Titanium-containing catalyst and preparation method thereof as well as depolymerization and preparation method of polyethylene furandicarboxylate

Abstract

The invention relates to the technical field of chemical degradation of polyester, and discloses a titanium-containing catalyst, a preparation method of the titanium-containing catalyst, and a depolymerization and preparation method of polyethylene furandicarboxylate. The titanium-containing catalyst comprises dihydric alcohol titanium, particles of the titanium-containing catalyst are in a sphere-like shape, the particles of the titanium-containing catalyst are formed by stacking nanorod-shaped crystal grains, and the diameter of the nanorod-shaped crystal grains is 100-600 nm; based on the total weight of the titanium-containing catalyst, the content of Ti is 21-30 wt%. The titanium-containing catalyst disclosed by the invention has a relatively small particle size, and has a relatively high depolymerization rate when being used for depolymerizing polyethylene furandicarboxylate, and the selectivity of 2, 5-furandicarboxylate bis (2-ethoxyl) ester is relatively high. The titanium-containing catalyst provided by the invention has no obvious harm to the environment and human body, and is an efficient green environment-friendly catalyst.

Description

Technical Field

[0001] This invention relates to the field of chemical degradation technology for waste polyester, specifically to a titanium-containing catalyst and its preparation method, and a method for depolymerizing and preparing polyethylene furanate. Background Technology

[0002] Polyethylene furanate (PEF) is a promising bio-based polyester product. Its reactive monomer, furanate, is a bio-based aromatic monomer with a structure and chemical properties very similar to the petroleum-based monomer terephthalic acid. This gives PEF high rigidity, high heat resistance, excellent mechanical properties, and chemical stability. At the same time, due to the presence of furan rings on the main chain, PEF exhibits a spirocyclic nonlinear structure, giving it excellent gas barrier properties (13-19 times and 6-11 times that of polyethylene terephthalate (PET) in terms of gas barrier properties against carbon dioxide and oxygen, respectively). It has certain advantages in the fields of fibers, food packaging films, and bottles.

[0003] PEF, as a promising bio-based aromatic polyester material, is used in beer packaging by Carlsberg Group due to its stable chemical properties and excellent gas barrier properties. Avantium has also reported on the use of PEF in the packaging of alcoholic beverages and soft drinks.

[0004] Due to its superior performance, PEF's monomer, furanyl dicarboxylic acid, is a bio-based monomer and is likely to become an ideal substitute for polyesters such as PET in the future. However, like PET, PEF is chemically stable and will not undergo effective natural or biodegradation for a long time. The accumulation of waste PEF products after its commercial application will harm the ecological environment and human health. Therefore, the effective recycling and reuse of waste PEF products is of great significance.

[0005] Therefore, in order to solve the above-mentioned problems, the present invention provides a catalyst and alcoholysis method for the alcoholysis of PEF polyester. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a titanium-containing catalyst, its preparation method, and a method for depolymerizing and preparing polyethylene furanate (PEF). The catalyst provided by this invention is inexpensive, simple to prepare, and exhibits high catalytic activity and selectivity. Furthermore, using this catalyst enables the depolymerization of PEF under mild conditions, is easy to implement, and results in low catalyst residue in the depolymerization products. The depolymerization reaction is pollution-free, and both the monomers and solvents obtained from the depolymerization process can be reused.

[0007] To achieve the above objectives, a first aspect of the present invention provides a titanium-containing catalyst comprising titanium diol, wherein the particles of the titanium-containing catalyst are spherical in shape and are formed by the stacking of nanorod-shaped grains, wherein the diameter of the nanorod-shaped grains is 100-600 nm; and the content of Ti is 21-30% by weight based on the total weight of the titanium-containing catalyst.

[0008] The second aspect of the present invention provides a method for preparing a titanium-containing catalyst, the method comprising: adding a diol dropwise to a solution of a titanium-containing precursor, heating to 70-100°C after the addition is completed to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein, the dropping rate of the diol is 6-8 mL / min relative to 10 g of titanium precursor.

[0009] Alternatively, the method may include: adding a solution containing a titanium precursor dropwise to a diol, heating to 70-100°C after the addition is complete to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein the dropping rate of the solution containing the titanium precursor is 6-10 mL / min relative to 10 g of diol.

[0010] A third aspect of the present invention provides a titanium-containing catalyst prepared by the method described above.

