Cr2O3@MOF loaded with Cr2O3;

[0036] The dosage ratio of the zirconium salt to 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand is such that the molar ratio of metal ions to organic ligands is 1:2 - 2.5;

[0037] The mass ratio of the chromium salt to the MOF material is 1:0.5 - 1.5.

[0038] Specifically, for the catalyst preparation: A 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand, a zirconium salt, dimethyl sulfoxide, and distilled water are added to a stainless-steel autoclave lined with polytetrafluoroethylene in a certain proportion, and then placed in a reaction oven and reacted at a temperature of 130-150 °C for 72 h. After cooling, an MOF material is prepared. Then, a chromium salt and the MOF are reacted together, and finally, an MOF catalyst Cr2O3@MOF loaded with Cr2O3 is obtained.

[0039] In some embodiments, the zirconium salt is zirconium chloride.

[0040] In some embodiments, the chromium salt is chromium(III) chloride hexahydrate.

[0041] In some embodiments, the solvent is a mixed solvent of dimethyl sulfoxide and distilled water, and the volume ratio of the two is 1:1-2.

[0042] A method for catalytic synthesis of azelaic acid based on a functionalized porous metal-organic framework material, comprising:

[0043] Mix oleic acid, Cr2O3@MOF, and tert-butanol evenly, introduce O2 at room temperature, and gradually add dropwise H2O2, and react at a constant temperature of 60-80 °C for 2-3 d;

[0044] Filter the reaction solution while it is hot to remove the catalyst; wash the filter cake with hot methanol, collect the filtrate; concentrate the washing methanol and the solvent tert-butanol by rotary evaporation; then extract the concentrated filtrate with hot water; further concentrate the extract and freeze out crystals, filter, wash, and dry to obtain azelaic acid.

[0045] Specifically, it includes:

[0046] S1. Synthesis of the metal-organic framework catalyst: Dissolve zirconium chloride and a 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand in a mixed solvent of dimethyl sulfoxide and distilled water, and after a crystallization reaction, a colorless transparent crystal is obtained;

[0047] S2. Dissolve chromium(III) chloride hexahydrate in distilled water, then add the product in step S1 and add a 0.1 mol / L sodium hydroxide solution. Transfer the reaction solution to a high-pressure reaction kettle, heat and react, wash with distilled water after cooling, air-dry at room temperature, collect, and obtain a metal-organic framework catalyst Cr2O3@MOF loaded with Cr2O3;

[0048] S3. Add 20 g of oleic acid and the Cr2O3@MOF catalyst to a three-necked flask reactor, then add 50 ml of tert-butanol, mix evenly and start magnetic stirring, reflux condensation, and the reaction device is introduced with a flow rate of 1 cm 3 s -1O2 and gradually add 30ml H2O2, the addition is completed within about 1 hour, and the device is heated to 70℃ and kept at this temperature for 2 days;

[0049] S4. Filter the reaction solution while hot to remove the catalyst; wash the filter cake with hot methanol for 3 times, 20 ml each time, and collect the filtrate; use rotary evaporation to concentrate the washing methanol and solvent tert-butanol; then extract the concentrated filtrate with hot water; further concentrate the extract, freeze to precipitate crystals, filter, wash, and dry to obtain azelaic acid.

[0050] In some embodiments, the molar ratio of oleic acid, hydrogen peroxide, and tert-butanol is: 1:1.0-3.0:1.0-50.

[0051] In some embodiments, the mass fraction of the hydrogen peroxide solution is 30-35%.

[0052] In some embodiments, the filter cake is washed with hot methanol 3 to 4 times, each time with 20 to 30 ml.

[0053] The present invention also provides azelaic acid synthesized by the above method.

[0054] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0055] In the following examples, 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid was prepared by the method described in Chem. Eur. J. 2011, 17, 11424-11427.

