A catalyst for polyester, its preparation method and application, and a polyester preparation method

Abstract

The application provides a polyester catalyst and a preparation method and application thereof and a polyester preparation method, and relates to the technical field of polyester synthesis.The preparation method of the polyester catalyst provided by the application comprises the following steps: forming MXene nanosheets through etching of an acid or an alkali, obtaining MXene nanodots through a water / solvent thermal reaction, and adding a functional group regulator to obtain the MXene nanodot catalyst suitable for polyester synthesis;the MXene nanodot catalyst does not contain toxic antimony, and simultaneously has a high specific surface area, rich active sites, rich functional groups and good dispersibility;the problems of the current antimony-based catalyst, i.e., the residual toxic antimony, and the problems of the current titanium-based catalyst, i.e., large catalyst particles, few active sites and poor dispersibility, are solved;the polyester prepared by using the MXene nanodot catalyst can also be endowed with functional characteristics, and is conducive to realizing the production of green and environmentally-friendly high-performance polyester.

Description

Technical Field

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

[0002] Polyesters are polymers formed by the esterification and polycondensation of polybasic acids and polyols. Due to their excellent mechanical properties, thermal stability, and solvent resistance, they have wide applications in aerospace, electronics, and manufacturing. Catalysts are a key and challenging issue in the polyester industry. Li, Na, K, Be, Mg, Ca, Sr, Al, Ge, Sb, Ti, Mn, Fe, and Co can all serve as active centers to promote polyester reactions, existing in the reaction system in the form of oxides, esters, and alcohols. Currently, over 90% of the catalysts used in polyester synthesis are antimony-based catalysts. Studies have found that in traditional antimony-based catalysts, about one-third of the Sb is released during production, while the remaining two-thirds often remain in the polyester. These remaining Sb are dissolved and released in large quantities during subsequent high-temperature, high-pressure processes and the breaking of ester bonds, leading to excessive levels of the heavy metal Sb in wastewater. Numerous studies have shown that Sb and its compounds have certain toxicity and carcinogenicity to humans, seriously threatening environmental safety and human health. Therefore, there is an urgent need to develop new, green, and environmentally friendly catalysts.

[0003] Patent application CN 117285704A discloses a method for preparing a highly active titanium-based nano-polyester catalyst, which solves the problem of hydrolysis deactivation in production and transportation, and is applied to the synthesis of PBAT products with low acid value and high color, realizing the production of high-performance products. However, the resulting catalyst particles are large and have few active sites, and still have the problems of easy agglomeration and difficulty in dispersion. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a catalyst for polyester, its preparation method and application, and a method for preparing polyester. The catalyst has high specific surface area, high catalytic activity, good dispersibility and low biotoxicity, solving the problems of toxic antimony residue in antimony-based catalysts and large catalyst particles, few active sites and difficulty in dispersion in titanium-based catalysts.

[0005] This invention provides a method for preparing a catalyst for polyester, comprising the following steps:

[0006] S1 and MAX phase raw materials are reacted with acid or alkali solution to obtain a mixture. The mixture is then post-processed to obtain MXene nanosheets. In the MAX phase raw material, M is a transition metal element Ti or a combination of Ti and one or more of Sc, Zr, V, Nb, Cr, Hf, Ta, W, Y and Mo, A is Al and / or Si, and X is carbon and / or nitrogen.

[0007] S2. The MXene nanosheets described in step S1 undergo an aqueous / solvothermal reaction in a solution containing a solvent and a functional group modifier to obtain a mixed solution containing MXene nanodots. The mixed solution is then post-treated to obtain an MXene nanodot catalyst with functional groups on its surface. The particle size of the MXene nanodots is less than 20 nm, and the surface of the MXene nanodot catalyst has one or more functional groups selected from -O, -OH, -COOH, -Cl, -F, -N, -P, and -S.

[0008] The present invention provides a method for preparing a polyester catalyst. First, MXene nanosheets are formed through acid or alkali etching. Then, MXene nanodots are obtained through a hydrothermal / solvothermal reaction. Finally, a functional group modifier is added to adjust the functional groups supported on the MXene nanodots, resulting in an MXene nanodot catalyst suitable for polyester synthesis. The MXene nanodot catalyst does not contain toxic antimony, and the size of the MXene nanodots is less than 20 nm, giving it a high specific surface area and abundant active sites. As a polyester catalyst, it not only exhibits highly efficient catalytic activity, but its abundant surface functional groups react with polyester to form covalent bonds, improving the interfacial interaction between the catalyst and polyester, enhancing catalyst dispersibility, and thus increasing the degree of polymerization of the polyester.

