What is the production process of DOTP?

DOTP is produced through continuous esterification of terephthalic acid (TPA) with 2-ethylhexanol using a titanium-based catalyst at 220-250°C under vacuum. The process includes raw material purification, multi-stage esterification, neutralization, high-vacuum stripping, and multi-stage filtration to achieve ester content ≥98% and volume resistivity ≥2×10¹² Ω·cm.

What catalyst is used in DOTP production?

Tetrabutyl titanate (TBT) is the primary catalyst, used at 0.05-0.15% by weight. This titanium-based catalyst provides high selectivity and conversion rates exceeding 99.8%, while producing minimal side reactions compared to traditional acid catalysts.

What are the key quality parameters of DOTP?

Key DOTP quality parameters include ester content (≥98%), color/APHA (≤150 for premium grade, ≤450 for qualified grade), acid value (≤0.035% as TPA), volume resistivity (≥2×10¹² Ω·cm), flash point (≥210°C), and moisture content (≤0.1%). Each batch is tested against 15+ parameters before release.

What is the difference between PET-based and TPA-based DOTP production?

TPA-based production uses virgin terephthalic acid as feedstock, while PET-based production recycles waste PET plastic through transesterification with 2-ethylhexanol. Both routes yield chemically identical DOTP. The PET route supports circular economy and reduces landfill waste. Learn more in our PET-to-DOTP recycling article.

What production capacity does Shandong Changxing have for DOTP?

Shandong Changxing group's total DOTP production capacity reaches 450,000 metric tons per year, including the 150,000-ton Wan Sheng facility using continuous esterification technology with fully automated DCS monitoring and ISO 9001:2015 certified quality management.

Advanced Production Technology of Dioctyl Terephthalate (DOTP)

Dioctyl Terephthalate (DOTP) has emerged as one of the most important non-phthalate plasticizers in the modern plastics industry. This comprehensive guide explores our advanced production technology and quality control systems for premium DOTP, manufactured at Shandong Changxing's ISO 9001:2015 certified facility.

Industrial-scale stainless steel reaction tanks for DOTP production with automated control systems — Advanced esterification reactors with precise temperature and pressure control

Chemical Reaction Principle

The production of DOTP involves the esterification of terephthalic acid with 2-ethylhexanol in the presence of a titanium-based catalyst. The overall chemical reaction can be represented as:

C₆H�?COOH)�?+ 2 C₈H₁₇OH �?C₆H�?COOC₈H₁₇)�?+ 2 H₂O
(TPA) + (2-Ethylhexanol) �?(DOTP) + (Water)

Manufacturing Process Overview

Raw Material Selection and Quality Control

The production of high-quality DOTP begins with careful selection and testing of raw materials according to strict specifications:

Terephthalic Acid (TPA): Purity �?9.9%, moisture content <0.1%, particle size optimized for rapid dissolution
2-Ethylhexanol (2-EH): Purity �?9.5%, water content <0.1%, distillation range within 1°C
Catalyst System: Proprietary titanium-based catalyst (tetrabutyl titanate), concentration precisely controlled at 0.05-0.15% by weight

Esterification Reaction Stage

The core of our DOTP production involves a carefully controlled continuous esterification process in multi-stage reactors:

Temperature Control: Precisely maintained at 220-250°C using advanced PID controllers with ±0.5°C accuracy
Pressure Management: Operated under vacuum conditions (-0.08 to -0.095 MPa) to facilitate water removal
Reaction Time: Optimized residence time of 4-6 hours for complete conversion (>99.8%)
By-product Removal: Continuous azeotropic distillation removes water, driving equilibrium toward product formation
Nitrogen Blanketing: Inert nitrogen atmosphere prevents oxidation and maintains product color stability

Purification and Finishing

After esterification, the crude DOTP undergoes multiple purification steps:

Neutralization: Residual acidity neutralized with sodium carbonate solution
Stripping: Unreacted alcohol removed under high vacuum (<1 mmHg) at 180-200°C
Filtration: Multi-stage filtration through 10μm, 5μm, and 1μm cartridge filters
Quality Testing: Every batch tested against 15+ quality parameters before release

Quality control laboratory technician analyzing DOTP sample using gas chromatography equipment — Our QC laboratory performs comprehensive analysis on every production batch

Comprehensive Quality Parameters

Our DOTP product meets or exceeds international industry standards including ASTM D5208 and ISO 10502. For a detailed comparison between premium grade and qualified grade DOTP, see our premium DOTP specifications guide.

Parameter	Premium Grade	Qualified Grade	Test Method
Ester Content	�?8%	�?8%	GC (ASTM D5208)
Color (APHA)	�?50	�?50	ASTM D1209
Acidity (% as TPA)	�?.035	�?.035	ASTM D974
Moisture Content	�?.1%	�?.1%	Karl Fischer
Density (20°C)	0.980�?.985 g/cm³	0.980�?.985 g/cm³	ASTM D4052
Volume Resistivity	�?×10¹² Ω·cm	�?×10¹² Ω·cm	ASTM D257
Flash Point	�?10°C	�?10°C	ISO 2592

Key Application Areas

DOTP's superior properties make it the preferred choice for demanding applications across multiple industries:

PVC Wire and Cable Compounds: Excellent electrical insulation properties (volume resistivity �?×10¹² Ω·cm), low volatility ensures long-term performance. Learn more about DOTP in wire and cable applications.
Medical-grade Flexible PVC: Non-phthalate formulation, biocompatible, complies with EU REACH and FDA regulations
Food Packaging Films: Low migration rate, odorless, suitable for direct food contact applications
Synthetic Leather Production: Superior flexibility at low temperatures (glass transition temperature <-40°C), excellent abrasion resistance
Automotive Interior Materials: Fogging resistance, UV stability, meets OEM specifications for interior components
PVC Flooring: Non-phthalate compliance for indoor air quality, meeting global flooring regulations

References and External Resources

Conclusion: Advanced Technology Ensures Consistent DOTP Quality

Shandong Changxing's DOTP production technology combines continuous esterification with titanium-based catalysis, multi-stage purification, and rigorous quality control to deliver plasticizers that meet the highest international standards. Key advantages include:

High conversion efficiency (>99.8%) through optimized temperature and pressure control
Consistent batch quality via 15+ parameter testing and full DCS automation
Circular economy integration �?waste PET recycling into DOTP reduces environmental impact
Comprehensive regulatory compliance �?REACH registered, FDA compliant, SGS triple-tested

Source Premium DOTP from a Leading Manufacturer

Shandong Changxing Plastic Additives operates a state-of-the-art facility with a group annual production capacity of 300,000 metric tons of DOTP, manufactured under ISO 9001:2015 certified processes using continuous esterification technology with fully automated DCS monitoring.

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