Dioctyl Terephthalate_terephthalate) (DOTP) is an environmentally friendly plasticizer usded in PVC. One of the main industrial methods to synthesize DOTP is the direct esterification method, also known as the TPA method, which uses terephthalic acid (TPA) and 2-ethylhexanol as raw materials. BASTONE is the leading DOTP manufacturer and supplier in China, with years of experience as a reliable producer and exporter of plasticizers.
1. Chemical Reaction
The core chemical reaction for producing DOTP via the TPA method is as follows:
Under the action of a catalyst and elevated temperatures, terephthalic acid reacts with 2-ethylhexanol to form DOTP and water. The reaction proceeds until the acid value of the mixture drops below 0.2 mg KOH/g, indicating the completion of esterification.
2. Process Flow
The production of DOTP by the direct esterification method involves several stages:
- Raw Materials Preparation
Mix Terephthalic acid (TPA) and 2-ethylhexanol (2-EH) in a reactor along with a suitable catalyst.
- Esterification Reaction
The mixture is heated under atmospheric pressure. Water formed during the reaction is continuously removed to drive the reaction to completion. Heat transfer oil is used to maintain the required temperature.
- Neutralization
Neutralized to remove residual acidity.
- Dehydration and De-alcoholization
Remove residual water and unreacted alcohol from the product.
- Water Washing and Filtration
The product is washed with water to remove impurities and neutral salts, then filtered to remove any suspended solids.
- Final Product Isolation
Get final DOTP after Isolation.
3. Equipment Layout
- A reactor vessel for esterification, fed with PTA (TPA) and 2-EH.
- A reflux and condensation system for recovering unreacted alcohol.
- A heat exchanger to control temperature.
- A vacuum line and vent for removing water and gases.
- Neutralization and separation units for purification.
- Filtration system to finalize product quality.
4. Advantages of the TPA Method
- Low production cost
PTA is cheaper than traditional phthalic anhydride.
- Better product performance
DOTP made via this route has low volatility, excellent electrical insulation, and environmental safety.
- Cleaner process
Minimal by-products and better environmental compliance.
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BASTONE, Leading DOTP Producer in China