Process for the production of 3-hydroxypropionic acid methyl ester and dimethyl terephthalate as co-products

Abstract

The application provides a preparation method of co-production of 3-hydroxypropionic acid methyl ester and terephthalic acid dimethyl ester, comprising the following steps: S1, carrying out halogenation reaction on a first material containing terephthalic acid ethylene glycol ester, a halogen-containing compound and an acidic catalyst to obtain halogenated terephthalic acid ethylene glycol ester; S2, carrying out a first reaction on a second material containing the halogenated terephthalic acid ethylene glycol ester, a cobalt catalyst, a ligand and an alkaline additive in the presence of carbon monoxide to obtain 3-hydroxypropionic acid methyl ester and terephthalic acid dimethyl ester. The application can realize high-value conversion of terephthalic acid ethylene glycol ester, and simultaneously efficiently co-produce 3-hydroxypropionic acid methyl ester and terephthalic acid dimethyl ester.

Description

Technical Field

[0001] This application belongs to the field of fine chemicals, and in particular relates to a method for preparing methyl 3-hydroxypropionate and dimethyl terephthalate co-produced. Background Technology

[0002] Dimethyl terephthalate (DMT), an important fine chemical raw material, is a white needle-like crystal at room temperature. It is easily sublimed, insoluble in water, but soluble in organic solvents such as methanol, ether, and chloroform. Its excellent chemical stability and reactivity make it a key intermediate in the synthesis of polyester materials, widely used in polyester resins, engineering plastics (such as PET, PBAT, and PTT), and fibers. Related materials possess excellent toughness, abrasion resistance, and mechanical properties. Traditional synthesis methods primarily involve esterification, specifically the esterification reaction of terephthalic acid and methanol catalyzed by sulfuric acid, or the Witton process (a continuous oxidative esterification process). However, traditional processes have significant drawbacks: the catalysts (such as sulfuric acid) are highly corrosive, leading to high equipment maintenance costs and safety hazards; the use of sulfuric acid results in the generation of large amounts of acidic wastewater, which is difficult to treat and easily causes environmental pollution; CN104072374A discloses a method using concentrated sulfuric acid as a catalyst to react terephthalic acid with excess methanol at 170-180℃ for 10-18 hours, and after multiple post-processing steps, a purity of 99.8%-99.9% can be obtained. This method uses excess alcohol as a dehydrating agent to improve esterification efficiency, simplify the process, and optimize product quality, but the use of concentrated sulfuric acid as a catalyst causes severe corrosion to equipment, and the production process generates large amounts of waste acid and washing wastewater, resulting in significant environmental pollution and making it unsuitable for long-term operation. Furthermore, the recovery efficiency of by-products (such as methanol) is low, increasing energy consumption and raw material loss. Therefore, developing environmentally friendly, efficient, and low-energy-consumption DMT synthesis technology has become an urgent direction to break through the bottlenecks of traditional processes and meet the needs of green chemical industry and sustainable development.

[0003] Methyl 3-hydroxypropionate, an important fine chemical raw material, is a colorless liquid under normal conditions, soluble in water and most organic solvents, and possesses good chemical stability and reactivity. This compound has wide applications in the pharmaceutical, pesticide, fragrance, and new materials fields, especially as a key linker in PROTAC technology for targeted protein degradation research. It can also be used as an intermediate in the synthesis of high-value-added chemicals (such as polyesters and epoxy resins). Notably, methyl 3-hydroxypropionate can be hydrogenated in one step to prepare propylene glycol, which has shown broad application value in plastics and polymers, the food industry, and pharmaceuticals and cosmetics. Traditional carbonyl methyl esterification uses ethylene oxide and carbon monoxide as raw materials, and the reaction is extremely hazardous, hindering industrialization. US4973741 discloses the synthesis of methyl 3-hydroxypropionate by hydroxymethyl esterification of ethylene oxide using a noble metal rhodium catalyst and triphenylphosphine ligand; however, the reaction requires a high pressure of 14 MPa, and the conversion rate of ethylene oxide and the selectivity of the target product are low. US6191321 discloses a catalyst system using Co2(CO)8 / 1,10-o-phenanthroline, with methyl tert-butyl ether as the solvent, and a reaction at 90°C and 1125 psi for 18 hours, resulting in an ethylene oxide conversion of only 11% and a selectivity of 74% for the target product, methyl 3-hydroxypropionate. Therefore, developing a green, efficient, and highly selective new technology for the synthesis of methyl 3-hydroxypropionate is of great significance for the efficient and large-scale production of propylene glycol, reducing production costs, and achieving environmentally friendly production.

[0004] In summary, developing an efficient method for the co-production of methyl 3-hydroxypropionate and dimethyl terephthalate is of great significance for promoting technological upgrading and green development in the field of fine chemicals. Summary of the Invention

[0005] This application provides a method for co-producing methyl 3-hydroxypropionate and dimethyl terephthalate, which can achieve the high-value conversion of ethylene terephthalate and simultaneously produce methyl 3-hydroxypropionate and dimethyl terephthalate efficiently.

[0006] This application provides a method for preparing methyl 3-hydroxypropionate and dimethyl terephthalate co-produced, comprising the following steps: S1, subjecting a first material containing ethylene terephthalate, a halogenated compound, and an acidic catalyst to a halogenation reaction to obtain ethylene terephthalate haloformatum; S2, subjecting a second material containing the ethylene terephthalate haloformatum, a cobalt catalyst, a ligand, and a basic additive to a first reaction in the presence of carbon monoxide to obtain methyl 3-hydroxypropionate and dimethyl terephthalate.

[0007] According to one embodiment of this application, the acidic catalyst comprises one or more of the following: acidic ion exchange resin, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, and phosphoric acid; and / or, the halogen-containing compound comprises metal halides and / or hydrohalic acids; the metal halide comprises one or more of the following: potassium iodide, sodium iodide, lithium iodide, ammonium iodide, hydroiodic acid, potassium bromide, sodium bromide, lithium bromide, ammonium bromide, hydrobromic acid, potassium chloride, sodium chloride, lithium chloride, and ammonium chloride; the hydrohalic acid comprises hydrochloric acid; and / or, the alkaline additive comprises one or more of the following: potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium phosphate, sodium phosphate, lithium phosphate, and ammonia water.

