Catalyst, preparation method and application thereof, and preparation method of dimethyl terephthalate

Abstract

The invention relates to the technical field of catalysis, and discloses a catalyst, a preparation method and application thereof, and a preparation method of dimethyl terephthalate. The catalyst comprises a polyester terephthalate carrier and an active component loaded on the polyester terephthalate carrier, the active component contains acetate ions and metal ions, and the metal ions are selected from at least one of IA group metal ions and IIB group metal ions. The catalyst can be conveniently and quickly separated from ester exchange and / or esterification products when applied to ester exchange and / or esterification reaction, is convenient to use for multiple times, and has relatively high catalytic activity; the product prepared by the catalyst has high purity and good hue.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a catalyst, its preparation method, and its applications. Furthermore, this invention also discloses a method for preparing dimethyl terephthalate using this catalyst. Background Technology

[0002] Dimethyl terephthalate (DMT) can be used as an intermediate in the production of polyester materials, including polyester resins, films and fibers, high-strength polyester insulating varnishes, synthetic polyester fibers, and engineering plastics. It can also be used to produce more environmentally friendly polymer polyester monomers such as dimethyl 1,4-cyclohexanedicarboxylate (DMCD) and 1,4-cyclohexanediethanol (CHDM).

[0003] There are two main industrial processes for DMT: the Witten process and the concentrated sulfuric acid process. The Witten process uses p-xylene (PX) as a raw material, and produces DMT through two steps of oxidation and esterification under the action of Co and Mn salts. In this process, oxidation and esterification occur simultaneously, solving the difficulty of oxidizing the second methyl group of PX. However, the Witten process has a long route, requires more equipment, consumes more energy, and has a long reaction time; some companies have designed oxidation reactions with reaction times reaching 15 hours, resulting in low efficiency for the entire production line. The concentrated sulfuric acid process involves the esterification of terephthalic acid (PTA or TA) and methanol under the catalysis of concentrated sulfuric acid. This technology uses concentrated sulfuric acid as a catalyst, which causes significant corrosion to equipment, severe pollution, and produces a product of poor quality that is difficult to meet the requirements of downstream processing. To overcome the shortcomings of the concentrated sulfuric acid process, research has been reported on using polyferric sulfate, toluenesulfonic acid, and solid acids as esterification catalysts, achieving better esterification results. However, problems still exist, such as the inability to recycle and reuse catalysts, difficulty in product purification, and insufficient product color.

[0004] CN104072374A discloses a method for preparing dimethyl terephthalate, comprising the following steps: adding terephthalic acid and excess methanol to a reaction vessel, adding concentrated sulfuric acid as a catalyst, controlling the temperature inside the reaction vessel at 170-180℃, reacting for 10-18 hours, and then filtering, removing alcohol, washing with water, removing impurities, and stripping to obtain dimethyl terephthalate with a purity of 99.8-99.9%. However, this method uses concentrated sulfuric acid as a catalyst, which leads to problems such as severe equipment corrosion, significant methanol loss, numerous side reactions, poor product color, and the generation of large amounts of waste.

[0005] CN102795967A provides a method for preparing dimethyl terephthalate from terephthalic acid. The method involves adding methanol, terephthalic acid, and polyferric sulfate to a high-pressure reactor, with methanol in excess. The mixture is stirred and heated to 140°C. After 4 hours of reaction, the reaction is checked for completeness, and the methanol is recovered to obtain dimethyl terephthalate. However, using polyferric sulfate as a catalyst presents problems such as the inability to recycle and reuse the catalyst, difficulty in purifying the product, and impact on the product's color. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems in the existing technology of the inability to recycle and reuse catalysts in the preparation of dimethyl terephthalate, as well as the difficulty in purifying the obtained products and insufficient color. This invention provides a catalyst, its preparation method, and its application, as well as a method for preparing dimethyl terephthalate. This catalyst, when applied to transesterification and / or esterification reactions, can conveniently and rapidly separate transesterification and / or esterification products, is easy to reuse multiple times, and has high catalytic activity. The products obtained using this catalyst have high purity and good color.

