Preparation method of modified UIO-66 catalyst, modified UIO-66 catalyst and application of synthetic polyester

Abstract

This invention discloses a method for preparing a modified UIO-66 catalyst, the modified UIO-66 catalyst itself, and its application in polyester synthesis. The method for preparing the modified UIO-66 catalyst includes: dissolving a zirconium source, a titanium source, acetic acid, and an organic ligand in a solvent and reacting them; then collecting, washing, and drying the product to obtain the modified UIO-66 catalyst. The modified UIO-66 catalyst of this invention is environmentally friendly, has a simple synthesis method, uses readily available and inexpensive raw materials, exhibits high catalytic activity in polyester synthesis, and is stable in the reaction system and not easily hydrolyzed.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a method for preparing a modified UIO-66 catalyst, the application of the modified UIO-66 catalyst in the synthesis of polyesters. Background Technology

[0002] Polyester is widely used in the production of fibers, films, various containers, and in all aspects of daily life. Global demand for polyester continues to grow at a rate of 8% annually. In the polyester production process, catalysts not only affect the molecular weight and polycondensation rate but also significantly influence the thermal stability and color of the polyester. Therefore, when selecting a polyester catalyst, it is necessary to comprehensively consider its catalytic activity, environmental performance, and thermal stability. Currently, the most widely used polyester polycondensation catalyst in industry is antimony-based catalysts, which produce products with uniform molecular weight, few byproducts, and are inexpensive. However, antimony ions are harmful to human health and can be separated from the product. Products containing antimony ions can also diffuse into the environment during spinning, causing environmental pollution. This limits the application of antimony-based catalysts in the polymerization process. Therefore, finding environmentally friendly, non-toxic, and harmless catalysts is a current research focus.

[0003] Titanium-based catalysts are environmentally friendly catalysts with high catalytic activity but poor selectivity, thus, the design of well-designed and highly efficient titanium-based catalysts has attracted widespread attention. However, current titanium-based catalysts suffer from the problem of easy hydrolysis and instability.

[0004] Patent CN112812286A reports a method for preparing polyester titanium-based catalysts using the sol-gel method. This catalyst is a modified titanium dioxide / silica composite catalyst; however, the titanium dioxide selectivity is poor, and the catalyst's improvement on polyester color is minimal. Patent CN113072692A reports a highly dispersible titanium-based catalyst, which enhances the dispersibility of the titanium-based catalyst in solvents through silica gel and organic guanidine compounds, thereby improving the catalyst's activity. However, the polyester b-value is also relatively high. Patent CN109337058A reports a titanium-based composite catalyst based on mesoporous nanospheres, which improves the hue of polyester through the adjustable pore structure; however, the catalyst synthesis process is quite complex.

[0005] Therefore, there is an urgent need for a titanium-based catalyst that is environmentally friendly, has high catalytic activity for polyester polycondensation, and exhibits good thermal stability and is not easily hydrolyzed. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing a modified UIO-66 catalyst, the modified UIO-66 catalyst itself, and its application in polyester synthesis. The modified UIO-66 catalyst of this invention is environmentally friendly, has a simple synthesis method, uses readily available and inexpensive raw materials, exhibits high catalytic activity in polyester synthesis, and remains stable in the reaction system without significant hydrolysis.

[0007] One of the objectives of this invention is to provide a method for preparing a modified UIO-66 catalyst.

[0008] The method includes:

[0009] The zirconium source, titanium source, acetic acid and organic ligand were dissolved in a solvent and reacted. The product was then collected, washed and dried to obtain the modified UIO-66 catalyst.

[0010] In a preferred embodiment of the present invention,

[0011] The zirconium source is at least one of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and zirconium chloride (ZrCl4); and / or,

[0012] The titanium source is at least one selected from tetrabutyl titanate, titanium isopropoxide, titanium dichlorodicyclopentadiene, and titanium citrate; and / or,

[0013] The organic ligand is at least one selected from terephthalic acid, 2-aminoterephthalic acid, 2-hydroxyterephthalic acid, 2-methylterephthalic acid, 2-nitroterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-diaminoterephthalic acid, 2,5-dinitroterephthalic acid, and 2,5-dimethylterephthalic acid; and / or

[0014] The solvent is at least one of N,N-dimethylformamide (DMF) and methanol, preferably a mixture of N,N-dimethylformamide and methanol.