[0011] The fourth aspect of the present invention provides a method for depolymerizing polyethylene furanate, the method comprising: under an inactive atmosphere, in the presence of a first catalyst and a diol, causing polyethylene furanate to undergo an alcoholysis reaction to obtain an alcoholysis reaction solution containing bis(2-hydroxyethyl) furanate, wherein the first catalyst is the titanium-containing catalyst described in the first aspect or the third aspect.

[0012] The fifth aspect of the present invention provides bis(2-hydroxyethyl) furanyldicarboxylate prepared by the method described in the fourth aspect.

[0013] The sixth aspect of the present invention provides a method for preparing polyethylene furanyl dicarboxylate, the method comprising carrying out a polycondensation reaction of bis(2-hydroxyethyl) furanyl dicarboxylate under an inactive atmosphere in the presence of a second catalyst; wherein the bis(2-hydroxyethyl) furanyl dicarboxylate is the bis(2-hydroxyethyl) furanyl dicarboxylate described in the fifth aspect.

[0014] Through the above technical solution, the present invention achieves the following beneficial effects:

[0015] (1) The titanium-containing catalyst of the present invention has a small particle size, exhibits a high depolymerization rate when used for the depolymerization of polyethylene furanyl dicarboxylate, and has high selectivity for bis(2-hydroxyethyl) furanyl dicarboxylate (BHEF). The titanium-containing catalyst of the present invention has no significant harm to the environment and human body, and is a highly efficient, green and environmentally friendly catalyst.

[0016] (2) The catalyst preparation method of the present invention is simple, the catalyst is inexpensive and readily available, the depolymerization conditions are mild, and the process is easy to implement. The monomers of the depolymerization product obtained by the method of the present invention can be directly used to prepare PEF polyester or copolymer products containing its structural units, realizing the closed-loop recycling of waste PEF.

[0017] (3) The catalyst of the present invention has low solubility in ethylene glycol, which can reduce the residue of the catalyst in the depolymerization liquid and reduce the influence of the residual catalyst on the polymerization performance of the depolymerized monomer. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the titanium-containing catalyst prepared in Example 1 at 50,000x magnification;

[0019] Figure 2 This is a scanning electron microscope image of the titanium-containing catalyst prepared in Example 1 at 5000x magnification;

[0020] Figure 3 This is a scanning electron microscope image of the titanium-containing catalyst prepared in Example 1 at 80,000x magnification;

[0021] Figure 4 This is the 1H NMR spectrum of the target product prepared in Example 1. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] The first aspect of the present invention provides a titanium-containing catalyst, which comprises titanium diol (preferably titanium ethylene glycol), wherein the particles of the titanium-containing catalyst are in a spherical shape, and the particles of the titanium-containing catalyst are formed by the stacking of nanorod-shaped grains, wherein the diameter of the nanorod-shaped grains is 100-600 nm; preferably 200-300 nm; and the Ti content is 21-30% by weight based on the total weight of the titanium-containing catalyst.

[0024] According to the present invention, preferably, the length of the nanorod-shaped crystals is 0.5-8 μm; more preferably, it is 1.5-3 μm.

[0025] The inventors of this invention have discovered that using the catalyst of this invention, which has a smaller particle size and a higher titanium content, can improve the catalytic activity and product conversion rate. The catalyst of this invention exhibits a high depolymerization rate when used for the depolymerization of polyethylene furanyl dicarboxylate, and also shows high selectivity for bis(2-hydroxyethyl) furanyl dicarboxylate (BHEF).

[0026] According to the present invention, preferably, the median particle size (D50) of the titanium-containing catalyst is 1-500 μm; more preferably, 1-300 μm, and even more preferably, 1-100 μm. Limiting the particle size of the titanium-containing catalyst to the above range can further improve the selectivity of BHEF.

[0027] The inventors of this invention have further discovered that the catalyst of this invention has low solubility in ethylene glycol, thus resulting in a low amount of catalyst residue in the depolymerization product and reducing the impact of residual catalyst on the polymerization performance of the depolymerized monomer. Preferably, at 20°C, the solubility of the titanium-containing catalyst in ethylene glycol is <50 mg / L, more preferably <30 mg / L, and even more preferably <10 mg / L.

[0028] The second aspect of the present invention provides a method for preparing a titanium-containing catalyst, the method comprising: adding a diol dropwise to a solution of a titanium-containing precursor, heating to 70-100°C after the addition is completed to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein, the dropping rate of the diol is 6-8 mL / min relative to 10 g of titanium precursor.

[0029] Alternatively, the method may include: adding a solution containing a titanium precursor dropwise to a diol, heating to 70-100°C after the addition is complete to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein the dropping rate of the solution containing the titanium precursor is 6-10 mL / min relative to 10 g of diol.

