Multi-element hybrid complex, preparation method and application thereof, and PET synthesis method

Abstract

The invention provides a multi-element hybrid complex, a preparation method and application thereof and a PET synthesis method, and particularly relates to the technical field of catalyst preparation. According to the multi-element hybrid complex, Ti atoms serve as core connection nodes, three hybrid elements of P, Al and Si are bridged through Ti-O bonds, and an organic multi-element hybrid framework containing Ti / P / Al / Si is formed; the organic chain segment is dispersed and combined in the organic multi-element hybrid skeleton through the coordination effect of carboxyl or hydroxyl and Ti / Al; the molar ratio of P to Si to Al to Ti is (0.1 to 5) to (0.1 to 1) to (0.1 to 20) to 1. According to the multi-element hybrid complex, the hydrolysis resistance is improved, the stability of a catalyst is improved, and the service life of the catalyst is prolonged; the introduction of the aluminum element optimizes the coordination structure of the catalyst and activates the titanium metal catalytic center by adjusting the electronic environment and steric hindrance of the titanium center, thereby enhancing the catalytic efficiency and selectivity of the polymerization reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to a multi-element hybrid complex and its preparation method and application, as well as a PET synthesis method. Background Technology

[0002] Polyethylene terephthalate (PET) is a widely used thermoplastic polyester material. Due to its excellent transparency, chemical resistance, high mechanical strength, good electrical insulation properties, ease of processing and molding, and low cost, it is widely used in textile fibers, packaging films, food and beverage bottles, engineering plastics and other fields.

[0003] In the synthesis of PET, the catalyst is a key factor determining the polymerization efficiency, product molecular weight, color, thermal stability, and by-product formation. Currently, the mainstream PET polymerization catalysts in industry are mainly divided into three categories: antimony-based, germanium-based, and titanium-based. Among them, antimony-based catalysts (such as antimony trioxide, antimony acetate, and antimony glycolate) have long held more than 90% of the global market share due to their moderate catalytic activity, mature technology, and low cost, making them the dominant catalyst system in current industrial PET production. However, antimony is a heavy metal element and easily undergoes reduction reactions during polymerization to generate elemental metals, leading to a "grayish" appearance in the final product and affecting its quality. Furthermore, antimony has potential biotoxicity, failing to meet increasingly stringent environmental and health safety standards, thus limiting its application in high-end food packaging, medical materials, and other fields.

[0004] To overcome the shortcomings of antimony-based catalysts, researchers have turned to developing alternative catalysts that are free of heavy metals and environmentally friendly. Titanium-based catalysts (such as tetrabutyl titanate and tetraisopropyl titanate) are considered the most promising next-generation PET catalysts due to their extremely high catalytic activity, abundant raw materials, low cost, absence of heavy metals, and green environmental protection.

[0005] However, titanium-based catalysts still have significant drawbacks in practical applications: First, the titanium centers in traditional titanium-based catalysts are excessively active and unstable, easily hydrolyzed by trace amounts of moisture during esterification and storage, leading to the aggregation and deactivation of titanium species, severely affecting the catalyst's stability and lifespan. Second, excessive activity easily induces excessive polycondensation and side reactions (such as the formation of phenyl hydroxyl compounds and quinone compounds, and an increase in cyclic oligomers), resulting in poor polymer color and easy degradation during post-processing, manifested as yellowing of the product (increased b-value) and decreased transparency. In addition, the resulting PET prepolymer exhibits a slow thickening rate in subsequent solid-state polycondensation processes, prolonging the production cycle and reducing production efficiency. These technical bottlenecks severely restrict the widespread application of titanium-based catalysts in the industrial production of high-quality PET.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-element hybrid complex, its preparation method and application, and a PET synthesis method, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The first aspect of the present invention provides a multi-element hybrid complex, which uses Ti atoms as core connecting nodes and connects three hybrid elements, P, Al and Si, through Ti-O bonds to form an organic multi-element hybrid framework containing Ti / P / Al / Si. Organic segments are dispersed and bound in the organic multi-element hybrid framework through coordination of carboxyl or hydroxyl groups with Ti / Al; wherein the molar ratio of P:Si:Al:Ti is (0.1~5):(0.1~1):(0.1~20):1.