[0008] According to one embodiment of this application, the alkaline additive includes sodium carbonate and sodium methoxide; and / or, the acidic catalyst includes an acidic ion exchange resin; and / or, the metal halide includes one or more of potassium bromide, sodium bromide, lithium bromide, and ammonium bromide.

[0009] According to one embodiment of this application, the cobalt catalyst includes one or more of cobalt octacarbonyl, cobalt acetylacetonate, cobalt iodide, cobalt chloride, cobalt acetate, and cobalt bromide; and / or, the ligand includes a nitrogen-containing heterocyclic ligand.

[0010] According to one embodiment of this application, the molar ratio of the polyethylene terephthalate to the halogenated compound is 1:(1~4); and / or, the molar ratio of the polyethylene terephthalate to the acidic catalyst is 1:(1~6); and / or, the mass ratio of the halogenated polyethylene terephthalate to the cobalt catalyst is (100-1000):1; and / or, the molar ratio of the ligand to the cobalt catalyst is (1-100):1; and / or, the molar ratio of the halogenated polyethylene terephthalate to the basic additive is 1:(1-4).

[0011] According to one embodiment of this application, the molar ratio of the polyethylene terephthalate to the acidic catalyst is 1:(1~3); and / or, the mass ratio of the halogenated polyethylene terephthalate to the cobalt catalyst is (500-600):1; and / or, the molar ratio of the ligand to the cobalt catalyst is (50-60):1.

[0012] According to one embodiment of this application, the temperature of the halogenation reaction is 60-150°C, and the time of the halogenation reaction is 1-8 hours; and / or, the temperature of the first reaction is 70-130°C, and the time of the first reaction is 2-12 hours.

[0013] According to one embodiment of this application, the first material further includes a first solvent, which includes one or more of ethyl acetate, propyl acetate, butyl acetate, γ-valerolactone, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valeronitrile, benzonitrile, toluene, benzene, N,N-dimethylformamide, and dimethyl sulfoxide; and / or, the second material further includes a second solvent, which includes one or more of water, acetic acid, and alcohol solvents.

[0014] According to one embodiment of this application, the process of halogenating a first material containing polyethylene terephthalate, a halogenated compound, and an acidic catalyst to obtain halogenated polyethylene terephthalate includes: halogenating the first material containing polyethylene terephthalate, a halogenated compound, a first solvent, and an acidic catalyst to obtain a halogenated intermediate; subjecting the halogenated intermediate to a first crystallization treatment to obtain the halogenated polyethylene terephthalate; and / or, the first reaction is carried out in an apparatus where the carbon monoxide pressure is 3-6 MPa; and / or, step S2 includes: halogenating a second material containing the halogenated polyethylene terephthalate, a cobalt catalyst, a ligand, and a basic additive to a first reaction in the presence of carbon monoxide to obtain a mixed product; subjecting the mixed product to vacuum distillation to obtain methyl 3-hydroxypropionate and a mother liquor; and subjecting the mother liquor to a second crystallization treatment to obtain dimethyl terephthalate.

[0015] According to one embodiment of this application, both the first crystallization treatment and the second crystallization treatment are carried out in a third solvent, the third solvent including one or more of ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, dioxane, tetrahydrofuran, acetonitrile, tert-valerate, benzonitrile, acetone, methanol, ethanol, and isopropanol; and / or, the first crystallization treatment includes a first cooling crystallization treatment, the first cooling crystallization treatment including cooling from 60-100°C to a first endpoint temperature at a cooling rate of 1-25°C / h, and holding at the first endpoint temperature for 4-5 hours, the first endpoint temperature being 0-40°C; and / or, the vacuum distillation temperature is 80-120°C, the vacuum distillation time is 20 min-2 h, and the vacuum distillation pressure is 100-300 kJ / min. mbar; and / or, the second crystallization process includes a second cooling crystallization process, which includes cooling from 80-120°C to a second endpoint temperature at a cooling rate of 1-25°C / h, and holding at the second endpoint temperature for 2-3 hours after cooling, wherein the second endpoint temperature is -10-40°C.

[0016] This application provides a method for the co-production of methyl 3-hydroxypropionate and dimethyl terephthalate. Under the acid catalysis of an acidic catalyst, the halogen element of a halogen-containing compound undergoes a substitution reaction with the ester group of BHET, introducing a halogenated group to obtain halo-BHET, providing an active site for the subsequent first reaction. Subsequently, under the synergistic effect of a cobalt catalyst, basic additives, and ligands, carbon monoxide (CO) reacts with the halo-BHET to generate 3-HPM and DMT. This method achieves the high-value conversion of ethylene terephthalate while efficiently co-producing methyl 3-hydroxypropionate and dimethyl terephthalate. Attached Figure Description

[0017] Figure 1 The 1H NMR spectrum of brominated BHET in Example 1 of this application;

[0018] Figure 2 This is the liquid chromatogram of brominated BHET in Example 1 of this application;

[0019] Figure 3 This is the 1H NMR spectrum of dimethyl terephthalate in Example 1 of this application;

[0020] Figure 4 This is the gas chromatogram of methyl 3-hydroxypropionate in Example 1 of this application;

[0021] Figure 5 This is a schematic diagram of the synthetic route for preparing 3-HPM and DMT from BHET in the embodiments of this application;

[0022] Figure 6 This is a schematic diagram of the BHET bromination reaction in the embodiments of this application;

[0023] Figure 7 This is a schematic diagram of the chemical formula of the first reaction in the embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] With the rapid development of the polyester textile industry, the amount of waste polyester textiles generated is increasing year by year. Recycling and reusing waste polyester textiles is of great significance for resource conservation, pollution reduction, and carbon reduction. Waste polyester textiles can be chemically depolymerized to recover polyethylene terephthalate (BHET) monomers. The high-value utilization of BHET not only achieves resource recycling but also creates economic value and reduces environmental pollution. As a key monomer in PET synthesis, BHET can be directly used as a raw material to repolymerize and prepare recycled polyester fibers, realizing a complete closed-loop cycle from "waste colored textiles" to "recyclable colorless fibers + reusable dyes." However, the high-value utilization of BHET through chemical transformation is still in its early stages of research, with several academic gaps remaining.

