A supported catalyst, a preparation method and application thereof, and a preparation method of polyethylene naphthalate

Abstract

The application provides a supported catalyst and a preparation method and application thereof, and a preparation method of polyethylene naphthalate, and relates to the technical field of polyester preparation.The supported catalyst provided by the application comprises a porous ClMg(OC2H5)C2H5OH carrier and nanometer titanium dioxide supported on the porous ClMg(OC2H5)C2H5OH carrier.The polyethylene naphthalate is prepared by using the supported catalyst provided by the application, the catalytic effect is good, the polyethylene naphthalate prepared has high molecular weight, good color and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polyester preparation technology, specifically to a supported catalyst, its preparation method and application, and a method for preparing polyethylene naphthalate. Background Technology

[0002] Polyethylene naphthalene glycol (PEN) is an important member of the polyester family. It is formed by the condensation polymerization of dimethyl 2,6-naphthalenedicarboxylate (NDC) or 2,6-naphthalenedicarboxylic acid (NDA) with ethylene glycol (EG), and is a new and excellent polymer. Its chemical structure is similar to PET, but the difference lies in the molecular chain: PEN uses a more rigid naphthalene ring instead of the benzene ring in PET. This naphthalene ring structure gives PEN higher physical and mechanical properties, gas barrier properties, chemical stability, and resistance to heat, ultraviolet radiation, and radiation than PET. Polyethylene naphthalene glycol (PEN) is a new polyester variety commercialized in the 1990s. Like PET, PEN can be processed into films, fibers, hollow containers, and sheets.

[0003] In recent years, PEN film has been mainly used in magnetic tape basebands, flexible printed circuit boards, capacitor films, and Class F insulating films. In addition, due to its good heat resistance and film strength, PEN film also shows promise for use in automotive sensors and insulating components. Furthermore, Class F insulating film has the most promising application prospects. Ordinary PET film can only reach Class E (long-term operating temperature of 120℃). To reach Class B (130℃), the viscosity needs to be significantly increased, and the oligomer content must be very low. Otherwise, when used for insulation of refrigerated sealed motors, the oligomers are easily extracted by the lubricating oil and refrigerant, causing motor failure. PEN, on the other hand, has an oligomer mass fraction of only 0.5%, water resistance four times that of PET, and good heat resistance, meeting the requirements of Class F (160℃) insulating film, thus showing excellent application prospects. Polyethylene naphthalate (PEN) is a novel polyester material with many properties that are significantly superior to PET. This has led many researchers to invest a great deal of effort and resources in its study, resulting in significant progress and rapid development of PEN worldwide.

[0004] Currently, PEN's three main product lines have been launched in overseas markets and are well-received. Their superior performance demonstrates their attractive business opportunities. Chips obtained from melt polycondensation are widely used in the production of polyester fibers and textile materials. Since the 1970s, in order to fully utilize resources and maximize the potential performance of materials, countries around the world have successively carried out research on the production process of high molecular weight polyester chips. Initially, people used extended melt polymerization time to produce high molecular weight polyesters. However, it is well known that the chain growth reaction of polyester is a reversible chemical reaction; the higher the reaction temperature and the longer the reaction time, the greater the amount of reverse reaction, limiting the rate of the forward reaction. Therefore, using melt polymerization to increase molecular weight has been proven to be an economically and theoretically unreasonable method.

[0005] In existing preparation processes, polyethylene naphthalate has a high melting temperature and high melt viscosity, which makes it difficult to process and shape. Moreover, the resulting product still contains unreacted monomers, resulting in low molecular weight and poor mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide a supported catalyst, its preparation method and application, and a method for preparing polyethylene naphthalate. The supported catalyst provided by this invention is used to prepare polyethylene naphthalate with good catalytic effect. The prepared polyethylene naphthalate has high molecular weight, good color and excellent mechanical properties.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] The present invention provides a supported catalyst comprising a porous ClMg(OC2H5)·C2H5OH support and nano-titanium dioxide supported on the porous ClMg(OC2H5)·C2H5OH support.

[0009] Preferably, the mass of the nano-titanium dioxide is 55-65% of the mass of the porous ClMg(OC2H5)·C2H5OH support.

