MOF (Metal Organic Framework) catalyst for synthesizing PET (Polyethylene Terephthalate) and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and discloses an MOF catalyst for synthesizing PET and a preparation method and application thereof.The MOF catalyst is Sb-SBME-coated UiO-66, Sb-SBME is loaded on the surface of UiO-66, and the Sb-SBME is an MOF material generated by coordination of antimony and thioanisole; the preparation method comprises the following steps: dispersing ZrCl4 and terephthalic acid into a solvent I to react, treating to obtain a UiO-66 matrix, mixing ethylene glycol antimony and thioanisole in ethylene glycol to react, centrifuging to obtain an antimony precursor, finally mixing and dispersing the UiO-66 matrix and the antimony precursor into a solvent II, and drying to obtain the UiO-66 composite material. And after the stirring reaction, post-processing the product to obtain the MOF catalyst for synthesizing PET (Polyethylene Terephthalate). The method can be used for synthesizing PET. The catalyst provided by the invention has high catalytic activity, selectivity and thermal stability, and no antimony element can be detected from the prepared PET at 110 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a MOF catalyst for synthesizing PET and a preparation method and application thereof. Background Art

[0002] PET materials are widely used in packaging materials, optical equipment, electrical appliances and many other fields due to their good mechanical strength and optical properties. Antimony (Sb) catalysts are currently commonly used in the polycondensation process of synthesizing PET, and containers made of Sb catalysts will release trace amounts of antimony elements during the storage of food and beverages, posing a threat to human health. Therefore, the prior art also considers the use of titanium catalysts to replace antimony catalysts, but the application effect and promotion of titanium catalysts are still not ideal, mainly because titanium catalysts have high catalytic activity, poor catalytic selectivity, obvious side reactions, and yellowish melt color.

[0003] MOF (metal organic framework) materials have excellent properties such as adjustable metal sites, easy separation from products, multiple catalytic active sites accessible to substrates, and easy modification. This type of material is a porous material composed of metals (Cu, Ni, Zn and other metals) and organic ligands (NH2-BDC, bpy, 1,10-phenanthroline, etc.). The porous framework of MOF materials can serve as a good supporting structure, making it easy to compound with other substances, which is conducive to the diffusion and adsorption of reactants.

[0004] The metal sites of MOF materials are generally transition metals, which have empty d or even empty f orbitals and a rich arrangement of extranuclear electrons. In chemical reactions, these metal sites can reduce activation energy by changing the reaction path, thereby improving catalytic efficiency. In addition, MOF materials can also improve catalytic performance by changing their electronic structure and energy band width through adjusting ligands, metal doping, structural modification, and other methods.

[0005] In the polyester production process, MOF catalysts have the advantages of high catalytic efficiency, good selectivity, narrow molecular weight distribution, and strong catalyst stability, which can effectively improve the production efficiency and product quality of polyester. However, MOF catalysts prepared using MOF materials in the prior art also have different disadvantages, such as high price, low catalytic efficiency, and poor catalyst stability.

[0006] Reference 1 (Study on coordination polymer catalysts for ε-caprolactone ring-opening polymerization [D]. Nanjing University of Science and Technology, 2021. DOI: 10.27241 / d.cnki.gnjgu.2021.000386.) used main group metals, transition metals and rare earth metals and nitrogen heterocyclic and carboxylic acid ligands respectively, and obtained multiple series of MOF materials through coordination self-assembly, and studied in detail the effects of their metal ions, organic ligands and guest molecules on the catalytic performance of caprolactone ring-opening polymerization. However, the MOF catalyst prepared in this document is used for the coordination of ε-caprolactone ring-opening polymerization, and has the problems of low catalytic efficiency and poor catalyst stability; in addition, the MOF catalyst is not suitable for the preparation of PET.