[0026] This application provides a method for the co-production of methyl 3-hydroxypropionate and dimethyl terephthalate, comprising the following steps: S1, subjecting a first material containing ethylene terephthalate, a halogenated compound, and an acidic catalyst to a halogenation reaction to obtain halogenated ethylene terephthalate; S2, subjecting a second material containing halogenated ethylene terephthalate, a cobalt catalyst, a ligand, and a basic additive to a first reaction in the presence of CO to obtain methyl 3-hydroxypropionate and dimethyl terephthalate. Thus, this application achieves the high-value conversion of ethylene terephthalate and efficiently co-produces methyl 3-hydroxypropionate and dimethyl terephthalate, offering both economic and environmental benefits.

[0027] This application achieves the high-value conversion of polyethylene terephthalate (BHET) through a halogenation reaction and a first reaction, simultaneously and efficiently producing methyl 3-hydroxypropionate (3-HPM) and dimethyl terephthalate (DMT). Specifically, in step S1, under the acid catalysis of an acidic catalyst, the halogen element of the halogen-containing compound undergoes a directed substitution reaction with the ester group of BHET, introducing a halogenated group to obtain halo-BHET, providing an active site for the subsequent first reaction. In step S2, under the synergistic catalytic system of a cobalt catalyst, a basic additive, and a ligand, CO undergoes a first reaction with the halo-BHET to generate 3-HPM and DMT.

[0028] Specifically, such as Figure 7As shown, the first reaction process in step S2 includes the following two reaction units proceeding simultaneously in the same reaction system: 1) Under the action of a basic additive, halo-BHET undergoes transesterification to generate dimethyl terephthalate (DMT) and 2-haloethanol. Specifically, the methoxy anion attacks the carbonyl carbon atom of halo-BHET to form an intermediate, which then decomposes to generate DMT and 2-haloethanol. 2) The halogen atom in 2-haloethanol, under the synergistic coordination of the cobalt catalyst and ligand, first combines with the cobalt center to form a metal-carbon bond intermediate; subsequently, CO molecules in the system are directionally inserted into this metal-carbon bond intermediate to generate an acyl cobalt active species; this acyl cobalt active species undergoes a nucleophilic substitution reaction with the methoxy ion in the system (derived from the dissociation of methanol solvent and basic additive) to obtain methyl 3-hydroxypropionate (3-HPM), while simultaneously removing the halide ion to complete the hydrogen esterification reaction.

[0029] It is worth mentioning that the halogenated compounds (i.e., halogenated reagents) consumed in the halogenation reaction can be regenerated in the first reaction of step S2, thus achieving reuse.

[0030] In this embodiment, BHET includes crude BHET obtained by alcoholysis of polyester raw materials under the action of an alcoholysis reagent. Generally, the alcoholysis reagent includes ethylene glycol.

[0031] In some embodiments, the acidic catalyst includes one or more of acidic ion exchange resins, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, and phosphoric acid. The above-mentioned acidic catalysts have excellent catalytic activity and selectivity, which is beneficial to the efficient conduct of halogenation reactions and reduces the occurrence of side reactions.

[0032] In some embodiments, the acidic ion exchange resin includes styrene-divinylbenzene copolymer sulfonate resin and / or styrene-divinylbenzene copolymer phosphonate resin.

[0033] In this embodiment, the acidic ion exchange resin consumed in the first reaction of step S2 can be activated by hydrochloric acid acidification and recycled.

[0034] In some embodiments, the halogen-containing compound includes metal halides and / or hydrohalic acids; the metal halides include one or more of potassium iodide, sodium iodide, lithium iodide, ammonium iodide, hydroiodic acid, potassium bromide, sodium bromide, lithium bromide, ammonium bromide, hydrobromic acid, potassium chloride, sodium chloride, lithium chloride, and ammonium chloride; the hydrohalic acid includes hydrochloric acid. Under acidic catalytic conditions, the above-mentioned halogen-containing compounds can directionally attack the active methylene sites in the BHET molecule, inhibiting side reactions such as monohalogenation and ester substitution.

[0035] In some embodiments, the halogenated compound includes sodium bromide, which is inexpensive, readily available, and chemically stable. It is also easy to recycle after the reaction, thus avoiding the generation of large amounts of waste salt and reducing the environmental treatment costs of industrial production.

[0036] In some embodiments, when the halogenated compound is sodium bromide, the synthesis process of 3-HPM and DMT prepared from BHET is as follows: Figure 5 As shown. Ethylene terephthalate, sodium bromide, and an acidic catalyst are mixed and subjected to a bromination reaction to obtain ethylene terephthalate bromide. Ethylene terephthalate bromide, a cobalt catalyst, a ligand, and a basic additive are mixed, and CO is introduced to carry out the first reaction, yielding methyl 3-hydroxypropionate and dimethyl terephthalate. The halogenation reaction process is as follows. Figure 6 As shown, ethylene terephthalate, sodium bromide, and an acidic catalyst are mixed and subjected to a halogenation reaction to obtain bromoethylene terephthalate.

[0037] In some embodiments, the cobalt catalyst includes one or more of cobalt octacarbonyl, cobalt acetylacetonate, cobalt iodide, cobalt chloride, cobalt acetate, and cobalt bromide. These cobalt catalysts exhibit high catalytic activity and excellent selectivity, which is beneficial for the efficient formation of the target products (methyl 3-hydroxypropionate and dimethyl terephthalate).

[0038] In some embodiments, the ligands include nitrogen-containing heterocyclic ligands. This facilitates the modulation of the active center of the cobalt catalyst, improves reaction efficiency, enhances the stability of cobalt catalysts, directionally suppresses side reactions, and improves the selectivity of the target products (methyl 3-hydroxypropionate and dimethyl terephthalate).

[0039] In some embodiments, the nitrogen-containing heterocyclic ligand includes at least one compound having the structure shown in Formulas 1 to 5:

[0040] .

[0041] In some embodiments, the alkaline additive includes one or more of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium phosphate, sodium phosphate, lithium phosphate, and ammonia. The alkaline additive can promote the transesterification reaction and, at the same time, act as an acid-binding agent in the hydrogen esterification process to neutralize the generated hydrogen halides, thus promoting the forward reaction.

[0042] In some embodiments, the alkaline additives include sodium carbonate and sodium methoxide. The addition of sodium carbonate and sodium methoxide as a mixed base can have a synergistic effect, increasing the rate of transesterification and hydrogen esterification reactions and promoting the forward reaction.