[0030] The inventors of this invention have discovered that by controlling the dropping rate of a solution containing a diol or titanium-containing precursor, a titanium-containing catalyst with a smaller particle size can be prepared, thereby improving the catalytic activity and product conversion rate. The catalyst prepared by the method of this invention exhibits a high depolymerization rate when used for the depolymerization of polyethylene furanyl dicarboxylate, and the depolymerization product, bis(2-hydroxyethyl) furanyl dicarboxylate (BHEF), shows high selectivity.

[0031] According to the present invention, preferably, the dropwise addition is carried out at 20-50°C. "The dropwise addition is carried out at 20-50°C" means controlling the temperature of the titanium-containing precursor solution at 20-50°C, and then adding the diol dropwise into it. Typically, the titanium-containing precursor solution is stirred simultaneously during the dropwise addition process.

[0032] According to the present invention, preferably, the diol is a C2-C10 diol (e.g., a C2-C4 diol), more preferably at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol and 1,2-butanediol.

[0033] According to the present invention, the titanium precursor can be an organotitanium compound commonly used in the art. Preferably, the titanium precursor includes at least one of alkyl titanate, titanium acetylacetone oxide, and diisopropyl titanate (acetylacetone). More preferably, the alkyl titanate is a C2-C8 alkyl titanate. Even more preferably, the alkyl titanate includes at least one of tetraisopropyl titanate, tetrabutyl titanate, and tetraethyl titanate.

[0034] According to the present invention, the amounts of the titanium precursor and the diol can be selected in a wide range. In order to promote the transesterification reaction of the titanium precursor and make the transesterification reaction more complete, preferably, the amount of the diol is 4-7.5 mol relative to 1 mol of titanium precursor.

[0035] According to the present invention, preferably, the transesterification reaction takes 1-4 hours.

[0036] According to the present invention, preferably, the temperature of the transesterification reaction is reached at a heating rate of 4-6 °C / min.

[0037] According to the present invention, the solvent can be a commonly used organic solvent, but in order to better dissolve and disperse the titanium precursor, preferably, the solvent in the solution containing the titanium precursor is at least one of petroleum ether, isopropanol, cyclohexane, toluene, tetrahydrofuran, chloroform, dichloromethane, xylene and N,N-dimethylformamide.

[0038] According to the present invention, in order to promote the transesterification reaction between the titanium precursor and the diol, preferably, the amount of solvent used is 30-200 mL relative to 10 g of titanium precursor.

[0039] A third aspect of the present invention provides a titanium-containing catalyst prepared by the method described above.

[0040] The fourth aspect of the present invention provides a method for depolymerizing polyethylene furanate, the method comprising: under an inactive atmosphere, in the presence of a first catalyst and a diol, causing polyethylene furanate to undergo an alcoholysis reaction to obtain an alcoholysis reaction solution containing bis(2-hydroxyethyl) furanate, wherein the first catalyst is the titanium-containing catalyst described in the first aspect or the third aspect.

[0041] In this invention, polyethylene furanate dicarboxylate can be alcoholyzed under the action of a titanium-containing catalyst to obtain bis(2-hydroxyethyl) furanate dicarboxylate and its dimers and trimers. Among them, bis(2-hydroxyethyl) furanate dicarboxylate can be repolymerized under the action of a polycondensation catalyst (e.g., antimony glycol ethylene glycol) to prepare polyethylene furanate dicarboxylate, thereby realizing the closed-loop recycling of PEF.

[0042] According to the present invention, the type of inactive atmosphere is not particularly limited, for example, it can be an inert gas or nitrogen, and preferably, the inactive atmosphere is a nitrogen atmosphere.

[0043] According to the present invention, preferably, the amount of the first catalyst is 0.05-0.5 wt% of polyethylene furanate, more preferably 0.1-0.4 wt%.

[0044] According to the present invention, preferably, the weight ratio of the polyethylene furanate to the diol is 1:3-7, more preferably 1:3-5.

[0045] According to the present invention, preferably, the diol is a C2-C10 diol, more preferably at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol and 1,2-butanediol.

[0046] The method of the present invention allows the depolymerization reaction to be carried out under milder conditions. Preferably, the temperature of the alcoholysis reaction is 190-250°C, more preferably 190-220°C.

[0047] According to the present invention, preferably, the pressure of the alcoholysis reaction is 0.2-0.6 MPa, more preferably 0.35-0.5 MPa. In the present invention, unless otherwise specified, the pressure is gauge pressure.