[0007] Therefore, it is of great significance to study a MOF catalyst for synthesizing PET and its preparation method and application to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a MOF catalyst for synthesizing PET and its preparation method and application. The present invention uses antimony as a metal site to prepare a MOF catalyst Sb-SBME@UiO-66. Compared with traditional antimony-based and titanium-based polycondensation catalysts, the present invention uses the constraint effect of the organic structure in the MOF material to fix the antimony atom, which can reduce the escape of metal elements when applied to the synthesis of PET materials. When used for the synthesis of food-grade polyester, it is highly safe for the human body and can reduce the graying problem of PET polyester caused by the escape and residue of the catalyst metal. At the same time, the present invention uses the characteristics of the organic framework structure to make the prepared MOF catalyst have high catalytic activity and selectivity while having high thermal stability, and can still remain stable at a temperature of 320°C to reduce the damage of PET materials to the human body.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A MOF catalyst for synthesizing PET is Sb-SBME@UiO-66, wherein Sb-SBME is loaded on the surface of UiO-66, and Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole.

[0011] As the preferred technical solution:

[0012] As described above, the MOF catalyst for synthesizing PET has a thermal decomposition temperature of 321.2 to 323.5°C.

[0013] The present invention also provides a method for preparing a MOF catalyst for synthesizing PET as described in any one of the above items, comprising the following steps:

[0014] (1) Dispersing ZrCl4 and terephthalic acid (H2BDC) in solvent I (the amount of solvent I is sufficient to completely disperse ZrCl4 and terephthalic acid), placing in a reactor at 188-192°C for 24-30 hours, and then centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix;

[0015] (2) mixing antimony glycolate and thioanisole in ethylene glycol (the amount of ethylene glycol used is sufficient to completely disperse the two substances), reacting at 228-232° C. for 4-5 hours, and obtaining a powder after centrifugation, indicating that an organic antimony ion compound containing a bridged sulfur atom ligand, i.e., an antimony precursor, is formed;

[0016] (3) The UiO-66 matrix and the antimony precursor are mixed and dispersed in solvent II (the amount of solvent II is sufficient to completely disperse the UiO-66 matrix and the antimony precursor), and stirred at 80-85°C for 2-3 hours to activate the UiO-66 and the antimony precursor. Then, the temperature is increased to 188-192°C and the reaction is continued for 1-1.5 hours. After the reaction is completed, the product is subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET. Among them, ultrasonic treatment helps to make it uniformly loaded, ethylene glycol cleaning is used to remove unreacted antimony precursor and by-products to avoid affecting the color value and transparency of the produced polyester, and heat treatment can further promote the insertion and exchange of antimony atoms.

[0017] As the preferred technical solution:

[0018] In the method for preparing a MOF catalyst for synthesizing PET as described above, the molar ratio of ZrCl4 to terephthalic acid in step (1) is 1:6.5-7.5.

[0019] In the method for preparing a MOF catalyst for synthesizing PET as described above, the solvent I in step (1) is a mixture of DMF (N,N-dimethylformamide) and ethylene glycol in a volume ratio of 1:5.

[0020] In the method for preparing a MOF catalyst for synthesizing PET as described above, the molar ratio of antimony ethylene glycol to thioanisole in step (2) is 1:5.7-6.3.

[0021] In the method for preparing a MOF catalyst for synthesizing PET as described above, the solvent II in step (3) is a mixture of DMF and ethylene glycol in a volume ratio of 1:3.

[0022] In the method for preparing a MOF catalyst for synthesizing PET as described above, the temperature of the heat treatment in step (3) is 249-251° C. and the time is 110-125 min.

[0023] The present invention also provides a use of a MOF catalyst for synthesizing PET as described in any one of the above items, for synthesizing PET;

[0024] Antimony cannot be detected in synthetic PET at 110°C, while PET synthesized using antimony-based catalysts in the prior art will become soft at 95°C and free antimony can be detected.

[0025] Beneficial effects:

[0026] (1) The present invention utilizes the restraining effect of the organic structure in the MOF material to fix the antimony atoms, thereby reducing or avoiding the escape of heavy metals in the PET material, and enables the prepared MOF catalyst to have high catalytic activity and selectivity while also having high thermal stability, and can remain stable at a temperature of 320°C, thereby reducing the damage of the PET material to the human body.

