Aromatic polyester-specific aromatic ring hydrogenation catalyst, preparation method and application

Abstract

The application discloses an aromatic polyester-specific aromatic ring hydrogenation catalyst, a preparation method and application, and belongs to the technical field of catalysts. The preparation method comprises the following steps: sequentially adding carbon materials into inorganic acid solution and hydrogen peroxide solution, and obtaining a pretreated carbon carrier after acid washing and oxidation; adding the pretreated carbon carrier into a nitrogen source precursor solution, impregnating the nitrogen source precursor, and obtaining a nitrogen-doped carbon carrier through calcination; adding the nitrogen-doped carbon carrier or the pretreated carbon carrier into a solution of an alkaline earth metal salt or an alkali, and obtaining an alkali-treated carbon carrier after modification; adding the nitrogen-doped carbon carrier or the alkali-treated carbon carrier into a mixed solution of a main active component and an auxiliary active component, adjusting the pH of the solution, precipitating active metal centers on the carrier, and obtaining the catalyst through calcination and reduction. The preparation method and application of the aromatic polyester-specific aromatic ring hydrogenation catalyst have the advantages that the obtained catalyst has good activity and the advantages of specific aromatic ring hydrogenation.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an aromatic polyester-specific aromatic ring hydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Polyethylene terephthalate (PET) has been widely used in high-end electronic fields such as packaging, textiles, integrated circuits, and semiconductor packaging due to its excellent mechanical strength, dielectric properties, dimensional stability, and processability.

[0003] In semiconductor manufacturing, PET (Polyester Resin) is the preferred material for flexible circuit substrates and chip packaging carriers due to its excellent flexibility, low cost, and good processability. Furthermore, PET exhibits good compatibility with functional fillers such as graphene nanosheets, polypyrrole, carbon nitride, and rare earth oxides; by combining these materials, the dielectric constant and conductivity of PET can be significantly altered, enabling its widespread application in low-power electronic devices. However, the high rigidity of the benzene ring structure in the PET molecular chain results in high modulus and brittleness, making it prone to microcracks under repeated bending or thermal stress, leading to decreased packaging reliability and limiting its further expansion in high-end flexible electronics and advanced packaging. Research shows that selectively hydrogenating the benzene rings in the PET molecular chain to introduce a cyclohexane structure can effectively reduce the rigidity of the molecular chain and increase chain segment flexibility while maintaining the integrity of the polymer backbone, thereby significantly improving the material's toughness and impact resistance. Simultaneously, the introduction of the cyclohexane structure can enhance the polymer's heat resistance and dimensional stability, making it more suitable for integrated circuit packaging scenarios with stringent reliability requirements. By partially or completely replacing terephthalic acid (dimethyl terephthalate) with 1,4-cyclohexanedicarboxylic acid (dimethyl terephthalate) in the polymerization process with ethylene glycol, PET containing cyclohexyl groups can be obtained, also known as PET-PECHD (partial substitution) or PECHD (complete substitution). However, because the polymerization activity of 1,4-cyclohexanedicarboxylic acid (dimethyl terephthalate) is lower than that of terephthalic acid (dimethyl terephthalate), the resulting polymer has a low molecular weight, which is far from the molecular weight required for practical applications. PET-PECHD / PECHD can also be obtained by partially or completely saturating the benzene ring in the existing PET polymer chain through catalytic hydrogenation. However, the PET benzene ring hydrogenation route faces a key bottleneck: during hydrogenation, while the catalyst activates the benzene ring, it easily induces non-selective ester bond breakage, leading to polymer backbone degradation, a significant decrease in molecular weight, and thus severe deterioration of the product's mechanical properties. Besides PET, other aromatic polyesters also exhibit the same problem, such as polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polycyclohexanediol terephthalate (PCT), polybutylene isophthalate (PBI), and polynaphthalene glycol (PEN). Therefore, it is necessary to develop a catalytic system that can specifically and efficiently catalyze the hydrogenation of the benzene ring while strictly protecting the integrity of the ester bonds.

[0004] Chinese patent CN118125917A discloses a method for preparing an xRu-yV / γ-Al2O3 catalyst, and US patent US20160326088A1 discloses a method for preparing a Ru2 / Al2O3 catalyst. Both can be used for the hydrogenation of PET monomer dimethyl terephthalate (DMT) to prepare dimethyl 1,4-cyclohexanedicarboxylate (DMCD). When used for DMT hydrogenation, the catalyst prepared by these methods exhibits a selectivity of over 99% for DMCD, but neither discloses or implies that the catalyst can be used for the catalytic hydrogenation of the polymer itself. Chinese patent CN121178168A discloses a magnetically separable reversed-phase catalyst MO. x The method for preparing / Ni for the hydrogenation of PET to prepare biodegradable polyester PECHD can convert the benzene ring in PET to a cyclohexane structure with a 100% conversion rate. However, the change in the molecular weight of PET during hydrogenation was not studied. Furthermore, the 1H NMR spectrum provided in the patent clearly shows the terminal hydrogen elution peaks caused by polymer chain breakage (corresponding to a decrease in molecular weight). Therefore, developing a specific aromatic ring hydrogenation catalyst for aromatic polyesters is crucial. Summary of the Invention

[0005] To address the molecular weight reduction caused by ester bond breakage in the prior art, this invention discloses a specific aromatic ring hydrogenation catalyst for aromatic polyesters, its preparation method, and its application. Specific catalytic hydrogenation of the aromatic ring is achieved through precise catalyst structure design. By synergistically modifying the carbon-based support with multiple elements such as nitrogen, calcium, magnesium, and cerium, the active metal centers are synergistically controlled from multiple aspects, including electronic structure, geometry, and surface properties, ultimately achieving efficient and specific hydrogenation of the aromatic ring while maintaining the integrity of the polymer backbone.

[0006] In this design, nitrogen-doped carbon materials play a central role as a support. The introduction of nitrogen atoms (such as pyridine nitrogen) can donate electrons to the supported metal nanoparticles (such as Pd, Pt, Ru, and Rh), making their surfaces electron-rich. This change in electronic structure weakens the adsorption of carbonyl groups in ester bonds on the metal surface, thereby inhibiting their hydrogenolysis and maintaining catalytic activity for aromatic ring hydrogenation. Furthermore, nitrogen sites can act as anchoring centers, promoting smaller metal particle sizes and increased dispersion. Smaller, more dispersed metal particles tend to expose more crystal planes favorable for aromatic ring hydrogenation and reduce continuous reaction sites that lead to chain breakage. The surface basic sites introduced by nitrogen doping can also weakly interact with the ester groups in aromatic polyesters, guiding the aromatic rings to preferentially approach the active centers to some extent.

[0007] The introduction of calcium and magnesium oxides mainly contributes stable alkaline sites. They can effectively neutralize acidic sites that may exist on the catalyst surface, inhibiting side reactions (such as excessive cracking and carbon deposition) caused by them, thereby improving the overall reaction selectivity and enhancing the stability of the catalyst.

[0008] Lanthanide elements, such as cerium, neodymium, lanthanum, and praseodymium, possess unique 4f electron configurations, variable valence states, and strong rare earth characteristics (large ionic radius, low electronegativity, and strong coordination ability). In this invention, their combination with co-activating components can effectively regulate the catalyst's orbital structure. Simultaneously, they synergistically promote the aromatic ring hydrogenation specificity of the active component with alkaline earth metals on the support surface, eliminating surface carbon deposition and maintaining the cleanliness and long-term effectiveness of the active sites. This multi-element synergistic support design strategy addresses the mechanistic challenge of selective hydrogenation of aromatic polyesters, laying the foundation for developing next-generation high-performance recovery catalysts and demonstrating significant industrial application prospects.

[0009] To achieve the above objectives, this invention discloses a method for preparing an aromatic polyester-specific aromatic ring hydrogenation catalyst, comprising the following steps: Step S1: The carbon material is added sequentially to an inorganic acid solution and a hydrogen peroxide solution, and after acid washing and oxidation, a pretreated carbon support is obtained. Step S2: Modify the pretreated carbon support obtained in step S1 to obtain a modified carbon support. Step S3: Add the modified carbon support to the mixed solution of the main active component and the co-active component, adjust the pH of the solution with alkali solution, and precipitate the metal centers of the main active component and the co-active component onto the modified carbon support. After calcination and reduction, the catalyst is obtained.