[0048] According to the present invention, preferably, the alcoholysis reaction time is 2-6 hours, more preferably 2-5 hours.

[0049] According to the present invention, in order to remove impurities and utilize the BHEF monomer in the alcoholysis reaction solution for polycondensation, the method further includes a step of extracting BHEF from the alcoholysis reaction solution. Since waste PEF may contain other polymers (e.g., polyethylene, polypropylene, etc.) or inorganic additives, in order to remove these insoluble substances, before extracting BHEF, the alcoholysis reaction solution is cooled to 100-120°C to remove the insoluble substances while hot; then recrystallization is performed to extract BHEF. The insoluble substances may also be other polymers or inorganic additives. Preferably, the method for extracting BHEF includes: cooling the alcoholysis reaction solution to 100-120°C and filtering it; directly adding the filtrate to deionized ice water at 0-4°C and placing it in an environment at 0-4°C; after the reaction solution has fully cooled and crystallized, filtering and drying (drying temperature is 50-80°C, drying time is 2-8h) to obtain a high-purity bis(2-hydroxyethyl) 2,5-furandicarboxylic acid product. The method for extracting BHEF in this invention involves first cooling the alcoholysis reaction solution to 100-120℃ and filtering to remove impurities. Then, the filtrate is directly added to ice water at 0-4℃ and cooled to a low temperature (0-4℃), which can improve the yield of BHEF and achieve full recycling of BHEF.

[0050] According to the present invention, in order to further improve the yield of BHEF, preferably, the volume ratio of the filtrate to water is 1:1-4, more preferably 1:1-3, and even more preferably 1:2-2.5.

[0051] According to the present invention, the placement time in an environment of 0-4℃ can be selected within a wide range. In order to improve the yield of BHEF and taking into account the extraction efficiency, it is preferable that the placement (standing) time in an environment of 0-4℃ is 4-24h.

[0052] In this invention, the depolymerized PEF is laboratory-prepared PEF, and the preparation method of the PEF is similar to the method for preparing polyethylene furanate dicarboxylate described in aspect six below. The number-average molecular weight of the depolymerized PEF can be (1-9)×10⁻⁶. 4 g / mol.

[0053] The fifth aspect of the present invention provides bis(2-hydroxyethyl) furanyldicarboxylate prepared by the method described in the fourth aspect.

[0054] The sixth aspect of the present invention provides a method for preparing polyethylene furanyl dicarboxylate, the method comprising carrying out a polycondensation reaction of bis(2-hydroxyethyl) furanyl dicarboxylate under an inactive atmosphere in the presence of a second catalyst; wherein the bis(2-hydroxyethyl) furanyl dicarboxylate is the bis(2-hydroxyethyl) furanyl dicarboxylate described in the fifth aspect.

[0055] According to the present invention, the type of inactive atmosphere is not particularly limited, for example, it can be an inert gas or nitrogen, and preferably, the inactive atmosphere is a nitrogen atmosphere.

[0056] According to the present invention, preferably, the second catalyst is at least one selected from antimony acetate, antimony glycolate, germanium dioxide, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, and titanium glycolate.

[0057] According to the present invention, preferably, the amount of the second catalyst is 0.001-0.8 wt% of bis(2-hydroxyethyl) furanyldicarboxylate, more preferably 0.01-0.6 wt%.

[0058] According to the present invention, preferably, the polycondensation reaction includes subjecting bis(2-hydroxyethyl) furanyl dicarboxylate to a first polycondensation reaction and a second polycondensation reaction in sequence, wherein the conditions for the first polycondensation reaction include: a reaction temperature of 190-220°C, an absolute pressure under vacuum of 1000-5000 Pa, and a reaction time of 1-3 h; the conditions for the second polycondensation reaction include: a reaction temperature of 210-240°C, an absolute pressure under vacuum ≤300 Pa, preferably ≤90 Pa, more preferably ≤50 Pa, and a reaction time of 0.5-3 h.

[0059] According to a particularly preferred embodiment of the present invention, a method for preparing a titanium-containing catalyst includes: dissolving 10-10.5 g of tetrabutyl titanate and 30-35 mL of isopropanol by stirring to obtain a solution of a titanium-containing precursor; slowly adding 13.2-13.5 g of ethylene glycol dropwise to the titanium-containing precursor solution at 45-50°C with stirring, wherein the ethylene glycol dropping rate is 6.5-7 mL / min relative to 10 g of tetrabutyl titanate. After the addition is complete, the temperature is increased to 85-90°C at a heating rate of 5-6°C / min, stirred for 3-3.2 h, heating is stopped, the mixture is cooled to room temperature, filtered, washed with ethanol, and vacuum dried to obtain the titanium-containing catalyst.

