MOF catalyst for synthesizing PET and preparation method thereof
By preparing the MOF catalyst Sb-SBME@UiO-66, the problems of low activity, poor selectivity and heavy metal precipitation of existing catalysts were solved, efficient and stable PET synthesis was achieved, and product safety and quality were improved.
Patent Information
- Application Number
- CN202510925860.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-07
- Publication Date
- 2025-10-10
AI Technical Summary
Existing antimony and titanium catalysts have low catalytic activity and poor selectivity in the process of synthesizing PET. The precipitation of antimony elements is harmful to human health. Titanium catalysts have obvious side reactions and the melt color is yellowish.
The MOF catalyst Sb-SBME@UiO-66 is used. Antimony is combined with the organic framework structure as a metal site. Thiobenzyl ether is used as a ligand for antimony during the preparation process to form a bridged sulfur atom ligand, which fixes the antimony atom, improves the catalytic activity and selectivity, and remains stable at 350°C.
It achieves high selectivity, high catalytic activity and thermal stability, reduces heavy metal escape, improves the safety and product quality of PET polyester, reduces the occurrence of side reactions, and maintains the stability of the catalyst.
Smart Images
Figure CN120757793A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of PET polyester, and in particular to a MOF catalyst for synthesizing PET and a preparation method thereof. Background Art
[0002] PET (polyethylene terephthalate) is widely used in packaging, optical equipment, electrical appliances, and other fields due to its excellent mechanical strength and optical properties. Currently, antimony (Sb)-based catalysts are commonly used in the polycondensation process of PET. During the manufacture of PET containers for food and beverages, trace amounts of antimony are leached, posing a health risk. While titanium-based catalysts hold promise as a replacement for antimony-based catalysts, their effectiveness and widespread adoption remain suboptimal. This is primarily due to their high catalytic activity, poor selectivity, significant side reactions, and a yellowish melt hue. Research on the use of organic catalysts in the synthesis of PET polyester is limited, and most have difficulty maintaining stability at reaction temperatures.
[0003] Metal-organic framework (MOF) materials have become an important class of catalysts in industrial catalysis due to their excellent properties, including adjustable metal sites, easy separation from products, numerous catalytically active sites accessible to substrates, and ease of modification. MOFs are porous materials composed of metals (such as Cu, Ni, and Zn) and organic ligands (such as NH2-BDC, bpy, and 1,10-phenanthroline). Their porous frameworks serve as a strong support structure, allowing for easy complexation with other materials and facilitating the diffusion and adsorption of reactants. The metal sites are typically transition metals, possessing vacant d or even f orbitals and a rich array of extranuclear electron configurations. These can alter reaction pathways and thus reduce activation energies. Furthermore, MOFs can be manipulated to improve their electronic structure and energy bandgap by adjusting ligands, metal doping, and structural modification, thereby enhancing catalytic performance. These advantages have made MOFs an excellent catalyst for industrial catalysis.
[0004] Antimony (Sb) catalysts are currently commonly used in the polycondensation process for PET synthesis. This leads to trace amounts of antimony precipitating during the manufacture of food and beverage containers, posing a threat to human health. While titanium-based catalysts offer promise as alternatives to antimony-based catalysts, their effectiveness and widespread adoption remain suboptimal. This is primarily due to their high catalytic activity, poor selectivity, significant side reactions, and a yellowish melt hue.
[0005] Therefore, the inventors provide a MOF catalyst for synthesizing PET and a preparation method thereof. Summary of the Invention
[0006] (1) Technical problems to be solved The embodiments of the present invention provide a MOF catalyst for synthesizing PET and a preparation method thereof, which solve the technical problem of poor catalytic activity and thermal stability of the catalyst for synthesizing PET.
[0007] (2) Technical solution One aspect of the present invention provides a MOF catalyst for synthesizing PET, the molecular formula of which is Sb-SBME@UiO-66, wherein SBME is thiobenzyl ether.
[0008] Another aspect of the present invention also provides a method for preparing a MOF catalyst for synthesizing PET, comprising the following steps: Dispersing zinc tetrachloride and terephthalic acid in a first mixed solution of N-N-dimethylamide and ethylene glycol to react at a first set temperature, and centrifuging to obtain a white precipitate after the reaction; The white precipitate is washed to obtain a UiO-66 matrix; mixing antimony glycolate and thiobenzyl ether in ethylene glycol, reacting at a second set temperature, and then centrifuging to obtain an antimony precursor; The UiO-66 matrix and the antimony precursor are mixed and dispersed in a second mixed solution of N-N-dimethylamide and ethylene glycol, and stirred at a third set temperature to activate the UiO-66 matrix and the antimony precursor. The temperature is raised to a fourth set temperature and the reaction is continued to obtain a MOF catalyst.
[0009] Optionally, the molar ratio of the zinc tetrachloride to the terephthalic acid is 1:(6.5-7.5).
[0010] Optionally, the volume ratio of N-N dimethylamide to ethylene glycol in the first mixed liquid is 1:(4.5-5.5).
[0011] Optionally, the molar ratio of the antimony ethylene glycol to the thiobenzyl ether is 1:(5.5-6.5).