[0010] Preferably, in step S1, the carbon material is any one of activated carbon, carbon nanofibers, or graphene carbon. The inorganic acid solution is any one of sulfuric acid, hydrochloric acid, and nitric acid, or a combination of two or three of them; The total mass concentration of inorganic acids is 0.5-15%; the concentration of hydrogen peroxide is 27.5%-70%.

[0011] Preferably, in step S2, the modification treatment is nitrogen doping treatment and / or alkali treatment; Nitrogen doping involves adding a pretreated carbon support to a nitrogen source precursor solution, impregnating the nitrogen source precursor, and then calcining to obtain a nitrogen-doped support. The alkaline treatment method is any one of the following: (1) Add the pretreated carbon support or nitrogen-doped support to a solution of alkaline earth metal salt or alkali, impregnate with alkaline earth metal salt or alkali, and then obtain the alkali-treated support by calcination. (2) Add the pretreated carbon support or nitrogen-doped support to the solution of alkaline earth metal salt or alkali, and load the alkaline earth metal carbonate onto the pretreated carbon support or nitrogen-doped support by introducing CO2 gas or ammonium carbonate solution into the solution of alkaline earth metal salt or alkali to obtain the alkali-treated support.

[0012] Preferably, the nitrogen source is any one of urea, dicyandiamide, melamine, ammonium nitrate, L-histidine, polyaniline, and polypyrrole; the calcination temperature is 300-700 ℃; and the calcination time is 1-10 h.

[0013] Preferably, the alkaline earth metal salt or alkali is one of magnesium acetate, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium acetate, calcium nitrate, calcium chloride, barium acetate, barium nitrate, barium chloride, and barium hydroxide; the mass concentration of the alkaline earth metal salt or alkali solution is 0~1.5%; in method (1), the calcination temperature is 300-600 ℃ and the calcination time is 1-5 h; in method (2), the CO2 gas flow rate is 100-300mL / min, the CO2 gas introduction time is 1-5 h, the mass concentration of the ammonium carbonate solution is 1-40%, and the mass-volume ratio of the modified carrier to the ammonium carbonate solution is 1:150-1:50 g / mL.

[0014] Preferably, in step S3, the main active component is any one or a combination of two of palladium, platinum, ruthenium, rhodium and iridium. When the main active component is two elements, the mole fraction of one element is 0.01-0.9 and the mole fraction of the other element is 0.99-0.1. The co-active component is any one of cerium, neodymium, lanthanum, and praseodymium, and the molar fraction of the co-active component in the mixed solution is 0-0.45.

[0015] Preferably, the alkaline solution is any one of an aqueous solution of sodium hydroxide or potassium hydroxide or ammonia; the pH value of the solution is adjusted to 8-11; the calcination temperature is 200-500 ℃, and the calcination time is 1-5 h; hydrogen gas is introduced for reduction, the reduction temperature is 200-500 ℃, and the reduction time is 2-10 h.

[0016] This invention also provides a catalyst prepared by the above-described method for the specific and efficient hydrogenation of aromatic rings in aromatic polyesters. This catalyst is applied to the aromatic ring hydrogenation of aromatic polyesters, which are polymers containing both aromatic rings and ester bonds, with the aromatic ring being a benzene ring and / or a naphthalene ring. Typical aromatic polyesters include polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polycyclohexanediol terephthalate (PCT), polybutylene isophthalate (PBI), and polyethylene naphthalate (PEN), etc.

[0017] Preferably, the application method is to add the catalyst, aromatic polyester and solvent into the hydrogenation reactor, start stirring, replace the air in the high pressure reactor with N2, raise the temperature to the hydrogenation temperature, and introduce hydrogen gas to 2-15 MPa, so that the aromatic ring in the polymer chain of the aromatic polyester undergoes specific and efficient hydrogenation. The solvent is any one of 1,4-dioxane, hexafluoroisopropanol, tetrahydrofuran, tetrahydropyran, cyclohexane, dichloromethane, or pyridine; the reaction temperature is 80-180 ℃; the feed ratio of catalyst to aromatic polyester is 1:10-5:1; the amount of aromatic polyester is 0.1-20 wt / vol of solvent.

[0018] Therefore, the present invention, employing the above-described aromatic polyester-specific aromatic ring hydrogenation catalyst, preparation method, and application, possesses the following beneficial effects: 1. By synergistic modification through nitrogen doping and alkali treatment, and by utilizing the main active component and the co-active component, the active center of the catalyst and the basic site of the support work together to improve hydrogenation selectivity and enhance the stability of the catalyst.

[0019] 2. The present invention specifically hydrogenates the aromatic ring of polymers containing both aromatic rings and ester bonds, and the absolute molecular weight of the polymer containing both hydrogenated aromatic ring structure and ester bond is comparable to that of polymers containing both aromatic rings and ester bonds. This avoids the problem of molecular weight reduction of hydrogenation products caused by hydrogenation of ester bonds during the hydrogenation process of polymers containing both aromatic rings and ester bonds.

[0020] The technical solution of the present invention will be further described in detail below through embodiments. Attached Figure Description

[0021] Figure 1 The above are the hydrogen NMR spectra of the hydrogenated polymers and PET raw materials in Examples 1 and 2. Figure 2 The GPC molecular weight curves of the hydrogenated polymer and PET raw material in Example 1 and Comparative Examples 1-3 are shown. Detailed Implementation

[0022] This invention discloses a method for the specific and efficient hydrogenation of aromatic polyester aromatic rings, comprising the following steps: 1. Pickling and oxidation treatment of the carrier Carbon material was added to an inorganic acid solution. The solution was heated and stirred in a water bath, followed by ultrasonic treatment to obtain a uniformly dispersed carbon suspension. After filtration, the filter cake was washed repeatedly with an alcohol-water solution until the pH of the washing liquid reached 7. The washed filter cake was then transferred to hydrogen peroxide, heated and stirred in a water bath, and then ultrasonicated. The mixture was washed repeatedly with an alcohol-water solution and filtered until the pH of the filtered liquid reached 7. The filter cake was dried and ground to obtain solid Al, which is the pretreated carbon support.

[0023] Among them, the carbon material is one of activated carbon, carbon nanofibers, or graphene carbon.

[0024] The activated carbon is one of the following: fruit shell-based, coal-based, petroleum-based, or synthetic polymer-based activated carbon; the average pore size is 0.5-50 μm, and the pore volume is 0.02-0.3 cm³. 3 / g, specific surface area of ​​100-2000 m² 2 / g.

[0025] The carbon nanofibers have an average diameter of 80-300 nm, a length of 1-10 μm, an average pore size of 1-500 nm, and a pore volume of 0.3-0.8 cm³. 3 / g, specific surface area of ​​100-500 m² 2 / g. Preferred values ​​are: average diameter 100-150 nm, length 2-5 μm, average pore size 2-50 nm, and pore volume 0.4-0.6 cm³. 3 / g, specific surface area is 150-300 m² 2 / g.

[0026] Graphene carbon is one of graphene or carbon nanotubes. Graphene can be single-layer graphene, bilayer graphene, few-layer graphene, or multilayer graphene, with a specific surface area of ​​200-2000 m². 2 / g. Preferred types are: single-layer, bilayer, and few-layer graphene, with a specific surface area of ​​500-1500 m². 2 / g.

[0027] Carbon nanotubes are a type of single-walled carbon nanotube or multi-walled carbon nanotube; their outer diameter is 5-100 nm, inner diameter is 2-10 nm, average length is 0.5-30 μm, and pore volume is 0.2-1.2 cm³. 3 / g, specific surface area of ​​50-400 m² 2 / g. Preferred options include: multi-walled carbon nanotubes with an outer diameter of 15-30 nm, an inner diameter of 6-10 nm, an average length of 1-5 μm, and a pore volume of 0.3-0.6 cm³. 3 / g, specific surface area is 200-350 m² 2 / g.