[0056] Example 1

[0057] Synthesis of Cr2O3-loaded metal organic framework catalyst: Weigh 23.3mg ZrCl4 and 53.8mg 5-[(E)-2-(4-pyridyl)vinyl]-1,3-phthalic acid ligand, mix evenly with 1ml dimethyl sulfoxide and 1.5ml distilled water, place in a stainless steel reactor lined with polytetrafluoroethylene, react at 140°C for 72h, cool to room temperature at a constant rate of 5°C / h to obtain transparent crystals. Filter the product, wash with distilled water, dry at room temperature, and collect. Then, dissolve 10mg CrCl3·6H2O in 10ml distilled water and add an equal amount of 0.1mol / L sodium hydroxide solution to distilled water, add 11mg MOF and stir at room temperature for 12h, transfer the reactants to a stainless steel autoclave lined with polytetrafluoroethylene and react at 120°C for 36h, and obtain the Cr2O3-loaded MOF catalyst Cr2O3@MOF after cooling. The synthesis flow chart of the catalyst is as follows, Figure 1 As shown. Scanning electron microscope image of MOF, Figure 2As shown in the thermogravimetric analysis diagram of the MOF, Figure 3 As shown in the experimental and simulated X-ray powder diffraction diagrams of the MOF, Figure 4 As shown, after the MOF material was immersed in distilled water, boiling water, and tert-butanol solvent at room temperature, the peak positions of the X-ray powder diffraction did not change significantly, indicating that the framework structure of the material remained unchanged under the above conditions. Therefore, the metal-organic framework material synthesized in this invention has high chemical stability.

[0058] Synthesis of azelaic acid by oxidation: Add 20 g of oleic acid, 0.5 g of Cr2O3@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a constant temperature controller, and a reflux condenser. After mixing evenly, start stirring and introduce O2 with a flow rate of 1 cm 3 s -1 and gradually add dropwise 30 ml of 30% hydrogen peroxide solution by mass within about 1 h. After the addition is completed, heat up to 70 °C and react in an O2 atmosphere for 2 days. Filter the reaction system while it is hot to remove the catalyst; wash the filter cake with hot methanol 3 times, 30 ml each time, and collect the filtrate; concentrate the obtained filtrate by rotary evaporation to 20 ml; extract the above concentrated filtrate with 60 ml of hot water in 3 portions; after concentrating the extract to 30 ml, freeze out crystals, filter, wash, and dry to obtain the azelaic acid product with a yield of 90.1%.

[0059] Example 2

[0060] Synthesis of a Cr2O3-loaded metal-organic framework catalyst: React at a constant temperature of 140 °C for 72 h according to the method and steps of Example 1, and cool down to room temperature at a uniform rate of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl3·6H2O in distilled water, add an equal volume of 0.1 mol / L sodium hydroxide solution and 8 mg of MOF, mix evenly, and place in an autoclave at 110 °C for 36 h.

[0061] Add 20 g of oleic acid, 0.5 g of Cr2O3@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a constant temperature controller, and a reflux condenser, mix evenly, stir, and introduce 1 cm of 3 s -1O2 and gradually add dropwise 30 ml of 30% hydrogen peroxide solution. The addition is completed within about 1 h. The device is continuously heated to 65 °C and reacted for 2 days in an O2 atmosphere under reflux. The reaction system is filtered while it is hot to remove the catalyst. The filter cake is washed 3 times with hot methanol, 30 ml each time. The obtained filtrate is concentrated to 20 ml by rotary evaporation; the concentrated filtrate above is extracted 3 times with 60 ml of hot water; after the extract is concentrated to 30 ml, crystals are precipitated by freezing, filtered, washed, and dried to obtain azelaic acid product, and the yield is 82.3%.

[0062] Example 3

[0063] Synthesize a Cr2O3@MOF catalyst supported on metal-organic framework: React at a constant temperature of 140 °C for 72 h according to the method and steps of Example 1, and cool down to room temperature at a uniform rate of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl3·6H2O in distilled water, mix it evenly with 5 mg of MOF, and add 0.1 mol / L sodium hydroxide solution equal to the amount of distilled water. Place it in an autoclave and react at 100 °C for 48 h.

[0064] Add 20 g of oleic acid, 0.5 g of Cr2O3@MOF catalyst, and 50 ml of tert-butanol to a three-necked flask reactor equipped with a magnetic stirrer, a constant temperature controller, and a reflux condenser. Mix evenly, stir, and introduce 1 cm 3 s -1 of O2 and gradually add dropwise 30 ml of 30% hydrogen peroxide solution. The addition is completed within about 1 h. The device is continuously heated to 70 °C and reacted for 2 days in an O2 atmosphere under reflux. The reaction system is filtered while it is hot to remove the catalyst. The filter cake is washed 3 times with hot methanol, 30 ml each time. The obtained filtrate is concentrated to 20 ml by rotary evaporation; the concentrated filtrate above is extracted 3 times with 60 ml of hot water; after the extract is concentrated to 30 ml, crystals are precipitated by freezing, filtered, washed, and dried to obtain azelaic acid product, and the yield is 73.2%.