[0009] Furthermore, in the multi-element hybrid complex, the molar ratio of P:Si:Al:Ti is (1.0~3):(0.1~0.5):(2~2.5):1.

[0010] The second aspect of the present invention provides a method for preparing the multi-element hybrid complex, wherein a phosphorus source, a silicon source and an aluminum source are added sequentially to an organic solution of a titanium source under a protective atmosphere and mixed evenly to carry out the reaction, and the mixture is concentrated after the reaction is completed to obtain the multi-element hybrid complex.

[0011] Furthermore, the titanium source includes at least one of tetrabutyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate.

[0012] Preferably, the phosphorus source includes at least one selected from phosphoric acid, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, diphenyl phosphate, and triphenyl phosphate.

[0013] Preferably, the silicon source includes at least one of tetraethyl orthosilicate, tetraisopropyl orthosilicate, and tetra-n-propyl orthosilicate.

[0014] Preferably, the aluminum source includes at least one of aluminum stearate, aluminum distearate, aluminum acetate, aluminum glycine, aluminum cyclohexanebutyrate, aluminum lactate, aluminum citrate, aluminum oleate, and aluminum salts of fatty acids.

[0015] Preferably, in the fatty acid aluminum salt, the carbon chain length of the fatty acid is C3~C18.

[0016] Further, the molar ratio of P in the phosphorus source, Si in the silicon source, Al in the aluminum source, and Ti in the titanium source is (0.1~5):(0.1~1):(0.1~20):1, preferably (1.0~3):(0.1~0.5):(2~2.5):1.

[0017] Preferably, the reaction temperature is 50~200℃ and the time is 0.5~3h.

[0018] Preferably, the organic solvent in the organic solution of the titanium source includes at least one of citric acid, tartaric acid, lactic acid, malic acid, and glycolic acid.

[0019] The third aspect of this invention provides the application of the aforementioned multi-element hybrid complex as a catalyst in PET synthesis.

[0020] Furthermore, the mass ratio of Ti in the catalyst to the theoretical PET yield is 1~20 ppm.

[0021] The fourth aspect of the present invention provides a method for synthesizing PET, wherein terephthalic acid and ethylene glycol are added to a reaction vessel for a prepolymerization reaction; then a catalyst is added for polycondensation and thickening to obtain the PET; wherein the catalyst is the multi-element hybrid complex.

[0022] Furthermore, the molar ratio of terephthalic acid to ethylene glycol is (1.05~1.3):1.

[0023] Preferably, the pressure of the prepolymerization reaction is atmospheric pressure to 0.4 MPa, the temperature is 230 to 250 °C, and the time is 1 to 6 hours.

[0024] Preferably, the mass ratio of Ti in the catalyst to the theoretical PET yield is 1~20 ppm.

[0025] Preferably, the pressure of the polycondensation reaction is 0~100Pa, the temperature is 260~280℃, and the time is 1~6h.

[0026] Preferably, the pressure of the thickening reaction is 0~100Pa, the temperature is 200~240℃, and the time is 5~30h.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: The multi-element hybrid complex provided by this invention significantly improves the hydrolysis resistance of the complex by constructing an organic multi-element hybrid framework of Ti / P / Al / Si and combining it with organic segments. This effectively inhibits the hydrolysis and aggregation deactivation of titanium components caused by moisture during storage and reaction, thereby improving the stability and service life of the catalyst. At the same time, the introduction of aluminum optimizes the coordination structure of the catalyst by adjusting the electronic environment and steric hindrance of the titanium center, which helps to expose more highly active titanium metal catalytic centers and enhance their coordination ability to carboxyl and hydroxyl groups, thereby improving the catalytic efficiency and selectivity of the polymerization reaction.

[0028] The preparation method provided by this invention is simple, controllable, easy to scale up, highly automated, and suitable for large-scale industrial production.

