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CN-122010725-A - Method for preparing DOTP from waste PET

CN122010725ACN 122010725 ACN122010725 ACN 122010725ACN-122010725-A

Abstract

The invention discloses a method for preparing DOTP from waste PET, and belongs to the technical field of depolymerization of polyester plastic high polymer materials. The invention solves the problems of high reaction temperature and difficult complete separation of products from the system in the prior PET alcoholysis. The invention firstly depolymerizes butanol under micro-positive pressure to obtain DBTP intermediate product, centrifugalizing, filtering, distilling, and performing isooctyl alcohol ester exchange under negative pressure to obtain DOTP, wherein the whole reaction process is performed under a milder temperature environment, finally, the high-efficiency preparation of DOTP and ethylene glycol serving as fine chemicals is realized, the purity of DOTP obtained after purification is more than or equal to 99%, the acid value is less than or equal to 0.03, the chromaticity of platinum-cobalt is less than or equal to 20, and the DOTP national standard and high-grade index is reached.

Inventors

  • WANG QINGGANG
  • XU GUANGQIANG
  • ZHU GUANGQIAN
  • WANG LIANG
  • YANG RULIN
  • YANG SHUXING

Assignees

  • 中国科学院青岛生物能源与过程研究所

Dates

Publication Date
20260512
Application Date
20260127

Claims (10)

  1. 1. A process for preparing DOTP from scrap PET comprising: (1) Dissolving PET waste in a mixed reaction solvent of butanol and ethylene glycol, heating and pressurizing for reaction in the presence of a catalyst, and performing aftertreatment to obtain a depolymerization product DBTP containing the catalyst; (2) Adding isooctanol into depolymerized product DBTP containing catalyst, performing transesterification reaction under negative pressure, evaporating butanol, and post-treating to obtain DOTP.
  2. 2. The method according to claim 1, wherein the catalyst in (1) is one or more of alkaline compounds with zinc, potassium, sodium, titanium and the like as metal centers, and the mass ratio of the catalyst to PET is 1:10000-1:20.
  3. 3. The method of claim 2, wherein the catalyst is one or more of a disilazide-based metal compound, potassium alkoxide, sodium alkoxide, and an organo-titanium compound.
  4. 4. A method according to claim 3, wherein the catalyst is one or more of Zn (HMDS) 2 、Mg(HMDS) 2 , potassium methoxide, potassium ethoxide, potassium tert-butoxide, potassium methyl siliconate, potassium trimethylsiliconate, potassium triethylsiliconate, potassium phenyl dimethyl siliconate, potassium phthalimide, potassium fluotitanate, potassium titanium oxalate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, sodium methyl siliconate, sodium trimethylsiliconate, tetrapropyl titanate, tetrabutyl titanate, n-butyl titanate, n-propyl titanate, isopropyl titanate, and the like.
  5. 5. The method of claim 1, wherein the reaction temperature in (1) is 50-150 ℃ and the pressure is 0.1-0.5 MPa.
  6. 6. The method of claim 1, wherein the post-treatment in (1) is a two-stage reduced pressure distillation to remove butanol and ethylene glycol, the butanol distillation temperature is 20-60 ℃, and the ethylene glycol distillation temperature is 80-120 ℃.
  7. 7. The method of claim 1, wherein the transesterification reaction temperature in (2) is 50 to 150 ℃ and the pressure is 0.01 to 0.15 MPa.
  8. 8. The method of claim 1, wherein the post-treatment in (2) is a secondary distillation to remove butanol and isooctanol, the butanol distillation temperature is 20 to 60 ℃, and the isooctanol distillation temperature is 80 to 120 ℃.
  9. 9. The method of claim 1, wherein the PET waste is polyester blended clothing.
  10. 10. The DOTP prepared by the method of any one of claims 1 to 9, characterized in that the purity is more than or equal to 99%, the acid value is less than or equal to 0.03, and the platinum-cobalt chromaticity is less than or equal to 20, and can be directly used as a plasticizer.