[0015] In a preferred embodiment of the present invention,

[0016] In the mixed solvent of N,N-dimethylformamide and methanol, the volume ratio of methanol to N,N-dimethylformamide is 1:(1-10), preferably 1:(2-5).

[0017] In a preferred embodiment of the present invention,

[0018] The molar ratio of the zirconium source, titanium source, organic ligand, acetic acid, and solvent is in the range of 1:(0.04~0.5):(1~3):(30~40):(260~300), preferably 1:(0.06~0.13):(1~1.5):(30~35):(280~300).

[0019] In a preferred embodiment of the present invention,

[0020] The reaction temperature is 100℃~150℃, preferably 120~130℃;

[0021] The reaction time is 2 to 48 hours, preferably 2 to 10 hours, and more preferably 2 to 5 hours.

[0022] A second objective of this invention is to provide a modified UIO-66 catalyst prepared by the method of one objective of this invention.

[0023] In a preferred embodiment of the present invention,

[0024] The atomic ratio of Ti:Zr in the modified UIO-66 catalyst is (3-50):100.

[0025] A third objective of this invention is to provide a method for synthesizing polyesters using the modified UIO-66 catalyst described in the second objective of this invention.

[0026] The method includes:

[0027] The modified UIO-66 catalyst was added to a mixture of diacid and diol for esterification and polycondensation to obtain the polyester.

[0028] The mixture of dicarboxylic acid and diol is one of the following: a mixture of terephthalic acid and ethylene glycol, a mixture of furanyl dicarboxylic acid and ethylene glycol, a mixture of terephthalic acid and propylene glycol, a mixture of terephthalic acid and 1,4-cyclohexanediol, or a mixture of terephthalic acid and butanediol.

[0029] In a preferred embodiment of the present invention,

[0030] The modified UIO-66 catalyst is added before the esterification reaction or the polycondensation reaction.

[0031] In a preferred embodiment of the present invention,

[0032] The amount of the modified UIO-66 catalyst is 0.002 to 0.05 wt% of the total weight of the mixture of the diacid and the diol, preferably 0.005 to 0.03 wt%.

[0033] The molar ratio of the diacid to the diol in the mixture is 0.5 to 1.5, preferably 0.7 to 1.2.

[0034] In a preferred embodiment of the present invention,

[0035] The esterification reaction is carried out at a temperature of 250–270°C; the polycondensation reaction is carried out at a temperature of 270–290°C for a time of 60–180 minutes.

[0036] The present invention can adopt the following specific technical solutions:

[0037] The preferred method for preparing the modified UIO-66 catalyst includes the following steps: dissolving zirconium source, titanium source, acetic acid and organic ligand in a solvent and reacting at 100℃-150℃ for 2-48h; collecting the product by centrifugation, washing with water and vacuum drying to obtain the modified UIO-66 material.

[0038] The preferred method for synthesizing polyesters using a modified UIO-66 catalyst includes the following steps:

[0039] 1) Place a mixture of terephthalic acid and ethylene glycol, or a mixture of furanyl dicarboxylic acid and ethylene glycol, or a mixture of terephthalic acid and propylene glycol, or a mixture of terephthalic acid and 1,4-cyclohexanediol, or a mixture of butylene terephthalate and modified UIO-66 catalyst in a reaction vessel, heat to 250-270°C, and react for 60-120 minutes;

[0040] 2) After the reaction is complete, control the vacuum of the system below 100 Pa, raise the temperature to 270-290℃, and react for 60-180 minutes.