[0029] The application provided by this invention offers a better catalyst for PET synthesis, significantly improving polymerization efficiency and product quality, and is suitable for large-scale application.

[0030] The PET synthesis method provided by this invention, given the advantages of the aforementioned multi-element hybrid complex, not only solves the problem of easy hydrolysis and instability of titanium catalysts, but also leverages the high-efficiency catalytic advantages of titanium active centers. While improving the PET polymerization rate, reducing the degree of side reactions, and improving the polymer color, it significantly accelerates the subsequent thickening rate, achieving a balance between high stability and high activity. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0033] The first aspect of the present invention provides a multi-element hybrid complex, with Ti atoms as the core connecting nodes, and P, Al and Si hybrid elements are connected by Ti-O bonds to form an organic multi-element hybrid framework containing Ti / P / Al / Si; organic segments are dispersed and combined in the organic multi-element hybrid framework through coordination with Ti / Al by carboxyl or hydroxyl groups; wherein the molar ratio of P:Si:Al:Ti is (0.1~5):(0.1~1):(0.1~20):1.

[0034] The multi-element hybrid complex provided by this invention significantly improves the hydrolysis resistance of the complex by constructing an organic multi-element hybrid framework of Ti / P / Al / Si and combining it with organic segments. This effectively inhibits the hydrolysis and aggregation deactivation of titanium components caused by moisture during storage and reaction, thereby improving the stability and service life of the catalyst. At the same time, the introduction of aluminum optimizes the coordination structure of the catalyst by adjusting the electronic environment and steric hindrance of the titanium center, which helps to activate the titanium metal catalytic center and enhance its coordination ability to carboxyl and hydroxyl groups, thereby improving the catalytic efficiency and selectivity of the polymerization reaction.

[0035] Organic segments (long chains containing carboxyl and hydroxyl groups) are dispersed and bound in the organic multi-element hybrid framework composed of Ti / P / Al through the coordination of carboxyl groups with Ti / Al and the interaction of hydroxyl groups (-OH) with the framework.

[0036] Furthermore, in the multi-element hybrid complex, the molar ratio of P:Si:Al:Ti is (1.0~3):(0.1~0.5):(2~2.5):1.

[0037] Typical, but not limiting, the molar ratio of P:Si:Al:Ti can be, for example, (0.1:0.1:0.1:1), (1:0.3:5:1), (2:0.5:10:1), (3:0.7:15:1), (5:1:20:1), or any combination within the range of (0.1~5):(0.1~1):(0.1~20):1; preferably, the molar ratio of P:Si:Al:Ti can also be (1.0:0.1:2:1), (2:0.2:2.2:1), (2.5:0.3:2.3:1), (3:0.5:2.5:1), or any combination within the range of (1.0~3):(0.1~0.5):(2~2.5):1.

[0038] The second aspect of the present invention provides a method for preparing the multi-element hybrid complex, wherein a phosphorus source, a silicon source and an aluminum source are added sequentially to an organic solution of a titanium source under a protective atmosphere and mixed evenly to carry out the reaction, and the mixture is concentrated after the reaction is completed to obtain the multi-element hybrid complex.

[0039] The preparation method provided by this invention is simple, controllable, easy to scale up, highly automated, and suitable for large-scale industrial production.

[0040] Furthermore, the titanium source includes at least one of tetrabutyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate.

[0041] Preferably, the phosphorus source includes at least one selected from phosphoric acid, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, diphenyl phosphate, and triphenyl phosphate.

[0042] Preferably, the silicon source includes at least one of tetraethyl orthosilicate, tetraisopropyl orthosilicate, and tetra-n-propyl orthosilicate.

[0043] Preferably, the aluminum source includes at least one of aluminum stearate, aluminum distearate, aluminum acetate, aluminum glycine, aluminum cyclohexanebutyrate, aluminum lactate, aluminum citrate, aluminum oleate, and aluminum salts of fatty acids.

[0044] Preferably, in the fatty acid aluminum salt, the carbon chain length of the fatty acid is C3~C18.