[0027] (2) The present invention uses SBME (thioanisole) as the ligand of antimony to form an organic antimony ion compound containing a bridged sulfur atom ligand as a precursor, and its preparation process is more stable.

[0028] (3) When the MOF catalyst prepared by the present invention is used to prepare PET, the prepared PET does not soften even at 110° C., and no antimony element can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a SEM image of the MOF catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0032] Thermal decomposition temperature: The MOF catalyst for synthesizing PET prepared in each embodiment is used as a sample. First, 20 mg of the sample is weighed and placed in the sample pan of the thermogravimetric analyzer. Then, heating is started at a heating rate of 10°C / min. The thermogravimetric analyzer will automatically record the relationship between the mass of the sample and the temperature to obtain a thermogravimetric curve. Then, by analyzing the thermogravimetric curve, tangents are drawn at the point where the thermogravimetric curve begins to decompose and at the point where the decomposition rate is fastest (i.e., the highest point of the curve) so that they intersect at one point. The horizontal coordinate of the point is the decomposition temperature.

[0033] Intrinsic viscosity: measured according to the provisions of 5.1 in GB / T 14190-2017 "Test method for fiber-grade polyester chips (PET)", wherein the sample amount is 0.125 g, the dissolution temperature is 110°C, and the constant temperature water bath temperature is 25.00°C.

[0034] Terminal carboxyl content: Determine according to the provisions of 6.4 of GB / T 14190-2017 "Test method for fiber-grade polyester chips (PET)". Specifically, first dissolve the sample in potassium hydroxide-methanol solution, then use potassium hydrogen phthalate as a standard sample, and determine by neutralization titration; wherein the sample size is 0.125g.

[0035] L value: measured in accordance with GB17931-1993 "PET resin for bottles".

[0036] b value: measured in accordance with GBT 14189-2015 "Fiber-grade polyester chips (PET)".

[0037] Example 1

[0038] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0039] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 190°C for 24 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:7, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0040] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 230° C. for 4 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:6;

[0041] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 80°C for 2h, and then the temperature was increased to 190°C and the reaction was continued for 1h. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET; wherein solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of UiO-66 matrix to antimony precursor is 1:2; the frequency of ultrasonic treatment is 25KHz, and the time of ultrasonic treatment is 20min; the temperature of heat treatment is 250°C, and the time is 120min.

[0042] The final MOF catalyst for synthesizing PET (its SEM image is as follows Figure 1 (shown) is Sb-SBME@UiO-66, Sb-SBME is loaded on the surface of UiO-66, Sb-SBME is a MOF material formed by the coordination of antimony and thioanisole; the thermal decomposition temperature of the MOF catalyst used to synthesize PET is 322.2°C.

[0043] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 250° C. for 1.5 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 239° C. for 0.8 hours, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 266° C. for 0.8 hours, and sliced ​​after extrusion by a small pelletizer to obtain PET slices.

[0044] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.655 dL / g, the terminal carboxyl content was 16.8 mol / t, the L value was 81, and the b value was 6.3.

[0045] Example 2

[0046] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0047] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 191°C for 30 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:6.5, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0048] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 228° C. for 4.5 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:5.7;

[0049] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 82°C for 2.5h, and then the temperature was increased to 188°C and the reaction was continued for 1.2h. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET; wherein solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of UiO-66 matrix to antimony precursor is 1:2; the frequency of ultrasonic treatment is 25KHz, and the time of ultrasonic treatment is 20min; the temperature of heat treatment is 249°C, and the time is 110min.

[0050] The final MOF catalyst for synthesizing PET is Sb-SBME@UiO-66. Sb-SBME is loaded on the surface of UiO-66. Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole. The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 321.6°C.

[0051] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 250° C. for 1.5 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 239° C. for 0.9 hours, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 266° C. for 0.8 hours, extruded by a small pelletizer and sliced ​​to obtain PET slices.