[0010] This invention provides a method for preparing the supported catalyst described in the above technical solution, comprising the following steps:

[0011] Magnesium powder, iodine, dichloromethane and ethanol are mixed and subjected to a redox reaction to obtain a reaction solution;

[0012] The reaction solution was mixed with n-hexane and crystallized to obtain a porous ClMg(OC2H5)·C2H5OH support;

[0013] The porous ClMg(OC2H5)·C2H5OH support, tetrabutyl titanate, and ethanol were mixed to obtain an ethanol dispersion.

[0014] The ethanol dispersion and the ethanol solution of hydrochloric acid were mixed to obtain the precursor of tetrabutyl titanate hydrolysis.

[0015] The precursor of the tetrabutyl titanate hydrolysis was mixed with a water-ethanol mixed solution and subjected to a hydrolysis reaction to obtain the supported catalyst.

[0016] Preferably, the molar ratio of magnesium powder to iodine is 1:0.1 to 0.5; the molar ratio of magnesium powder to dichloromethane is 1:2 to 4; and the molar ratio of magnesium powder to ethanol is 1:1.5 to 3.

[0017] Preferably, the redox reaction is carried out in a nitrogen atmosphere; the temperature of the redox reaction is 40–60°C; and the time of the redox reaction is 4–8 hours.

[0018] Preferably, the hydrolysis reaction temperature is 60–90°C; the hydrolysis reaction time is 30–45 min.

[0019] This invention provides the application of the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution in the preparation of polyethylene naphthalate.

[0020] This invention provides a method for preparing polyethylene naphthalate, comprising the following steps:

[0021] 2,6-Naphthalenedicarboxylic acid, ethylene glycol, and a supported catalyst are mixed and subjected to esterification and polycondensation reactions sequentially under a protective atmosphere to obtain polyethylene naphthalate; the supported catalyst is the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution.

[0022] Preferably, the temperature of the esterification reaction is 180–230°C; and the pressure of the esterification reaction is 0.8–1.2 MPa.

[0023] Preferably, the temperature of the polycondensation reaction is 270–300°C; the pressure of the polycondensation reaction is 0.2–0.4 MPa; and the time of the polycondensation reaction is 0.5–2 h.

[0024] This invention provides a supported catalyst with a three-dimensional structure. The supported nano-titanium dioxide serves as the active catalytic center, exhibiting polydispersity on the support, allowing for more complete contact with the reactants. Its catalytic activity is particularly pronounced in the polycondensation stage, with the Ti active center showing a high affinity for polyethylene naphthalate (PEN). The presence of Mg in the support also inhibits Ti's catalytic effect on side reactions and suppresses the thermal degradation of chain segments. The supported catalyst provided by this invention not only exhibits good catalytic performance in the esterification stage but also demonstrates excellent polycondensation catalytic performance. The catalyst exhibits good stability, and PEN has a high molecular weight and good color.

[0025] This invention provides a method for preparing polyethylene naphthalate, comprising the following steps: mixing 2,6-naphthalic acid, ethylene glycol, and a supported catalyst, and sequentially carrying out esterification and polycondensation reactions under a protective atmosphere to obtain polyethylene naphthalate. This invention uses 2,6-naphthalic acid and ethylene glycol as monomers and a supported catalyst as the catalyst to achieve the preparation of polyethylene naphthalate under mild conditions. Both the esterification and polycondensation reactions utilize the supported catalyst provided by this invention. Using the supported catalyst provided by this invention to prepare polyethylene naphthalate can effectively reduce the esterification reaction time, lower the polycondensation reaction temperature, reduce raw material loss, and reduce the probability of side reactions in the system. Attached Figure Description

[0026] Figure 1 The image shows a SEM image of the supported catalyst prepared in Example 1. Detailed Implementation

[0027] The present invention provides a supported catalyst comprising a porous ClMg(OC2H5)·C2H5OH support and nano-titanium dioxide supported on the porous ClMg(OC2H5)·C2H5OH support.

[0028] In this invention, the mass of the nano-titanium dioxide is preferably 55-65% of the mass of the porous ClMg(OC2H5)·C2H5OH support, more preferably 60-63%. In this invention, the nano-titanium dioxide is preferably spherical. In this invention, the porous ClMg(OC2H5)·C2H5OH support is preferably spherical; the average pore size of the porous ClMg(OC2H5)·C2H5OH support is preferably 50-100 nm; and the porosity is preferably 0.8-1 cm³. 3 / g.