[0043] In some embodiments, the molar ratio of polyethylene terephthalate to the halogenated compound is 1:(1~4), preferably 1:(2~3). This facilitates efficient and complete halogenation, achieving high conversion rates and avoiding polyhalogenation side reactions caused by excess halogenated compounds, thereby increasing the yield of halogenated polyethylene terephthalate.

[0044] For example, the molar ratio of polyethylene terephthalate and the halogenated compound can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc.

[0045] In some embodiments, the molar ratio of polyethylene terephthalate to the acidic catalyst is 1:(1~6), preferably 1:(1~3). This facilitates efficient and complete halogenation, improves the selectivity of the halogenation reaction, reduces the occurrence of side reactions, and thus increases the yield of halogenated polyethylene terephthalate.

[0046] For example, the molar ratio of polyethylene terephthalate and acidic catalyst can be 1:1, 1:2, 1:3, 1:4, 1:5 or 1:6, etc.

[0047] In some embodiments, the mass ratio of halogenated ethylene terephthalate to cobalt catalyst is (100-1000):1, preferably (500-600):1. This is beneficial for improving the efficiency and stability of the first reaction, avoiding side reactions caused by excess catalyst (such as dehalogenation and hydrogenation, polycarbonylation, and the generation of alkanes and polyesters), and improving product selectivity, thereby further increasing the yields of methyl 3-hydroxypropionate and dimethyl terephthalate.

[0048] For example, the mass ratio of ethylene terephthalate halophthalate to cobalt catalyst can be 100:1, 200:1, 300:1, 400:1, 600:1, 700:1 or 1000:1, etc.

[0049] In some embodiments, the molar ratio of ligand to cobalt catalyst is (1-100):1, preferably (50-60):1. This facilitates sufficient coordination between the ligand and the cobalt catalyst, forming a structurally stable cobalt-ligand complex active center, preventing cobalt ions from agglomerating or decomposing in the reaction system. This complex structure can significantly reduce the activation energy of the CO carbonyl insertion reaction, promoting efficient first-stage reaction. Simultaneously, within the above-mentioned molar ratio of ligand to cobalt catalyst, the steric hindrance and electronic effects of the ligand can better suppress side reactions such as dehalogenation hydrogenation and polycarbonylation. This further improves the yields of methyl 3-hydroxypropionate and dimethyl terephthalate.

[0050] For example, the molar ratio of ligand to cobalt catalyst can be 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, etc.

[0051] In some embodiments, the molar ratio of ethylene terephthalate halophthalate to the basic additive is 1:(1-4), preferably 1:(1-2). The basic additive promotes the transesterification reaction and acts as an acid-binding agent to neutralize the acidic hydrogen halide byproducts generated in the first reaction, preventing catalyst deactivation caused by the binding of acidic substances to the cobalt-ligand complexing active center. Furthermore, a molar ratio of ethylene terephthalate halophthalate to the basic additive in the range of 1:(1-4) can maintain a suitable weakly basic environment in the reaction system, avoiding side reactions such as catalyst activity attenuation due to insufficient basicity or excessive hydrolysis of ester bonds caused by excessive basicity.

[0052] For example, the molar ratio of halogenated ethylene terephthalate and alkaline additive can be 1:1, 1:2, 1:3 or 1:4, etc.

[0053] In some embodiments, the halogenation reaction is carried out at a temperature of 60-150°C and for a time of 1-8 hours, which is conducive to the full halogenation reaction and improves the efficiency of the halogenation reaction.

[0054] For example, the temperature of the halogenation reaction can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc.

[0055] For example, the halogenation reaction time can be 1h, 2h, 4h, 6h, 8h or 10h, etc.

[0056] In some embodiments, the halogenation reaction described above is carried out under a protective atmosphere. The protective atmosphere may include one or more of nitrogen, argon, and helium.

[0057] In some implementations, the temperature of the first reaction is 70-130°C and the reaction time is 2-12 hours, which is conducive to the full occurrence of the first reaction and improves the efficiency of the first reaction.

[0058] For example, the temperature of the first reaction can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or 130°C, etc.

[0059] For example, the time for the first reaction can be 2h, 4h, 6h, 8h, 10h or 12h, etc.

[0060] In some embodiments, the first material further includes a first solvent, which comprises one or more of ethyl acetate, propyl acetate, butyl acetate, γ-valerate, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valerate, benzonitrile, toluene, benzene, N,N-dimethylformamide, and dimethyl sulfoxide. The aforementioned first solvents, as polar aprotic solvents, can effectively dissolve nucleophiles (halogenated compounds) and substrates (BHET), accelerating the SN2 reaction by enhancing the solvation of the reactants. In some embodiments, the first solvent includes acetonitrile and / or dioxane; such solvents can better dissolve the reaction substrate (BHET) and nucleophiles and significantly enhance the nucleophilic reactivity.

[0061] In some embodiments, the second material further includes a second solvent, which includes one or more of water, acetic acid, and alcohol solvents. In some embodiments, the second solvent includes an alcohol solvent, which includes one or more of methanol, ethanol, isopropanol, tert-butanol, and benzyl alcohol. Alcohol solvents have better solubility for CO gas than water and acetic acid, which can increase the concentration of CO in the reaction system, accelerate the carbonyl insertion reaction (the binding of CO to the halogenated BHET active site), shorten the reaction induction period, and increase the first reaction rate. The moderate protonicity and polarity of alcohol solvents can stabilize the complexed active center formed by the cobalt catalyst and nitrogen-containing heterocyclic ligands through solvation effects, preventing catalyst aggregation or decomposition, ensuring stable catalytic activity throughout the reaction, and reducing the amount of catalyst used.

[0062] In this embodiment of the application, the process of halogenating a first material containing polyethylene terephthalate, a halogenated compound, and an acidic catalyst to obtain halogenated polyethylene terephthalate includes: halogenating a first material containing polyethylene terephthalate, a metal halide, a first solvent, and an acidic catalyst to obtain a halogenated intermediate product; and performing a first crystallization treatment on the halogenated intermediate product to obtain halogenated polyethylene terephthalate.

