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CN-121972230-A - Method for preparing BHET by catalyzing glycol alcoholysis PET

CN121972230ACN 121972230 ACN121972230 ACN 121972230ACN-121972230-A

Abstract

The invention belongs to the technical field of polyester recovery, and relates to a method for preparing BHET by catalyzing glycol alcoholysis PET. The catalyst adopted by the method is gamma-Fe 2 O 3 @meso-SiO 2 -DBU,γ-Fe 2 O 3 @meso-SiO 2 -DBU which consists of gamma-Fe 2 O 3 @meso-SiO 2 and DBU, wherein gamma-Fe 2 O 3 @meso-SiO 2 has a core-shell structure, the core is gamma-Fe 2 O 3 , the shell consists of meso-SiO 2 , and the DBU and the shell form ion pairs through electrostatic attraction and are enriched in mesopores of meso-SiO 2 . The invention solves the problem of low yield of the existing magnetic separation heterogeneous catalytic system BHET, effectively improves the conversion rate of PET and the yield of BHET, has stable catalyst structure and durable catalytic activity, can be magnetically separated and recycled, and is suitable for catalyzing the severe reaction condition of depolymerizing PET with ethylene glycol.

Inventors

  • SUN BIN
  • Gai Zening
  • ZENG ZHIHONG
  • SHEN JING
  • FAN SHUJING
  • JIANG XIAOZE

Assignees

  • 东华大学
  • 上海慧翌新材料科技有限公司
  • 绍兴惠群新材料科技有限公司

Dates

Publication Date
20260505
Application Date
20260403

Claims (8)

  1. 1. A method for preparing BHET by catalyzing glycol to alcoholysis PET is characterized in that a catalyst is adopted, wherein the catalyst is gamma-Fe 2 O 3 @meso-SiO 2 -DBU,γ-Fe 2 O 3 @meso-SiO 2 -DBU and consists of gamma-Fe 2 O 3 @meso-SiO 2 and DBU, the gamma-Fe 2 O 3 @meso-SiO 2 has a core-shell structure, the core is gamma-Fe 2 O 3 , the shell consists of meso-SiO 2 , and the DBU and the shell form ion pairs through electrostatic attraction and are enriched in mesopores of meso-SiO 2 .
  2. 2. The method for preparing BHET by catalyzing glycolysis PET according to claim 1, wherein the average particle size of the core is 218-220nm, the average thickness of the shell is 12-16nm, the average pore diameter of the shell is 2.3-3nm, and the content of DBU in gamma-Fe 2 O 3 @meso-SiO 2 -DBU is 1.2-8.83 wt%.
  3. 3. The method for preparing BHET by catalyzing glycolysis PET according to claim 1, wherein the preparation process of gamma-Fe 2 O 3 @meso-SiO 2 -DBU comprises dispersing gamma-Fe 2 O 3 @meso-SiO 2 in a mixed solution of ethanol and water, adding DBU, stirring for reaction, and performing post-treatment to obtain gamma-Fe 2 O 3 @meso-SiO 2 -DBU; Wherein the volume ratio of the ethanol to the water is 0.1:1-0.5:1, the mass volume ratio of the mixed solution of the gamma-Fe 2 O 3 @meso-SiO 2 and the ethanol to the water is 1g:155mL-5g:155mL, the temperature of the stirring reaction is 50-60 ℃, the rotating speed of the stirring reaction is 200-300r/min, and the stirring reaction time is 12-36h.
  4. 4. The method for preparing BHET by catalyzing glycol to alcoholysis of PET according to claim 1, wherein the preparation process of gamma-Fe 2 O 3 @meso-SiO 2 is as follows: (a) Ultrasonically dispersing the CTAB solution to form a micelle solution, adding gamma-Fe 2 O 3 into the micelle solution, sequentially stirring, ultrasonically treating, then dropwise adding an ammonia water solution, then dropwise adding a TEOS solution, continuously stirring for reaction, and performing post-treatment to obtain gamma-Fe 2 O 3 @SiO 2 ; (b) After the gamma-Fe 2 O 3 @SiO 2 is placed in a muffle furnace for calcination, the gamma-Fe 2 O 3 @meso-SiO 2 is obtained after cooling to 25-30 ℃.
  5. 5. The method for preparing BHET by catalyzing glycol to alcoholyze PET according to claim 1, wherein the specific process comprises mixing PET, glycol and gamma-Fe 2 O 3 @meso-SiO 2 -DBU, transferring into a hydrothermal kettle for alcoholysis reaction, and performing post-treatment to obtain BHET.
  6. 6. The method for preparing BHET by catalyzing glycolysis of PET according to claim 5, wherein the feeding mass ratio of PET to glycol is 1:3-1:8, and the feeding mass of gamma-Fe 2 O 3 @meso-SiO 2 -DBU is 1.6% -4.8% of the feeding mass of PET; the alcoholysis reaction temperature is 210-240 ℃, the time is 3-5h, and the pressure is 0.25-0.9MPa.
  7. 7. The method for preparing BHET by catalyzing glycolysis of PET as set forth in claim 5, wherein the PET is in the form of one or more of a film, a bottle, a fiber, and a powder.
  8. 8. The method for preparing BHET by catalyzing glycolysis of PET according to any one of claims 1-7, wherein the conversion rate of PET is 99.98% -100%, and the yield of BHET is 80.27% -84.85%.