[0045] Further, the molar ratio of P in the phosphorus source, Si in the silicon source, Al in the aluminum source, and Ti in the titanium source is (0.1~5):(0.1~1):(0.1~20):1, preferably (1.0~3):(0.1~0.5):(2~2.5):1.

[0046] Preferably, the reaction temperature is 50~200℃ and the time is 0.5~3h.

[0047] Typically, but not limitingly, the reaction temperature can be, for example, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, or 200°C, or any value within the range of 50°C to 200°C; the reaction time can be, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h, or any value within the range of 0.5h to 3h.

[0048] Preferably, the organic solvent in the organic solution of the titanium source includes at least one of citric acid, tartaric acid, lactic acid, malic acid, and glycolic acid.

[0049] The third aspect of this invention provides the application of the aforementioned multi-element hybrid complex as a catalyst in PET synthesis.

[0050] The application provided by this invention offers a better catalyst for PET synthesis, significantly improving polymerization efficiency and product quality, and is suitable for large-scale application.

[0051] Furthermore, the mass ratio of Ti in the catalyst to the theoretical PET yield is 1~20 ppm.

[0052] Typically, but not limitingly, the mass ratio of Ti in the catalyst to the theoretical PET yield can be, for example, 1 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, or any value in the range of 1 to 20 ppm.

[0053] The fourth aspect of the present invention provides a method for synthesizing PET, wherein terephthalic acid and ethylene glycol are added to a reaction vessel for a prepolymerization reaction; then a catalyst is added for polycondensation and thickening to obtain the PET; wherein the catalyst is the multi-element hybrid complex.

[0054] The PET synthesis method provided by this invention, given the advantages of the aforementioned multi-element hybrid complex, not only solves the problem of easy hydrolysis and instability of titanium catalysts, but also leverages the high-efficiency catalytic advantages of titanium active centers. While improving the PET polymerization rate, reducing the degree of side reactions, and improving the polymer color, it significantly accelerates the subsequent thickening rate, achieving a balance between high stability and high activity.

[0055] Furthermore, the molar ratio of terephthalic acid to ethylene glycol is (1.05~1.3):1.

[0056] Typically, but not limitingly, the molar ratio of terephthalic acid to ethylene glycol can be, for example, 1.05:1, 1.1:1, 1.2:1, 1.22:1, 1.25:1, 1.28:1, 1.3:1, or any value within the range of (1.05 to 1.3):1.

[0057] Preferably, the pressure of the prepolymerization reaction is atmospheric pressure to 0.4 MPa, the temperature is 230 to 250 °C, and the time is 1 to 6 hours.

[0058] Typically, but not limitingly, the pressure of the prepolymerization reaction can be, for example, atmospheric pressure, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, or any value within the range of atmospheric pressure to 0.4 MPa; the temperature of the prepolymerization reaction can be, for example, 230°C, 235°C, 240°C, 245°C, 250°C, or any value within the range of 230°C to 250°C; the time of the prepolymerization reaction can be, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any value within the range of 1 to 6 h.

[0059] Preferably, the mass ratio of Ti in the catalyst to the theoretical PET yield is 1~20 ppm.

[0060] Preferably, the pressure of the polycondensation reaction is 0~100Pa, the temperature is 260~280℃, and the time is 1~6h.

[0061] Typically, but not limitingly, the pressure of the polycondensation reaction can be, for example, 0 Pa, 20 Pa, 50 Pa, 80 Pa, 100 Pa, or any value within the range of 0 to 100 Pa; the temperature of the polycondensation reaction can be, for example, 260°C, 265°C, 270°C, 275°C, 280°C, or any value within the range of 260 to 280°C; the time of the polycondensation reaction can be, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any value within the range of 1 to 6 h.

[0062] Preferably, the pressure of the thickening reaction is 0~100Pa, the temperature is 200~240℃, and the time is 5~30h.

[0063] Typically, but not limitingly, the pressure of the thickening reaction can be, for example, 0 Pa, 20 Pa, 50 Pa, 80 Pa, 100 Pa, or any value within the range of 0 to 100 Pa; the temperature of the thickening reaction can be, for example, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or any value within the range of 200 to 240 °C; the time of the thickening reaction can be, for example, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, or any value within the range of 5 to 30 h.