[0007] To achieve the above objectives, the present invention provides a catalyst comprising a polyterephthalate support and an active component supported on the polyterephthalate support, wherein the active component contains acetate ions and metal ions, and the metal ions are selected from at least one group IA metal ions and group IIB metal ions.

[0008] A second aspect of the present invention provides a method for preparing a catalyst, the method comprising: mixing a polyterephthalate and an active component, and during the mixing process, introducing an inert gas into the mixture of the polyterephthalate and the active component; The active component contains acetate ions and metal ions, wherein the metal ions are selected from at least one group of group IA metal ions and group IIB metal ions, and the inert gas is selected from at least one group of nitrogen, helium, neon and argon.

[0009] A third aspect of the present invention provides a catalyst prepared by the preparation method described in the second aspect above.

[0010] The fourth aspect of the present invention provides the use of the catalyst described in the first aspect or the catalyst described in the second aspect as an ester exchange catalyst and / or an esterification catalyst.

[0011] The fifth aspect of the present invention provides a method for preparing dimethyl terephthalate, the method comprising: reacting terephthalate, methanol and the above-mentioned catalyst under transesterification conditions.

[0012] Through the above technical solution, the catalyst provided by the present invention, by loading the active component on a polyterephthalate support and limiting the active component to contain acetate ions and metal ions, and limiting the metal ions to at least one selected from Group IA metal ions and Group IIB metal ions, has high catalytic activity and catalytic stability when applied to transesterification or esterification reactions, and can be easily and quickly separated from transesterification and / or esterification products, facilitating multiple uses; at the same time, the products obtained by the catalyst have high purity and good color, which is convenient for subsequent applications.

[0013] Moreover, the catalyst uses a polyterephthalate support, which is less expensive than traditional metal supports, has a higher dispersion of active sites, and thus higher catalytic activity. Compared with traditional carbon-based catalysts, it has higher strength, a higher dispersion of active sites, and thus higher catalytic activity, which is beneficial for reducing reaction temperature and accelerating reaction rate. Detailed Implementation

[0014] 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.

[0015] As previously stated, a first aspect of the present invention provides a catalyst comprising a polyterephthalate support and an active component supported on the polyterephthalate support, the active component containing acetate ions and metal ions, wherein the metal ions are selected from at least one group IIA metal ions and group IIB metal ions.

[0016] Among them, metal ions can be qualitatively or quantitatively determined by ICP, while acetate ions can be qualitatively or quantitatively determined by ion chromatography.

[0017] The inventors unexpectedly discovered during their research that by loading a catalytically active component onto a polyterephthalate support, and limiting the active component to contain acetate ions and metal ions, specifically at least one metal ion selected from Group IA and Group IIB metal ions, the resulting catalyst exhibits high catalytic activity and stability when applied to transesterification or esterification reactions. Furthermore, it allows for convenient and rapid separation from transesterification and / or esterification products, facilitating repeated use. Simultaneously, the products obtained using this catalyst possess high purity and favorable color, facilitating subsequent applications.

[0018] Moreover, this catalyst uses a polyterephthalate (PTFE) support, which is less expensive than traditional metal supports and has a higher dispersion of active sites, resulting in higher catalytic activity. Compared with traditional carbon-based catalysts, it has higher strength, a higher dispersion of active sites, and higher catalytic activity, which is beneficial for lowering the reaction temperature and accelerating the reaction rate. Studies have found that the catalyst provided by this invention can be used continuously for more than 8000 hours. Analysis of product conversion rate and purity shows that the conversion rate and purity remain above 99%, indicating that the catalyst has a long service life and high stability.

[0019] Preferably, the polyterephthalate support is selected from at least one of polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate. Studies have found that the interaction between the above-mentioned polyterephthalates and the active components is better, thereby further improving the catalytic activity and catalytic stability of the catalyst. Considering the potential for further improvement in catalytic activity and catalytic stability, it is further preferred that the polyterephthalate support is a polyethylene terephthalate support.