Description

Method for preparing BHET by catalyzing glycol alcoholysis PET Technical Field The invention belongs to the technical field of polyester recovery, and relates to a method for preparing BHET by catalyzing glycol alcoholysis PET. Background Polyethylene terephthalate (PET) is a thermoplastic polyester material synthesized from refined terephthalic acid (PTA) and Ethylene Glycol (EG) by a direct esterification method or dimethyl terephthalate (DMT) and EG by an ester interchange method, and is one of the polyester plastics with the highest global yield because of its excellent mechanical strength, chemical stability, barrier property and transparency, which is widely used in the fields of food packaging, textiles, construction and medical treatment. Most PET products are disposable, the weight ratio of the waste in the global solid waste is up to 8.0 percent, the volume ratio of the waste in the global solid waste is up to 12.0 percent, the PET products are extremely difficult to degrade in natural environment, and heavy pressure is brought to ecological environment. Under the background, the recycling of PET waste becomes an important research in the field of global plastic recycling economy. The PET is converted into high-purity terephthalic acid bis (2-hydroxyethyl) ester (BHET) monomer through chemical depolymerization, and can be directly remelted and polycondensed to prepare the regenerated PET (rPET) with the performance equivalent to that of the original PET, so that the method has remarkable advantages in the aspects of atom economy, environmental protection and realization of PET closed-loop recycling, and is a core research direction in the field of PET chemical recovery. PET glycol alcoholysis is a main process path for preparing BHET by depolymerizing the PET glycol, and the selection of a catalytic system plays a decisive role in the alcoholysis reaction efficiency, the yield and the purity of the BHET. The conventional catalytic system for PET alcoholysis is divided into two types, i.e. homogeneous phase and heterogeneous phase, wherein the heterogeneous catalyst exists in a solid state form and forms a heterogeneous system with a liquid phase reaction system, and the heterogeneous catalyst has the advantages of easy separation and recovery, recycling, environmental friendliness, capability of reducing metal ion residues, improving the purity of a product, good stability, suitability for continuous operation and the like, so that the heterogeneous catalyst is widely applied to PET alcoholysis recovery processes. The heterogeneous catalyst capable of being magnetically attracted and separated has the inherent advantages of the heterogeneous catalyst, can realize rapid and efficient solid-liquid separation through an external magnetic field, does not need complicated operations such as filtration, centrifugation and the like, greatly simplifies the recovery process of the catalyst after reaction, reduces the separation energy consumption and the operation cost, can reduce the loss of the catalyst in the separation process, improves the recycling efficiency of the catalyst, and becomes the preferential direction of a PET alcoholysis catalytic system. For example, nano-Fe@ZIF-8 adopted in literature （Sequential extraction, depolymerization and quantification of polyethylene terephthalate nanoplastics using magnetic ZIF-8 nanocomposites[J]. Chemical Engineering Journal, 2024, 490: 151453.） takes Nano iron-based magnetic particles as an inner core, gives magnetic response separation capability to the material, takes zeolite imidazole ester framework material ZIF-8 as an outer shell to provide catalytic active sites for alcoholysis reaction, but has limited catalytic activity, and the highest yield of BHET is only 49%. In summary, the problem of low yield of BHET generally exists in the existing heterogeneous catalytic system capable of magnetic separation, and development of a novel heterogeneous catalytic system which has high-efficiency magnetic separation characteristics, stable structure and excellent catalytic performance is needed to promote industrialization development of the technology for recovering BHET by PET alcoholysis. Disclosure of Invention The invention aims to solve the problems in the prior art and provides a method for preparing BHET by catalyzing glycol alcoholysis PET. In order to achieve the above purpose, the invention adopts the following technical scheme: A method for preparing BHET by catalyzing glycol to alcoholysis PET adopts a catalyst of gamma-Fe 2O3@meso-SiO2-DBU,γ-Fe2O3@meso-SiO2 -DBU composed of gamma-Fe 2O3@meso-SiO2 and DBU (1, 8-diazabicyclo [5.4.0] undec-7-ene), wherein gamma-Fe 2O3@meso-SiO2 has a core-shell structure, the core is gamma-Fe 2O3, the shell is composed of meso-SiO 2 (mesoporous silica), and the DBU and the shell form ion pairs through electrostatic attraction and are enriched in mesopores of meso-SiO 2. The invention can pertinently solve the probl