[0064] The following detailed description of some embodiments of the present invention is provided in conjunction with examples. Unless otherwise specified, the following embodiments and features can be combined with each other. In the present invention, the raw materials used in Example 5 and the comparative examples, unless otherwise specified, were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products that can be purchased commercially.

[0065] Example 1 This embodiment provides a multi-element hybrid complex. The specific preparation method is as follows: Under nitrogen protection, 42.64g of tetraisopropyl titanate (0.15mol) and citric acid solution (200g citric acid) are added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 29.4g of phosphoric acid (0.3mol) is slowly added to the reactor and mixed evenly. Then, 3.12g of tetraethyl orthosilicate (0.015mol) is slowly added and mixed evenly. Finally, 263.1g (0.3mol) of aluminum stearate is slowly added. The temperature is controlled at 100℃ and the reaction is continued with stirring for 2 hours. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0066] Example 2 This embodiment provides a multi-element hybrid complex, which is prepared as follows: Under nitrogen protection, 42.64g of tetraisopropyl titanate (0.15mol) and citric acid solution (150g citric acid) are added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 29.4g of phosphoric acid (0.3mol) is slowly added to the reactor and mixed evenly. Then, 3.12g of tetraethyl orthosilicate (0.015mol) is slowly added and mixed evenly. Finally, 42g of aluminum acetate (0.35mol) is slowly added. The temperature is controlled at 100℃ and the reaction is continued with stirring for 2 hours. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0067] Example 3 This embodiment provides a multi-element hybrid complex, which is prepared as follows: Under nitrogen protection, 42.64g of tetraisopropyl titanate (0.15mol) and citric acid solution (100g citric acid) are added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 39.2g of phosphoric acid (0.4mol) is slowly added to the reactor and mixed evenly. Then, 12.48g of tetraethyl orthosilicate (0.06mol) is slowly added and mixed evenly. Finally, 42g of aluminum acetate (0.35mol) is slowly added. The temperature is controlled at 100℃ and the reaction is continued with stirring for 2 hours. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0068] Example 4 This embodiment provides a multi-element hybrid complex. The specific preparation method is as follows: Under nitrogen protection, 42.64g of tetraisopropyl titanate (0.15mol) and tartaric acid solution (150g tartaric acid) are added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 54.6g of triethyl phosphate (0.3mol) is slowly added to the reactor and mixed evenly. Then, 3.12g of tetraethyl orthosilicate (0.015mol) is slowly added and mixed evenly. Finally, 183.3g (0.3mol) of aluminum distearate is slowly added. The temperature is controlled at 150℃ and the reaction is continued with stirring for 2.5h. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0069] Example 5 This embodiment provides a multi-element hybrid complex. The specific preparation method is as follows: Under nitrogen protection, 51g of tetrabutyl titanate (0.15mol) tartaric acid solution (150g tartaric acid) is added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 54.6g of triethyl phosphate (0.3mol) is slowly added to the reactor and mixed evenly. Then, 15.6g of tetraethyl orthosilicate (0.075mol) is slowly added and mixed evenly. Finally, 42g of aluminum acetate (0.35mol) is slowly added. The temperature is controlled at 120℃ and the reaction is continued with stirring for 3 hours. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0070] Example 6 This embodiment provides a multi-element hybrid complex. The specific preparation method is as follows: Under nitrogen protection, 51g of tetrabutyl titanate (0.15mol) and tartaric acid solution (120g tartaric acid) are added to a temperature-controlled reactor equipped with a stirrer, a separatory funnel, and a condenser. Under mechanical stirring, 39.2g of phosphoric acid (0.4mol) is slowly added to the reactor and mixed evenly. Then, 15.6g of tetraethyl orthosilicate (0.075mol) is slowly added and mixed evenly. Finally, 42g of aluminum acetate (0.35mol) is slowly added. The temperature is controlled at 120℃ and the reaction is continued with stirring for 3 hours. After the reaction is completed, the mixture is concentrated and small molecules are removed to obtain the multi-element hybrid complex.