[0009] In one possible implementation, the functional group modifier includes one or more of nitrogen-containing, phosphorus-containing, sulfur-containing, carboxyl-containing, chlorine-containing, fluorine-containing, and hydroxyl-containing functional group modifiers. Using these functional group modifiers allows for the surface loading of the MXene nanodot catalyst with abundant functional groups, improving the surface properties of the MXene nanodot catalyst and giving it better catalytic efficiency and activity.

[0010] Furthermore, the nitrogen-containing functional group modifier includes one or more of amino acids, octadecylamine, hexadecylamine, 3-aminopropyltriethoxysilane, ethylenediamine, o-phenylenediamine, aniline, p-phenylenediamine, triethylamine, and triethylenetetramine.

[0011] Furthermore, the phosphorus-containing functional group modifier includes one or more of phosphoric acid, phytic acid, phospholipids, triphenyl phosphate, and diphenyl phosphate.

[0012] Furthermore, the sulfur-containing functional group modifier includes one or more of dimethyl sulfoxide, ethanethiol, isopropanethiol, 2-hydroxyethanethiol, m-toluenethiophenol, anisole, and phenyl sulfide.

[0013] Furthermore, the carboxyl functional group modifier is one or more of citric acid, oxalic acid, acetic acid, malonic acid, succinic acid, glutaric acid, and adipic acid.

[0014] Furthermore, the chlorine-containing functional group modifier includes one or more of hydrochloric acid, sodium chlorate, calcium hypochlorite, trisodium phosphate chloride, sodium dichloroisocyanurate, and trichloroisocyanuric acid.

[0015] Furthermore, the fluorinated functional group modifier includes one or more of hydrofluoric acid, sodium fluoride, 3,5-bis(trifluoromethyl)benzoic acid, 3,5-bis(trifluoromethyl)bromobenzene, 3,5-bis(trifluoromethyl)aniline, hexafluoroacetone, and hexafluoroisopropanol.

[0016] The aforementioned functional group modifiers not only provide functional groups, but also have the advantages of readily available raw materials and low cost.

[0017] In one possible implementation, the functional group modifier in step S2 has a mass percentage of 0.1-30 wt% in the solution.

[0018] In one possible implementation, the post-processing in step S1 involves: centrifuging the mixture to obtain a precipitate, washing the precipitate with deionized water, followed by sonication and centrifugation, and then collecting the supernatant for freeze-drying. This post-processing separates MXene nanosheets from the mixture, resulting in a relatively pure MXene nanosheet powder.

[0019] Furthermore, the centrifugation speed in step S1 is ≥5000 rpm. Centrifugation can remove unreacted acid or alkali.

[0020] Furthermore, the pH of the precipitate after washing is 5-8. By controlling the pH of the precipitate after washing, it can be ensured that unreacted acids and bases are effectively removed.

[0021] In one possible implementation, the water / solvothermal reaction in step S2 is carried out at a temperature of 80-200°C for a time of 10-72 hours. By controlling the temperature and time of the water / solvothermal reaction, the reaction can proceed normally while also promoting the formation of abundant functional groups on the surface of MXene nanodots.

[0022] In one possible implementation, the pH value of the water / solvothermal reaction in step S2 is 6-9. Controlling the pH value of the water / solvothermal reaction can help increase its rate.

[0023] In one possible implementation, the post-processing step S2 involves: after the mixed solution is subjected to ultrasonication in a water bath and centrifugation, the supernatant is taken for dialysis and freeze-drying. This post-processing separates the MXene nanoparticle catalyst from the mixed solution, and MXene nanoparticle powder can be obtained using this method.

[0024] Furthermore, the centrifugation speed in step S2 is ≤5000 rpm. By using a lower centrifugation speed, MXene nanodots can be separated from the mixed solution while avoiding unnecessary damage to the structure of the MXene nanodots.

[0025] In one possible implementation, the solvent of the solution in step S2 is one or more of water, dimethyl sulfoxide (DMSO), ethanol, methanol, dimethylformamide (DMF), dimethylacetamide (DMAC), oleylamine, and octadecylamine.

[0026] The present invention also provides an MXene nanodot catalyst prepared according to the above-described method for preparing a polyester catalyst, wherein the surface of the MXene nanodot catalyst has functional groups, and the functional groups are one or more of -O, -OH, -COOH, -Cl, -F, -N, -P and -S.