[0041] The present invention has the following beneficial effects:

[0042] (1) The modified UIO-66 catalyst for polyester synthesis proposed in this invention is environmentally friendly, has a simple synthesis method, and has high catalytic activity for polyester synthesis.

[0043] (2) The modified UIO-66 catalyst proposed in this invention is inexpensive and the raw materials are readily available. The catalyst is stable at high temperatures, and compared with other titanium-based catalysts, the modified UIO-66 catalyst is stable in the reaction system and is not easily hydrolyzed.

[0044] (3) Modified UIO-66 can be added before esterification or polycondensation reaction as a catalyst for polyester polycondensation reaction. The resulting product has a better color and the process is simple to operate, with broad prospects for industrial application. Detailed Implementation

[0045] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0046] All raw materials used in the examples are commercially available.

[0047] In the examples, the atomic ratio of Ti:Zr was obtained by ICP characterization, and the testing instrument was a PerkinElmer 8300 ICP-OES.

[0048] In the examples, the intrinsic viscosity of the polyester was measured using a Ubbelohde viscometer (φ=0.80mm) of Shanghai Jianqiang Glass Instrument Co., Ltd.;

[0049] The reference standard for polyester hue testing in the examples is GB / T 17931-2003.

[0050] Example 1

[0051] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, terephthalic acid, and DMF were reacted at 120 °C for 8 h in a molar ratio of 1:0.08:1:32:285. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.05).

[0052] 1000g of terephthalic acid, 485g of ethylene glycol, and 0.4g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 250℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 275℃ and below 100 Pa. The polymerization reaction was terminated after 80 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The product's intrinsic viscosity was 0.69, terminal carboxyl group concentration was 24.0 mol / ton, and the hue was L85, a-0.26, b3.5.

[0053] Example 2

[0054] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, terephthalic acid, and methanol in a mixed solvent of DMF (methanol to DMF volume ratio of 1:3) were reacted at 120 °C for 2 h in a molar ratio of 1:0.08:1:32:285. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.07).

[0055] 1000g of terephthalic acid, 485g of ethylene glycol, and 0.2g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 270℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 90 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.64, the terminal carboxyl group concentration was 17.5 mol / ton, and the hue was L86.1, a-0.35, b2.5.

[0056] Example 3

[0057] Zirconium chloride, titanium citrate, acetic acid, 2-aminoterephthalic acid, and DMF were reacted at 120 °C for 12 h in a molar ratio of 1:0.35:1.5:35:280. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.34).

[0058] 955g of furanyl dicarboxylic acid, 485g of ethylene glycol, and 0.15g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 270℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, and then a polycondensation reaction was carried out at 278℃ and below 100 Pa. The polymerization reaction was terminated after 85 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.67, the terminal carboxyl group concentration was 20.5 mol / ton, and the hue was L87, a-0.37, b2.9.

[0059] Example 4

[0060] The modified UIO-66 catalyst (Zr / Ti = 1:0.47) was obtained by reacting zirconium chloride, tetrabutyl titanate, acetic acid, terephthalic acid, methanol, and DMF in a mixed solvent (methanol to DMF volume ratio of 1:2) at a molar ratio of 1:0.5:2.1:36:295 at 120 °C for 3 h. The precipitate was collected by centrifugation, washed three times with water (15 min each time), and dried under vacuum at 150 °C for 8 h.

[0061] 1000g of terephthalic acid, 500g of propylene glycol, and 0.16g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 260℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.60, the terminal carboxyl group concentration was 16.8 mol / ton, and the hue was L88.5, a-0.2, b2.6.

[0062] Example 5

[0063] Zirconium chloride, tetrabutyl titanate, acetic acid, 2,5-dihydroxyterephthalic acid, and DMF were reacted at 150 °C for 48 h in a molar ratio of 1:0.45:1.9:40:273. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.41).

[0064] 1000g of terephthalic acid, 500g of butanediol, and 0.4g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, and then a polycondensation reaction was carried out at 278℃ and below 100 Pa. The polymerization reaction was terminated after 90 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.62, the terminal carboxyl group concentration was 21.8 mol / ton, and the hue was L85.8, a-0.38, b3.1.