[0029] This invention provides a method for preparing the supported catalyst described in the above technical solution, comprising the following steps:

[0030] Magnesium powder, iodine, dichloromethane and ethanol are mixed and subjected to a redox reaction to obtain a reaction solution;

[0031] The reaction solution was mixed with n-hexane and crystallized to obtain a porous ClMg(OC2H5)·C2H5OH support;

[0032] The porous ClMg(OC2H5)·C2H5OH support, tetrabutyl titanate, and ethanol were mixed to obtain an ethanol dispersion.

[0033] The ethanol dispersion and the ethanol solution of hydrochloric acid were mixed to obtain the precursor of tetrabutyl titanate hydrolysis.

[0034] The precursor of the tetrabutyl titanate hydrolysis was mixed with a water-ethanol mixed solution and subjected to a hydrolysis reaction to obtain the supported catalyst.

[0035] This invention involves mixing magnesium powder, iodine, dichloromethane, and ethanol, and carrying out a redox reaction to obtain a reaction solution. In this invention, the molar ratio of magnesium powder to iodine is preferably 1:0.1–0.5, more preferably 1:0.2–0.3; the molar ratio of magnesium powder to dichloromethane is preferably 1:2–4, more preferably 1:3; and the molar ratio of magnesium powder to ethanol is preferably 1:1.5–3, more preferably 1:2. In this invention, the iodine is preferably iodine granules.

[0036] In this invention, the mixing of magnesium powder, iodine, dichloromethane and ethanol preferably includes: adding magnesium powder to a reactor under nitrogen protection, then adding iodine and dichloromethane, stirring evenly in the range of 40-60°C, and then adding ethanol dropwise.

[0037] In this invention, the redox reaction is preferably carried out in a nitrogen atmosphere; the temperature of the redox reaction is preferably 40–60°C, more preferably 50°C; and the time of the redox reaction is preferably 4–8 hours, more preferably 6 hours. In this invention, the redox reaction time is calculated from the completion of the dropwise addition of the ethanol. In this invention, the redox reaction is preferably carried out under stirring conditions; the stirring rate is preferably 100–120 r / min.

[0038] In the redox reaction process described in this invention, the reaction is vigorous and generates a large number of bubbles.

[0039] Preferably, after the redox reaction, the solution is cooled to room temperature to obtain a reaction solution. In this invention, the reaction solution is a colorless and transparent solution.

[0040] After obtaining the reaction solution, the present invention mixes the reaction solution with n-hexane and crystallizes the mixture to obtain a porous ClMg(OC2H5)·C2H5OH support. In the present invention, the mixing of the reaction solution and n-hexane preferably includes adding n-hexane to the reaction solution under stirring conditions. In the present invention, the stirring rate is preferably 100–120 r / min.

[0041] In this invention, the mass of the n-hexane is preferably 150-250% of the mass of the reaction solution, more preferably 200%.

[0042] In this invention, the crystallization temperature is preferably 40–50°C; the crystallization is preferably carried out under stirring conditions; and the stirring rate is preferably 100–120 r / min. In this invention, crystals begin to precipitate after hexane is added to the reaction solution, and the crystallization process ends when no more crystals precipitate, after stirring.

[0043] Preferably, after crystallization, the resulting system is sequentially filtered and washed with n-hexane to obtain a porous ClMg(OC2H5)·C2H5OH support.

[0044] In this invention, the porous ClMg(OC2H5)·C2H5OH support is a white crystal.

[0045] After obtaining the porous ClMg(OC2H5)·C2H5OH support, the present invention mixes the porous ClMg(OC2H5)·C2H5OH support with tetrabutyl titanate and ethanol to obtain an ethanol dispersion. In the present invention, the molar ratio of the tetrabutyl titanate to the porous ClMg(OC2H5)·C2H5OH support is preferably 5-25:1, more preferably 10-20:1; the volume ratio of the ethanol to the tetrabutyl titanate is preferably 2-5:1, more preferably 3-4:1.

[0046] In this invention, the mixing preferably includes: adding tetrabutyl titanate to ethanol, stirring until homogeneous, and then adding the porous ClMg(OC2H5)·C2H5OH support for dispersion to obtain an ethanol dispersion.

[0047] After obtaining the ethanol dispersion, the present invention mixes the ethanol dispersion with an ethanol solution of hydrochloric acid to obtain a precursor for the hydrolysis of tetrabutyl titanate. In the present invention, the mixing preferably includes: heating the ethanol dispersion to 60–80°C under stirring conditions and holding at this temperature for 10–30 min; then adding the ethanol solution of hydrochloric acid to adjust the pH of the solution to 3–5, and continuing to hold at this temperature for another 10–30 min to obtain the precursor for the hydrolysis of tetrabutyl titanate.