[0027] This invention also provides the application of the above-mentioned polyester catalyst in the field of polyester synthesis.

[0028] This invention also provides a method for preparing polyester, comprising the following steps:

[0029] M1, diacid and / or diacid esters are mixed evenly with diol, and then an esterification catalyst is added. The esterification reaction is carried out under an inert atmosphere to obtain monomers.

[0030] M2. The above-mentioned polyester catalyst is added to the monomer described in step M1, and a polycondensation reaction is carried out under vacuum conditions to obtain polyester.

[0031] The polyester preparation method provided by this invention uses a polyester catalyst (MXene nanodot catalyst) that does not contain toxic antimony metal, thus avoiding the residue of toxic antimony metal in the polyester. At the same time, the MXene nanodot catalyst also has a high specific surface area, abundant active sites, abundant functional groups and good dispersibility, which is beneficial to improving the degree of polymerization and mechanical properties of polyester. Furthermore, the MXene nanodot catalyst has low biotoxicity, good biocompatibility and conductivity, which can endow polyester with functional properties and facilitate the production of green and environmentally friendly high-performance polyester.

[0032] In one possible implementation, the dicarboxylic acid in step M1 is one or both of terephthalic acid and furanyl dicarboxylic acid.

[0033] In one possible implementation, the diesterified compound in step M1 is one or both of terephthalate esterified compound and furanate esterified compound.

[0034] In one possible implementation, the diol in step M1 is one or more of aliphatic and aromatic diols.

[0035] In one possible implementation, the molar ratio of the diacid and / or diacid ester to the diol in step M1 is 1.1-2.5. Controlling the ratio of the diacid and / or diacid ester to the diol is more conducive to monomer synthesis.

[0036] In one possible implementation, the esterification reaction in step M1 is carried out at a temperature of 180-240°C for 2-6 hours. When the temperature and time of the esterification reaction are within the above range, a higher esterification rate can be obtained.

[0037] In one possible implementation, the amount of polyester catalyst added in step M2 is 0.5-10‰ of the mass percentage of the theoretical polyester product. When the amount of polyester catalyst is within the above range, it is beneficial to increase the degree of polymerization of the polyester.

[0038] In one possible implementation, the polycondensation reaction in step M2 is carried out at a temperature of 200-300°C, for a time of 1-5 hours, and under a vacuum of 10-200 Pa. When the temperature, time, and vacuum of the polycondensation reaction are within the above ranges, the efficiency of the polycondensation reaction can be improved.

[0039] Based on common knowledge in the field, the above-described embodiments can be combined arbitrarily.

[0040] The reagents and raw materials used in this invention are all commercially available.

[0041] The positive and progressive effects of this invention are as follows:

[0042] This invention utilizes MXene nanodot catalysts, avoiding the residual hazards of toxic antimony in existing antimony-based catalysts. MXene nanodot catalysts possess a large specific surface area and abundant functional groups, exhibiting strong adsorption capacity with monomers and high catalytic activity. They are also easier to disperse than spherical or sheet-like catalysts, overcoming the problem of uneven dispersion in traditional catalysts. Furthermore, MXene nanodot catalysts exhibit strong interfacial interactions with polyester, overcoming the weakness of the catalyst-polyester interface. The nanodot catalyst also provides a nano-constraint effect within the polyester, acting as a heterogeneous nucleating agent to enhance the polyester's crystallinity. The resulting polyester product possesses excellent mechanical properties and heat resistance, making it widely applicable in engineering plastics, films, and fibers. Attached Figure Description

[0043] Figure 1 The Ti3C2T prepared in Example 1 x Transmission electron microscopy (TEM) image of nanodot catalyst.

[0044] Figure 2 The Ti3C2T prepared in Example 1 x X-ray photoelectron spectroscopy (XPS) curves of nanodot catalysts.

[0045] Figure 3 This is a cross-sectional SEM image of the polyethylene terephthalate prepared in Example 12.

[0046] Figure 4 This is a cross-sectional TEM image of the polyethylene terephthalate prepared in Example 12.

[0047] Figure 5 The visible light transmittance spectrum of the polyethylene terephthalate prepared in Example 12 is shown.

[0048] Figure 6 The stress-strain curves are for the polyesters prepared in Examples 12 and 13. Detailed Implementation

[0049] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0050] It should be noted that 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. 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.