[0071] Application Example 1 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 775g (12.5mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 235℃; the pressure is atmospheric pressure of 0.35MPa, and the reaction is stirred for 2h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 1 is added as a catalyst, and the amount of titanium catalyst added is controlled at 7.5ppm, the temperature is controlled at 270℃, the pressure is controlled at 10pa, and the reaction is stirred for 3h to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 20h to obtain the PET polyester product.

[0072] Application Example 2 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 744g (12mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 235℃; the pressure is atmospheric pressure of 0.35MPa, and the reaction is stirred for 2h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 2 is added as a catalyst, and the amount of titanium catalyst added is controlled at 8ppm, the temperature is controlled at 270℃, the pressure is controlled at 10pa, and the reaction is stirred for 3h to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 20h to obtain the PET polyester product.

[0073] Application Example 3 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 744g (12mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 235℃; the pressure is atmospheric pressure of 0.4MPa, and the reaction is stirred for 2h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 3 is added as a catalyst, and the amount of titanium catalyst added is controlled at 6ppm, the temperature is controlled at 270℃, the pressure is controlled at 10pa, and the reaction is stirred for 3h to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 20h to obtain the PET polyester product.

[0074] Application Example 4 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 806g (13mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 240℃; the pressure is atmospheric pressure of 0.35MPa, and the reaction is stirred for 2h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 4 is added as a catalyst, and the amount of titanium catalyst added is controlled at 8ppm, the temperature is controlled at 270℃, the pressure is controlled at 30pa, and the reaction is stirred for 3.5 hours to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 25h to obtain the PET polyester product.

[0075] Application Example 5 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 806g (13mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 240℃; the pressure is atmospheric pressure of 0.35MPa, and the reaction is stirred for 2.5h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 5 is added as a catalyst, and the amount of titanium catalyst added is controlled at 10ppm, the temperature is controlled at 270℃, the pressure is controlled at 50pa, and the reaction is stirred for 3.5h to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 20h to obtain PET polyester product.

[0076] Application Example 6 This application example provides a method for synthesizing PET. The specific process is as follows: 1661g (10mol) of terephthalic acid and 806g (13mol) of ethylene glycol are added to a reactor, and the temperature is controlled at 240℃; the pressure is atmospheric pressure of 0.35MPa, and the reaction is stirred for 2.5h to carry out the esterification reaction; the multi-element hybrid complex provided in Example 6 is added as a catalyst, and the amount of titanium catalyst added is controlled at 10ppm, the temperature is controlled at 270℃, the pressure is controlled at 50pa, and the reaction is stirred for 3.5h to carry out the polycondensation reaction; the drum reaction temperature is controlled at 220℃, the vacuum degree is controlled at 50Pa, and the thickening reaction is carried out for 23h to obtain the PET polyester product.

[0077] Comparative Application Example 1 This comparative application example provides a method for synthesizing PET. The difference from Application Example 1 is that tetrabutyl titanate is used instead of the multi-element hybrid complex in Application Example 1. All other processes are the same as in Example 1 and will not be described again here.

[0078] Test Example 1 The intrinsic viscosity of the PET obtained from the corresponding use cases and comparative application examples was tested. The L value, a value and b value of the PET were measured using a spectrophotometer, and the data were recorded in Table 1.

[0079] Table 1

[0080] As shown in Table 1, the intrinsic viscosity (IV) of the PET polymers obtained in Application Examples 1-6 is generally higher than that of Comparative Application Example 1, reaching a maximum of 0.8045 dL / g (Application Example 5), while Comparative Application Example 1 is only 0.7540 dL / g. This indicates that the multi-element hybrid complex significantly enhances the molecular weight growth capability of the polymerization reaction and has higher catalytic efficiency. Regarding hue performance, the b-values ​​of all application examples are much lower than those of Comparative Application Example 1 (4.12), ranging from -1.39 to -0.12, indicating that the products have almost no yellow tint and even exhibit a slight blue tint, significantly improving the hue quality of PET. At the same time, the L-values ​​are generally higher, reaching a maximum of 79.49, indicating better product transparency and gloss. Furthermore, the a-values ​​of most application examples are close to neutral or slightly greenish, indicating good overall color stability.