[0063] Generally, after the halogenation reaction is complete, the system contains, in addition to the halogenated polyethylene terephthalate, unreacted raw materials (ethylene terephthalate, halogenated compounds), acidic catalyst, byproducts (polymetallic halides, ester hydrolysis products, macromolecular condensation polymers), and the first solvent. The first crystallization process utilizes the difference in solubility between the halogenated polyethylene terephthalate and impurities in the solvent to achieve efficient separation of the halogenated polyethylene terephthalate from the impurities, thereby improving the purity of the halogenated polyethylene terephthalate.

[0064] In some embodiments, the mass percentage of the halogenated intermediate in the first crystallization solvent is 10-20 wt%, preferably 15 wt%. Within this mass percentage range, it is beneficial to promote a balance between the nucleation rate and crystal growth rate of the halogenated polyethylene terephthalate. Under these conditions, the target product molecules can attach orderly to the crystal nucleus surface and grow, avoiding the problems of insufficient crystallization driving force due to insufficient supersaturation, or rapid nucleation and crystal agglomeration caused by excessive supersaturation, thereby further improving the purity of the halogenated polyethylene terephthalate.

[0065] In some embodiments, the first crystallization treatment includes a first cooling crystallization treatment, which involves cooling from 60-100°C (i.e., the first initial temperature) to a first endpoint temperature at a cooling rate of 1-25°C / h, and holding at the first endpoint temperature for 4-5 hours. This facilitates the orderly precipitation of the target product, ethylene halogenated terephthalate, and reduces the probability of impurities from the mother liquor being trapped in the crystals, thereby increasing the yield of ethylene halogenated terephthalate. The first endpoint temperature is 0-40°C, preferably 0-10°C. This significantly reduces the solubility of ethylene halogenated terephthalate, allowing for complete product precipitation; simultaneously, it avoids excessively low temperatures (<0°C) that could lead to solvent solidification or impurity co-crystallization, thus improving product purity. The cooling rate of the first cooling crystallization treatment is preferably 5-20°C / h.

[0066] For example, the cooling rate of the first cooling crystallization can be 1℃ / h, 5℃ / h, 8℃ / h, 10℃ / h, 13℃ / h, 16℃ / h, 18℃ / h, 20℃ / h or 25℃ / h, etc.

[0067] For example, the first endpoint temperature can be 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃, etc.

[0068] For example, the holding time after cooling to the first endpoint temperature can be 4h, 4.2h, 4.4h, 4.6h, 4.8h or 5h, etc.

[0069] For example, the first initial temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C, etc.

[0070] In some embodiments, the first reaction described above is carried out in an apparatus where the carbon monoxide pressure is 3-6 MPa.

[0071] For example, the carbon monoxide pressure inside the device can be 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa or 6 MPa, etc.

[0072] In some embodiments, the first reaction described above is carried out in a high-pressure reactor. The reactor is purged with CO gas, and the syngas pressure is maintained at 3 MPa-6 MPa. After the CO gas is introduced, heating is performed to carry out the first reaction. Heating is stopped and the reaction is terminated once the CO gas pressure no longer changes.

[0073] In some embodiments, step S2 includes: subjecting a second material containing halogenated ethylene terephthalate, a cobalt catalyst, a ligand, and a basic additive to a first reaction in the presence of carbon monoxide to obtain a mixed product; subjecting the mixed product to vacuum distillation to obtain methyl 3-hydroxypropionate and a mother liquor; and subjecting the mother liquor to a second crystallization treatment to obtain dimethyl terephthalate.

[0074] In some embodiments, the temperature of vacuum distillation is 80-120°C, the time of vacuum distillation is 20 min-2 h, and the pressure of vacuum distillation is 100-300 mbar, which is beneficial to achieve efficient separation of 3-HPM and DMT while avoiding hydrolysis or thermal decomposition of ester bonds in 3-HPM.

[0075] For example, the temperature of vacuum distillation can be 80°C, 90°C, 100°C, 110°C or 120°C, etc.

[0076] For example, the time for vacuum distillation can be 20 min, 40 min, 50 min, 60 min, 1.5 h or 2 h, etc.

[0077] For example, the pressure of vacuum distillation can be 100 mbar, 150 mbar, 200 mbar, 250 mbar or 300 mbar, etc.

[0078] In some embodiments, the second crystallization process includes a second cooling crystallization process, which involves cooling from 80-120°C (i.e., the second initial temperature) to the second endpoint temperature at a cooling rate of 1-25°C / h, and holding at the second endpoint temperature for 2-3 hours. This facilitates the orderly precipitation of the target product DMT and reduces the probability of impurities from the mother liquor being trapped in the crystals, thereby increasing the DMT yield. The endpoint temperature of the second cooling crystallization is -10-40°C, preferably -5-5°C. This significantly reduces the solubility of DMT, allowing for complete precipitation of DMT and thus improving DMT purity. The cooling rate of the second cooling crystallization process is preferably 5-20°C / h.

[0079] For example, the cooling rate of the second cooling crystallization can be 1℃ / h, 5℃ / h, 8℃ / h, 10℃ / h, 13℃ / h, 16℃ / h, 18℃ / h, 20℃ / h, 22℃ / h or 25℃ / h, etc.

[0080] For example, the second initial temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, etc.

[0081] For example, the second endpoint temperature can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, or 3h, etc.

[0082] For example, the second endpoint temperature can be -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃, etc.

[0083] In some embodiments, both the first and second crystallization processes are carried out using a third solvent, which includes one or more of ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, dioxane, tetrahydrofuran, acetonitrile, tert-valerate, benzonitrile, acetone, methanol, ethanol, and isopropanol. Preferably, the third solvent includes acetonitrile and / or dioxane. In this type of third solvent, the product (i.e., the aforementioned halogenated intermediate and mother liquor) has good solubility at high temperatures, can precipitate at room temperature or low temperatures, and the solvent is easily volatile, facilitating crystallization and separation.

[0084] In some embodiments, after the second crystallization treatment, the obtained solid component is washed with a third solvent at around 0°C to obtain dimethyl terephthalate.

[0085] The technical solution of this application will be further described below with reference to specific embodiments.

[0086] Unless otherwise specified, all chemical reagents and chemical products mentioned in this application are chemical reagents and chemical products that are known and commonly used in the prior art; unless otherwise specified, all percentages in this application are mass percentages; room temperature and ambient temperature in this application generally refer to temperatures between 15°C and 25°C, and are generally defined as 25°C. Atmospheric pressure in this application generally refers to standard atmospheric pressure.