[0028] The inorganic acid solution is one of sulfuric acid, hydrochloric acid, and nitric acid, or a combination of two or all three. Diprotic acid combinations include sulfuric acid-hydrochloric acid, sulfuric acid-nitric acid, and hydrochloric acid-nitric acid, with the former having a mole fraction range of 0.1-0.9 and the latter correspondingly ranging from 0.9-0.1. For ternary acid combinations, the mole fractions are 0.4-0.9 for nitric acid, 0.1-0.4 for hydrochloric acid, and 0.1-0.6 for sulfuric acid. The total mass concentration of the inorganic acid is 0.5-15%.

[0029] The ratio of carbon material mass to acid solution volume is 1:20-1:200 g / mL. A more favorable ratio is 1:50-1:140 g / mL.

[0030] The alcohols are mainly lower carbon alcohols, such as methanol, ethanol, ethylene glycol, n-propanol, isopropanol, 1,2-propanediol, 1,3-propanediol, n-butanol, 2-butanol, tert-butanol, etc. The preferred lower carbon alcohols are methanol, ethanol, and isopropanol.

[0031] The volume fraction of alcohol in the alcohol-water solution is 0-1%. Preferably, the volume fraction of alcohol is 0.25-0.65%.

[0032] The concentration of hydrogen peroxide is 27.5%-70%. Preferred concentrations are 27.5%, 30%, and 35%.

[0033] The ratio of carbon material mass to hydrogen peroxide volume is 1:20-1:200 g / mL. A more favorable ratio is 1:50-1:140 g / mL.

[0034] 2. Perform nitrogen doping and / or alkali treatment on the pretreated carbon support. 2-1. Nitrogen doping treatment A nitrogen-containing compound (nitrogen source) was dissolved in a polar solvent—water—to prepare a solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and then sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under inert gas protection, the temperature was increased to the calcination temperature at a constant heating rate and calcined for a period of time. The sample was then cooled to room temperature under an inert gas atmosphere to obtain solid A2, i.e., the nitrogen-doped support.

[0035] The nitrogen source can be one of urea, dicyandiamide, melamine, ammonium nitrate, L-histidine, polyaniline, or polypyrrole, with dicyandiamide and urea being the preferred nitrogen sources.

[0036] The polar solvent is selected according to the nitrogen source used, and is one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. The preferred polar solvents are methanol, ethanol, isopropanol, tetrahydrofuran, and dioxane.

[0037] The mass fraction of polar solvent in the polar solvent-aqueous solution is 0-1, with a preferred mass fraction of 0.3-0.5.

[0038] Different nitrogen source compounds have varying solubility in water. Solutions of different concentrations are prepared based on these differences in solubility. For example, urea solutions have a mass concentration of 0-1.2%, with an optimal mass concentration of 0-0.8%; dicyandiamide and melamine solutions have a mass concentration of 0-0.9%, with an optimal mass concentration of 0.2-0.6%; ammonium nitrate solutions have a mass concentration of 0-1.7%, with an optimal mass concentration of 0.9-1.1%; L-histidine solutions have a mass concentration of 0-2.2%, with an optimal mass concentration of 1-1.4%; polyaniline solutions have a mass concentration of 0-4%, with an optimal mass concentration of 1.9-2.5%; and polypyrrole solutions have a mass concentration of 0-2.9%, with an optimal mass concentration of 1.3-1.8%.

[0039] The mass ratio of solid A1 to the volume of the nitrogen source solution is 1:100-1:2 g / mL, with a preferred ratio of 1:50-1:4 g / mL. Since the nitrogen source concentration varies, the nitrogen content in the nitrogen source compound also varies; therefore, the solution should, in principle, be prepared according to the nitrogen doping amount of solid A2.

[0040] The heating rate is 2-20 ℃ / min, the calcination temperature is 300-700 ℃, and the calcination time is 1-10 h. The preferred heating rate is 4-6 ℃ / min, the calcination temperature is 450-650 ℃, and the calcination time is 1-6 h.

[0041] Nitrogen content in solid A2 is 0-30% of the total mass, with 12-20% being the most desirable.

[0042] 2-2. Alkali treatment: There are two types of alkali treatment: alkaline earth metal oxide modification treatment and alkaline earth metal carbonate modification treatment.

[0043] (1) Alkali earth metal oxide modified carrier An alkaline earth metal salt or metal alkali (precursor) is dissolved in deionized water to prepare a solution, and solid A2 or solid A1 is added. The solution is stirred in a water bath at room temperature. Subsequently, it is dried and dehydrated. After grinding, the sample is heated to the calcination temperature at a constant heating rate under inert gas protection and calcined for a period of time. The sample is then cooled to room temperature under an inert gas atmosphere to obtain solid B1.

[0044] Alkaline earth metal salts are one of the following: magnesium salts (magnesium acetate, magnesium nitrate, magnesium chloride, or magnesium sulfate), calcium salts (calcium acetate, calcium nitrate, or calcium chloride), and barium salts (barium acetate, barium nitrate, or barium chloride).

[0045] The alkaline earth metal base is barium hydroxide.

[0046] The mass concentration of alkaline earth metal salts or alkaline solutions is 0-1.5%. A preferred concentration is 0.3-1%.

[0047] The mass ratio of solid A2 or solid A1 to the volume ratio of the alkaline earth metal salt or alkali solution is 1:150-1:50, with a preferred ratio of 1:120-1:80.

[0048] The heating rate is 2-20 ℃ / min, the calcination temperature is 300-600 ℃, and the calcination time is 1-5 h. The preferred heating rate is 4-6 ℃ / min, the calcination temperature is 450-550 ℃, and the calcination time is 2-4 h.

[0049] The mass of alkaline earth metal elements in solid B1 accounts for 0-20% of the total mass, with a better proportion of 8-12%.

[0050] (2) Alkaline earth metal carbonate modified carrier A solution of alkaline earth metal salt or hydroxide (precursor) is prepared by dissolving it in deionized water, and then solid A2 or solid A1 is added. The mixture is stirred in a water bath at room temperature. During stirring, CO2 gas is bubbled into the solution at room temperature or ammonium carbonate solution is added dropwise to convert the alkaline earth metal element into carbonate, which is then deposited on the surface of solid A2 or solid A1. The pH of the solution is adjusted by using an alkaline solution to control the precipitation process of the alkaline earth metal carbonate. The mixture is washed repeatedly with an alcohol-water solution and filtered until the pH of the filtered liquid reaches 7. The filter cake is dried and ground to obtain solid B2.

[0051] Alkaline earth metal salts are one of the following: magnesium salts (magnesium acetate, magnesium nitrate, magnesium chloride, magnesium sulfate), calcium salts (calcium acetate, calcium nitrate, calcium chloride), and barium salts (barium acetate, barium nitrate, or barium chloride).

[0052] The alkaline earth metal base is barium hydroxide.

[0053] The mass concentration of alkaline earth metal salts or alkaline solutions is 0-1.5%. A preferred concentration is 0.3-1%.

[0054] The mass ratio of solid A2 or A1 on an undoped carbon support to the volume ratio of the alkaline earth metal solution is 1:150-1:50, with a preferred ratio of 1:120-1:80.

[0055] The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide or ammonia, with ammonia being the preferred alkaline solution.

[0056] The pH of the solution adjusted with alkali is 8-11, with the optimal pH being 9-10.

[0057] The CO2 gas flow rate is 100-300 mL / min, and the CO2 gas introduction time is 1-5 h, with a preferred CO2 gas flow rate of 150-200 mL / min and a preferred CO2 gas introduction time of 2-3 h; the mass concentration of the ammonium carbonate solution is 1-40%, and the mass-to-volume ratio of the modified carrier to the ammonium carbonate solution is 1:150-1:50 g / mL, with a preferred mass concentration of the ammonium carbonate solution of 20-30% and a preferred mass-to-volume ratio of 1:120-1:80 g / mL.

[0058] The alcohols are mainly low-carbon alcohols, such as methanol, ethanol, ethylene glycol, n-propanol, isopropanol, 1,2-propanediol, 1,3-propanediol, n-butanol, 2-butanol, tert-butanol, etc. The preferred low-carbon alcohols are methanol, ethanol, and isopropanol.

[0059] The volume fraction of alcohol in an alcohol-water solution is 0-1%. A better alcohol has a volume fraction of 0.4-0.6%.

