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Synthesis of DOTP from PET and Octanol

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Synthesis of DOTP from PET and Octanol

The synthesis of dioctyl terephthalate (DOTP) from polyethylene terephthalate (PET) and octanol primarily relies on transesterification, which enables the depolymerization of PET and its combination with octanol. Below is a detailed method based on industrial practices and scientific research:

I. Reaction Principle

Under the action of octanol and catalysts, the ester bonds in PET molecular chains break, and ethylene glycol is replaced by octanol, generating DOTP and by-product ethylene glycol:
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This process involves alcoholysis to break down the polymer structure of PET, followed by transesterification to complete functional group substitution.

II. Key Steps and Process Parameters

1. Raw Material Pretreatment

  • PET Handling
  • Octanol Selection

2. Catalyst System Selection

  • Traditional Catalysts
  • Novel Catalysts
    • Deep Eutectic Solvents (DES)
    • Titanium-based Composite Catalysts

3. Optimization of Reaction Conditions

  • Temperature Control
    • Laboratory Scale
    • Industrial Scale
  • Reaction Time
  • Stirring Rate

4. Continuous Production Process

  • Equipment Configuration
  • Process Design

III. Separation and Purification

  1. Crude Product Treatment
  2. Distillation Recovery
  1. Deep Purification

IV. Optimization Directions and Challenges

  1. Energy Efficiency Improvements
  1. Environmental Upgrades
  1. Raw Material Expansion

V. Safety and Economics

  • Risk Control
  • Cost Advantages
    • Using waste PET reduces raw material costs by 40%-60% while lowering plastic waste disposal fees.
    • Equipment investment in continuous processes can be recovered within 2-3 years through raw material savings and increased productivity.

VI. Typical Case

A Shandong enterprise adopted a continuous transesterification process, using waste PET bottle flakes and octanol as raw materials, with tetrabutyl titanate as the catalyst (0.3% dosage). The reaction was carried out at 220°C for 6 hours, achieving a DOTP yield of 92% and an ethylene glycol recovery rate of 85%. After optimizing negative pressure rectification, ethylene glycol purity increased from 95% to 99.8%, and the product quality met the IEC 70°C cable material standard.

VII. References and Tools

  • Catalyst Selection "Choline-based Deep Eutectic Solvents for Catalyzing Alcoholysis of PET to Prepare DOTP" 
  • Industrial Process "Alcoholysis Method and Device System for Producing DOTP from Polyester Waste" 
  • Equipment Design
Through the above methods, efficient resource utilization of PET can be achieved, while producing high-performance, environmentally friendly plasticizer DOTP, which combines economic and environmental benefits. In actual production, process parameters should be adjusted according to raw material characteristics and equipment conditions to achieve optimal results.
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