[0051] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0052] Example 1

[0053] This embodiment provides a Ti3C2T x Nanoparticle catalysts are prepared by the following method:

[0054] (1) The MAX phase Ti3AlC2 was placed in a tetrafluoroethylene container, followed by the addition of hydrofluoric acid (HF) solution. The mixture was etched in an oil bath at 35°C for 48 hours. After washing with deionized water until the solution pH > 5, the solution was centrifuged at 6000 rpm to obtain the precipitate. After freeze-drying, Ti3C2T was obtained. x Nanosheets;

[0055] (2) The Ti3C2T obtained in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and water were sealed and subjected to a hydrothermal / solventic reaction at 120°C for 24 h. The mixture was then ultrasonicated in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain the Ti3C2Tx nanodot catalyst.

[0056] The transmission electron microscope (TEM) image of the Ti3C2Tx nanodot catalyst prepared in this embodiment is shown below. Figure 1 As shown in the figure, the average diameter of the Ti3C2Tx nanodots is 2 nm.

[0057] The X-ray photoelectron spectroscopy (XPS) curve of the Ti3C2Tx nanodot catalyst prepared in this embodiment is shown below. Figure 2 As shown, XPS analysis reveals that the obtained Ti3C2Tx nanodots contain -F and -Cl functional groups.

[0058] Example 2

[0059] This embodiment provides a Ti3C2T x Nanoparticle catalysts are prepared by the following method:

[0060] (1) The MAX phase Ti3AlC2 was placed in a tetrafluoroethylene container, and then sodium hydroxide (NaOH) solution was added. After stirring evenly, the mixture was etched at 200℃ for 48 h. The solution was washed with deionized water until the pH was < 8. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti3C2T. x Nanosheets;

[0061] (2) The Ti3C2T obtained in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and water were sealed and subjected to a hydrothermal / solvothermal reaction at 120°C for 24 h. The mixture was then ultrasonicated in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Ti3C2T. x Nanoparticle catalysts.

[0062] Example 3

[0063] This embodiment provides a Ti2CT x Nanoparticle catalysts are prepared by the following method:

[0064] (1) The MAX phase Ti2AlC was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti2CT. x Nanosheets;

[0065] (2) The Ti2CT prepared in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and water were sealed and subjected to a hydrothermal / solvothermal reaction at 120°C for 24 h. The mixture was then ultrasonicated in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Ti2CT. x Nanoparticle catalysts.

[0066] Example 4

[0067] This embodiment provides a Ti2CT x Nanoparticle catalysts are prepared by the following method:

[0068] (1) The MAX phase Ti2AlC was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti2CT. x Nanosheets;

[0069] (2) The Ti2CT prepared in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and ethanol were sealed and subjected to a hydrothermal / solvothermal reaction at 120°C for 24 h. The mixture was then ultrasonically reacted in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Ti2CT. x Nanoparticle catalysts.

[0070] Example 5

[0071] This embodiment provides a Ti3C2T x- The N-nano dot catalyst was prepared by the following method:

[0072] (1) Place the MAX phase Ti3AlC2 in a tetrafluoro container, then add hydrofluoric acid (HF) solution, and etch away the Al in the oil bath at 35°C. After 48h, wash with deionized water until the solution pH > 5, then centrifuge at 6000rpm to obtain the precipitate, and freeze-dry to obtain Ti3C2Tx nanosheets.

[0073] (2) The Ti3C2Tx nanosheets and DMF prepared in step (1) were added sequentially to a polytetrafluoroethylene reactor. After sealing, the reactor was subjected to a hydrothermal / solvothermal reaction at 150°C for 18 h. The mixture was obtained by ultrasonication in a water bath. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Ti3C2Tx. x- N-nano dot catalyst.

[0074] Example 6

[0075] This embodiment provides a Ti3C2T x- The S nanoparticle catalyst was prepared by the following method:

[0076] (1) The MAX phase Ti3AlC2 was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti3C2T. x Nanosheets;

[0077] (2) The Ti3C2T obtained in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and DMSO were sealed and subjected to a hydrothermal / solvothermal reaction at 180℃ for 15 h. The mixture was then ultrasonically reacted in a water bath to obtain a mixed solution. After centrifugation at 1500 rpm for 8 min, the supernatant was dialyzed and freeze-dried to obtain Ti3C2T. x- S nanodot catalyst.