[0020] The Group IA metal ion can be sodium ion and / or potassium ion, and the Group IIB metal ion can be zinc ion and / or cadmium ion. Preferably, the Group IA metal ion is potassium ion and the Group IIB metal ion is zinc ion. Studies have found that the combination of these two metal ions with acetate ions and a polyethylene terephthalate support enhances the catalyst's catalytic activity, thereby further improving the selectivity of the catalytic reaction products. Further preferably, considering the potential for further enhancing the catalyst's catalytic activity, the metal ions are potassium ion and zinc ion.

[0021] Preferably, the mass ratio of zinc ions to potassium ions is 1:0.08-1.15, and can be 1:0.08, 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1.0, 1:1.15, or any value between these ratios. More preferably, the mass ratio of zinc ions to potassium ions is 1:0.2-0.85. Studies have found that the above-mentioned mass ratios of zinc ions, potassium ions, and acetate ions have a better coordination effect, thereby further improving the catalytic activity of the catalyst.

[0022] In one specific embodiment of the present invention, the polyterephthalate support is a polyethylene terephthalate support, and the metal ions are potassium ions and zinc ions. The catalyst defined above exhibits better catalytic activity and catalytic stability.

[0023] According to the present invention, preferably, the catalyst has a specific surface area of ​​350-600 m². 2 / g, with a porosity of 93-99%. Studies have found that the above catalyst exhibits good catalytic activity. Further preferably, considering the potential to improve the catalytic stability of the catalyst, the specific surface area of ​​the catalyst is 420-500 m² / g. 2 / g, with a porosity of 97.5-99%.

[0024] According to the present invention, the specific surface area of ​​the catalyst is obtained by testing according to GB / T 19587-2004. The porosity test method is as follows: the catalyst is completely dried at room temperature, weighed to obtain the initial mass, and then immersed in a saturated liquid to reach saturation to remove air from the pores. The immersed mass is then weighed again. By comparing the difference between the two weighings, the porosity of the sample can be calculated.

[0025] Preferably, in the catalyst, the loading of acetate ions is 1-8 wt%, which can be 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, or any value between these values; the loading of metal ions is 1-5.5 wt%, which can be 1 wt%, 2.5 wt%, 4 wt%, 5.5 wt%, or any value between these values. Catalysts with the above-mentioned loadings of carbonate ions and metal ions exhibit better catalytic activity and catalytic stability. Further preferably, considering the potential to further improve the catalytic activity of the catalyst, the loading of the coarse acetate ions is 2.5-6 wt%, and the loading of the metal ions is 1.4-3.6 wt%.

[0026] A second aspect of the present invention provides a method for preparing a catalyst, the method comprising: mixing a polyterephthalate and an active component, and during the mixing process, introducing an inert gas into the mixture of the polyterephthalate and the active component; The active component contains acetate ions and metal ions, wherein the metal ions are selected from at least one group of group IA metal ions and group IIB metal ions, and the inert gas is selected from at least one group of nitrogen, helium, neon and argon.

[0027] Studies have shown that the above method enables the formation of a porous support structure for polyethylene terephthalate (PET), successfully loading the active component onto PET while simultaneously producing a catalyst with high catalytic activity. Furthermore, the catalyst prepared by this method exhibits high catalytic stability.

[0028] Preferably, the mass ratio of the polyethylene terephthalate (PET) to the active component is 1:0.02-0.15, and can be 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.12, 0.14, 0.15, or any value between these values. Controlling the mass ratio of PET to the active component within the above range can reduce preparation costs while ensuring the loading, resulting in a catalyst with good catalytic activity and stability. Further preferably, considering the potential to further improve the catalytic activity of the prepared catalyst, the mass ratio of PET to the active component is 1:0.04-0.1.