[0060] According to a particularly preferred embodiment of the present invention, the depolymerization method of polyethylene furanate includes: adding PEF, ethylene glycol, and a titanium-containing catalyst to a reaction vessel, wherein the weight ratio of PEF to ethylene glycol is 1:4.5-5 (preferably 1:4.8-5), and the amount of titanium-containing catalyst is 0.3-0.4 wt% (preferably 0.35-0.4 wt%) of polyethylene furanate. After purging the air in the vessel with nitrogen, a certain amount of nitrogen is introduced to maintain the pressure in the reaction vessel at 0.4-0.5 MPa, stirring is started, and the alcoholysis reaction is carried out at 190-200℃ (preferably 190-195℃) for 3-4 hours to obtain an alcoholysis reaction solution. The alcoholysis reaction solution is cooled to 100-110℃, and then the insoluble matter is filtered off while hot to obtain a filtrate. The filtrate was then added directly to deionized ice water at 0-4℃, with the filtrate and deionized ice water mixed at a volume ratio of 1:2-2.5. The mixture was then placed in an environment of 0-4℃ for 20-24 hours to precipitate the product. The precipitate was obtained by filtration and then dried in a drying oven at 70-80℃ for 7-8 hours to obtain the target product bis(2-hydroxyethyl) furanyl dicarboxylate (BHEF).

[0061] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0062] Antimony glycol is a commercially available product from McLean Company with a purity of 97%.

[0063] Preparation Example 1

[0064] 10 g of tetrabutyl titanate and 30 mL of isopropanol were dissolved by stirring to obtain a titanium-containing precursor solution. Ethylene glycol (13.2 g) was slowly added dropwise to the titanium-containing precursor solution at 50 °C with stirring. The ethylene glycol dropping rate was 7 mL / min relative to 10 g of tetrabutyl titanate. After the addition was complete, the temperature was increased to 90 °C at a rate of 5 °C / min, and stirred for 3 h. Heating was then stopped, and the mixture was cooled to room temperature, filtered, washed with ethanol, and vacuum dried to obtain titanium-containing catalyst A1.

[0065] Scanning electron microscope image of titanium-containing catalyst A1 is shown below Figure 1-3 As shown, by Figure 1-3 It can be seen that the catalyst particles are spherical in shape, and the spherical particles are formed by the accumulation of nanorod-shaped crystals.

[0066] Preparation Example 2

[0067] A titanium-containing precursor solution was prepared by dissolving 10 g of diisopropyl di(acetylacetone)titanate in 50 mL of toluene under stirring. Ethylene glycol (10.3 g) was then slowly added dropwise to the titanium-containing precursor solution at 40 °C with stirring. The dropping rate of ethylene glycol was 6 mL / min relative to 10 g of diisopropyl di(acetylacetone)titanate. After the addition was complete, the temperature was increased to 80 °C at a rate of 5 °C / min, and stirred for 2.5 h. Heating was then stopped, and the solution was cooled to room temperature, filtered, washed with methanol, and vacuum dried to obtain titanium-containing catalyst A2.

[0068] Preparation Example 3

[0069] A solution of titanium-containing precursor was prepared by dissolving 10 g of titanium acetylacetone oxide in 40 mL of cyclohexane under stirring. Ethylene glycol (14.3 g) was then slowly added dropwise to the titanium-containing precursor solution at 30 °C with stirring. The dropping rate of ethylene glycol was 6 mL / min relative to 10 g of titanium acetylacetone oxide. After the addition was complete, the temperature was increased to 75 °C at a rate of 5 °C / min, and stirred for 3.5 h. Heating was then stopped, and the solution was cooled to room temperature, filtered, washed with methanol, and dried under vacuum to obtain titanium-containing catalyst A3.

[0070] Preparation Example 4

[0071] A titanium-containing precursor solution was prepared by dissolving 10 g of isopropyl titanate, 30 mL of tetrahydrofuran, and 10 mL of toluene under stirring. Ethylene glycol (10.9 g) was then slowly added dropwise to the titanium-containing precursor solution at 25 °C with stirring. The dropping rate of ethylene glycol was 6 mL / min relative to 10 g of isopropyl titanate. After the addition was complete, the temperature was slowly increased to 70 °C at a rate of 5 °C / min. Heating was stopped after 4 h, and the solution was cooled to room temperature, filtered, washed with methanol, and dried under vacuum to obtain titanium-containing catalyst A4.