[0078] Example 7

[0079] This embodiment provides a Ti3C2T x- The P-nanodot catalyst was prepared by the following method:

[0080] (1) The MAX phase Ti3AlC2 was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti3C2T. x Nanosheets;

[0081] (2) The Ti3C2T obtained in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and phosphoric acid were sealed and subjected to a hydrothermal / solvothermal reaction at 200℃ for 10 h. The mixture was then ultrasonically reacted in a water bath to obtain a mixed solution. After centrifugation at 2000 rpm for 5 min, the supernatant was dialyzed and freeze-dried to obtain Ti3C2T. x- P-nanodot catalyst.

[0082] Example 8

[0083] This embodiment provides a Ti3C2T x- The N-nano dot catalyst was prepared by the following method:

[0084] (1) The MAX phase Ti3AlC2 was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Ti3C2T. x Nanosheets;

[0085] (2) The Ti3C2T obtained in step (1) is added sequentially to the polytetrafluoroethylene reactor. x Nanosheets and ethylenediamine were sealed and subjected to a hydrothermal / solvothermal reaction at 150°C for 18 h. The mixture was then ultrasonically reacted in a water bath to obtain a homogenous solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Ti3C2T. x- N-nano dot catalyst.

[0086] Example 9

[0087] This embodiment provides an Nb2CT x Nanoparticle catalysts are prepared by the following method:

[0088] (1) The MAX phase Nb2AlC was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was >5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Nb2CT. x Nanosheets;

[0089] (2) Add the Nb2CT obtained in step (1) to the polytetrafluoroethylene reactor in sequence. x Nanosheets and water were sealed and subjected to a hydrothermal / solvothermal reaction at 150°C for 24 h. The mixture was then sonicated in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Nb2CT. x Nanoparticle catalysts.

[0090] Example 10

[0091] This embodiment provides an Nb4C3T x Nanoparticle catalysts are prepared by the following method:

[0092] (1) The MAX phase Nb4AlC3 was placed in a tetrafluoroethylene container, and then hydrofluoric acid (HF) solution was added. The Al was removed by etching in an oil bath at 35°C. After 48 h, the solution was washed with deionized water until the pH was > 5. The precipitate was then obtained by centrifugation at 6000 rpm and freeze-dried to obtain Nb4C3T. x Nanosheets;

[0093] (2) Add the Nb4C3T obtained in step (1) to the polytetrafluoroethylene reactor in sequence. x Nanosheets and water were sealed and subjected to a hydrothermal / solvothermal reaction at 150°C for 24 h. The mixture was then ultrasonically reacted in a water bath to obtain a mixed solution. After centrifugation at 1000 rpm for 10 min, the supernatant was dialyzed and freeze-dried to obtain Nb4C3T. x Nanoparticle catalysts.

[0094] Example 11

[0095] This embodiment provides a polyethylene terephthalate, which is prepared by the following method:

[0096] Terephthalic acid and ethylene glycol were added to the reactor at a molar ratio of 1:3, along with 0.5‰ of Ti3C2T prepared in Example 1 by mass. xThe nanodot catalyst serves as both an esterification catalyst and a polycondensation catalyst. The esterification temperature is set at 240℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 285℃. After low-vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20Pa) for 4 hours is performed. After the polycondensation is completed, polyethylene terephthalate (PET) can be obtained by discharging the material.

[0097] Example 12

[0098] This embodiment provides a polyethylene terephthalate, which is prepared by the following method:

[0099] Dimethyl terephthalate and ethylene glycol were added to the reactor at a molar ratio of 1:2.5, along with 0.5‰ of Ti3C2T prepared in Example 1 by mass. x The nanodot catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 220℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, a 1‰ mass fraction of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 285℃. After low-vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20Pa) for 4.5 hours is performed. After the polycondensation is completed, polyethylene terephthalate (PET) can be obtained by discharging the material.

[0100] Figure 3 The image shows a cross-sectional SEM image of the polyethylene terephthalate (PET) prepared in this embodiment. As can be seen from the image, the obtained PET cross-section is smooth and no phase separation is observed, indicating that the obtained catalyst has good compatibility with PET.

[0101] Figure 4 This is a cross-sectional TEM image of the polyethylene terephthalate (PET) prepared in this embodiment. As can be seen from the image, no obvious agglomeration was observed, indicating that Ti3C2T… x Nanodots disperse well in PET.