[0029] Preferably, the polyterephthalate is selected from at least one of polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate. The aforementioned polyterephthalates exhibit better loading effects on the active component, and through the synergy between the two, the catalytic activity and catalytic stability of the prepared catalyst can be effectively improved. Further preferably, considering the potential to further improve the catalytic activity and catalytic stability of the prepared catalyst, the polyterephthalate is polyethylene terephthalate.

[0030] Preferably, the active component is potassium acetate and / or zinc acetate, both of which exhibit good catalytic activity when combined with polyethylene terephthalate. Further preferably, considering the potential to improve the catalytic activity of the prepared catalyst, the active component is potassium acetate and zinc acetate.

[0031] Preferably, the mass ratio of potassium acetate to zinc acetate is 0.07-1:1. This mass ratio of potassium acetate to zinc acetate has a good synergistic effect, thereby further improving the catalytic activity of the prepared catalyst. Further preferably, considering the ability to further improve the catalytic activity of the prepared catalyst, the mass ratio of potassium acetate to zinc acetate is 0.15-0.75:1.

[0032] Preferably, the mixing conditions include at least the following: temperature of 240-280℃, time of 0.5-4h, rotation speed of 100-300rpm, and aeration rate of 0.5-0.8L / min. This method allows the prepared support to be loaded with more active material, thereby further improving the catalytic activity of the prepared catalyst.

[0033] Preferably, the method further includes: granulating and drying the mixture. The catalyst prepared by the above method can be more easily separated from the reaction system.

[0034] Preferably, the drying conditions include a temperature of 60-85°C, more preferably 75-85°C.

[0035] A third aspect of the present invention provides a catalyst prepared by the above-described preparation method.

[0036] This catalyst comprises a polyterephthalate (PTFE) support and an active component supported on the PTFE support. The active component contains acetate ions and a metal ion selected from at least one group IA and group IIB metal ions. When applied to transesterification or esterification reactions, it exhibits high catalytic activity and stability, and can be easily and rapidly separated from transesterification and / or esterification products, facilitating repeated use. Furthermore, the products obtained using this catalyst have high purity and good color, facilitating subsequent applications.

[0037] Moreover, research has found that the catalyst provided by this invention can be used continuously for more than 8,000 hours, with a long service life and high catalyst stability.

[0038] A fourth aspect of this invention provides the application of the catalyst provided in the first or third aspect above as a transesterification catalyst and / or esterification catalyst. This catalyst exhibits good catalytic performance and stability in transesterification and esterification reactions, and can be easily separated from the products.

[0039] The fifth aspect of the present invention provides a method for preparing dimethyl terephthalate, the method comprising: reacting terephthalate, methanol and the above-mentioned catalyst under transesterification conditions.

[0040] The above method has high yield and product selectivity, and the catalyst can be directly separated from the product by solid-liquid separation, which is convenient and fast, resulting in products with high purity and color.

[0041] Preferably, the mass ratio of the terephthalate to the catalyst is 1:0.005-0.02, which can be 1:0.005, 1:0.01, 1:0.015, 1:0.02, or any value between these values. Controlling the amount of catalyst added within the above range can reduce the preparation cost while ensuring the catalytic effect.

[0042] Preferably, the mass ratio of the terephthalate to the methanol is 1:1.2-2, and can be 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:2, or any value between these values. The above-mentioned mass ratios of terephthalate and methanol exhibit good reaction performance.

[0043] Preferably, the conditions for the ester exchange include at least a temperature of 80-110°C. Under these conditions, the scaffold exchange effect is better.

[0044] Preferably, the terephthalate is selected from at least one of polyethylene terephthalate, propylene terephthalate, butylene terephthalate, and pentylene terephthalate. Diethyl terephthalate is preferred.

[0045] Terephthalic acid esters can be prepared or commercially available. In one specific embodiment of the present invention, terephthalic acid esters are prepared by means of a contact reaction between terephthalic acid and a diol under esterification conditions.