[0065] Example 6

[0066] Zirconium chloride, tetrabutyl titanate, acetic acid, 2-hydroxyterephthalic acid, and DMF were reacted at 130 °C for 10 h in a molar ratio of 1:0.2:2.9:40:265. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.18).

[0067] 1000g of furanyl dicarboxylic acid, 485g of ethylene glycol, and 0.13g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and a pressure of 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, and then a polycondensation reaction was carried out at 280℃ and a pressure below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.68, the terminal carboxyl group concentration was 16.3 mol / ton, and the hue was L86.9, a-0.13, b3.2.

[0068] Example 7

[0069] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, 2-chloroterephthalic acid, and DMF were reacted at 110 °C for 24 h in a molar ratio of 1:0.25:1:34:260. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.23).

[0070] 1000g of terephthalic acid, 895g of 1,4-cyclohexanediol, and 0.13g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.66, the terminal carboxyl group concentration was 19.2 mol / ton, and the hue was L84.9, a-0.35, b3.4.

[0071] Example 8

[0072] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, 2-bromoterephthalic acid, and methanol in a mixed solvent of DMF (methanol to DMF volume ratio of 1:2) were reacted at 120 °C for 4 h in a molar ratio of 1:0.07:1:35:260. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.05).

[0073] 1000g of terephthalic acid, 895g of 1,4-cyclohexanediol, and 0.10g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.64, the terminal carboxyl group concentration was 15.8 mol / ton, and the hue was L88.7, a-0.21, b2.8.

[0074] Example 9

[0075] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, 2,5-dimethylterephthalic acid, and DMF were reacted at 100 °C for 48 h in a molar ratio of 1:0.2:1:39:278. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.19).

[0076] 1000g of terephthalic acid, 500g of propylene glycol, and 0.14g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The product's intrinsic viscosity was 0.63, terminal carboxyl group concentration was 18.3 mol / ton, and the hue was L86.3, a-0.15, b3.2.

[0077] Example 10

[0078] Zirconium chloride, tetrabutyl titanate, acetic acid, 2,5-dinitroterephthalic acid, and DMF were reacted at 150 °C for 48 h in a molar ratio of 1:0.45:1:38:295. The product was collected by centrifugation, washed three times with water (15 minutes each time), and dried under vacuum at 150 °C for 8 h to obtain the modified UIO-66 catalyst (Zr / Ti = 1:0.40).

[0079] 1000g of terephthalic acid, 500g of butanediol, and 0.18g of the prepared modified UIO-66 catalyst were added to a 5L reactor. Esterification was then carried out at 265℃ and 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, followed by a polycondensation reaction at 280℃ and below 100 Pa. The polymerization reaction was terminated after 120 minutes when the desired intrinsic viscosity was reached. The product was then removed and pelletized to obtain polyester. The intrinsic viscosity of the product was 0.65, the terminal carboxyl group concentration was 14.9 mol / ton, and the hue was L87.2, a-0.20, b3.1.

[0080] Comparative Example 1

[0081] Zirconium oxychloride octahydrate, acetic acid, terephthalic acid and DMF were reacted at 120 °C for 48 h in a molar ratio of 1:1:32:285. The precipitate was collected by centrifugation, washed three times with water for 15 minutes each time, and dried under vacuum at 150 °C for 8 h to obtain UIO-66 material.

[0082] 1000g of terephthalic acid, 500g of ethylene glycol, and 0.14g of the prepared UIO-66 material were added to a 5L reactor. Esterification was then carried out at 265℃ and a pressure of 0.1–0.3 MPa. The esterification reaction was considered complete when the amount of water produced reached 95% of the theoretical amount. Subsequently, the reaction system was gradually heated and the pressure reduced, and then a polycondensation reaction was carried out at 280℃ and a pressure below 100 Pa. After 3 hours, no product was obtained through polymerization.