[0087] Example 1

[0088] 1. Preparation of brominated BHET:

[0089] Under nitrogen protection, 25 g BHET, 300 mL acetonitrile, 26 g sodium bromide, and 100 g Amberlyst 15 ion exchange resin (Leyan, catalog number 1159263, Amberlyst ion exchange resin 36, hydrogen form, wet form, pore volume ≥0.20 cm³ / g) were added to a 500 mL three-necked flask equipped with a reflux condenser. After the addition was complete, the bromination reaction was carried out at 90 °C for 4 hours. Subsequently, the mixture was cooled to room temperature, and the bromination reaction mixture was poured into a 1000 mL flask and evaporated to dryness to obtain the first filter cake. The first filter cake was washed and filtered sequentially with approximately 50 mL of methanol to obtain the second filter cake. The second filter cake was washed with ice water (temperature 0-5 °C) and dried to obtain the crude bromination product. The above-mentioned crude brominated product was transferred to a 500 mL crystallizer, and about 250 g of acetonitrile was added. The temperature was increased to 60 °C at a rate of 10 °C / min. After the crude brominated product was completely dissolved, the temperature was decreased from 60 °C to 0 °C at a rate of 20 °C / h. The temperature was maintained at 0 °C for 5 h (to complete the first cooling crystallization process). The product was then filtered to obtain a crude product filter cake. The crude product filter cake was decolorized with activated carbon, washed, and dried to obtain brominated BHET.

[0090] The molar ratio of BHET to Amberlyst15 ion exchange resin is 1:3.

[0091] Figure 1 The image shows the 1H NMR spectrum of brominated BHET, indicating the successful synthesis of brominated BHET.

[0092] Figure 2 The liquid chromatogram of brominated BHET is shown below. Figure 2 It can be seen that high-purity brominated BHET is obtained through bromination reaction, first cooling crystallization treatment, activated carbon decolorization, washing, and drying.

[0093] 2. Preparation of methyl 2-hydroxypropionate and dimethyl terephthalate

[0094] In a 100 mL high-pressure sealed reactor, 2.37 g of bromo-BHET, 4 mg of Co2(CO)8, 24 mg of 2-pyridone (i.e., the structure shown in Formula 3), 0.53 g of sodium carbonate, 0.54 g of sodium methoxide, and 30 mL of anhydrous methanol were added sequentially. CO gas was introduced into the reactor, and after three CO gas replacements, the gas pressure inside the reactor was maintained at 4 MPa. The reactor was stirred at 80 °C for 4 h to obtain the first reaction solution. After the first reaction was completed, the reactor was thoroughly cooled to room temperature, and the gas was slowly released to atmospheric pressure. The reaction solution was transferred to a vacuum distillation apparatus to obtain methyl 3-hydroxypropionate by vacuum distillation. The remaining mother liquor was dissolved in ethyl acetate, and the temperature was gradually lowered in a crystallizer at a rate of 20 °C / h to 0 °C. This temperature was then maintained at 0 °C for 3 h to precipitate dimethyl terephthalate. The vacuum distillation temperature was 90 °C, the vacuum distillation time was 20 min, and the vacuum distillation pressure was 120 mbar. The mass ratio of bromo-BHET to Co2(CO)8 is 592.5:1, and the molar ratio of 2-pyridone to Co2(CO)8 is 7.8:1.

[0095] Figure 3 The image shows the 1H NMR spectrum of dimethyl terephthalate in Example 1 of this application, indicating the successful synthesis of dimethyl terephthalate.

[0096] Figure 4 The image shows a gas chromatogram of methyl 3-hydroxypropionate in Example 1 of this application, indicating that high-purity methyl 3-hydroxypropionate was obtained after a first reaction, vacuum distillation, and a second cooling crystallization treatment.

[0097] Example 2

[0098] This embodiment is basically the same as the preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in Example 1. The difference is that in the preparation of brominated BHET, the acid catalyst for the bromination reaction is replaced by phosphoric acid in an equal amount with Amberlyst 15 ion exchange resin.

[0099] Example 3

[0100] This embodiment is basically the same as the preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in Example 1. The difference is that in the preparation process of methyl 3-hydroxypropionate and dimethyl terephthalate, the alkaline additive in the first reaction is replaced by a mixed base of sodium carbonate and sodium methoxide with sodium carbonate. After the replacement, the mass of sodium carbonate is equal to the total mass of sodium carbonate and sodium methoxide before the replacement.

[0101] Example 4

[0102] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1, except that the halogenated compounds are replaced by sodium iodide in equal amounts with sodium bromide.

[0103] Example 5

[0104] This embodiment is basically the same as the preparation methods of brominated BHET, methyl 3-hydroxypropionate and dimethyl terephthalate in Example 1, except that the second solvent of the first reaction is replaced by an equal amount of tetrahydrofuran instead of methanol.

[0105] Example 6

[0106] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of brominated BHET, the molar ratio of BHET to Amberlyst 15 ion exchange resin is 1:1.

[0107] Example 7

[0108] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of brominated BHET, the molar ratio of BHET to Amberlyst 15 ion exchange resin is 1:6.

[0109] Example 8

[0110] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of brominated BHET, the molar ratio of BHET to Amberlyst 15 ion exchange resin is 1:3.

[0111] Example 9

[0112] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, the mass ratio of brominated BHET to Co2(CO)8 is 100:1.

[0113] Example 10

[0114] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, the mass ratio of brominated BHET to Co2(CO)8 is 1000:1.

[0115] Example 11

[0116] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, the molar ratio of 2-pyridone and Co2(CO)8 is 1:1.

[0117] Example 12

[0118] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, the molar ratio of 2-pyridone and Co2(CO)8 is 100:1.

[0119] Example 13

[0120] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, the molar ratio of 2-pyridone and Co2(CO)8 is 50:1.

[0121] Example 14

[0122] The preparation methods of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in this embodiment are basically the same as those in Example 1. The difference is that in the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate, triphenylphosphine ligand is used to replace 2-pyridone in an equal amount.