[0046] Preferably, the diol is selected from at least one of ethylene glycol, propylene glycol, butanediol, and pentanediol. The esterification conditions include at least: a temperature of 220-260°C, a time of 0.5-1 h, and a stirring rate of 100-400 rpm. The molar ratio of the terephthalic acid to the diol is 1:2-6.

[0047] According to a particularly preferred embodiment of the present invention, a method for preparing a catalyst is provided, comprising: Polyterephthalate and active components are mixed at 240-280℃ and 100-300rpm for 2-10 minutes and then fed into a twin-screw extruder. During extrusion, inert gas is introduced into the mixture of polyterephthalate and active components at a purge rate of 0.5-0.8L / min. After 0.5-4 hours, the mixture is pelletized and dried. The pelletizer speed is 250-350rpm, and the drying is carried out in a forced-air oven at 75-85℃ for 4-5 hours. The mass ratio of the polyterephthalate to the active component is 1:0.02-0.15; the active component is zinc acetate and potassium acetate, the mass ratio of zinc acetate to potassium acetate is 1:0.07-1, the polyterephthalate is selected from at least one of polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate, and the inert gas is selected from at least one of nitrogen, helium, neon and argon.

[0048] The present invention will be described in detail below through examples. In the following examples, the purity and conversion rate parameters were measured by gas chromatography, and the Lab value was measured by a 6801 colorimeter; the PET, PBT, and PTT raw materials were commercially available industrial-grade products from Sinopec Yizheng Chemical Fiber Co., Ltd., with the number average molecular weight of PET being 25,000; the number average molecular weight of PBT being 25,000; the number average molecular weight of PTT being 20,000; and the number average molecular weight of polystyrene being 40,000.

[0049] Example 1-1 (1) Mix 91.5g zinc acetate, 49g potassium acetate and 1920g PET chips at 300rpm for 5min to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.8 L / min. The screw temperature was controlled at 260 °C. After 2 hours, the mixture was extruded and pelletized at a feeding speed of 10 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in a 75 °C oven to obtain catalyst-1.

[0050] Examples 1-2 (1) Mix 91.5g zinc acetate, 67.5g potassium acetate and 1536g PET chips at 200rpm for 6min to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.7 L / min. The screw temperature was controlled at 240 °C. After 4 hours, the mixture was extruded and pelletized at a feeding speed of 9 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in an 85 °C oven to obtain catalyst-2.

[0051] Examples 1-3 (1) Mix 137.3g zinc acetate, 24.5g potassium acetate and 3840g PET chips at 100rpm for 10min to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.5 L / min. The screw temperature was controlled at 280℃. After 0.5 h, the mixture was extruded and pelletized at a feeding speed of 11 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in an 80℃ forced-air oven to obtain catalyst-3.

[0052] Examples 1-4 Catalyst-4 was prepared according to the method of Examples 1-2, except that the amount of zinc acetate was 68.6 g and the amount of potassium acetate was 67.5 g.

[0053] Examples 1-5 Catalyst-5 was prepared according to the methods of Examples 1-3, except that the amount of zinc acetate was 160.1 g and the amount of potassium acetate was 12.3 g.

[0054] Examples 1-6 Catalyst-6 was prepared according to the method of Examples 1-2, except that the amount of zinc acetate was 137.3 g and the amount of potassium acetate was 67.5 g.

[0055] Examples 1-7 Catalyst-7 was prepared according to the methods of Examples 1-3, except that the amount of zinc acetate was 91.5 g and the amount of potassium acetate was 32.7 g.

[0056] Examples 1-8 Catalyst-8 was prepared according to the method of Examples 1-2, except that the amount of zinc acetate used was 218g.

[0057] Examples 1-9 Catalyst-9 was prepared according to the methods of Examples 1-3, except that the amount of potassium acetate used was 98g.

[0058] Examples 1-10 Catalyst-10 was prepared according to the methods of Examples 1-8, except that 1536g of PET was replaced with 4400g of PBT.