[0083] Comparative Example 2

[0084] Zirconium oxychloride octahydrate, tetrabutyl titanate, acetic acid, terephthalic acid and methanol were reacted at 120 °C for 8 h in a molar ratio of 1:0.08:1:32:285, but UIO-66 material was not obtained.

[0085] As can be seen from Examples 1-10 and Comparative Examples 1-2, titanium-free UIO-66 materials cannot be used as catalysts for polyester synthesis in this invention. However, the modified UIO-66 catalyst of this invention has a simple synthesis method, readily available raw materials, and low price. It has high catalytic activity for polyester synthesis, is stable in the reaction system, and is not easily hydrolyzed. Furthermore, when the modified UIO-66 catalyst is prepared using a mixed solvent of N,N-dimethylformamide and methanol, the preparation time can be greatly shortened compared to preparing the modified UIO-66 catalyst using N,N-dimethylformamide alone.

Claims

1. A method for preparing a modified UIO-66 catalyst, characterized in that... The method includes: Zirconium source, titanium source, acetic acid, and organic ligand are dissolved in a solvent and reacted. The product is then collected, washed, and dried to obtain the modified UIO-66 catalyst. The solvent is a mixture of N,N-dimethylformamide and methanol, wherein the volume ratio of methanol to N,N-dimethylformamide in the mixture is 1:(1~10). The zirconium source is at least one of zirconium oxychloride octahydrate and zirconium chloride. The titanium source is tetratitanate titanate. At least one of butyl acetate, titanium isopropoxide, titanium dichlorocerocene, and titanium citrate; wherein the organic ligand is at least one of terephthalic acid, 2-aminoterephthalic acid, 2-hydroxyterephthalic acid, 2-methylterephthalic acid, 2-nitroterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-diaminoterephthalic acid, 2,5-dinitroterephthalic acid, and 2,5-dimethylterephthalic acid.

2. The preparation method of the modified UIO-66 catalyst as described in claim 1, characterized in that: The molar ratio of the zirconium source, titanium source, acetic acid, organic ligand, and solvent is 1:(0.04~0.5):(1~3):(30~40):(260~300).

3. The method for preparing the modified UIO-66 catalyst as described in claim 2, characterized in that: The molar ratio of the zirconium source, titanium source, acetic acid, organic ligand, and solvent is 1:(0.06~0.13):(1~1.5):(30~35):(280~300).

4. The method for preparing the modified UIO-66 catalyst as described in claim 1, characterized in that: The reaction temperature is 100℃~150℃; The reaction time is 2 to 48 hours.

5. The method for preparing the modified UIO-66 catalyst as described in claim 4, characterized in that: The reaction temperature is 120~130℃; The reaction time is 2 to 10 hours.

6. A modified UIO-66 catalyst prepared by the method according to any one of claims 1-5.

7. A method for synthesizing polyester using the modified UIO-66 catalyst as described in claim 6, characterized in that... The method includes: The modified UIO-66 catalyst was added to a mixture of diacid and diol for esterification and polycondensation to obtain the polyester. The mixture of dicarboxylic acid and diol is one of the following: a mixture of terephthalic acid and ethylene glycol, a mixture of furanyl dicarboxylic acid and ethylene glycol, a mixture of terephthalic acid and propylene glycol, a mixture of terephthalic acid and 1,4-cyclohexanediol, or a mixture of terephthalic acid and butanediol.

8. The method for synthesizing polyester as described in claim 7, characterized in that: The modified UIO-66 catalyst is added before the esterification reaction or the polycondensation reaction.

9. The method for synthesizing polyester as described in claim 7, characterized in that: The modified UIO-66 catalyst is used in an amount of 0.002~0.05 wt% of the total weight of the mixture of the diacid and diol; The molar ratio of the diacid to the diol in the mixture is 0.5 to 1.5:

1.

10. The method for synthesizing polyester as described in claim 7, characterized in that: The reaction temperature for the esterification reaction is 250~270℃; The reaction temperature of the polycondensation reaction is 270~290℃, and the reaction time is 60~180 minutes.