DOTP Eco-Friendly Production: Quality and Affordability Through Efficient Recycling

For procurement teams sourcing DOTP (Dioctyl Terephthalate) and monoethylene glycol (MEG), the central question is not merely "who can supply?" but "how is it made?" The production process determines everything that matters to a buyer: quality consistency, cost structure, supply stability, environmental footprint, and regulatory traceability. This article provides a detailed, stage-by-stage walkthrough of Shandong Changxing Plastic Additives' 8-step PET circular-economy process—the route that makes our DOTP both environmentally responsible and cost-competitive. Every photograph below is taken from our actual production facilities.

Why Recycling Is the Key to Both Quality and Affordability

The conventional route to DOTP runs through virgin terephthalic acid (PTA) and 2-ethylhexanol—both derived from petroleum. When oil prices surge, feedstock costs follow, and DOTP buyers absorb the shock. Shandong Changxing chose a different path: we use waste PET as our terephthalate source. Every year, we collect over 40,000 tons of polyester textile offcuts, beverage bottles, fishing nets, and agricultural film that would otherwise be landfilled or incinerated, and convert them into premium-grade DOTP through chemical recycling.

This is not a downcycling story. Through depolymerization and re-esterification, the molecular structure of DOTP from waste PET is identical to DOTP from virgin petrochemicals. What changes is the cost equation: waste PET is cheaper than PTA, our octanol recovery loop returns over 95% of unreacted alcohol to the reactor, and the co-produced MEG generates additional revenue. The result is DOTP that meets the same specifications as virgin material—ester content ≥98%, color ≤150 APHA, volume resistivity ≥2×10¹² Ω·cm—while costing less to produce and carrying a lower carbon footprint. That is what we mean by "quality and affordability through efficient recycling."

Process at a Glance

40,000+ t

Waste PET recycled per year

300,000 t

DOTP annual production capacity

8,500 t

Carbon emissions reduced per year

Step 1 — Waste PET Recycling: The Raw-Material Foundation

The process begins long before any chemical reaction. Our recycling network spans the textile, packaging, and agricultural sectors, collecting polyester waste from diverse sources: textile offcuts from garment factories, post-consumer beverage bottles, discarded fishing nets, and used agricultural film. Annual collection volume exceeds 40,000 tons.

Waste PET raw materials: textile offcuts, fishing nets, and agricultural film awaiting processing

Every incoming batch is recorded by source, weight, and preliminary impurity profile. This traceability is not just internal bookkeeping—it is the documentation your procurement team needs for ESG reporting, sustainability audits, and increasingly stringent extended-producer-responsibility (EPR) compliance in the EU and other markets. When you source DOTP from Shandong Changxing, you can tell your stakeholders exactly where the terephthalate in your plasticizer came from.

Buyer significance: Diversified raw-material sourcing insulates DOTP supply from single-feedstock disruptions. If virgin PTA prices spike due to oil volatility, our cost structure remains stable because waste PET pricing is driven by recycling logistics, not crude oil. This stability is passed on to buyers through long-term contract pricing.

Step 2 — Sorting and Shredding: Controlling What Enters the Reactor

Recovered PET is anything but uniform. It arrives mixed with metals (zippers, bottle caps), rubber, paper labels, adhesives, and non-PET plastics. Our sorting line combines manual pre-selection with magnetic separation to remove ferrous metals, then shredding reduces the material to flakes. Air separation and density sorting further purify the flake stream, separating PET from lighter contaminants.

Sorting and shredding: the shredder breaks fabric strips into flakes on the conveyor belt

Buyer significance: Rigorous upstream impurity removal is the first line of defense for product quality. Metal and rubber contamination that enters the reactor will carry through to finished DOTP, potentially damaging your downstream processing equipment and causing batch failures. Our multi-stage sorting ensures that only PET enters the chemical process—protecting your product integrity.

Step 3 — Washing and Impurity Removal: Purity Before Chemistry

Shredded flakes carry surface contaminants that sorting cannot remove: adhesives from labels, residual beverages, oils, and dirt. Our washing circuit combines three technologies in sequence: hot alkaline wash (dissolves oils and adhesives), friction wash (mechanically scrubs surface contaminants), and floatation separation (removes materials with different densities). Multi-stage rinsing with clean water follows, and centrifugal dewatering produces dry, clean PET flakes ready for melt pelletizing.