[0012] Optionally, the volume ratio of N-N dimethylamide to ethylene glycol in the second mixed liquid is 1:(2.5-3.5).
[0013] Optionally, after the temperature is raised to the fourth set temperature and the reaction is continued, the method further comprises: performing ultrasonic treatment on the reaction product.
[0014] Optionally, after the temperature is raised to the fourth set temperature and the reaction is continued, the method further comprises: cleaning the reaction product to remove unreacted antimony precursor and by-products.
[0015] Optionally, the cleaned product is heated and dried at a fifth set temperature.
[0016] Optionally, the second set temperature is greater than the first set temperature, the first set temperature is greater than the third set temperature, and the fifth set temperature is greater than the second set temperature.
[0017] (3) Beneficial effects In summary, the present invention reduces or avoids the escape of heavy metal elements during the synthesis of PET materials by utilizing the restraining effect of the organic structure of the MOF material on the metal groups. This makes the synthesis of food-grade polyester highly safe for the human body and can reduce the escape and residue of catalyst metals that cause the PET polyester to turn gray. At the same time, SBME is selected as the antimony ligand to form an organic antimony ion compound containing a bridged sulfur atom ligand as a precursor, making the preparation process more stable. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0019] Figure 1 The figure is a schematic flow chart of a method for preparing a MOF catalyst for synthesizing PET provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0020] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments.
[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0022] An embodiment of the present invention provides a MOF catalyst for synthesizing PET, whose molecular formula is Sb-SBME@UiO-66, wherein SBME is thiobenzyl ether.
[0023] This catalyst exhibits high selectivity and minimal side reactions. Using antimony as the metal site, a MOF catalyst was prepared. Leveraging the properties of the organic framework (MOF), this catalyst combines high catalytic activity and selectivity with high thermal stability, remaining stable at temperatures up to 350°C. Furthermore, the confinement of the MOF's organic structure secures the antimony atoms, minimizing or preventing the release of heavy metals from the PET material and reducing its potential harm to the human body. Furthermore, MOF materials are easily modifiable, offering new avenues for further reducing catalyst costs. For example, the MOF catalyst Sb-SBME@UiO-66 could be loaded with magnetic materials, such as iron, cobalt, and nickel, evenly distributing them. The catalyst could then be recovered using an external magnetic field.
[0024] MOF catalysts can play the following important roles in polyester production: 1. Catalytic polycondensation: The polycondensation reaction in polyester production involves the polymerization of monomer molecules to form high-molecular-weight polyester. MOF catalysts can accelerate the polycondensation reaction, reduce the activation energy of the reaction, and increase the reaction rate.
[0025] 2. Improved selectivity: There are multiple side reactions in the polycondensation reaction, such as hydrolysis and alcoholysis of monomers. MOF catalysts can selectively promote the polycondensation reaction and inhibit the occurrence of side reactions, thereby increasing the yield and purity of polyester.
[0026] 3. Controlling Molecular Weight Distribution: The molecular weight distribution of polyester is a key factor affecting its performance and application. MOF catalysts can regulate molecular weight distribution by controlling the rate and extent of the polycondensation reaction, thereby obtaining polyesters with narrow molecular weight distributions.
[0027] 4. Enhance catalyst stability: MOF catalysts have a large specific surface area and pore structure, which can provide abundant catalytic active sites and are also conducive to the dispersion and stability of the catalyst.
[0028] In summary, MOF catalysts offer advantages in polyester production, including high catalytic efficiency, good selectivity, narrow molecular weight distribution, and strong catalytic stability, effectively improving polyester production efficiency and product quality. For example, PET-Ni-MOF, a polyacid-based metal-organic framework (MOF) material developed by Professor Lan Yaqian and Dr. Chen Yifa of Nanjing Normal University, can efficiently catalyze the synthesis of cyclic carbonate compounds (precursors of polycarbonate plastics). Experimental studies have confirmed that PET-Ni-MOF can efficiently catalyze the synthesis of a range of cyclic carbonate compounds, outperforming most previously reported catalysts. Furthermore, the catalyst exhibits excellent stability, maintaining its structural integrity and catalytic efficiency even after ten cycles.
[0029] Figure 1 is a preparation method of a MOF catalyst for synthesizing PET provided by an embodiment of the present application, see Figure 1 The method can include the following steps: S100, dispersing zinc chloride and terephthalic acid into a first mixed solution of N-N dimethylformamide and ethylene glycol to react at a first set temperature, and obtaining white precipitate after centrifugation.
[0030] In step S100, ZrCl4 and H2BDC (terephthalic acid) are dispersed into a sufficient amount (i.e., to make ZrCl4 and H2BDC into a stable solution state) of mixed solution of DMF (N-N dimethylformamide) and ethylene glycol (volume ratio of 1:4.5-1:5.5, preferably 1:5) at a molar ratio of 1:6.5-1:7.5 (preferably 1:7), and then put into a reaction kettle to react at 190±1.0℃ (i.e., the first set temperature) for 24±0.5h, and obtain white precipitate after centrifugation.
[0031] S200, washing the white precipitate to obtain a UiO-66 matrix.