[0060] The mass of alkaline earth metal elements in solid B2 accounts for 0-20% of the total mass, with a better proportion of 8-12%.

[0061] 3. Supporting of the active component of the catalyst A solution was prepared by dissolving a combination of precursor compounds of the active component in deionized water, and then adding one of three solids, B1, B2, or A2. The pH of the solution was adjusted using an alkaline solution. The solution was stirred in a water bath at room temperature. The mixture was washed repeatedly with an alcohol-water solution and filtered until the pH of the filtered liquid reached 7. The filter cake was then dried. After grinding, the filter cake was heated to the calcination temperature at a constant heating rate under an inert gas atmosphere and calcined for a period of time. Hydrogen gas was then introduced at the reduction temperature to reduce the catalyst. The sample was then cooled to room temperature under an inert gas atmosphere to obtain the catalyst.

[0062] The combination of precursor compounds is a combination of the main active component and the secondary active component.

[0063] The main active component is one or a combination of two of the five elements: palladium, platinum, ruthenium, rhodium, and iridium. A combination of palladium and iridium is preferred as the main active component.

[0064] The main active component precursor compound is one of the following: palladium salt (palladium chloride, palladium nitrate, chloropalladium acid or palladium acetate), platinum salt (chloroplatinic acid, platinum nitrate, potassium chloroplatinate, sodium chloroplatinate, platinum acetate or dinitrosodiammonium platinum), ruthenium salt (ruthenium chloride, ruthenium nitrate or potassium ruthenate), rhodium salt (rhodium chloride, rhodium nitrate or dirhodium acetate), or iridium salt (iridium chloride, chloroiridium acid, ammonium chloroiridium or iridium nitrate).

[0065] Among the five elements palladium, platinum, ruthenium, rhodium, and iridium, when they are binary combinations, there are Pd-Pt, Pd-Ru, Pd-Rh, Pd-Ir, Pt-Ru, Pt-Rh, Pt-Ir, Ru-Rh, Ru-Ir, and Rh-Ir. In the binary combinations, the mole fraction of the former is 0.01-0.9.

[0066] The molar fractions of the auxiliary active elements cerium, neodymium, lanthanum, and praseodymium are 0-0.45, with a preferred molar fraction of 0.3-0.4.

[0067] The aqueous solution of the precursor compound of the main active metal element has a mass concentration of 0.05-5%, with a preferred mass concentration of 0.5-1.5%.

[0068] The precursor compound for the active component is one of the following: cerium salt (cerium nitrate or cerium chloride), neodymium salt (neodymium nitrate or neodymium chloride), lanthanum salt (lanthanum nitrate or lanthanum chloride), or praseodymium salt (praseodymium nitrate or praseodymium chloride).

[0069] The aqueous solution of the precursor compound for the active component has a mass concentration of 0-1.25%, with a preferred mass concentration of 0.25-0.75%.

[0070] The mass ratio of one of the three solids B1, B2, and A2 to the volume ratio of the auxiliary active metal precursor solution is 1:20-1:7 g / mL, with a preferred ratio of 1:14-1:8 g / mL.

[0071] The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide or ammonia, with ammonia being the preferred alkaline solution.

[0072] The pH of the solution adjusted by alkali is 8-11.5, with the optimal pH being 8.5-11.

[0073] The alcohols are mainly low-carbon alcohols, such as methanol, ethanol, ethylene glycol, n-propanol, isopropanol, 1,2-propanediol, 1,3-propanediol, n-butanol, 2-butanol, tert-butanol, etc. Methanol, ethanol, and isopropanol are considered the preferred low-carbon alcohols.

[0074] The volume fraction of alcohol in the alcohol-water solution is 0-1%. A preferred volume fraction of alcohol is 0.4-0.6%.

[0075] The heating rate is 2-20 ℃ / min, the calcination temperature is 200-500 ℃, and the calcination time is 1-5 h. The preferred heating rate is 4-6 ℃ / min, the calcination temperature is 250-450 ℃, and the calcination time is 2-4 h.

[0076] The hydrogen reduction temperature is 200-500 ℃, and the hydrogen reduction time is 2-10 h. The preferred reduction temperature is 250-450 ℃, and the reduction time is 4-6 h.

[0077] The main active component metal element accounts for 0.2-8% of the total mass of the catalyst, with a preferred proportion of 4-6%. The co-active component metal element accounts for 0-5% of the total mass of the catalyst, with a preferred proportion of 2-3%.

[0078] 4. Catalytic hydrogenation reaction The catalyst, aromatic polyester, and solvent were added together into a high-pressure reactor. After purging the reactor of air, H2 was introduced into the reactor, and stirring was started until the hydrogen pressure stabilized. Stirring was then stopped. The reactor temperature was set, and the reaction was allowed to proceed for a period of time. After the reaction was complete, the reactor was opened, the mixture was removed, filtered, and the filtrate was dried to obtain the product. Samples were taken for analysis to determine the degree of hydrogenation and the molecular weight of the product.

[0079] Aromatic polyesters include polyethylene terephthalate (PET) and other aromatic polyesters containing phenyl cyclocarboxylate, naphthyl cyclocarboxylate, and diols, such as: polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polycyclohexanediol terephthalate (PCT), polybutylene isophthalate (PBI), and polynaphthalene dicarboxylate (PEN).

[0080] The solvents are 1,4-dioxane, hexafluoroisopropanol, tetrahydrofuran, tetrahydropyran, cyclohexane, dichloromethane, and pyridine, with 1,4-dioxane or tetrahydrofuran being preferred.

[0081] The feed ratio of catalyst to aromatic polyester is 1:10-5:1; the amount of aromatic polyester is 0.1-20 wt / vol% of the solvent amount, preferably the feed ratio of catalyst to aromatic polyester is 1:6-1:1, and the amount of aromatic polyester is 1-3 wt / vol% of the solvent amount.

[0082] The reaction hydrogen pressure is 2-15 MPa; the reaction temperature is 80-180 ℃; and the reaction time is 0.5-10 h. The preferred conditions are: hydrogen pressure 5-7 MPa; reaction temperature 100-130 ℃; and reaction time 2-6 h.

[0083] The technical solution of the present invention will be further described below through embodiments.

[0084] To more clearly illustrate the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present invention, and are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0085] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0086] The molecular weight of the hydrogenation product was analyzed by gel permeation chromatography (GPC), and the calibrated molecular weight was calculated by the Mark-Houwink equation. The difference between the molecular weight of the feed and the product before and after hydrogenation was compared.

[0087] use 1 The degree of hydrogenation of the benzene ring in the hydrogenation product was analyzed by 1H NMR, and the degree of hydrogenation of the benzene ring in PET was calculated by equation (1).

[0088] (1) In equation (1), S a , S b , S c , S d for 1 The peak integral areas of a, b, c, and d in H NMR, where the positions of a, b, c, and d are as follows: Figure 1 As shown.

[0089] Example 1 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of multi-walled carbon nanotubes were added to 100 mL of nitric acid solution (nitric acid concentration: 5%). After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed repeatedly with a 50 vol% methanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 35% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed repeatedly with a tert-butanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0090] S2. A 0.6 wt% solution containing dicyandiamide was prepared by dissolving it in 50 wt% ethanol-water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 ℃ at a heating rate of 10 ℃ / min and calcined for 5 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0091] S3. Dissolve 0.8 g of calcium acetate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 300 °C at a heating rate of 20 °C / min for 2.5 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0092] S4. Dissolve 0.033 g palladium chloride, 0.033 g iridium chloride, and 0.063 g neodymium chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 11.5 with alkaline solution. Stir in a water bath at room temperature for 6 h. Wash and filter repeatedly with ethanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 1 h under nitrogen protection, heated at a rate of 2 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 350 °C to reduce the catalyst for 6 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0093] S5. Add 1 g of catalyst, 5 g of polyethylene terephthalate (PET), and 100 mL of 1,4-dioxane to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 26%, a weight-average molecular weight of 31.0 kJ, and a weight-average molecular weight of PET raw material of 31.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0094] Example 2 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of single-walled carbon nanotubes were added to a mixed solution of nitric acid and sulfuric acid in 20 mL. The molar fraction of nitric acid in the mixed acid was 0.9, and the total mass concentration of the acid in the mixed solution was 8%. After filtration, the filter cake was washed repeatedly with 50 vol% n-propanol-water solution until the pH of the washing solution was 7. The washed filter cake was transferred to 35% hydrogen peroxide, heated and stirred in a water bath, and sonicated. The filter cake was washed repeatedly with 1,3-propanediol-water solution and filtered repeatedly until the pH of the filtered liquid was 7. After drying and grinding, solid Al was obtained.