[0059] Examples 1-11 Catalyst-11 was prepared according to the methods of Examples 1-3, except that 1920g PET was replaced with 2060g PTT.

[0060] Examples 1-12 Catalyst-12 was prepared according to the method described in Example 1-1, except that 91.5 g of zinc acetate and 49 g of potassium acetate were replaced with 190 g of cadmium acetate.

[0061] Examples 1-13 Catalyst-13 was prepared according to the method described in Example 1-1, except that 91.5 g of zinc acetate and 49 g of potassium acetate were replaced with 82 g of sodium acetate.

[0062] Example 2-1 (1) PTA and ethylene glycol in a molar ratio of 1:2 were esterified at a temperature of 260℃ and a rotation speed of 400rpm for 1.5h to obtain the esterified product; (2) The esterification product, methanol and catalyst-1 were subjected to transesterification reaction at a temperature of 100℃. After the reaction was completed, the solid and liquid phases were separated. The liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The conversion rate was 99.8% and the purity of dimethyl terephthalate was 99.6%. The mass ratio of esterification product to catalyst-1 is 1:0.005, and the molar ratio of esterification product to methanol is 1:1.5.

[0063] After the catalyst was used continuously for 8000 hours, it was applied to the above reaction again, and the reaction conversion rate was 99.0%, and the purity of dimethyl terephthalate was 99.5%.

[0064] Example 2-2 (1) PTA and ethylene glycol in a molar ratio of 1:3 were esterified at a temperature of 240℃ and a rotation speed of 200rpm for 1h to obtain the esterified product; (2) The esterification product, methanol and catalyst-2 were subjected to transesterification reaction at a temperature of 110°C. After the reaction was completed, the solid and liquid phases were separated. The liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The conversion rate was 99.9% and the purity of dimethyl terephthalate was 99.6%. The mass ratio of esterification product to catalyst-2 is 1:0.01, and the molar ratio of esterification product to methanol is 1:2.

[0065] After the catalyst was used continuously for 8000 hours, it was applied to the above reaction again, and the reaction conversion rate was 99.2%, and the purity of dimethyl terephthalate was 99.5%.

[0066] Example 2-3 (1) PTA and ethylene glycol in a molar ratio of 1:3 were esterified at a temperature of 250℃ and a rotation speed of 400rpm for 1h to obtain the esterified product; (2) The esterification product, methanol and catalyst-3 were subjected to transesterification reaction at a temperature of 80°C. After the reaction was completed, the solid and liquid phases were separated. The liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The conversion rate was 99.8% and the purity of dimethyl terephthalate was 99.7%. The mass ratio of esterification product to catalyst-3 is 1:0.02, and the molar ratio of esterification product to methanol is 1:2.

[0067] After the catalyst was used continuously for 8000 hours, it was applied to the above reaction again, and the reaction conversion rate was 99.1%, and the purity of dimethyl terephthalate was 99.6%.

[0068] Examples 2-4 (1) PTA and ethylene glycol in a molar ratio of 1:4 were esterified at a temperature of 250℃ and a rotation speed of 400rpm for 1h to obtain the esterified product. (2) The esterification product, methanol and catalyst-1 were subjected to transesterification reaction at a temperature of 100℃. After the reaction was completed, the solid and liquid phases were separated. The liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The conversion rate was 99.8% and the purity of dimethyl terephthalate was 99.7%. The mass ratio of esterification product to catalyst-1 is 1:0.02, and the molar ratio of esterification product to methanol is 1:1.5.

[0069] Examples 2-5 Dimethyl terephthalate was prepared according to the method described in Examples 2-2, except that catalyst-2 was replaced with catalyst-4.

[0070] Examples 2-6 Dimethyl terephthalate was prepared according to the method described in Examples 2-3, except that catalyst-3 was replaced with catalyst-5.

[0071] Examples 2-7 Dimethyl terephthalate was prepared according to the method described in Examples 2-2, except that catalyst-2 was replaced with catalyst-6.