[0102] Figure 5 The visible light transmittance spectrum of the polyethylene terephthalate prepared in this embodiment is shown in the figure. As can be seen from the figure, the obtained PET film has good transmittance, with visible light transmittance exceeding 80% at 800 nm.

[0103] Example 13

[0104] This embodiment provides a poly(ethylene furanate) dicarboxylate, which is prepared by the following method:

[0105] Furan dicarboxylic acid and ethylene glycol were added to the reactor at a molar ratio of 1:2.4, along with 1‰ of Ti3C2T prepared in Example 2 by mass. xThe nanodot catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 180℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 235℃. After low-vacuum pre-polymerization (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 10Pa) is carried out for 5 hours. After the polycondensation is completed, the product can be discharged to obtain polyethylene furanate dicarboxylate (PEF).

[0106] Figure 6 The stress-strain curves of the polyesters prepared in Examples 12 and 13 are shown in the figure. As can be seen from the figure, the prepared PEF and PET have good mechanical properties. The tensile strength of PEF is >90MPa and the elongation is >5%, while the tensile strength of PET is >70MPa and the elongation is >80%.

[0107] Example 14

[0108] This embodiment provides a poly(ethylene furanate) dicarboxylate, which is prepared by the following method:

[0109] Dimethyl furanate and ethylene glycol were added to the reactor at a molar ratio of 1:2.2, along with 1‰ of Ti3C2T prepared in Example 5 by mass. x- The N nanoparticle catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 190℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the mass fraction of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 245℃. After low-vacuum pre-polymerization (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 10Pa) is carried out for 5 hours. After the polycondensation is completed, the product is discharged to obtain polyethylene furanate dicarboxylate (PEF).

[0110] Example 15

[0111] This embodiment provides a polybutylene furanate dicarboxylate, which is prepared by the following method:

[0112] Dimethyl furanate and butanediol were added to the reactor at a molar ratio of 1:2.2, along with 1‰ of Ti3C2T prepared in Example 5 by mass. x- The N nanoparticle catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 175℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 220℃. After low-vacuum pre-polymerization (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 10Pa) is carried out for 3 hours. After the polycondensation is completed, polybutylene furanate (PBF) can be obtained by discharging the material.

[0113] Example 16

[0114] This embodiment provides a poly(ethylene furanate) dicarboxylate, which is prepared by the following method:

[0115] Dimethyl furanate and ethylene glycol were added to the reactor at a molar ratio of 1:2.2, along with 1.5‰ of Ti3C2T prepared in Example 7 by mass. x- The P nanodot catalyst is used as both an esterification catalyst and a polycondensation catalyst. The esterification temperature is set at 185℃, and the reaction is carried out under nitrogen protection. When the esterification rate reaches 90% of the theoretical value, 1‰ of the mass fraction of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 245℃. After low vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high vacuum polycondensation (vacuum degree less than 10Pa) for 5 hours is carried out. After the polycondensation is completed, the product can be discharged to obtain polyethylene furanate dicarboxylate (PEF).

[0116] Example 17

[0117] This embodiment provides a polypropylene furanate dicarboxylate, which is prepared by the following method:

[0118] Dimethyl furanate and propylene glycol were added to the reactor at a molar ratio of 1:2.1, along with 2‰ of Ti3C2T prepared in Example 1 by mass. x The nanodot catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 180℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 255℃. After low-vacuum pre-polymerization (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 10Pa) is carried out for 5 hours. After the polycondensation is completed, polypropylene glycol furanate (PPF) can be obtained by discharging the material.

[0119] Example 18

[0120] This embodiment provides a polybutylene terephthalate, which is prepared by the following method:

[0121] Dimethyl terephthalate and butanediol were added to the reactor at a molar ratio of 1:2.3, along with 1.5‰ of Ti3C2T prepared in Example 1 by mass. x The nanodot catalyst serves as both an esterification catalyst and a polycondensation catalyst. The esterification temperature is set at 240℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 285℃. After low-vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20Pa) for 4.5 hours is performed. After the polycondensation is completed, polybutylene terephthalate (PBT) can be obtained by discharging the material.

[0122] Example 19

[0123] This embodiment provides a polycyclohexanediol terephthalate, which is prepared by the following method:

[0124] Dimethyl furanyl dicarboxylate and nonanediol were added to the reactor at a molar ratio of 1:2.3, along with 1.3‰ of Ti3C2T prepared in Example 1 by mass. x The nanodot catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 225℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 260℃. After low-vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20Pa) is carried out for 4.5 hours. After the polycondensation is completed, poly(cyclohexanediol terephthalate) (PNF) can be obtained by discharging the material.