[0032] In step S200, the white precipitate is washed with ethylene glycol to obtain the matrix UiO-66. The introduction of antimony (Sb) in UiO-66 is achieved through a post-synthetic modification method, which generally involves replacing part of the zirconium (Zr) nodes in the UiO-66 structure with antimony nodes. This modification can change the chemical and physical properties of UiO-66, thereby expanding its application range and making it useful for catalyzing PET synthesis.
[0033] S300, mixing antimony glycol with thiobenzyl ether in ethylene glycol, and obtaining an antimony precursor after centrifugation after reaction at a second set temperature.
[0034] In step S300, an organic ligand capable of forming a stable complex with antimony is selected. Antimony usually reacts with four-coordinated ligands, such as sulfur-containing ligands or phosphates. In this application, SBME (thiobenzyl ether) is selected. Antimony glycol is mixed with thiobenzyl ether (molar ratio of 1:5.5-1:6.5, preferably 1:6) in ethylene glycol, and the mixture is reacted at 230±1℃ (i.e., the second set temperature) for 4±0.5h, and then centrifuged to obtain a powder, indicating the formation of an organic antimony ion compound containing a bridging sulfur atom ligand, i.e., an antimony precursor.
[0035] S400, mixing and dispersing the UiO-66 matrix and the antimony precursor in a second mixed solution of N-N dimethylformamide and ethylene glycol, and stirring at a third set temperature to activate the UiO-66 matrix and the antimony precursor, and continuing the reaction after warming to a fourth set temperature to obtain a MOF catalyst.
[0036] In step S400, UiO-66 and an antimony precursor are mixed and dispersed in a sufficient amount (i.e., to form a stable solution of the UiO-66 and antimony precursor) of a mixture of DMF (N-dimethylformamide) and ethylene glycol (volume ratio of 1:2.5 to 1:3.5, preferably 1:3). The mixture is stirred at 80±5°C (i.e., the third set temperature) for 2±0.2 hours to activate the UiO-66 and antimony precursor. The temperature is then raised to 190±5°C (i.e., the fourth set temperature) and the reaction is continued for 1±0.2 hours.
[0037] A simple ultrasonic treatment of the reaction product helps to make it uniformly loaded.
[0038] After the reaction is complete, the product needs to be thoroughly washed with ethylene glycol to remove unreacted antimony precursors and byproducts, which can affect the color and transparency of the polyester produced. To further promote the insertion and exchange of antimony atoms, the washed product can be subjected to a simple heat treatment. After the catalyst is synthesized, it is dried at 250±2°C (the fifth set temperature) for 2±0.2h. This yields the MOF catalyst Sb-SBME@UiO-66.
[0039] As an optional implementation, the second set temperature is greater than the first set temperature, the first set temperature is greater than the third set temperature, and the fifth set temperature is greater than the second set temperature.
[0040] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.
[0041] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.
Claims
1. A MOF catalyst for synthesizing PET, characterized in that: The molecular expression is Sb-SBME@UiO-66, where SBME is thiobenzyl ether.
2. The method for preparing a MOF catalyst for synthesizing PET according to claim 1, wherein The method comprises the following steps: Dispersing zinc tetrachloride and terephthalic acid in a first mixed solution of N-N-dimethylamide and ethylene glycol to react at a first set temperature, and centrifuging to obtain a white precipitate after the reaction; The white precipitate is washed to obtain a UiO-66 matrix; mixing antimony glycolate and thiobenzyl ether in ethylene glycol, reacting at a second set temperature, and then centrifuging to obtain an antimony precursor; The UiO-66 matrix and the antimony precursor are mixed and dispersed in a second mixed solution of N-N-dimethylamide and ethylene glycol, and stirred at a third set temperature to activate the UiO-66 matrix and the antimony precursor. The temperature is raised to a fourth set temperature and the reaction is continued to obtain a MOF catalyst.
3. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: The molar ratio of the zinc tetrachloride to the terephthalic acid is 1:(6.5-7.5).
4. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: The volume ratio of N-N-dimethylamide to ethylene glycol in the first mixed liquid is 1:(4.5-5.5).
5. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: The molar ratio of the antimony ethylene glycol to the thiobenzyl ether is 1:(5.5-6.5).
6. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: The volume ratio of N-N-dimethylamide to ethylene glycol in the second mixed liquid is 1:(2.5-3.5).
7. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: After the temperature is raised to the fourth set temperature and the reaction is continued, the method further includes: performing ultrasonic treatment on the reaction product.
8. The method for preparing a MOF catalyst for synthesizing PET according to claim 2, wherein: After the temperature is raised to the fourth set temperature and the reaction is continued, the method further includes: cleaning the reaction product to remove unreacted antimony precursor and by-products.
9. The method for preparing a MOF catalyst for synthesizing PET according to claim 8, wherein: The cleaned product is heated and dried at a fifth set temperature.
10. The method for preparing a MOF catalyst for synthesizing PET according to claim 9, wherein: The second set temperature is greater than the first set temperature, the first set temperature is greater than the third set temperature, and the fifth set temperature is greater than the second set temperature.