[0095] S2. A 0.6 wt% solution containing dicyandiamide was prepared by dissolving it in 50 wt% methanol-water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 700 ℃ at a heating rate of 2 ℃ / min and calcined for 1 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0096] S3. Dissolve 0.8 g of calcium nitrate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 0.5 h. Then dry and dehydrate. After grinding, calcine at 300 °C at a heating rate of 10 °C / min for 5 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0097] S4. Dissolve 0.050 g palladium nitrate, 0.067 g rhodium nitrate, and 0.076 g cerium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 10 using an alkaline solution. Stir in a water bath at room temperature for 6 hours. Wash and filter repeatedly with ethylene glycol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 350 °C for 2.5 hours under nitrogen protection, heated at a rate of 20 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 350 °C to reduce the catalyst for 2 hours. The sample is then cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0098] S5. Add 1 g of catalyst, 0.2 g of polyethylene terephthalate (PET), and 100 mL of tetrahydrofuran to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 ℃ and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 31.0 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is also 31.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0099] Example 3 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. Add 1 g of few-layer graphene to 20 mL of nitric acid solution (nitric acid concentration: 5%). After filtration, wash the filter cake repeatedly with 20 vol% tert-butanol-water solution until the pH of the washing solution is 7. Transfer the washed filter cake to 70% hydrogen peroxide, heat in a water bath, stir, and sonicate. Wash the filter cake repeatedly with ethanol-water solution and filter again until the pH of the filtered liquid is 7. After drying and grinding, obtain solid Al.

[0100] S2. Dissolve urea in water to prepare a 0.6 wt% solution. Add solid A1 to the nitrogen source solution, heat and stir in a water bath, and sonicate to obtain a uniformly dispersed suspension. Then dry and dehydrate. Under nitrogen atmosphere, heat to 500 ℃ at a heating rate of 10 ℃ / min and calcine for 10 h. Cool the sample to room temperature under nitrogen atmosphere to obtain solid A2.

[0101] S3. Dissolve 0.8 g of magnesium sulfate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 450 ℃ for 5 h under nitrogen protection at a heating rate of 20 ℃ / min. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0102] S4. Dissolve 0.050 g ruthenium chloride, 0.033 g iridium chloride, and 0.076 g cerium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 11.5 with alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with ethylene glycol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 500 °C at a heating rate of 20 °C / min for 2.5 h under nitrogen protection. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 200 °C for 6 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0103] S5. Add 1 g of catalyst, 0.2 g of polyethylene terephthalate (PET), and 150 mL of 1,4-dioxane to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 43%, a weight-average molecular weight of 30.1 kJ, and a weight-average molecular weight of 31.0 kJ for the polyethylene terephthalate (PET) raw material. The molecular weight of the product decreases by 3% compared to the hydrogenated product.

[0104] Example 4 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of petroleum-based activated carbon was added to 20 mL of nitric acid solution (nitric acid concentration: 15%). After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed repeatedly with 30 vol% 1,3-propanediol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 35% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed repeatedly with isopropanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid A1.

[0105] S2. Dicyandiamide was dissolved in N-methylpyrrolidone to prepare a 0.6 wt% solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 °C at a heating rate of 10 °C / min and calcined for 10 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0106] S3. Dissolve 1.5 g of magnesium chloride in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 450 °C for 1 h under nitrogen protection at a heating rate of 2 °C / min. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0107] S4. Dissolve 0.180 g rhodium chloride, 0.013 g iridium chloride, and 0.074 g praseodymium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 10 using an alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with 1,2-propanediol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 500 °C for 5 h under nitrogen protection at a heating rate of 10 °C / min. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 350 °C for 6 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0108] S5. Add 1 g of catalyst, 5 g of polyethylene terephthalate (PET), and 100 mL of tetrahydrofuran to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 30.4 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is 31.0 kJ. The molecular weight of the product decreases by 2% compared to before hydrogenation.

[0109] Example 5 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of polymer-based activated carbon was added to 20 mL of sulfuric acid solution with a mass concentration of 15%. After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed repeatedly with 50 vol% ethylene glycol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 35% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed repeatedly with 1,3-propanediol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0110] S2. A 1.2 wt% solution containing polyaniline was prepared by dissolving it in N-methylpyrrolidone. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 700 °C at a heating rate of 2 °C / min and calcined for 5 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0111] S3. Dissolve 0.6 g of barium calcium acetate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. During stirring, add 50 mL of 40% ammonium carbonate solution dropwise to the solution at room temperature to convert the alkaline earth metal element into carbonate and deposit it on the surface of solid A. Adjust the pH of the solution to 11 during the deposition process with alkali solution to control the precipitation process of alkaline earth metal carbonate. Wash and filter repeatedly with ethanol-water solution until the pH of the filtered liquid is 7. After drying and grinding, solid B2 is obtained.

[0112] S4. Dissolve 0.170 g palladium acetate and 0.064 g lanthanum chloride in 100 mL deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 8 using alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with n-propanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 5 h under nitrogen protection at a heating rate of 2 °C / min. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 350 °C for 2 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0113] S5. Add 1 g of catalyst, 5 g of polyethylene terephthalate (PET), and 200 mL of tetrahydrofuran to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 2 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 ℃ and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 67%, a weight-average molecular weight of 31.0 kJ, and a weight-average molecular weight of PET raw material of 31.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0114] Example 6 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of petroleum-based activated carbon was added to 200 mL of a mixed solution of nitric acid and hydrochloric acid. The molar fraction of nitric acid in the mixed acid was 0.9, and the total mass concentration of acid in the mixed solution was 15%. After filtration, the filter cake was washed repeatedly with a 30 vol% 1,2-propanediol-water solution until the pH of the washing solution was 7. The washed filter cake was transferred to 30% hydrogen peroxide, heated in a water bath with stirring, and sonicated. The filter cake was washed repeatedly with a tert-butanol-water solution and filtered repeatedly until the pH of the filtered liquid was 7. After drying and grinding, solid A1 was obtained.

[0115] S2. A 0.6 wt% solution containing ammonium nitrate was prepared by dissolving it in water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 700 °C at a heating rate of 2 °C / min and calcined for 1 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0116] S3. Dissolve 1.5 g of magnesium chloride in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. Then dry and dehydrate. After grinding, calcine at 450 °C for 2.5 h under nitrogen protection at a heating rate of 20 °C / min. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0117] S4. Dissolve 0.097 g chloroplatinic acid, 0.007 g iridium chloride, and 0.064 g lanthanum chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 8 using alkaline solution. Stir in a water bath at room temperature for 6 h. Wash and filter repeatedly with methanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 350 °C for 5 h under nitrogen protection at a heating rate of 2 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 350 °C to reduce the catalyst for 10 h. The sample is then cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0118] S5. Add 1 g of catalyst, 0.2 g of polyethylene terephthalate (PET), and 150 mL of 1,4-dioxane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 80 °C and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 70%, a weight-average molecular weight of 31.0 kJ, and a weight-average molecular weight of PET raw material of 31.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0119] Example 7 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of single-walled carbon nanotubes were added to 200 mL of a mixed solution of nitric acid and hydrochloric acid. The molar fraction of nitric acid in the mixed acid was 0.9, and the total mass concentration of the acid in the mixed solution was 5%. After filtration, the filter cake was washed repeatedly with a 50 vol% ethanol-water solution until the pH of the washing solution was 7. The washed filter cake was transferred to 50% hydrogen peroxide, heated and stirred in a water bath, and sonicated. The filter cake was washed repeatedly with an ethylene glycol-water solution and filtered again until the pH of the filtered liquid was 7. After drying and grinding, solid Al was obtained.