[0072] Examples 2-8 Dimethyl terephthalate was prepared according to the method described in Examples 2-3, except that catalyst-3 was replaced with catalyst-7.

[0073] Examples 2-9 Dimethyl terephthalate was prepared according to the method described in Examples 2-2, except that catalyst-2 was replaced with catalyst-8.

[0074] Example 2-10 Dimethyl terephthalate was prepared according to the method described in Examples 2-3, except that catalyst-3 was replaced with catalyst-9.

[0075] Example 2-11 (1) PTA and butanediol with a molar ratio of 1:3 were esterified at a temperature of 240℃ and a rotation speed of 200rpm for 1h to obtain the esterified product; (2) The esterification product, methanol and catalyst-10 were subjected to transesterification reaction at a temperature of 100°C. After the reaction was completed, the solid and liquid phases were separated, the liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The mass ratio of esterification product to catalyst-10 is 1:0.01, and the molar ratio of esterification product to methanol is 1:2.

[0076] Example 2-12 (1) PTA and propylene glycol in a molar ratio of 1:3 were esterified at a temperature of 250℃ and a rotation speed of 400rpm for 1h to obtain the esterified product. (2) The esterification product, methanol and catalyst-11 were subjected to transesterification reaction at a temperature of 100°C. After the reaction was completed, the solid and liquid phases were separated, the liquid phase was returned for reuse, and the solid phase was dimethyl terephthalate. The mass ratio of esterification product to catalyst-11 is 1:0.02, and the molar ratio of esterification product to methanol is 1:2.

[0077] Example 2-13 Dimethyl terephthalate was prepared according to the method described in Examples 2-2, except that catalyst-2 was replaced with catalyst-12.

[0078] Example 2-14 Dimethyl terephthalate was prepared according to the method described in Examples 2-3, except that catalyst-3 was replaced with catalyst-13.

[0079] Comparative Example 1-1 (1) Mix 117g of cobalt acetate and 1920g of PET chips to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.8 L / min. The screw temperature was controlled at 260°C. After 2 hours, the mixture was extruded and pelletized at a feeding speed of 10 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in a 75°C forced-air oven to obtain catalyst-14.

[0080] Comparative Examples 1-2 (1) Mix 173g of manganese acetate and 1920g of PET chips to obtain a mixture; (2) The mixture was added to a twin-screw extruder. Nitrogen was introduced at the screw inlet at a rate of 0.8 L / min. The screw temperature was controlled at 260°C. After 2 hours, the mixture was extruded and pelletized at a feeding rate of 10 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in a 75°C forced-air oven to obtain catalyst-15.

[0081] Comparative Examples 1-3 (1) Mix 226.5g of palladium acetate and 1920g of PET chips to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.8 L / min. The screw temperature was controlled at 260 °C. After 2 hours, the mixture was extruded and pelletized at a feeding speed of 10 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in a 75 °C forced-air oven to obtain catalyst-16.

[0082] Comparative Examples 1-4 (1) Mix 91.5g zinc acetate, 49g potassium acetate and 1920g polystyrene chips for 5 minutes to obtain a mixture; (2) The mixture was added to a twin-screw extruder, and nitrogen was introduced at the screw inlet at a rate of 0.8 L / min. The screw temperature was controlled at 260°C. After 2 hours, the mixture was extruded and pelletized at a feeding speed of 10 g / min, a screw speed of 100 rpm, and a pelletizer speed of 250 rpm. The pellets were then dried in a 75°C forced-air oven to obtain catalyst-17.

[0083] Comparative Example 2-1 Dimethyl terephthalate was prepared according to the method of Example 2-1, except that catalyst-1 was replaced with catalyst-14.

[0084] Comparative Example 2-2 Dimethyl terephthalate was prepared according to the method of Example 2-1, except that catalyst-1 was replaced with catalyst-15.

[0085] Comparative Examples 2-3 Dimethyl terephthalate was prepared according to the method of Example 2-1, except that catalyst-1 was replaced with catalyst-16.