[0048] In this invention, the hydrochloric acid ethanol solution is preferably obtained by mixing hydrochloric acid solution and ethanol; the mass concentration of the hydrochloric acid solution is preferably 36.5%; the volume ratio of the hydrochloric acid solution to ethanol is preferably 0.5-15:1-20, more preferably 1-10:2-20.

[0049] In this invention, the volume ratio of the ethanol dispersion to the hydrochloric acid ethanol solution is preferably 1 to 10:1, more preferably 2 to 5:1.

[0050] After obtaining the precursor of tetrabutyl titanate hydrolysis, the present invention mixes the precursor of tetrabutyl titanate hydrolysis with a water-ethanol mixed solution to carry out a hydrolysis reaction to obtain the supported catalyst. In the present invention, the volume ratio of water to ethanol in the water-ethanol mixed solution is preferably 4-10:15-40, more preferably 5-8:20-35. In the present invention, the volume ratio of the precursor of tetrabutyl titanate hydrolysis to the water-ethanol mixed solution is preferably 10-30:30-60, more preferably 15-25:40-55.

[0051] In this invention, the temperature of the hydrolysis reaction is preferably 60–90°C, more preferably 70–85°C; the time of the hydrolysis reaction is preferably 30–45 min. In this invention, during the hydrolysis reaction, tetrabutyl titanate hydrolyzes into titanium dioxide under ethanol, water, and acidic conditions.

[0052] Preferably, after the hydrolysis reaction, the obtained product is washed with water and dried sequentially to obtain a supported catalyst. In this invention, the drying temperature is preferably 150–200°C; the drying time is preferably 4–6 hours.

[0053] This invention provides the application of the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution in the preparation of polyethylene naphthalate.

[0054] This invention provides a method for preparing polyethylene naphthalate, comprising the following steps:

[0055] 2,6-Naphthalenedicarboxylic acid, ethylene glycol, and a supported catalyst are mixed and subjected to esterification and polycondensation reactions sequentially under a protective atmosphere to obtain polyethylene naphthalate; the supported catalyst is the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution.

[0056] In this invention, the mass of the supported catalyst is preferably 0.01 to 0.05% of the total mass of 2,6-naphthalenedicarboxylic acid, ethylene glycol, and the supported catalyst, more preferably 0.03 to 0.035%. In this invention, the molar ratio of 2,6-naphthalenedicarboxylic acid and ethylene glycol is preferably 1:2 to 3, more preferably 1:2.2 to 2.5.

[0057] In this invention, the mixing of 2,6-naphthalenedicarboxylic acid, ethylene glycol, and the supported catalyst preferably comprises: adding preheated 2,6-naphthalenedicarboxylic acid and ethylene glycol to a reaction vessel under a protective atmosphere, followed by the addition of the supported catalyst. In this invention, the preheating temperature of the 2,6-naphthalenedicarboxylic acid is preferably 130–140°C; the preheating temperature of the ethylene glycol is preferably 120–130°C. Preheating the raw materials in this invention is to facilitate rapid mixing of the two.

[0058] In this invention, the protective atmosphere is preferably a nitrogen atmosphere.

[0059] In this invention, the preferred temperature for the esterification reaction is 180–230°C, more preferably 210–215°C; the preferred pressure for the esterification reaction is 0.8–1.2 MPa, more preferably 1.0–1.1 MPa. In this invention, the esterification reaction is considered complete when the esterification rate reaches 95% or more of the theoretically calculated value, yielding an oligomer. In this invention, the oligomer obtained from the esterification reaction is used directly as a raw material for the polycondensation reaction without further treatment.

[0060] In this invention, the temperature of the polycondensation reaction is preferably 270–300°C, more preferably 285–290°C; the pressure of the polycondensation reaction is preferably 0.2–0.4 MPa, more preferably 0.3–0.35 MPa; and the time of the polycondensation reaction is preferably 0.5–2 h, more preferably 1–1.5 h. In this invention, the polycondensation reaction is preferably carried out under stirring conditions; the stirring rate is preferably 25–50 r / min.