[0072] Preparation Example 5

[0073] The preparation method was followed as in Example 1, except that a solution containing a titanium precursor was added dropwise to ethylene glycol at a rate of 10 mL / min relative to 10 g of glycol. The resulting catalyst was designated as titanium-containing catalyst A5.

[0074] Comparative Preparation Example 1

[0075] The preparation was carried out according to the method of Example 1, except that the dropping rate of ethylene glycol was 10 mL / min relative to 10 g of titanium-containing precursor. The resulting catalyst was designated as titanium-containing catalyst DA1.

[0076] Comparative Preparation Example 2

[0077] The preparation method was followed as in Example 1, except that after the dropwise addition was completed, the temperature was increased to 95°C at a rate of 10°C / min, and the mixture was stirred for 2 hours before heating was stopped. The resulting catalyst was designated as titanium-containing catalyst DA2.

[0078] Test Example 1

[0079] The titanium content, particle size, and solubility in ethylene glycol of the catalyst prepared above were tested.

[0080] (1) The method for testing the titanium content in the titanium-containing catalyst was as follows: ICP-OES was performed using a Zetium X-ray fluorescence spectrometer from Panaco GmbH, Netherlands. The elemental testing conditions are shown in Table 1. The test results are shown in Table 2.

[0081] Table 1

[0082] element Spectral lines crystals Pulse height detector Voltage / KV Current / mA Test time / s Ti KA LiF200 25-75 Flow 25 100 43.75

[0083] (2) The method for testing the diameter and length of the nanorod-shaped grains was as follows: The microstructure of the samples was observed using a Hitachi S-4800 high-resolution cold field emission scanning electron microscope. Then, 50 nanorod-shaped grains were randomly selected to calculate the average diameter and average length, which were taken as the diameter and length of the nanorod-shaped grains, respectively. The test results are shown in Table 2.

[0084] (3) The test method for the median particle size (D50) of the titanium-containing catalyst is as follows: the catalyst powder is dispersed in water at a concentration of 0.2M, and stirred at a certain speed to disperse it evenly. The resulting dispersion has good dispersion stability and no visible precipitation. Then, a laser particle size analyzer is used for testing. The test results are shown in Table 2.

[0085] (4) The method for testing the solubility of titanium-containing catalysts is as follows: At 20℃, a certain amount of solvent (ethylene glycol, denoted as V) is measured and placed in a beaker. A certain mass of catalyst (ensuring complete dissolution) is weighed and denoted as m1. The catalyst is added to the solvent in small amounts multiple times, so that the solution gradually approaches saturation. Then, the mass of undissolved catalyst is weighed and denoted as m2. If there is undissolved catalyst in the solution, it needs to be filtered, dried, and included in the mass of undissolved catalyst. Then, the solubility is calculated. The calculation formula is: (m1-m2) / V. The test results are shown in Table 2.

[0086] Table 2

[0087]

[0088] Example 1

[0089] PEF, ethylene glycol, and titanium-containing catalyst A1 were added to a reactor, with the weight ratio of PEF to ethylene glycol being 1:4.5, and the amount of titanium-containing catalyst A1 being 0.3 wt% of poly(ethylene furanate dicarboxylate). After purging the air in the reactor with nitrogen, a certain amount of nitrogen was introduced to maintain the pressure inside the reactor at 0.4 MPa. Stirring was started, and the alcoholysis reaction was carried out at 200℃ for 3 hours to obtain the alcoholysis reaction solution. The depolymerization rate of the alcoholysis reaction is shown in Table 3.

[0090] The alcoholysis reaction solution was cooled to 100°C, and then the insoluble matter was filtered off while hot to obtain a filtrate. The filtrate was then directly added to deionized ice water at 0-4°C, with the filtrate and deionized ice water mixed at a volume ratio of 1:2. The mixture was then refrigerated at 0-4°C for 24 hours to precipitate. The precipitate was filtered to obtain the precipitate, and then dried in a drying oven at 70°C for 8 hours to obtain the target product, bis(2-hydroxyethyl) furanyldicarboxylate (BHEF).

[0091] The proton NMR spectrum of the target product is shown below. Figure 4 As shown, analysis revealed that the target product was BHEF. The NMR test method was as follows: the instrument was an Agilent DD2 600MHz NMR spectrometer, the solvent was deuterated DMSO (dimethyl sulfoxide) at a concentration of approximately 30 mg / mL, the test temperature was room temperature, a 45° pulse was used, and the cycle delay time was 10 s.