[0052] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.651 dL / g, the terminal carboxyl content was 14.8 mol / t, the L value was 81, and the b value was 4.6.

[0053] Example 3

[0054] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0055] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 189°C for 27 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:7.5, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0056] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 232° C. for 5 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:6.3;

[0057] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 85°C for 3 hours, and then the temperature was increased to 192°C for further reaction for 1.5 hours. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, i.e., a MOF catalyst for synthesizing PET; wherein solvent II was a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of the UiO-66 matrix to the antimony precursor was 1:2; the frequency of the ultrasonic treatment was 25 kHz, and the time of the ultrasonic treatment was 20 min; the temperature of the heat treatment was 251°C, and the time was 125 min.

[0058] The final MOF catalyst for synthesizing PET is Sb-SBME@UiO-66. Sb-SBME is loaded on the surface of UiO-66. Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole. The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 321.2°C.

[0059] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 251° C. for 1.5 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 238° C. for 0.9 hours, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 266° C. for 0.9 hours, and sliced ​​after extrusion by a small pelletizer to obtain PET slices.

[0060] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.652 dL / g, the terminal carboxyl content was 15.1 mol / t, the L value was 81, and the b value was 4.8.

[0061] Example 4

[0062] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0063] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 192°C for 26 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:7, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0064] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 230° C. for 4 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:6;

[0065] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 80°C for 2h, and then the temperature was increased to 190°C and the reaction was continued for 1h. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET; wherein solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of UiO-66 matrix to antimony precursor is 1:2; the frequency of ultrasonic treatment is 25KHz, and the time of ultrasonic treatment is 20min; the temperature of heat treatment is 250°C, and the time is 120min.

[0066] The final MOF catalyst for synthesizing PET is Sb-SBME@UiO-66. Sb-SBME is loaded on the surface of UiO-66. Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole. The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 323.5°C.

[0067] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 251° C. for 2 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 240° C. for 1.2 hours, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 267° C. for 0.8 hours, and sliced ​​after extrusion by a small pelletizer to obtain PET slices.

[0068] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.652 dL / g, the terminal carboxyl content was 15.4 mol / t, the L value was 82, and the b value was 5.6.

[0069] Example 5

[0070] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0071] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 188°C for 28 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:6.5, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0072] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 228° C. for 4.5 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:5.7;

[0073] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 82°C for 2.5h, and then the temperature was increased to 188°C and the reaction was continued for 1.2h. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET; wherein solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of UiO-66 matrix to antimony precursor is 1:2; the frequency of ultrasonic treatment is 25KHz, and the time of ultrasonic treatment is 20min; the temperature of heat treatment is 249°C, and the time is 110min.

[0074] The final MOF catalyst for synthesizing PET is Sb-SBME@UiO-66. Sb-SBME is loaded on the surface of UiO-66. Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole. The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 322.5°C.

[0075] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 252° C. for 1.5 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 238° C. for 1 hour, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 266° C. for 1.2 hours, extruded by a small pelletizer and sliced ​​to obtain PET slices.

[0076] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.653 dL / g, the terminal carboxyl content was 15.7 mol / t, the L value was 81, and the b value was 5.3.

[0077] Example 6

[0078] A method for preparing a MOF catalyst for synthesizing PET, comprising the following steps:

[0079] (1) Dispersing ZrCl4 and terephthalic acid in solvent I, placing the mixture in a reactor at 191°C for 30 hours, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; wherein the molar ratio of ZrCl4 to terephthalic acid is 1:7.5, and solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:5;

[0080] (2) mixing antimony glycolate and thioanisole (manufacturer: Shanghai Siyan Biotechnology Co., Ltd., content: 99%, first-class product) in ethylene glycol, reacting at 232° C. for 5 h, and obtaining an antimony precursor after centrifugation; wherein the molar ratio of antimony glycolate to thioanisole is 1:6.3;

[0081] (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 85°C for 3 hours, and then the temperature was increased to 192°C and the reaction was continued for 1.5 hours. After the reaction was completed, the product was subjected to ultrasonic treatment, ethylene glycol cleaning and heat treatment in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET; wherein solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:3; the molar ratio of UiO-66 matrix to antimony precursor is 1:2; the frequency of ultrasonic treatment is 25 kHz, the time of ultrasonic treatment is 20 min, and the temperature of heat treatment is 251°C and the time is 125 min.