[0081] As can be seen, compared with the comparative application example using traditional tetrabutyl titanate catalyst, the multi-element hybrid complex provided by the present invention not only effectively improves the degree of polymerization and reactivity of PET, but also significantly improves the optical properties of the product and inhibits yellowing, demonstrating its comprehensive advantages in catalytic efficiency, selectivity and product quality control.

[0082] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-element hybrid complex, characterized in that, Ti atoms are used as core connecting nodes, and P, Al and Si are connected by Ti-O bonds to form an organic multi-element hybrid skeleton containing Ti / P / Al / Si; The organic segments are dispersed and combined in the organic multi-element hybrid skeleton through the coordination of carboxyl or hydroxyl with Ti / Al; The molar ratio of P:Si:Al:Ti is (0.1-5):(0.1-1):(0.1-20):

1.

2. The multi-element hybrid complex of claim 1, wherein, The molar ratio of P:Si:Al:Ti is (1.0-3):(0.1-0.5):(2-2.5):

1.

3. A method for producing the multi-element hybrid complex according to claim 1 or 2, characterized by, The phosphorus source, silicon source and aluminum source are sequentially added into the organic solution of the titanium source under a protective atmosphere, mixed uniformly and reacted, and the multi-element hybrid complex is obtained after the reaction is completed.

4. The production method according to claim 3, characterized by, The titanium source includes at least one of n-butyl titanate, tetrabutyl titanate, tetraethyl titanate and tetraisopropyl titanate. Preferably, the phosphorus source includes at least one of phosphoric acid, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, diphenyl phosphate and triphenyl phosphate.

5. The preparation method according to claim 3, characterized in that, The silicon source includes at least one of tetraethyl orthosilicate, tetraisopropyl orthosilicate and tetra-n-propyl orthosilicate. Preferably, the aluminum source includes at least one of aluminum stearate, aluminum bis-stearate, aluminum acetate, aluminum glycolate, aluminum cyclohexane butyrate, aluminum lactate, aluminum citrate, aluminum oleate and aluminum fatty acid salt. Preferably, in the aluminum fatty acid salt, the carbon chain length of the fatty acid is C3-C18.

6. The preparation method according to claim 3, characterized in that, The molar ratio of P in the phosphorus source, Si in the silicon source, Al in the aluminum source and Ti in the titanium source is (0.1-5):(0.1-1):(0.1-20):1, and preferably (1.5-3):(0.1-0.5):(2-2.5):

1. Preferably, the temperature of the reaction is 50-200°C, and the time is 0.5-3h. Preferably, in the organic solution of the titanium source, the organic solvent includes at least one of citric acid, tartaric acid, lactic acid, malic acid and glycolic acid.

7. Use of the multi-element hybrid complex of claim 1 or 2 as a catalyst in PET synthesis.

8. Use according to claim 7, characterized in that, The mass ratio of Ti in the catalyst to the theoretical PET yield is 1-20ppm.

9. A method of PET synthesis, characterized by, Terephthalic acid and ethylene glycol are added into a reaction container to perform a prepolymerization reaction, and then a catalyst is added to perform a polycondensation and tackification reaction, so as to obtain the PET. The catalyst is the multi-element hybrid complex of claim 1 or 2.

10. The method of PET synthesis according to claim 9, wherein, The molar ratio of the terephthalic acid to the ethylene glycol is (1.05-1.3):

1. Preferably, the pressure of the prepolymerization reaction is normal pressure-0.4MPa, the temperature is 230-250°C, and the time is 1-6h. Preferably, the mass ratio of Ti in the catalyst to the theoretical PET yield is 1-20ppm. Preferably, the pressure of the polycondensation reaction is 0-100Pa, the temperature is 260-280°C, and the time is 1-6h. Preferably, the pressure of the tackification reaction is 0-100Pa, the temperature is 200-240°C, and the time is 5-30h.

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