DOTP Production Process
From Recycled PET to Premium Dioctyl Terephthalate (DOTP) Plasticizer
Production Flowchart
Our closed-loop production system transforms waste PET into high-value DOTP plasticizer while recovering byproducts for circular economy.
PET Sorting
Clean and sort recycled PET bottles, removing labels, caps, and other contaminants to ensure raw material purity.
Crushing
PET bottles are crushed into small flakes, increasing surface area for efficient chemical reactions in the next stage.
Feeding
Measured octanol and PET flakes are transferred into the pre-dissolution tank under vacuum with continuous stirring.
Esterification
Catalyst is added and transesterification occurs at controlled temperature, converting PET and octanol into crude DOTP ester.
Distillation
Crude ester is distilled under vacuum to separate DOTP from byproducts like ethylene glycol and excess octanol.
Neutralization
Crude DOTP is neutralized with sodium hydroxide solution and washed with water to remove residual acidity.
Alcohol Removal
Residual alcohol is removed under vacuum using steam stripping, then condensed and recovered for recycling.
Filtration
Diatomite is added as filter aid to remove fine impurities, producing pure DOTP ready for storage and delivery.
DOTP Product
High-purity DOTP plasticizer is transferred to finished product tanks, meeting ISO and SGS quality standards.
Octanol Recovery
Recovered octanol is refined through distillation and recycled back to the feeding stage, achieving closed-loop utilization and reducing raw material consumption.
Ethylene Glycol Recovery
Ethylene glycol generated during transesterification is purified to commercial grade through distillation and sold as MEG (monoethylene glycol), creating additional value from byproducts.
8-Step Production Process
2. Transesterification
The mixed material is pumped into the esterification reactor, heated, and catalyst is added for transesterification. Generated ethylene glycol and partial octanol vapor are condensed into the alcohol-water separator. Octanol returns to the reactor, while ethylene glycol aqueous solution goes to the distillation column.
3. Distillation
The crude ester from esterification enters the distillation kettle under negative pressure. Controlling vacuum and temperature, DOTP and octanol are distilled, condensed into the receiver, and non-condensable gases enter the vacuum system. Distillation residue is treated as hazardous waste.
4. Neutralization & Water Washing
The distilled DOTP crude ester contains acidity and requires neutralization. Material is transferred to the neutralization tank under vacuum, sodium hydroxide solution is added for neutralization, followed by water washing. Wastewater undergoes acid precipitation to recover organic acid, and sodium sulfate brine is treated by MVR evaporation.
5. Alcohol Removal
The neutralized and washed crude ester is transferred to the alcohol removal kettle under negative pressure. Temperature is raised and pressure reduced for alcohol removal. Steam stripping removes residual alcohol. The distilled octanol and water vapor are condensed into the recovered alcohol receiver.
6. Pressure Filtration
Diatomite is added as filter aid. The crude ester is filtered and pumped into the DOTP finished product storage tank. Filter residue is sent to the hazardous waste temporary storage room.
7. Recovered Alcohol Distillation
After settling and water separation, the alcohol layer is transferred to the recovered alcohol tank for distillation. The process includes alkali preparation, neutralization, octanone distillation, and octanol distillation. Distillation residue is handled by qualified disposal units.
8. Ethylene Glycol Distillation
The No.1 distillation column feeds under vacuum and heats to evaporate water, which is condensed and returned to the alcohol-water separator. When kettle temperature reaches the set point, continuous feeding and reflux ratio adjustment separate ethylene glycol. When content meets standard, it enters the ethylene glycol finished product tank.
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High-quality DOTP plasticizer from recycled PET. ISO-certified, SGS-tested, globally delivered.
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