[0065] Example 4

[0066] Synthesize a Cr2O3@MOF catalyst supported on metal-organic framework: React at a constant temperature of 130 °C for 72 h according to the method and steps of Example 1, and cool down to room temperature at a uniform rate of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl3·6H2O in distilled water, mix it evenly with 12 mg of MOF, and add 0.1 mol / L sodium hydroxide solution equal to the amount of distilled water. Place it in an autoclave and react at 120 °C for 36 h.

[0067] Add 20 g of oleic acid, 0.5 g of Cr2O3@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a thermostatic controller, and a reflux condenser. Mix evenly, stir, and introduce 1 cm 3 s -1 of O2 into the reaction device at room temperature and gradually add 30 ml of 30% hydrogen peroxide solution dropwise. The addition is completed within about 1 h. The device is continuously heated to 70 °C and reacted for 2 days in an O2 atmosphere under reflux. Filter the reaction system while it is hot to remove the catalyst, and wash the filter cake with hot methanol 3 times, 30 ml each time. Filter the reaction system while it is hot to remove the catalyst, wash the filter cake with hot methanol 3 times, 30 ml each time, and concentrate the obtained filtrate to 20 ml by rotary evaporation; extract the above-concentrated filtrate with 60 ml of hot water in 3 portions; after concentrating the extract to 30 ml, freeze out crystals, filter, wash, and dry to obtain azelaic acid product with a yield of 60.4%.

[0068] Example 5

[0069] Synthesize the Cr2O3-loaded metal-organic framework catalyst: Carry out a constant-temperature reaction at 150 °C for 72 h according to the method and steps of Example 1, and cool down to room temperature at a uniform speed of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl3·6H2O in distilled water, mix it evenly with 15 mg of MOF, and add 0.1 mol / L sodium hydroxide solution equal to the volume of distilled water. Place it in an autoclave and react at 125 °C for 24 h.

[0070] Add 20 g of oleic acid, 0.5 g of Cr2O3@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a thermostatic controller, and a reflux condenser. Mix evenly, stir, and introduce 1 cm 3 s -1 of O2 into the reaction device at room temperature and gradually add 30 ml of 30% hydrogen peroxide solution dropwise. The addition is completed within about 1 h. The device is continuously heated to 80 °C and reacted for 2 days in an O2 atmosphere under reflux. Filter the reaction system while it is hot to remove the catalyst, wash the filter cake with hot methanol 3 times, 30 ml each time, and concentrate the obtained filtrate to 20 ml by rotary evaporation; extract the above-concentrated filtrate with 60 ml of hot water in 3 portions; after concentrating the extract to 30 ml, freeze out crystals, filter, wash, and dry to obtain azelaic acid product with a yield of 41.3%.

[0071] Example 6

[0072] Synthesis of Cr₂O₃-supported metal-organic framework catalyst: Prepared according to the method and steps of Example 1, react at a constant temperature of 140 °C for 72 h, and cool down to room temperature at a uniform rate of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl₃·6H₂O in distilled water, mix it evenly with 14 mg of MOF, and add 0.1 mol / L sodium hydroxide solution equal to the amount of distilled water. Place it in an autoclave and react at 120 °C for 36 h.

[0073] Add 20 g of oleic acid, 0.5 g of Cr₂O₃@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a constant temperature controller, and a reflux condenser. Mix evenly, stir, and introduce 1 cm 3 s -1 of O₂ into the reaction device at room temperature and gradually add 30 ml of 40% by mass H₂O₂ solution dropwise. The addition is completed within about 1 h. The device is continuously heated to 75 °C and reacted in an O₂ atmosphere under reflux for 2 days. Filter the reaction system while it is hot to remove the catalyst, wash the filter cake with hot methanol 3 times, 30 ml each time. Concentrate the obtained filtrate to 20 ml by rotary evaporation; extract the above-concentrated filtrate 3 times with 60 ml of hot water; after concentrating the extract to 30 ml, freeze out crystals, filter, wash, and dry to obtain azelaic acid product with a yield of 50.6%.