[0061] In this invention, the oligomer obtained from the esterification reaction is heated to the temperature of the polycondensation reaction, and the polycondensation reaction is carried out under a protective atmosphere with stirring. In this invention, both the esterification reaction and the polycondensation reaction use the supported catalyst provided by this invention as the catalyst.

[0062] Preferably, after the polycondensation reaction, the resulting polymer is extruded and granulated to obtain polyethylene naphthalate.

[0063] In this invention, the intrinsic viscosity of the polyethylene naphthalate is preferably 1.38 to 1.61 dl / g; the color L* (brightness / whiteness) is preferably 79.8 to 81.3, and the color b* (yellowness) is preferably 4.3 to 5.1; the conversion rate of 2,6-naphthalenedicarboxylic acid is preferably 95.47 to 96.71%.

[0064] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0065] (1) The intrinsic viscosity of polyethylene naphthalate was determined according to the national standard GB / T 1632.5-2008; the color was determined according to ASTM D1003.

[0066] (2) The tensile strength and elongation at break of the film prepared by polyethylene naphthalate were determined according to GB / T13022-1991. The sample used in the test was a dumbbell-shaped type III sample.

[0067] Example 1

[0068] 24.3 g of magnesium powder was added to a reactor under nitrogen protection, followed by 76.14 g of I2 and 254.7 g of dichloromethane. The mixture was stirred at 50 °C until homogeneous, and then 92.14 g of ethanol was added dropwise. The reaction was vigorous and produced a large number of bubbles. After the addition was complete, the mixture was stirred at 50 °C for 6 hours to allow the magnesium powder to react completely. The reactants were cooled to room temperature to obtain a colorless and transparent solution. 470 g of n-hexane was added to the solution under stirring, and white crystals precipitated. The mixture was stirred until no more crystals precipitated. The solution was filtered and washed with n-hexane to obtain a porous ClMg(OC2H5)·C2H5OH support.

[0069] 103g of tetrabutyl titanate was added to 276.5g of ethanol and stirred until homogeneous. Then, 2.6g of the porous ClMg(OC2H5)·C2H5OH support was dispersed in the solution to obtain an ethanol dispersion. The mixture was heated to 70℃ under stirring and kept at that temperature for 15min. Then, 150mL of hydrochloric acid in ethanol solution (HCl concentration of 11wt%) was added to adjust the pH of the solution to 4, and the mixture was kept at that temperature for another 15min to obtain the precursor of tetrabutyl titanate hydrolysis. 1200mL of water-ethanol mixed solution (water to ethanol volume ratio of 6:30) was added, and the reaction was continued at 70℃ for 30min to obtain nano-titanium dioxide catalyst supported on the porous ClMg(OC2H5)·C2H5OH support. The catalyst was centrifuged, washed with water, and dried at 150℃ for 6h to obtain the supported catalyst.

[0070] The supported catalyst prepared in this embodiment consists of a porous ClMg(OC2H5)·C2H5OH support and nano-titanium dioxide supported on the porous ClMg(OC2H5)·C2H5OH support; the mass of the nano-titanium dioxide is 60.2% of the mass of the porous ClMg(OC2H5)·C2H5OH support; the nano-titanium dioxide is spherical; the porous ClMg(OC2H5)·C2H5OH support is spherical, the average pore size of the porous ClMg(OC2H5)·C2H5OH support is 80 nm, and the porosity is 0.936 cm⁻¹. 3 / g.

[0071] The SEM image of the supported catalyst prepared in this embodiment is shown below. Figure 1 As shown in the figure, the surface of the support is covered with a layer of small particles, indicating that the porous ClMg(OC2H5)·C2H5OH support is loaded with spherical titanium dioxide.

[0072] Application Example 1

[0073] 1) Esterification reaction: 2,6-naphthalenedicarboxylic acid preheated to 130°C and ethylene glycol preheated to 120°C were added to the reactor in a molar ratio of 1:2 under a nitrogen atmosphere. Then, the supported catalyst prepared in Example 1 (the mass of the supported catalyst was 0.01% of the total mass of 2,6-naphthalenedicarboxylic acid, ethylene glycol and the supported catalyst) was added. The pressure of the esterification reaction was 0.8 MPa and the temperature of the esterification reaction was 180°C. When the esterification rate reached more than 95% of the theoretically calculated value, the esterification reaction was confirmed to be over, and oligomers were obtained.