[0086] Comparative Examples 2-4 Dimethyl terephthalate was prepared according to the method of Example 2-1, except that catalyst-1 was replaced with catalyst-17.

[0087] Test Example 1 The performance of the catalysts in the examples and comparative examples is shown in Table 1.

[0088] Table 1

[0089] Test Example 2 The conversion rates and product purity of the examples and comparative examples are recorded in Table 2. The colorimetry of the products of the examples and comparative examples was measured using a 6801 colorimeter, and the results are recorded in Table 2.

[0090] Table 2

[0091] As can be seen from the results in Table 2, the transesterification conversion rate of the above-mentioned embodiment is higher than that of the comparative example, the product purity is higher than that of the comparative example, and the color value of the product is higher than that of the comparative example. This indicates that the catalyst of the present invention has the effects of high conversion rate, high product purity, and good color when used in transesterification reaction.

[0092] 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 catalyst characterized in that, The catalyst contains a polyterephthalate carrier and an active component supported on the polyterephthalate carrier, the active component containing acetate ions and metal ions selected from at least one of Group IA metal ions and Group IIB metal ions.

2. The catalyst according to claim 1, characterized in that, The polyterephthalate carrier is selected from at least one of polyethylene terephthalate carriers, polytrimethylene terephthalate carriers and polybutylene terephthalate carriers, preferably polyethylene terephthalate carriers; The Group IA metal ions are potassium ions and the Group IIB metal ions are zinc ions; Preferably, the metal ions are potassium ions and zinc ions, and the mass ratio of the potassium ions to the zinc ions is 0.08-1.15:1, further preferably 0.2-0.85:1; Preferably, the specific surface area of the catalyst is comprised between 350 and 600 m 2 / g, further preferably between 420 and 500 m 2 / g; the porosity is comprised between 93 and 99%, further preferably between 97.5 and 99%.

3. Catalyst according to claim 1 or 2, characterized in that In the catalyst, the loading of the acetate ions is 1-8wt%, preferably 2.5-6wt%; and the loading of the metal ions is 1-5.5wt%, preferably 1.4-3.6wt%.

4. A process for the preparation of a catalyst, characterized in that The preparation method comprises mixing a polyterephthalate and an active component, and introducing an inert gas into the mixture of the polyterephthalate and the active component during the mixing; The active component contains acetate ions and metal ions selected from at least one of Group IA metal ions and Group IIB metal ions, and the inert gas is selected from at least one of nitrogen, helium, neon and argon.

5. The production method according to claim 4, characterized by, The mass ratio of the polyterephthalate to the active component is 1:0.02-0.15, preferably 1:0.04-0.1; Preferably, the polyterephthalate is selected from at least one of polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate, preferably polyethylene terephthalate; The active component is potassium acetate and / or zinc acetate, preferably potassium acetate and zinc acetate; Preferably, the mass ratio of the potassium acetate to the zinc acetate is 0.07-1:1; further preferably 0.15-0.75:

1.

6. The production method according to claim 4 or 5, characterized by, The conditions of the mixing at least include a temperature of 240-280℃, a time of 0.5-4h, a rotation speed of 100-300rpm and a gas flow rate of 0.5-0.8L / min; The method further comprises granulating and drying the mixture.

7. The catalyst prepared by the preparation method of any one of claims 4 to 6.

8. Use of the catalyst of any one of claims 1 to 3 and claim 7 as an ester exchange catalyst and / or an esterification catalyst.

9. A process for the preparation of dimethyl terephthalate, characterized in that, The preparation method comprises contacting the catalyst of any one of claims 1 to 3 and claim 7, a terephthalate and methanol under ester exchange conditions.

10. The method of claim 9, wherein, The mass ratio of the terephthalate to the catalyst is 1:0.005-0.02; Preferably, the molar ratio of the terephthalate to the methanol is 1:1.2-2; Preferably, the conditions of the ester exchange at least include a temperature of 80-110℃.

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