[0074] Example 7

[0075] Synthesis of Cr₂O₃-supported metal-organic framework catalyst: Prepared according to the method and steps of Example 1, react at a constant temperature of 140 °C for 72 h, and cool down to room temperature at a uniform rate of 5 °C / h to obtain MOF. Dissolve 10 mg of CrCl₃·6H₂O in distilled water, mix it evenly with 13 mg of MOF, and add 0.1 mol / L sodium hydroxide solution equal to the amount of distilled water. Place it in an autoclave and react at 110 °C for 36 h.

[0076] Add 20 g of oleic acid, 0.5 g of Cr₂O₃@MOF catalyst, and 50 ml of tert-butanol into a three-necked flask reactor equipped with a magnetic stirrer, a constant temperature controller, and a reflux condenser. Mix evenly, stir, and introduce 1 cm 3 s -1 of O₂ into the reaction device at room temperature and gradually add 30 ml of 50% by mass H₂O₂ solution dropwise. The addition is completed within about 1 h. The device is continuously heated to 60 °C and reacted in an O₂ atmosphere under reflux for 2 days. Filter the reaction system while it is hot to remove the catalyst, wash the filter cake with hot methanol 3 times, 30 ml each time. Concentrate the obtained filtrate to 20 ml by rotary evaporation; extract the above-concentrated filtrate 3 times with 60 ml of hot water; after concentrating the extract to 30 ml, freeze out crystals, filter, wash, and dry to obtain azelaic acid product with a yield of 55.5%.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that the MOF materials synthesized by using copper salt, nickel salt or cadmium salt instead of zirconium salt as the metal center were used to prepare the catalyst. Catalyzing the above reaction, azelaic acid products were obtained, and the yields were 26.4%, 35.7% and 40.2% respectively.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that the MO x @MOF catalyst was synthesized by using FeCl3·6H2O, CoCl2·6H2O or NiCl2·6H2O instead of CrCl3·6H2O. Catalyzing the above reaction, azelaic acid products were obtained, and the yields were 11.5%, 22.1% and 30.9% respectively.

[0081] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials, characterized in that, Comprising: Mix 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand, zirconium salt and solvent evenly, and carry out crystallization reaction at 130 - 150 °C for 48 - 72 hours, then cool down to obtain the MOF material; Then mix the chromium salt solution with the MOF material evenly and add 0.1 - 0.15 mol / L sodium hydroxide solution, and carry out reaction at 100 - 125 °C for 24 - 48 h, then cool down to obtain the porous metal-organic framework material Cr2O3@MOF loaded with Cr2O3; The dosage ratio of the zirconium salt to 5-[(E)-2-(4-pyridyl)vinyl]-1,3-benzenedicarboxylic acid ligand is such that the molar ratio of metal ion to organic ligand is 1:(2 - 2.5); The mass ratio of the chromium salt to the MOF material is 1:(0.5 - 1.5); Mix oleic acid, the Cr2O3@MOF, and tert-butanol evenly, and introduce O2 with a flow rate of 1 cm 3 s -1 at room temperature, and gradually add hydrogen peroxide solution dropwise, and carry out a constant temperature reaction at 60~80°C for 2~3 days; Filter the reaction solution while it is hot to remove the catalyst; Wash the filter cake with hot methanol and collect the filtrate; Use rotary evaporation to concentrate the washing methanol and tert-butanol; then extract the concentrated filtrate with hot water; further concentrate the extract and then freeze out crystals, filter, wash and dry to obtain azelaic acid.

2. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials according to claim 1, characterized in that, The zirconium salt is zirconium chloride.

3. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials according to claim 1, wherein The chromium salt is chromium(III) chloride hexahydrate.

4. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials as claimed in claim 1, wherein The solvent is a mixed solvent of dimethyl sulfoxide and distilled water, and the volume ratio of dimethyl sulfoxide to distilled water is 1:(1 - 2).

5. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials as claimed in claim 1, wherein The molar ratio of oleic acid, hydrogen peroxide and tert-butanol is 1:(1.0 - 3.0):(1.0 - 50).

6. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials according to claim 1, characterized in that, The mass fraction of the hydrogen peroxide solution is 30 - 35%.

7. The method for catalytic synthesis of azelaic acid based on functionalized porous metal-organic framework materials according to claim 1, characterized in that, Wash the filter cake with hot methanol 3 - 4 times, 20 - 30 mL each time.

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