[0074] 2) Polycondensation reaction: The oligomer is heated to 270°C and stirred under a nitrogen atmosphere at a stirring rate of 50 r / min. The pressure of the polycondensation reaction is 0.2 MPa and the reaction time is 0.5 h. The resulting polymer is extruded and granulated to obtain polyethylene naphthalate.

[0075] The intrinsic viscosity of polyethylene naphthalate is 1.38 dl / g; the color L* (brightness / whiteness) is 79.8, and the color b* (yellowness) is 5.1; the conversion rate of 2,6-naphthalenedicarboxylic acid is 95.47%.

[0076] The film prepared from this polyethylene naphthalate has a tensile strength of 73.8 MPa and an elongation at break of 265%.

[0077] Application Example 2

[0078] 1) Esterification reaction: 2,6-naphthalenedicarboxylic acid preheated to 140°C and ethylene glycol preheated to 130°C were added to the reactor in a molar ratio of 1:3 under a nitrogen atmosphere. Then, the supported catalyst prepared in Example 1 (the mass of the supported catalyst was 0.05% of the total mass of 2,6-naphthalenedicarboxylic acid, ethylene glycol and the supported catalyst) was added. The pressure of the esterification reaction was 1.2 MPa and the temperature of the esterification reaction was 230°C. When the esterification rate reached more than 95% of the theoretically calculated value, the esterification reaction was confirmed to be over, and oligomers were obtained.

[0079] 2) Polycondensation reaction: The oligomer is heated to 300°C and stirred under a nitrogen atmosphere at a stirring rate of 25 r / min. The pressure of the polycondensation reaction is 0.4 MPa and the reaction time is 2 h. The resulting polymer is extruded and granulated to obtain polyethylene naphthalate.

[0080] The intrinsic viscosity of polyethylene naphthalate is 1.42 dl / g; the color L* (brightness / whiteness) is 80.1, and b* (yellowness) is 4.9; the conversion rate of 2,6-naphthalenedicarboxylic acid is 96.09%.

[0081] The film prepared from this polyethylene naphthalate has a tensile strength of 73.9 MPa and an elongation at break of 273%.

[0082] Application Example 3

[0083] 1) Esterification reaction: 2,6-naphthalenedicarboxylic acid preheated to 133°C and ethylene glycol preheated to 122°C were added to the reactor in a molar ratio of 1:2.5 under a nitrogen atmosphere. Then, the supported catalyst prepared in Example 1 (the mass of the supported catalyst was 0.03% of the total mass of 2,6-naphthalenedicarboxylic acid, ethylene glycol and the supported catalyst) was added. The pressure of the esterification reaction was 1.0 MPa and the temperature of the esterification reaction was 210°C. When the esterification rate reached more than 95% of the theoretically calculated value, the esterification reaction was confirmed to be over, and oligomers were obtained.

[0084] 2) Polycondensation reaction: The oligomer is heated to 285°C and stirred under a nitrogen atmosphere at a stirring rate of 30 r / min. The pressure of the polycondensation reaction is 0.3 MPa and the reaction time is 1.5 h. The resulting polymer is extruded and granulated to obtain polyethylene naphthalate.

[0085] The intrinsic viscosity of polyethylene naphthalate is 1.56 dl / g; the color L* (brightness / whiteness) is 81.2, and b* (yellowness) is 4.5; the conversion rate of 2,6-naphthalenedicarboxylic acid is 96.71%.

[0086] The film prepared from this polyethylene naphthalate has a tensile strength of 74.7 MPa and an elongation at break of 289%.

[0087] Application Example 4

[0088] 1) Esterification reaction: 2,6-naphthalenedicarboxylic acid preheated to 137°C and ethylene glycol preheated to 125°C were added to the reactor in a molar ratio of 1:2.2 under a nitrogen atmosphere. Then, the supported catalyst prepared in Example 1 (the mass of the supported catalyst was 0.035% of the total mass of 2,6-naphthalenedicarboxylic acid, ethylene glycol and the supported catalyst) was added. The pressure of the esterification reaction was 1.1 MPa and the temperature of the esterification reaction was 215°C. When the esterification rate reached more than 95% of the theoretically calculated value, the esterification reaction was confirmed to be over, and oligomers were obtained.

[0089] 2) Polycondensation reaction: The oligomer is heated to 290°C and stirred under a nitrogen atmosphere at a stirring rate of 35 r / min. The pressure of the polycondensation reaction is 0.35 MPa and the reaction time is 1 h. The resulting polymer is extruded and granulated to obtain polyethylene naphthalate.