[0092] The yield and purity of BHEF are shown in Table 2.

[0093] The formula for calculating the depolymerization rate in an alcoholysis reaction is:

[0094]

[0095] The formula for calculating the yield of BHEF is:

[0096]

[0097] The purity of BHEF was tested using a Waters 2695 HPLC system with a PDA detector to directly determine the sample purity.

[0098] The method for testing the residual amount of catalyst in the target product is as follows: the Agilent ICP-OES 720 inductively coupled plasma atomic emission spectrometer is used for testing.

[0099] Examples 2-4

[0100] The procedure was carried out according to Example 1, except that titanium catalyst A1 was replaced with titanium catalyst A2, titanium catalyst A3, and titanium catalyst A4 in sequence, while the amount of catalyst remained the same.

[0101] Example 5

[0102] The method was carried out according to Example 1, except that the weight ratio of PEF to ethylene glycol was 1:5, the amount of titanium-containing catalyst A1 was 0.4 wt% of polyethylene furanate, and the alcoholysis reaction temperature was 190°C.

[0103] Example 6

[0104] The procedure was carried out according to Example 1, except that the weight ratio of PEF to ethylene glycol was 1:3, and the amount of titanium-containing catalyst A1 was 0.2 wt% of polyethylene furanate.

[0105] Example 7

[0106] The procedure was carried out according to Example 1, except that the weight ratio of PEF to ethylene glycol was 1:4, the pressure was 0.35 MPa, and the reaction time was 4 h.

[0107] Example 8

[0108] The procedure was carried out according to Example 1, except that “0-4℃ deionized ice water” was replaced with “40℃ deionized water”.

[0109] Example 9

[0110] The method was carried out according to Example 1, except that the filtrate was mixed with deionized ice water at a volume ratio of 1:4.

[0111] Example 10

[0112] The procedure was carried out according to Example 1, except that titanium catalyst A1 was replaced with an equal weight of titanium catalyst A5.

[0113] Comparative Examples 1-2

[0114] The procedure was carried out according to Example 1, except that titanium catalyst A1 was replaced sequentially with titanium catalyst DA1 and titanium catalyst DA2, while the amount of catalyst remained the same.

[0115] Comparative Example 3

[0116] The procedure was carried out according to Example 1, except that the titanium-containing catalyst A1 was replaced with an equal weight of tetrabutyl titanate.

[0117] Table 3

[0118]

[0119] As can be seen from the results in Table 3, the depolymerization method of polyethylene furanate of the present invention not only has a high depolymerization rate and the yield and purity of the target product, but also has a low residual amount of catalyst in the target product.

[0120] Example 10

[0121] This example illustrates the preparation of PEF using BHEF.

[0122] 100g of the target product BHEF prepared in Example 1 and 0.2g of antimony glycol were added to a three-necked flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190°C, and the absolute pressure of the system was gradually adjusted to 4500 Pa. The reaction was carried out under these conditions for 1 hour. Then, the apparatus was switched to vacuum distillation, and the temperature was increased to 230°C. The absolute pressure of the system was gradually adjusted to less than 300 Pa. The reaction was carried out under these conditions for 2.5 hours to obtain the PEF product. The number average molecular weight of PEF was 2.0 × 10⁻⁶. 4 g / mol.

[0123] The number-average molecular weight of the PEF prepared using the product of Example 1 as a monomer is almost the same as that of the PEF before degradation in Example 1; the target product obtained by the degradation method of the present invention can not only be used for polymerization reaction, but the properties of the PEF obtained by polymerization remain basically unchanged.

[0124] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A titanium-containing catalyst, comprising titanium diol, characterized in that, The titanium-containing catalyst particles are spherical in shape and are composed of stacked nanorod-shaped grains, wherein the diameter of the nanorod-shaped grains is 100-600 nm; and the Ti content is 21-30% by weight based on the total weight of the titanium-containing catalyst.

2. The titanium-containing catalyst according to claim 1, wherein, The length of the nanorod-shaped crystals is 0.5-8 μm; And / or, at 20°C, the solubility of the titanium-containing catalyst in ethylene glycol is <50 mg / L, preferably <30 mg / L, more preferably <10 mg / L; And / or, the median particle size D50 of the titanium-containing catalyst is 1-500 μm, preferably 1-300 μm, and more preferably 1-100 μm.