[0125] Example 20

[0126] This embodiment provides a polyhexanediol terephthalate, which is prepared by the following method:

[0127] Dimethyl furanate and hexanediol were added to the reactor at a molar ratio of 1:2.1, along with 2‰ (by mass) of Ti3C2T prepared in Example 1. x The nanodot catalyst serves as both an esterification and polycondensation catalyst. The esterification temperature is set at 210℃, and the reaction is carried out under nitrogen protection. Once the esterification rate reaches 90% of the theoretical value, 1‰ of the stabilizer triphenyl phosphate is added, and the polycondensation temperature is set at 255℃. After low-vacuum pre-polycondensation (vacuum degree greater than 200Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20Pa) is carried out for 4.5 hours. After the polycondensation is completed, the product can be discharged to obtain polyhexyl terephthalate (PHF).

[0128] Comparative Example 1

[0129] Terephthalic acid and ethylene glycol were added to the reactor at a molar ratio of 1:3. Simultaneously, 0.5‰ antimony trioxide was added as both an esterification and polycondensation catalyst. The esterification temperature was set at 240℃, and the reaction was carried out under nitrogen protection. Once the esterification rate reached 90% of the theoretical value, 1‰ triphenyl phosphate stabilizer was added, and the polycondensation temperature was set at 285℃. After low-vacuum pre-polymerization (vacuum degree greater than 200 Pa) for 1 hour, high-vacuum polycondensation (vacuum degree less than 20 Pa) was performed for 4 hours. After the polycondensation was completed, polyethylene terephthalate (PET) was obtained by discharging the material.

[0130] Comparative Example 2

[0131] Furan dicarboxylic acid and ethylene glycol were added to the reactor at a molar ratio of 1:2.4. At the same time, 1‰ of antimony trioxide was added as an esterification catalyst and a polycondensation catalyst. The esterification temperature was set at 180℃ and the reaction was carried out under nitrogen protection. When the esterification rate reached 90% of the theoretical value, 1‰ of triphenyl phosphate stabilizer was added and the polycondensation temperature was set at 235℃. After low vacuum pre-polymerization (vacuum degree greater than 200Pa) for 1 hour, high vacuum polycondensation (vacuum degree less than 10Pa) for 5 hours was carried out. After the polycondensation was completed, the product was discharged to obtain polyethylene furanate dicarboxylate (PEF).

[0132] The test results of tensile strength, elongation, intrinsic viscosity and color of the polyesters prepared in Examples 12, 13, Comparative Example 1 and Comparative Example 2 are shown in Table 1. As can be seen from Table 1, when the prepared MXene quantum dot catalyst is used for the catalytic polymerization of polyester, the catalytic effect of MXene quantum dots is better than that of traditional antimony trioxide catalysts in terms of color, viscosity and mechanical properties. MXene quantum dot catalysts are not only highly efficient, but also environmentally friendly, green, non-toxic and harmless, and are a kind of highly efficient new green catalyst.

[0133] Table 1 Comparison of mechanical properties between the embodiments and the comparative examples

[0134]

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst for polyester, characterized in that, Includes the following steps: S1 and MAX phase raw materials are reacted with acid or alkali solution to obtain a mixture. The mixture is then post-processed to obtain MXene nanosheets. In the MAX phase raw material, M is a transition metal element Ti or a combination of Ti and one or more of Sc, Zr, V, Nb, Cr, Hf, Ta, W, Y and Mo, A is Al and / or Si, and X is carbon and / or nitrogen. S2. The MXene nanosheets described in step S1 undergo an aqueous / solvothermal reaction in a solution containing a solvent and a functional group modifier to obtain a mixed solution containing MXene nanodots. The mixed solution is then post-treated to obtain an MXene nanodot catalyst with functional groups on its surface. The particle size of the MXene nanodots is less than 20 nm. The surface of the MXene nanodot catalyst has one or more functional groups selected from -OH, -COOH, -Cl, -F, -N, -P, and -S. The functional group modifier includes one or more of nitrogen-containing functional group modifiers, phosphorus-containing functional group modifiers, sulfur-containing functional group modifiers, carboxyl functional group modifiers, chlorine-containing functional group modifiers, fluorine-containing functional group modifiers, and hydroxyl functional group modifiers.