[0090] The intrinsic viscosity of polyethylene naphthalate is 1.61 dl / g; the color L* (brightness / whiteness) is 81.3, and b* (yellowness) is 4.3; the conversion rate of 2,6-naphthalenedicarboxylic acid is 96.68%.

[0091] The film prepared from this polyethylene naphthalate has a tensile strength of 74.3 MPa and an elongation at break of 293%.

[0092] The results of the above examples demonstrate that the nano-titanium dioxide catalyst supported on the porous ClMg(OC2H5)·C2H5OH support exhibits excellent catalytic performance, not only in the esterification stage but also in the polycondensation stage. Polyethylene naphthalate can be prepared through a two-step reaction of esterification and polycondensation, yielding a polyester with high viscosity, good color, and good mechanical properties.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A supported catalyst, characterized in that, The invention comprises a porous ClMg(OC2H5)·C2H5OH support and nano-titanium dioxide supported on the porous ClMg(OC2H5)·C2H5OH support; the mass of the nano-titanium dioxide is 55-65% of the mass of the porous ClMg(OC2H5)·C2H5OH support. The preparation method of the supported catalyst includes the following steps: Magnesium powder, iodine, dichloromethane and ethanol are mixed and subjected to a redox reaction to obtain a reaction solution; The reaction solution was mixed with n-hexane and crystallized to obtain a porous ClMg(OC2H5)·C2H5OH support; The porous ClMg(OC2H5)·C2H5OH support, tetrabutyl titanate, and ethanol were mixed to obtain an ethanol dispersion. The ethanol dispersion and the ethanol solution of hydrochloric acid were mixed to obtain the precursor of tetrabutyl titanate hydrolysis. The precursor of the tetrabutyl titanate hydrolysis and a water-ethanol mixed solution are mixed and subjected to hydrolysis to obtain the supported catalyst; the hydrolysis reaction temperature is 60~90℃.

2. The method for preparing the supported catalyst according to claim 1, comprising the following steps: Magnesium powder, iodine, dichloromethane and ethanol are mixed and subjected to a redox reaction to obtain a reaction solution; The reaction solution was mixed with n-hexane and crystallized to obtain a porous ClMg(OC2H5)·C2H5OH support; The porous ClMg(OC2H5)·C2H5OH support, tetrabutyl titanate, and ethanol were mixed to obtain an ethanol dispersion. The ethanol dispersion and the ethanol solution of hydrochloric acid were mixed to obtain the precursor of tetrabutyl titanate hydrolysis. The precursor of the tetrabutyl titanate hydrolysis and a water-ethanol mixed solution are mixed and subjected to hydrolysis to obtain the supported catalyst; the hydrolysis reaction temperature is 60~90℃.

3. The preparation method according to claim 2, characterized in that, The molar ratio of magnesium powder to iodine is 1:0.1~0.5; the molar ratio of magnesium powder to dichloromethane is 1:2~4; and the molar ratio of magnesium powder to ethanol is 1:1.5~3.

4. The preparation method according to claim 2, characterized in that, The redox reaction is carried out in a nitrogen atmosphere; the temperature of the redox reaction is 40~60℃; and the time of the redox reaction is 4~8h.

5. The preparation method according to claim 2, characterized in that, The hydrolysis reaction takes 30-45 minutes.

6. The use of the supported catalyst according to claim 1 or the supported catalyst prepared by any one of claims 2 to 5 in the preparation of polyethylene naphthalate.

7. A method for preparing polyethylene naphthalate, characterized in that, Includes the following steps: 2,6-Naphthalenedicarboxylic acid, ethylene glycol, and a supported catalyst are mixed and subjected to esterification and polycondensation reactions sequentially under a protective atmosphere to obtain polyethylene naphthalate; the supported catalyst is the supported catalyst according to claim 1 or the supported catalyst prepared by any one of claims 2 to 5; the temperature of the esterification reaction is 180-230°C; the temperature of the polycondensation reaction is 270-300°C.

8. The preparation method according to claim 7, characterized in that, The pressure of the esterification reaction is 0.8~1.2 MPa.

9. The preparation method according to claim 7, characterized in that, The pressure of the polycondensation reaction is 0.2~0.4 MPa; the time of the polycondensation reaction is 0.5~2 h.

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