[0123] Comparative Example 1

[0124] The preparation methods of this comparative example and the preparation methods of brominated BHET, methyl 3-hydroxypropionate and dimethyl terephthalate in Example 1 are basically the same, except that the ligand 2-pyridone was not added during the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate.

[0125] Comparative Example 2

[0126] The preparation methods of this comparative example and the preparation methods of brominated BHET, methyl 3-hydroxypropionate and dimethyl terephthalate in Example 1 are basically the same, except that no alkaline additives sodium carbonate and sodium methoxide are added during the preparation of methyl 3-hydroxypropionate and dimethyl terephthalate.

[0127] Comparative Example 3

[0128] The preparation methods of this comparative example and the preparation methods of brominated BHET, methyl 3-hydroxypropionate and dimethyl terephthalate in Example 1 are basically the same, except that no acidic catalyst Amberlyst 15 ion exchange resin was added during the preparation of brominated BHET.

[0129] The conversion rate, selectivity, purity of brominated BHET, separation yield of brominated BHET, purity of methyl 3-hydroxypropionate, separation yield of methyl 3-hydroxypropionate, purity of DMT, separation yield of DMT, conversion rate of the first reaction, and selectivity of the first reaction were determined in the preparation of brominated BHET, methyl 3-hydroxypropionate, and dimethyl terephthalate in the above examples and comparative examples. The test results are shown in Table 1.

[0130] 1) Conversion rate of bromination reaction: determined by high performance liquid chromatography (HPLC). The principle is as follows: BHET and the brominated product have different polarities, resulting in different retention times in the reversed-phase column of the HPLC. Quantification is performed using either external standard or internal standard methods. After the bromination reaction is complete, a sample is taken, and a quencher is added to terminate the reaction. The sample is then diluted, filtered (using a 0.22 μm organic filter membrane), and injected into the HPLC system. A standard curve is plotted using BHET standards, and the remaining amount is calculated based on the peak area of ​​BHET in the sample. The conversion rate of the bromination reaction = (initial BHET mass - remaining BHET mass) × 100%.

[0131] 2) Selectivity of the bromination reaction: The selectivity of the bromination reaction refers to the proportion of target brominated BHET produced. It requires quantitative detection of the content of brominated BHET and byproducts in the reaction solution, determined by high-performance liquid chromatography (HPLC). Method principle: Utilizing the separation characteristics of brominated BHET and byproducts in the chromatographic column, the content of each component is quantified separately. The same HPLC conditions as for conversion detection are used; standards for brominated BHET, monobrominated BHET, and reactant BHET are prepared, and their respective standard curves are plotted; the selectivity of the bromination reaction = (molar amount of target product / molar amount of reacted BHET) × 100%.

[0132] 3) Determination of the purity of brominated BHET: The purity was determined by high-performance liquid chromatography (HPLC) using the area normalization method. The purified solid sample was dissolved in methanol and filtered. After injection into the HPLC system, the peak area percentage of brominated BHET was taken as 100%. Solvent residue detection: The residual methanol solvent content was detected using headspace gas chromatography (HS-GC). Brominated BHET purity = (peak area of ​​brominated BHET / total peak area) × 100%.

[0133] 4) Separation Yield of BromoBHET: The separation yield refers to the ratio of the actual mass of the final purified product to the theoretical mass, which is calculated using the gravimetric method. Method Principle: Based on the initial mass of BHET and the conversion rate, the theoretical maximum mass of bromoBHET is calculated, and then the separation yield is calculated by combining this with the actual mass of the purified product. Separation Yield of BromoBHET = (Effective Mass of BromoBHET / Theoretical Mass of BromoBHET) × 100%. Theoretical Mass of BromoBHET = Initial Mass of BHET × Conversion Rate × (Molar Mass of BromoBHET / Molar Mass of BHET). Effective Mass of BromoBHET = Actual Weighing Mass of Purified Product × Purity. The purified product is bromoBHET after decolorization with activated carbon, washing, and drying.

[0134] 5) Purity of methyl 3-hydroxypropionate: Determined by high-performance liquid chromatography (HPLC) area normalization method. The purified liquid sample (methyl 3-hydroxypropionate obtained by vacuum distillation above) was dissolved in methanol and filtered; after injection into HPLC, the peak area ratio of methyl 3-hydroxypropionate was taken as 100% of the total chromatographic peak area, and this ratio represents the purity. Solvent residue detection: The residual methanol solvent content was detected using headspace gas chromatography (HS-GC). Purity of methyl 3-hydroxypropionate = (Peak area of ​​methyl 3-hydroxypropionate / Total area of ​​chromatographic peaks) × 100%.

[0135] 6) Separation yield of methyl 3-hydroxypropionate: methyl 3-hydroxypropionate was obtained by vacuum distillation of the reaction solution, and the mass of 3-HPM was recorded. The separation yield of methyl 3-hydroxypropionate = (effective mass of 3-HPM / theoretical mass of 3-HPM) × 100%. The theoretical mass of 3-HPM = 2 × mass of brominated BHET × (molar mass of 3-HPM / molar mass of brominated BHET). The effective mass of 3-HPM = actual weight of the purified product × purity. The actual weight of the purified product is the mass of methyl 3-hydroxypropionate obtained by vacuum distillation of the reaction solution.

[0136] 7) DMT purity: Determined by high-performance liquid chromatography (HPLC) area normalization method. The purified solid sample was dissolved in methanol and filtered; after injection into the HPLC, the peak area ratio of DMT was taken as 100%, and this ratio represents the purity. Solvent residue detection: The methanol residue solvent content was detected using headspace gas chromatography (HS-GC). DMT purity = (DMT peak area / total peak area) × 100%.

[0137] 8) DMT Separation Yield: DMT was obtained by recrystallization (i.e., a second cooling crystallization process), and the mass of DMT was recorded. The separation yield of DMT = (effective mass of DMT / theoretical mass of DMT) × 100%. Theoretical mass of DMT = mass of brominated BHET × (molar mass of DMT / molar mass of brominated BHET). Effective mass = actual weight of the purified product × purity. The actual weight of the purified product is the mass of DMT obtained after the second cooling crystallization process.