[0120] S2. Urea was dissolved in methanol to prepare a 0.6 wt% solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under argon atmosphere, the temperature was increased to 500 ℃ at a heating rate of 20 ℃ / min and calcined for 5 h. The sample was then cooled to room temperature under argon atmosphere to obtain solid A2.

[0121] S3. Dissolve 1.5 g of barium nitrate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. Then dry and dehydrate. After grinding, calcine at 300 °C at a heating rate of 10 °C / min for 1 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0122] S4. Dissolve 0.067 g palladium chloride, 0.108 g chloroplatinic acid, and 0.135 g neodymium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 8 using alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with tert-butanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 20 °C / min for 10 h under argon protection, heated to 200 °C, and then reduced with hydrogen at a reduction temperature of 500 °C for 10 h. The sample is then cooled to room temperature under argon atmosphere to obtain the catalyst.

[0123] S5. Add 1 g of catalyst, 10 g of polybutylene terephthalate (PBT), and 200 mL of 1,4-dioxane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 80 °C and react for 10 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 44.0 kJ, and the weight-average molecular weight of the polybutylene terephthalate (PBT) raw material is also 44.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0124] Example 8 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of multilayer graphene was added to 100 mL of a mixed solution of nitric acid and sulfuric acid, where the molar fraction of nitric acid in the mixed acid was 0.9 and the total mass concentration of acid in the mixed solution was 8%. After filtration, the filter cake was washed repeatedly with a 30 vol% 1,2-propanediol-water solution until the pH of the washing solution was 7. The washed filter cake was transferred to 30% hydrogen peroxide, heated in a water bath with stirring, and sonicated. The filter cake was washed repeatedly with an ethylene glycol-water solution and filtered again until the pH of the filtered liquid was 7. After drying and grinding, solid Al was obtained.

[0125] S2. A 0.6 wt% solution containing dicyandiamide was prepared by dissolving it in water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 °C at a heating rate of 2 °C / min and calcined for 10 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0126] S3. Dissolve 0.7 g of magnesium chloride in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. During stirring, add 150 mL of 1% ammonium carbonate solution dropwise to the solution at room temperature to convert the alkaline earth metal element into carbonate and deposit it on the surface of solid A. Adjust the pH of the solution to 10 during the deposition process with alkali solution to control the precipitation process of alkaline earth metal carbonate. Wash and filter repeatedly with tert-butanol-water solution until the pH of the filtered liquid is 7. After drying and grinding, solid B2 is obtained.

[0127] S4. Dissolve 0.108 g of chloroplatinic acid and 0.143 g of lanthanum nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 11.5 with alkaline solution. Stir in a water bath at room temperature for 12 h. Wash and filter repeatedly with ethylene glycol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 500 °C for 1 h under nitrogen protection at a heating rate of 10 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 500 °C to reduce the catalyst for 2 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0128] S5. Add 1 g of catalyst, 5 g of polycyclohexanediol terephthalate (PCT), and 200 mL of tetrahydrofuran to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 °C and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 58%, a weight-average molecular weight of 50.0 kJ, and a PCT weight-average molecular weight of 50.0 kJ. The product molecular weight did not decrease compared to before hydrogenation.

[0129] Example 9 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of petroleum-based activated carbon was added to 100 mL of sulfuric acid solution with a mass concentration of 8%. After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed multiple times with 80 vol% ethanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 30% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed multiple times with n-butanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0130] S2. Urea was dissolved in 50 wt% water to prepare a 1.2 wt% solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 ℃ at a heating rate of 10 ℃ / min and calcined for 10 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0131] S3. Dissolve 0.8 g of magnesium sulfate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 300 °C at a heating rate of 20 °C / min for 2.5 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0132] S4. Dissolve 0.060 g palladium chloride, 0.010 g ruthenium chloride, and 0.074 g praseodymium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 10 using alkaline solution. Stir in a water bath at room temperature for 12 h. Wash repeatedly with n-propanol-water solution and filter until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 350 °C at a heating rate of 10 °C / min for 2.5 h under nitrogen protection. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 200 °C for 10 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0133] S5. Add 1 g of catalyst, 10 g of polycyclohexanediol terephthalate (PCT), and 200 mL of dichloromethane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 2 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 ℃ and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 48.5 kJ, and the weight-average molecular weight of the PCT feedstock is 50.0 kJ. The molecular weight of the product decreases by 3% compared to before hydrogenation.

[0134] Example 10 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of multi-walled carbon nanotubes were added to 20 mL of a mixed solution of nitric acid and sulfuric acid. The molar fraction of nitric acid in the mixed acid was 0.1%, and the total mass concentration of the acid in the mixed solution was 15%. After filtration, the filter cake was washed repeatedly with a 30 vol% 1,2-propanediol-water solution until the pH of the washing solution was 7. The washed filter cake was transferred to 27.5% hydrogen peroxide, heated in a water bath with stirring, and sonicated. The filter cake was washed repeatedly with a 1,3-propanediol-water solution and filtered repeatedly until the pH of the filtered liquid was 7. After drying and grinding, solid A1 was obtained.

[0135] S2. A 1.2 wt% solution containing L-histidine was prepared by dissolving it in water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 °C at a heating rate of 20 °C / min and calcined for 10 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0136] S3. Dissolve 0.8 g of magnesium chloride in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. During stirring, introduce CO2 gas into the solution at a flow rate of 100 mL / min at room temperature to convert the alkaline earth metal elements into carbonates that are deposited on the surface of solid A. Adjust the pH of the solution to 9 during the deposition process using an alkaline solution to control the precipitation process of the alkaline earth metal carbonates. Wash and filter repeatedly with methanol-water solution until the pH of the filtered liquid is 7. After drying and grinding, the filter cake is used to obtain solid B2.

[0137] S4. Dissolve 0.167 g rhodium acetate dimer, 0.020 g ruthenium chloride, and 0.135 g cerium chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 11.5 with alkaline solution. Stir in a water bath at room temperature for 6 h. Wash and filter repeatedly with tert-butanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 350 °C for 5 h under nitrogen protection at a heating rate of 20 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 350 °C to reduce the catalyst for 10 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0138] S5. Add 1 g of catalyst, 10 g of polynaphthalene glycol ester (PEN), and 200 mL of tetrahydrofuran to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 62%, a weight-average molecular weight of 25.0 kJ, and a weight-average molecular weight of 25.0 kJ for both the PEN and the product. The product molecular weight did not decrease compared to before hydrogenation.

[0139] Example 11 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of multi-walled carbon nanotubes were added to 200 mL of a mixed solution of nitric acid, sulfuric acid, and hydrochloric acid. The molar ratio of nitric acid, sulfuric acid, and hydrochloric acid in the mixed acid was 0.4:0.4:0.2, and the total mass concentration of the acid in the mixed solution was 8%. After heating and stirring in a water bath and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. After filtration, the filter cake was washed multiple times with 80 vol% ethanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 30% hydrogen peroxide, heated and stirred in a water bath, and ultrasonically treated. The filter cake was washed multiple times with isopropanol-water solution and filtered until the pH of the filtered liquid was 7. After drying and grinding, solid Al was obtained.

[0140] S2. Melamine was dissolved in water to prepare a 0.6 wt% solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 300 °C at a heating rate of 10 °C / min and calcined for 10 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0141] S3. Dissolve 1.5 g of calcium acetate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. Then dry and dehydrate. After grinding, calcine at 600 °C at a heating rate of 10 °C / min for 2.5 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0142] S4. Dissolve 0.072 g of dinitrosodiammineplatinum, 0.008 g of iridium chloride, and 0.068 g of neodymium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 10 using alkaline solution. Stir in a water bath at room temperature for 6 h. Wash repeatedly with n-butanol-water solution and filter until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 500 °C for 5 h under nitrogen protection at a heating rate of 10 °C / min. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 350 °C for 6 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0143] S5. Add 1 g of catalyst, 10 g of polybutylene isophthalate (PBI), and 150 mL of 1,4-dioxane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 15 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 ℃ and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 54.0 kJ, and the weight-average molecular weight of the polybutylene isophthalate (PBI) raw material is also 54.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0144] Example 12 This embodiment provides an aromatic polyester-specific aromatic ring hydrogenation catalyst, the preparation method and application method of which include the following steps: S1. 1 g of few-layer graphene was added to 200 mL of nitric acid solution (nitric acid concentration: 5%). After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed repeatedly with 50 vol% ethanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 27.5% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed repeatedly with isopropanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0145] S2. Dissolve ammonium nitrate in water to prepare a 1.2 wt% solution. Add solid A1 to the nitrogen source solution, heat in a water bath with stirring and sonication to obtain a uniformly dispersed suspension. Then dry and dehydrate. Under nitrogen atmosphere, heat to 700 ℃ at a heating rate of 10 ℃ / min and calcine for 1 h. Cool the sample to room temperature under nitrogen atmosphere to obtain solid A2.