Description

Method for preparing DOTP from waste PET Technical Field The invention relates to a method for preparing DOTP from waste PET, belonging to the technical field of depolymerization of polyester plastic high polymer materials. Background Polyethylene terephthalate (PET) is a highly crystalline thermoplastic polyester, and is widely used in the fields of packaging, textile, electronic devices, automobile industry, etc., because of its excellent mechanical properties, chemical stability and portability. The annual output of global PET is more than 7000 ten thousand tons, but the recovery rate is less than 15%, and a large amount of waste PET is treated by landfill or incineration, so that serious microplastic pollution and resource waste are caused. Therefore, efficient recovery and recycling of PET is an important issue for sustainable development. Among the chemical recovery methods, the alcoholysis method has been attracting attention because the reaction conditions are mild and the product can be directly used for the synthesis of recycled polyesters. The traditional alcoholysis technology takes Ethylene Glycol (EG) as a solvent to depolymerize PET into monomers such as dihydroxyethyl terephthalate (BHET) or dimethyl terephthalate (DMT), but has the problems of low depolymerization product purity, complex process flow and the like. In recent years, isooctyl alcohol decomposition has become a research hotspot because of the possibility of preparing high-added-value products such as plasticizer diisooctyl terephthalate (DOTP). For example, the industrial application of the Chinese patent CN118439951A faces two major challenges, namely, the reaction temperature is too high, the traditional isooctyl alcohol decomposition needs to be carried out at a high temperature of more than 200 ℃, the energy consumption is high, side reactions (such as EG oxidation and PET thermal degradation) are easy to cause, and the impurity of the product is increased. Secondly, the separation is difficult, the boiling point of EG is close to that of isooctyl alcohol, the distillation separation energy consumption is high, the efficiency is low, the residual EG can influence the purity of DOTP, multistage rectification or adsorption treatment is needed, and the cost is obviously increased. On the other hand, there are reports on the preparation of DOTP by DMT-isooctanol transesterification, such as China patent CN119954645A discloses transesterification of DMT and isooctanol at 160 ℃, but the preparation and purification of intermediate DMT are complicated, the post-treatment of DOTP is complicated, liu Bifang et al (Hubei chemical, 1990, 1, 27-29) report on the method for preparing DOTP by transesterification at 140-165 ℃, the post-treatment adopts steam vacuum distillation to introduce new impurity solvent, and the isooctanol solvent separated after the reaction cannot be effectively recovered. How to reduce the energy consumption and realize the preparation of high-purity DOTP under simple process conditions is important. Therefore, the development of the PET alcoholysis method which has mild reaction conditions, high yield, high purity and easy separation of EG and isooctyl alcohol has important significance. Disclosure of Invention The invention aims to solve the problems of the prior PET alcoholysis and provides a method for preparing DOTP from waste PET. The technical scheme of the invention is as follows: it is an object of the present invention to provide a process for preparing DOTP from waste PET, comprising the steps of: (1) Dissolving PET waste in a mixed reaction solvent of butanol and ethylene glycol, heating and pressurizing for reaction in the presence of a catalyst, and performing aftertreatment to obtain a depolymerization product DBTP containing the catalyst; (2) Adding isooctanol into depolymerized product DBTP containing catalyst, performing transesterification reaction under negative pressure, evaporating butanol, and post-treating to obtain DOTP. Further defined, the catalyst in (1) is one or more of basic compounds having zinc, potassium, sodium, titanium, etc. as metal center. Further defined, the catalyst is one or more of a disilazide-based metal compound, potassium alkoxide, sodium alkoxide, and an organo-titanium compound. Still further defined, the catalyst is one or more of Zn (HMDS) 2、Mg(HMDS)2, potassium methoxide, potassium ethoxide, potassium t-butoxide, potassium methyl siliconate, potassium trimethylsiliconate, potassium triethylsiliconate, potassium phenyl dimethyl siliconate, potassium phthalimide, potassium fluorotitanate, potassium titanyl oxalate, sodium methoxide, sodium ethoxide, sodium t-butoxide, sodium methyl siliconate, sodium trimethylsiliconate, tetrapropyl titanate, tetrabutyl titanate, n-butyl titanate, n-propyl titanate, isopropyl titanate, and the like. Further defined, the mass ratio of the catalyst to PET is 1:10000-1:20. Further defined, the mass ratio of catalyst to PET is 4:10