2. The method for preparing the catalyst for polyester according to claim 1, characterized in that, The nitrogen-containing functional group modifiers include one or more of the following: amino acids, octadecylamine, hexadecylamine, 3-aminopropyltriethoxysilane, ethylenediamine, o-phenylenediamine, aniline, p-phenylenediamine, triethylamine, and triethylenetetramine; And / or, the phosphorus-containing functional group modifier includes one or more of phosphoric acid, phytic acid, phospholipids, triphenyl phosphate and diphenyl phosphate; And / or, the sulfur-containing functional group modifier includes one or more of dimethyl sulfoxide, ethanethiol, isopropanethiol, 2-hydroxyethanethiol, m-toluenethiophenol, anisole, and phenyl sulfide; And / or, the carboxyl functional group modifier includes one or more of citric acid, oxalic acid, acetic acid, malonic acid, succinic acid, glutaric acid, and adipic acid; And / or, the chlorine-containing functional group modifier includes one or more of hydrochloric acid, sodium chlorate, calcium hypochlorite, trisodium phosphate chloride, sodium dichloroisocyanurate, and trichloroisocyanuric acid; And / or, the fluorinated functional group modifier includes one or more of hydrofluoric acid, sodium fluoride, 3,5-bis(trifluoromethyl)benzoic acid, 3,5-bis(trifluoromethyl)bromobenzene, 3,5-bis(trifluoromethyl)aniline, hexafluoroacetone, and hexafluoroisopropanol. And / or, the hydroxyl functional group modifier includes one or more of water, methanol, ethanol and propanol.

3. The method for preparing the catalyst for polyester according to claim 1, characterized in that, The water / solvothermal reaction in step S2 is carried out at a temperature of 80-200 °C for a time of 10-72 h. And / or, the pH value of the water / solvothermal reaction in step S2 is 6-9; And / or, the solvent of the solution in step S2 is one or more of water, dimethyl sulfoxide (DMSO), ethanol, methanol, dimethylformamide (DMF), dimethylacetamide (DMAC), oleylamine, and octadecylamine.

4. The method for preparing the catalyst for polyester according to claim 1, characterized in that, The post-processing process described in step S1 is as follows: the mixture is centrifuged to obtain a precipitate, the precipitate is washed with deionized water, and then subjected to ultrasonication and centrifugation. The supernatant is then collected and freeze-dried. And / or, the post-processing process described in step S2 is as follows: after the mixed solution is subjected to ultrasonication in a water bath and centrifugation, the upper layer solution is taken for dialysis and freeze-drying.

5. The method for preparing the catalyst for polyester according to claim 4, characterized in that, The centrifugation speed in step S1 is ≥5000 rpm; And / or, the pH value of the precipitate after washing in step S1 is 5-8; And / or, the centrifugation speed in step S2 is ≤5000 rpm.

6. A catalyst for polyester, characterized in that, The polyester catalyst is an MXene nanodot catalyst prepared by the method for preparing the polyester catalyst according to any one of claims 1-5, wherein the surface of the MXene nanodot catalyst has functional groups, and the functional groups are one or more of -OH, -COOH, -Cl, -F, -N, -P and -S.

7. The application of the polyester catalyst of claim 6 in the field of polyester synthesis.

8. A method for preparing polyester, characterized in that, Includes the following steps: M1, diacid and / or diacid esters are mixed evenly with diol, and then an esterification catalyst is added. The esterification reaction is carried out under an inert atmosphere to obtain monomers. M2. Add the polyester catalyst of claim 6 to the monomer described in step M1, and carry out a polycondensation reaction under vacuum conditions to obtain polyester.

9. The method for preparing polyester according to claim 8, characterized in that, The dicarboxylic acid mentioned in step M1 is one or both of terephthalic acid and furanyl dicarboxylic acid; And / or, the diesterified compound in step M1 is one or both of terephthalate ester and furanate ester; And / or, the diol in step M1 is one or more of aliphatic and aromatic diols; And / or, the molar ratio of the dicarboxylic acid and / or dicarboxylic acid ester to the diol in step M1 is 1.1-2.5; And / or, the esterification reaction in step M1 is carried out at a temperature of 180-240 °C for a time of 2-6 h; And / or, the amount of catalyst added to the polyester in step M2 is 0.5-10‰ of the mass percentage of the theoretical polyester product; And / or, the polycondensation reaction in step M2 is carried out at a temperature of 200-300 °C, for a time of 1-5 h, and under a vacuum of 10-200 Pa.

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