3. A method for preparing a titanium-containing catalyst, characterized in that, The method includes: adding a diol dropwise to a solution containing a titanium precursor, heating to 70-100°C after the addition is complete to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein, the dropping rate of the diol is 6-8 mL / min relative to 10 g of titanium precursor. Alternatively, the method may include: adding a solution containing a titanium precursor dropwise to a diol, heating to 70-100°C after the addition is complete to carry out an ester exchange reaction, and then performing solid-liquid separation; wherein the dropping rate of the solution containing the titanium precursor is 6-10 mL / min relative to 10 g of diol.

4. The method according to claim 3, wherein, The dripping is carried out at 20-50℃; And / or, the diol is a C2-C10 diol, preferably at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol and 1,2-butanediol; And / or, the titanium precursor comprises at least one of alkyl titanate, titanium acetylacetonate, and diisopropyl titanate; preferably, the alkyl titanate comprises at least one of tetraisopropyl titanate, tetrabutyl titanate, and tetraethyl titanate. And / or, the amount of diol used is 4-7.5 mol relative to 1 mol of titanium precursor; And / or, the transesterification reaction takes 1-4 hours; And / or, the solvent in the solution containing the titanium precursor is at least one of petroleum ether, isopropanol, cyclohexane, toluene, tetrahydrofuran, chloroform, dichloromethane, xylene, and N,N-dimethylformamide; Preferably, the amount of solvent used is 30-200 mL per 10 g of titanium precursor.

5. The titanium-containing catalyst prepared by the method of claim 3 or 4.

6. A method for depolymerizing polyethylene furanate, characterized in that, The method includes: in an inactive atmosphere, in the presence of a first catalyst and a diol, causing polyethylene furanate to undergo an alcoholysis reaction to obtain an alcoholysis reaction solution containing bis(2-hydroxyethyl) furanate, wherein the first catalyst is a titanium-containing catalyst as described in any one of claims 1-2 and 5.

7. The depolymerization method according to claim 6, wherein, The inactive atmosphere is a nitrogen atmosphere; And / or, the amount of the first catalyst is 0.05-0.5 wt% of polyethylene furanate, preferably 0.1-0.4 wt%; And / or, the weight ratio of the polyethylene furanate to the diol is 1:3-7, preferably 1:3-5; And / or, the diol is a C2-C10 diol, preferably at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol and 1,2-butanediol; And / or, the conditions for the alcoholysis reaction include: a reaction temperature of 190-250℃, preferably 190-220℃; a reaction pressure of 0.2-0.6MPa, preferably 0.35-0.5MPa; and a reaction time of 2-6h, preferably 2-5h.

8. The method according to claim 6, wherein, The method further includes: cooling the alcoholysis reaction solution to 100-120℃ and filtering it, adding the filtrate directly to water at 0-4℃ and placing it in an environment at 0-4℃, and then obtaining bis(2-hydroxyethyl) 2,5-furandicarboxylic acid through solid-liquid separation.

9. The method according to claim 8, wherein, The volume ratio of the filtrate to water is 1:1-4.

10. 2,5-furandicarboxylic acid bis(2-hydroxyethyl) ester prepared by the method according to any one of claims 6-9.

11. A method for preparing polyethylene furanate, characterized in that, The method includes polycondensation of bis(2-hydroxyethyl) 2,5-furandicarboxylate in an inactive atmosphere and in the presence of a second catalyst; wherein the bis(2-hydroxyethyl) 2,5-furandicarboxylate is the bis(2-hydroxyethyl) 2,5-furandicarboxylate of claim 10.

12. The method according to claim 11, wherein, The second catalyst is at least one of antimony acetate, antimony glycolate, germanium dioxide, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, and titanium glycolate. And / or, the amount of the second catalyst is 0.001-0.8 wt% of bis(2-hydroxyethyl) furanyldicarboxylate, preferably 0.01-0.6 wt%; And / or, the polycondensation reaction includes subjecting bis(2-hydroxyethyl) furanate to a first polycondensation reaction and a second polycondensation reaction sequentially, wherein the conditions for the first polycondensation reaction include: a reaction temperature of 190-220°C, an absolute pressure under vacuum of 1000-5000 Pa, and a reaction time of 1-3 h; the conditions for the second polycondensation reaction include: a reaction temperature of 210-240°C, an absolute pressure under vacuum ≤300 Pa, preferably ≤90 Pa, more preferably ≤50 Pa, and a reaction time of 0.5-3 h.

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