[0146] S3. Dissolve 0.8 g of calcium nitrate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. During stirring, introduce CO2 gas into the solution at a flow rate of 300 mL / min at room temperature to convert the alkaline earth metal elements into carbonates that are deposited on the surface of solid A. Adjust the pH of the solution to 8 during the deposition process using an alkaline solution to control the precipitation process of the alkaline earth metal carbonates. Wash and filter repeatedly with isopropanol-water solution until the pH of the filtered liquid is 7. After drying and grinding, the filter cake is used to obtain solid B2.

[0147] S4. Dissolve 0.186 g of rhodium dimer acetate and 0.143 g of lanthanum nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 8 using alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with 1,3-propanediol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 2.5 h under nitrogen protection at a heating rate of 10 °C / min. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 350 °C for 10 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0148] S5. Add 1 g of catalyst, 5 g of polypropylene terephthalate (PTT), and 150 mL of tetrahydrofuran to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 15 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 10 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 28.0 kJ, and the weight-average molecular weight of the PTT raw material is also 28.0 kJ. The molecular weight of the product did not decrease compared to before hydrogenation.

[0149] Comparative Example 1 (No nitriding + No alkali treatment + No auxiliary active ingredients) S1. 1 g of polymer-based activated carbon was added to 200 mL of hydrochloric acid solution (mass concentration: 20%). After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed multiple times with a 50 vol% ethylene glycol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 70% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed multiple times with a n-propanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid A1.

[0150] S2. Dissolve 0.300 g of ruthenium chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid Al. Adjust the pH of the solution to 12 with alkaline solution. Stir in a water bath at room temperature for 6 h. Wash and filter repeatedly with tert-butanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 20 °C / min for 6 h under nitrogen protection, heated to 200 °C. Then, hydrogen is introduced at a reduction temperature of 500 °C to reduce the catalyst for 2 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0151] S3. Add 1 g of catalyst, 10 g of polyethylene terephthalate (PET), and 100 mL of pyridine to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 7 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 160 °C and react for 10 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 16.4 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is 31.0 kJ. The molecular weight of the product decreases by 47% compared to before hydrogenation.

[0152] Comparative Example 2 (without active ingredient) S1. 1 g of petroleum-based activated carbon was added to 200 mL of a mixed solution of nitric acid and hydrochloric acid. The molar fraction of nitric acid in the mixed acid was 0.9, and the total mass concentration of acid in the mixed solution was 20%. After filtration, the filter cake was washed repeatedly with 50 vol% n-propanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 27.5% hydrogen peroxide, heated in a water bath with stirring, and sonicated. The filter cake was washed repeatedly with n-propanol-water solution and filtered repeatedly until the pH of the filtered liquid was 7. After drying and grinding, solid A1 was obtained.

[0153] S2. L-histidine was dissolved in 50 wt% N-methylpyrrolidone-water to prepare a 0.6 wt% solution. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 200 ℃ at a heating rate of 2 ℃ / min and calcined for 1 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0154] S3. Dissolve 1.5 g of magnesium chloride in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 5 h. Then dry and dehydrate. After grinding, calcine at 600 ℃ for 1 h under nitrogen protection at a heating rate of 10 ℃ / min. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0155] S4. Dissolve 0.125 g of ruthenium chloride and 0.167 g of rhodium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to assist dissolution, and then add solid B1. Adjust the pH of the solution to 10 with alkaline solution. Stir in a water bath at room temperature for 6 h. Wash and filter repeatedly with ethylene glycol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 6 h under nitrogen protection, heated at a rate of 2 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 600 °C to reduce the catalyst for 12 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0156] S5. Add 1 g of catalyst, 0.2 g of polyethylene terephthalate (PET), and 100 mL of cyclohexane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 °C and react for 10 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 20.2 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is 31.0 kJ. The molecular weight of the product decreases by 35% compared to before hydrogenation.

[0157] Comparative Example 3 (Undoped with nitrogen) S1. 1 g of multilayer graphene was added to 200 mL of hydrochloric acid solution with a mass concentration of 20%. After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed multiple times with a 50 vol% methanol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 20% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed multiple times with an ethylene glycol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0158] S2. Dissolve 1.5 g of barium nitrate in 100 mL of deionized water to prepare a solution, and add solid A1. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 600 °C at a heating rate of 10 °C / min for 5 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0159] S3. Dissolve 0.140 g rhodium acetate dimer, 0.100 g iridium chloride, and 0.068 g neodymium nitrate in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 12 using alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with n-butanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 1 h under nitrogen protection at a heating rate of 10 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 200 °C to reduce the catalyst for 12 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0160] S4. Add 1 g of catalyst, 5 g of polyethylene terephthalate (PET), and 200 mL of hexafluoroisopropanol to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 9 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 200 °C and react for 5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 20.8 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is 31.0 kJ. The molecular weight of the product decreases by 33% compared to before hydrogenation.

[0161] Comparative Example 4 (Untreated with alkali) S1. 1 g of multi-walled carbon nanotubes were added to 20 mL of sulfuric acid solution with a mass concentration of 15%. After water bath heating, stirring, and ultrasonic treatment, a uniformly dispersed carbon suspension was obtained. The suspension was filtered, and the filter cake was washed repeatedly with a 30 vol% 1,3-propanediol-water solution until the pH of the washing liquid was 7. The washed filter cake was transferred to 30% hydrogen peroxide, heated in a water bath, stirred, and ultrasonically treated. The filter cake was washed repeatedly with a methanol-water solution and filtered until the pH of the filtered liquid was 7. The filter cake was dried and ground to obtain solid Al.

[0162] S2. A 1.2 wt% solution containing dicyandiamide was prepared by dissolving it in water. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 500 °C at a heating rate of 2 °C / min and calcined for 5 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0163] S3. Dissolve 0.182 g of ammonium chloroiridate and 0.068 g of cerium chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to assist dissolution, and then add solid A2. Adjust the pH of the solution to 8 with alkaline solution. Stir in a water bath at room temperature for 1 h. Wash and filter repeatedly with 1,3-propanediol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C for 5 h under nitrogen protection, heated at a rate of 2 °C / min. Then, hydrogen gas is introduced at a reduction temperature of 500 °C to reduce the catalyst for 10 h. The sample is cooled to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0164] S4. Add 1 g of catalyst, 5 g of polyethylene terephthalate (PET), and 100 mL of dichloromethane to a high-pressure reactor. After purging the reactor of air, introduce H2 into the reactor to 15 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 180 °C and react for 10 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows that the degree of hydrogenation is 100%, the weight-average molecular weight of the product is 27.9 kJ, and the weight-average molecular weight of the polyethylene terephthalate (PET) raw material is 31.0 kJ. The molecular weight of the product decreases by 10% compared to before hydrogenation.

[0165] Comparative Example 5 (Unoxidized) S1. 1 g of carbon nanofibers was added to 20 mL of a mixed solution of nitric acid and hydrochloric acid. The molar fraction of nitric acid in the mixed acid was 0.9, and the total mass concentration of the acid in the mixed solution was 15%. After filtration, the filter cake was washed multiple times with a 50 vol% ethylene glycol-water solution until the pH of the washing solution was 7. The filter cake was dried and ground to obtain solid A1.

[0166] S2. A 0.6 wt% solution containing polyaniline was prepared by dissolving it in N-methylpyrrolidone. Solid A1 was added to the nitrogen source solution, heated and stirred in a water bath, and sonicated to obtain a uniformly dispersed suspension. The suspension was then dried and dehydrated. Under nitrogen atmosphere, the temperature was increased to 300 °C at a heating rate of 2 °C / min and calcined for 5 h. The sample was then cooled to room temperature under nitrogen atmosphere to obtain solid A2.