[0138] 9) Conversion and selectivity of the first reaction: The conversion and selectivity of the first reaction were determined by high-performance gas chromatography (HPLC) area normalization method. An internal standard curve was prepared for the reactants and products of the first reaction. The mass of the reactants and products was determined by the relative peak areas of the internal standard additive with respect to the reactants and products. The conversion rate of the first reaction was calculated based on the amount of reactants added. First reaction conversion rate = ((total mass of 2-bromoethanol - residual mass of 2-bromoethanol) / total mass of 2-bromoethanol) × 100%. First reaction selectivity = (molar amount of 3-HPM / molar amount of 2-bromoethanol) × 100%.

[0139] The total mass of 2-bromoethanol is calculated as follows: 2 × mass of BHET × relative molecular mass of 2-bromoethanol / relative molecular mass of BHET. The remaining mass of 2-bromoethanol is characterized as follows: the remaining mass of 2-bromoethanol is determined by high-performance liquid chromatography (HPLC) using the area normalization method. By constructing an internal standard curve for 2-bromoethanol, the mass of 2-bromoethanol is calculated based on the relative peak areas of the internal standard additive and 2-bromoethanol; this mass is the remaining mass of 2-bromoethanol.

[0140] Table 1

[0141]

[0142] In Table 1, Comparative Examples 1-2, "-" indicates that the corresponding test item cannot be measured.

[0143] Analysis of Table 1 shows that, comparing Examples 1-14 and Comparative Example 1, Comparative Example 1, without the addition of the ligand 2-pyridone, could not undergo the carbon monoxide-directed insertion reaction, and the target product methyl 3-hydroxypropionate (3-HPM) was not generated, resulting in a 0% yield of 3-HPM and making it impossible to determine the purity of 3-HPM. Comparing Examples 1-14 and Comparative Example 2, Comparative Example 2, without the addition of the basic additives sodium carbonate and sodium methoxide, could not undergo the transesterification reaction, leading to a conversion rate of only 5% for the first reaction, and the selectivity of the first reaction could not be effectively measured due to the low product content. Comparing Examples 1-14 and Comparative Example 3, Comparative Example 3, without the addition of an acidic catalyst, resulted in a bromination reaction conversion rate of only 20%. Therefore, ligands, basic additives, and acidic catalysts are necessary conditions for efficient reaction.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 therein. Such 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 this application.

Claims

1. A method for preparing methyl 3-hydroxypropionate and dimethyl terephthalate co-produced, characterized in that, Includes the following steps: S1. The first material containing polyethylene terephthalate, a halogenated compound, and an acidic catalyst is subjected to a halogenation reaction to obtain halogenated polyethylene terephthalate. S2. The second material containing the halo-substituted ethylene terephthalate, cobalt catalyst, ligand, basic additive, and second solvent is subjected to a first reaction in the presence of carbon monoxide to obtain the methyl 3-hydroxypropionate and the dimethyl terephthalate. The alkaline additives include sodium carbonate and sodium methoxide; The acidic catalyst includes Amberlyst 15 acidic ion exchange resin and / or phosphoric acid; The halogen-containing compound includes metal halides, and the metal halide includes one or more of potassium bromide, sodium bromide, and lithium bromide; The cobalt catalyst is cobalt octacarbonyl; The ligand is pyridinone; The second solvent is methanol.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the ethylene terephthalate to the halogenated compound is 1:(1~4). And / or, the mass ratio of the halogenated ethylene terephthalate to the cobalt catalyst is (100-1000):1; And / or, the molar ratio of the ligand to the cobalt catalyst is (1-100):1; And / or, the molar ratio of the halogenated ethylene terephthalate to the basic additive is 1:(1-4).

3. The preparation method according to claim 2, characterized in that, The molar ratio of the ethylene terephthalate to the acidic catalyst is 1:(1~3). And / or, the mass ratio of the halogenated ethylene terephthalate to the cobalt catalyst is (500-600):1; And / or, the molar ratio of the ligand to the cobalt catalyst is (50-60):

1.

4. The preparation method according to claim 1, characterized in that, The halogenation reaction is carried out at a temperature of 60-150℃ for 1-8 hours. And / or, the temperature of the first reaction is 70-130°C, and the time of the first reaction is 2-12 hours.

5. The preparation method according to claim 1, characterized in that, The first material further includes a first solvent, which includes one or more of ethyl acetate, propyl acetate, butyl acetate, γ-valerolactone, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valeronitrile, benzonitrile, toluene, benzene, N,N-dimethylformamide, and dimethyl sulfoxide.

6. The preparation method according to claim 1, characterized in that, The process of halogenating a first material containing polyethylene terephthalate, a halogenated compound, and an acidic catalyst to obtain halogenated polyethylene terephthalate includes: halogenating a first material containing polyethylene terephthalate, a halogenated compound, a first solvent, and an acidic catalyst to obtain a halogenated intermediate product; and performing a first crystallization treatment on the halogenated intermediate product to obtain the halogenated polyethylene terephthalate. And / or, the first reaction is carried out in an apparatus where the carbon monoxide pressure is 3-6 MPa; And / or, step S2 includes: subjecting a second material containing the halogenated ethylene terephthalate, a cobalt catalyst, a ligand, and a basic additive to a first reaction in the presence of carbon monoxide to obtain a mixed product; subjecting the mixed product to vacuum distillation to obtain methyl 3-hydroxypropionate and a mother liquor; and subjecting the mother liquor to a second crystallization treatment to obtain the dimethyl terephthalate.

7. The preparation method according to claim 6, characterized in that, Both the first crystallization treatment and the second crystallization treatment are carried out in a third solvent, which includes one or more of ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, dioxane, tetrahydrofuran, acetonitrile, tert-valerate, benzonitrile, acetone, methanol, ethanol, and isopropanol. And / or, the first crystallization process includes a first cooling crystallization process, which includes cooling from 60-100°C to a first endpoint temperature at a cooling rate of 1-25°C / h, and holding at the first endpoint temperature for 4-5 hours after cooling to the first endpoint temperature, wherein the first endpoint temperature is 0-40°C. And / or, the temperature of the vacuum distillation is 80-120℃, the time of the vacuum distillation is 20min-2h, and the pressure of the vacuum distillation is 100-300 mbar; And / or, the second crystallization process includes a second cooling crystallization process, which includes cooling from 80-120°C to a second endpoint temperature at a cooling rate of 1-25°C / h, and holding at the second endpoint temperature for 2-3 hours after cooling, wherein the second endpoint temperature is -10-40°C.

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