[0082] The final MOF catalyst for synthesizing PET is Sb-SBME@UiO-66. Sb-SBME is loaded on the surface of UiO-66. Sb-SBME is a MOF material generated by the coordination of antimony and thioanisole. The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 321.2°C.

[0083] An application of a MOF catalyst for synthesizing PET, the specific process is: first, 12 kg of PTA (purified terephthalic acid), 5 kg of MEG (ethylene glycol) and 0.15 kg of the MOF catalyst prepared above are added into an esterification reactor, stirred evenly, and reacted at 250° C. for 2 hours, then transferred to a polycondensation reactor 1, vacuumed and reacted at 238° C. for 0.8 hours, after the reaction is completed, transferred to a polycondensation reactor 2, vacuumed and reacted at 266° C. for 1 hour, extruded by a small pelletizer and sliced ​​to obtain PET slices.

[0084] No antimony element was detected in the final PET at 110°C, the intrinsic viscosity of PET was 0.655 dL / g, the terminal carboxyl content was 16.6 mol / t, the L value was 82, and the b value was 5.6.

Claims

1. A MOF catalyst for synthesizing PET, characterized in that: It is Sb-SBME@UiO-66, Sb-SBME is loaded on the surface of UiO-66, and Sb-SBME is a MOF material formed by the coordination of antimony and thioanisole.

2. A MOF catalyst for synthesizing PET according to claim 1, characterized in that: The thermal decomposition temperature of the MOF catalyst used to synthesize PET is 321.2~323.5℃.

3. A method for preparing a MOF catalyst for synthesizing PET as claimed in claim 1 or 2, characterized in that The steps include: (1) Dispersing ZrCl4 and terephthalic acid in solvent I, reacting at 188-192°C for 24-30h, centrifuging and washing with ethylene glycol to obtain a UiO-66 matrix; (2) mixing ethylene glycol antimony and thioanisole in ethylene glycol, reacting at 228-232° C. for 4-5 hours, and obtaining an antimony precursor after centrifugation; (3) The UiO-66 matrix and the antimony precursor were mixed and dispersed in solvent II, stirred at 80-85 °C for 2-3 h, and then the temperature was increased to 188-192 °C and the reaction was continued for 1-1.5 h. After the reaction was completed, the product was ultrasonically treated, cleaned with ethylene glycol, and heat treated in sequence to obtain Sb-SBME@UiO-66, which is a MOF catalyst for synthesizing PET.

4. The method for preparing a MOF catalyst for synthesizing PET according to claim 3, characterized in that: The molar ratio of ZrCl4 to terephthalic acid in step (1) is 1:6.5-7.

5.

5. The method for preparing a MOF catalyst for synthesizing PET according to claim 3, characterized in that: In step (1), solvent I is a mixture of DMF and ethylene glycol in a volume ratio of 1:

5.

6. The method for preparing a MOF catalyst for synthesizing PET according to claim 3, characterized in that: In step (2), the molar ratio of antimony glycol to thioanisole is 1:5.7-6.

3.

7. The method for preparing a MOF catalyst for synthesizing PET according to claim 3, characterized in that: In step (3), solvent II is a mixture of DMF and ethylene glycol in a volume ratio of 1:

3.

8. The method for preparing a MOF catalyst for synthesizing PET according to claim 3, characterized in that: The heat treatment temperature in step (3) is 249-251° C. and the time is 110-125 min.

9. The use of a MOF catalyst for synthesizing PET as claimed in claim 1 or 2, characterized in that: Used for the synthesis of PET; No antimony element can be detected in the synthesized PET at 110°C.

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