[0167] S3. Dissolve 1.5 g of magnesium nitrate in 100 mL of deionized water to prepare a solution, and add solid A2. Stir in a water bath at room temperature for 3 h. Then dry and dehydrate. After grinding, calcine at 600 °C at a heating rate of 2 °C / min for 1 h under nitrogen protection. Cool the sample to room temperature under nitrogen atmosphere to obtain solid B1.

[0168] S4. Dissolve 0.054 g of chloroplatinic acid, 0.050 g of rhodium chloride, and 0.0676 g of cerium chloride in 100 mL of deionized water to prepare a solution. Add hydrochloric acid to aid dissolution, and then add solid B1. Adjust the pH of the solution to 11.5 with alkaline solution. Stir in a water bath at room temperature for 12 h. Wash and filter repeatedly with n-butanol-water solution until the pH of the filtered liquid is 7. Then, dry the filter cake. After grinding, the filter cake is calcined at 200 °C at a heating rate of 10 °C / min for 2.5 h under nitrogen protection. Then, reduce the catalyst by introducing hydrogen gas at a reduction temperature of 500 °C for 10 h. Cool the sample to room temperature under a nitrogen atmosphere to obtain the catalyst.

[0169] S5. Add 1 g of catalyst, 0.2 g of polyethylene terephthalate (PET), and 100 mL of tetrahydrofuran to a high-pressure reactor. After purging the air from the reactor, introduce H2 into the reactor to 6 MPa, start stirring, and continue stirring until the hydrogen pressure stabilizes. Set the reactor temperature to 120 °C and react for 0.5 h. After the reaction is complete, open the reactor, remove the mixture, filter, and dry the filtrate to obtain the product. Sample analysis shows a hydrogenation degree of 77%, a weight-average molecular weight of 26.7 kJ, and a weight-average molecular weight of PET of 31.0 kJ. The molecular weight of the product decreased by 14% compared to before hydrogenation.

[0170] By using the method described in Example 1, a polymer containing a benzene ring, cyclohexane, and ester bonds was prepared, and its 1H NMR spectrum was as follows: Figure 1 As shown, the absolute molecular weight of this polymer is comparable to that of polymers containing both aromatic rings and ester bonds, such as... Figure 2 As shown. Using the method described in Example 2, a polymer containing both cyclohexane and ester bonds was prepared, and its 1H NMR spectrum is shown below. Figure 1 As shown. By using the methods described in Examples 1, 2, and 3, polymers containing both cyclohexane and ester bonds were obtained. The absolute molecular weight of these polymers was significantly lower than that of polymers containing both aromatic rings and ester bonds, such as... Figure 2 As shown.

[0171] Therefore, when the catalyst prepared in this invention is used for the hydrogenation of aromatic polyesters, it specifically hydrogenates the aromatic ring of polymers containing both aromatic rings and ester bonds. The absolute molecular weight of the polymer containing both cyclohexane and ester bonds is comparable to that of the polymer containing both aromatic rings and ester bonds, thus avoiding the problem of molecular weight reduction of hydrogenation products caused by ester bond hydrogenation during the hydrogenation process of polymers containing both aromatic rings and ester bonds.

[0172] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an aromatic polyester-specific aromatic ring hydrogenation catalyst, characterized in that, Includes the following steps: Step S1: The carbon material is added sequentially to an inorganic acid solution and a hydrogen peroxide solution, and after acid washing and oxidation, a pretreated carbon support is obtained. Step S2: Modify the pretreated carbon support obtained in step S1 to obtain a modified carbon support. Step S3: Add the modified carbon support to the mixed solution of active components. The active components are the main active component and the co-active component. Adjust the pH of the solution with alkali solution to precipitate the metal centers of the main active component and the co-active component onto the modified carbon support. After calcination and reduction, the catalyst is obtained. In step S2, the modification treatment consists of nitrogen doping and alkali treatment; Nitrogen doping involves adding a pretreated carbon support to a nitrogen source precursor solution, impregnating the nitrogen source precursor, and then calcining to obtain a nitrogen-doped support. The alkaline treatment method is any one of the following: Method (1) Nitrogen-doped support is added to a solution of alkaline earth metal salt or alkali, impregnated with alkaline earth metal salt or alkali, and then calcined to obtain modified carbon support; Method (2) Nitrogen-doped support is added to a solution of alkaline earth metal salt or alkali, and alkaline earth metal carbonate is loaded onto nitrogen-doped support by passing CO2 gas or ammonium carbonate solution into the solution of alkaline earth metal salt or alkali to obtain modified carbon support. The alkaline earth metal salt or alkali is one of magnesium acetate, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium acetate, calcium nitrate, calcium chloride, barium acetate, barium nitrate, barium chloride, and barium hydroxide; in method (1), the calcination temperature is 300-600 ℃ and the calcination time is 1-5 h; in method (2), the CO2 gas flow rate is 100-300 mL / min, the CO2 gas introduction time is 1-5 h, the mass concentration of ammonium carbonate solution is 1-40%, and the mass-volume ratio of nitrogen doped carrier to ammonium carbonate solution is 1:150-1:50 g / mL; In step S3, the molar fraction of the co-active component is 0.3-0.

4. The main active component is any one or a combination of two of palladium, platinum, ruthenium, rhodium and iridium. When the main active component includes the first element and the second element, the mole fraction of the first element is 0.01-0.9 and the mole fraction of the second element is 0.99-0.

1. The active ingredient is any one of cerium, neodymium, lanthanum, and praseodymium; The mass-to-volume ratio of the modified carbon support to the mixed solution was 1:20-1:7 g / mL.

2. The method for preparing an aromatic polyester-specific aromatic ring hydrogenation catalyst according to claim 1, characterized in that: In step S1, the carbon material is any one of activated carbon, carbon nanofibers, or graphene carbon. The inorganic acid solution is any one or more of sulfuric acid, hydrochloric acid, and nitric acid; The total mass concentration of inorganic acids is 0.5-15%; The hydrogen peroxide concentration is 27.5%-50%.

3. The method for preparing an aromatic polyester-specific aromatic ring hydrogenation catalyst according to claim 1, characterized in that: The nitrogen source is any one of urea, dicyandiamide, melamine, ammonium nitrate, L-histidine, polyaniline, and polypyrrole; the mass concentration of the nitrogen source precursor solution is 0-3%; the calcination temperature is 300-700 ℃; and the calcination time is 1-10 h.

4. The method for preparing an aromatic polyester-specific aromatic ring hydrogenation catalyst according to claim 1, characterized in that: The alkaline solution is any one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, or ammonia solution; the pH value of the solution is adjusted to 8-11.5; the calcination temperature is 200-500 ℃, and the calcination time is 1-5 h; Hydrogen gas is introduced for reduction at a temperature of 200-500 ℃ for 2-10 h.

5. An aromatic polyester-specific aromatic ring hydrogenation catalyst, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1-4.

6. The application of the aromatic polyester-specific aromatic ring hydrogenation catalyst as described in claim 5, characterized in that: The catalyst is used in the aromatic ring hydrogenation of aromatic polyesters, which are polymers containing both aromatic rings and ester bonds, and the aromatic rings are benzene rings and / or naphthalene rings.

7. The application of the aromatic polyester-specific aromatic ring hydrogenation catalyst according to claim 6, characterized in that: The application method involves adding the catalyst, aromatic polyester, and solvent into a hydrogenation reactor, starting the stirrer, replacing the air in the high-pressure reactor with N2, raising the temperature to the hydrogenation temperature, and introducing hydrogen gas at 2-15 MPa. The aromatic rings in the polymer chain of the aromatic polyester undergo specific and efficient hydrogenation. The solvent is any one of 1,4-dioxane, hexafluoroisopropanol, tetrahydrofuran, tetrahydropyran, cyclohexane, dichloromethane, or pyridine; the reaction temperature is 80-180 ℃; the feed ratio of catalyst to aromatic polyester is 1:10-5:1; the amount of aromatic polyester is 0.1-20 wt / vol of solvent.

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