Washed and purified PET flakes in various colors, ready for melt pelletizing

Buyer significance: Deep cleaning at this stage directly determines downstream quality. Residual adhesives and oils would introduce color bodies and acid precursors into the final DOTP, raising acid value and degrading color. Our combined hot-alkaline + friction + floatation approach achieves the purity level needed for premium-grade DOTP (color ≤150 APHA).

Step 4 — Melt Pelletizing: Standardizing the Feedstock

Clean flakes are fed into a screw extruder operating at high temperature. The PET melts, and a filter screen captures any trace impurities that survived washing. The molten PET exits through a die head, is cut into uniform pellets, and cooled. These pellets are the standardized feedstock for the transesterification reaction.

Melt pelletizing: PET blocks cooled after extrusion, ready for transesterification

Buyer significance: Pelletizing standardizes the feedstock form factor, enabling consistent reactor charging and reproducible reaction kinetics. This is the engineering step that makes batch-to-batch DOTP uniformity possible—without standardized feedstock, no amount of downstream QC can guarantee consistent product.

Step 5 — Transesterification: Where DOTP and MEG Are Born

This is the heart of the process. PET pellets react with 2-ethylhexanol (isooctanol, CAS 104-76-7) in the presence of a catalyst at controlled temperature. The ester bonds in PET break and reform with the octanol, producing dioctyl terephthalate (DOTP) and releasing monoethylene glycol (MEG) as a co-product. The MEG is continuously separated from the reaction mixture via a water separator, which drives the equilibrium toward complete conversion.

Transesterification workshop: reaction vessels and storage tanks where PET becomes DOTP and MEG

PET + 2 C₈H₁₇OH → DOTP + MEG (by-product)

(Waste polyester) + (2-ethylhexanol) → (Dioctyl Terephthalate) + (Ethylene Glycol)

For a deeper dive into the chemistry and economics of this reaction, see our article on PET-to-DOTP transesterification process.

Buyer significance: This single reaction step produces two commercial products simultaneously. If you procure both DOTP and MEG, sourcing from the same supplier means one quality system, one compliance audit, one logistics chain—and the assurance that both products originate from the same verified process. The MEG we co-produce is refined to premium grade (purity >99.5%), suitable for antifreeze, coolant, and polyester fiber applications.

Step 6 — Alcohol Recovery: The Cost-Reduction Engine

Not all 2-ethylhexanol reacts in Step 5. The crude ester leaving the reactor carries residual alcohol that must be removed. We heat the crude under negative pressure and inject steam for stripping. The evaporated alcohol is condensed and returned to the reaction stage for reuse. Our recovery rate exceeds 95%—meaning that of every 100 tons of octanol fed to the process, less than 5 tons is lost.

Buyer significance: This is the single most important cost-control mechanism in the entire process. 2-Ethylhexanol is the most expensive raw material in DOTP production. By closing the loop on octanol, we stabilize our cost structure against feedstock price volatility and pass the savings to buyers through competitive long-term contract pricing. When you compare DOTP quotes, ask suppliers about their octanol recovery rate—it is a direct indicator of cost efficiency.

Step 7 — Distillation and Purification: Achieving Premium Specifications

The de-alcoholized crude ester still contains low-boiling impurities, high-boiling residues, and co-produced MEG. It enters a multi-stage distillation tower operating under negative pressure, which separates these components by boiling point. The finished DOTP achieves color ≤150 APHA—well within premium grade specification. A final polish filtration through diatomaceous earth removes any micro-particulates.

Multi-stage distillation tower: the refining unit that purifies DOTP to premium grade

Buyer significance: Multi-stage distillation under negative pressure is what separates premium-grade DOTP from commodity-grade. For applications where color stability is non-negotiable—wire & cable insulation, medical devices, food-contact films, transparent PVC—color ≤150 APHA is the threshold that matters. Our qualified grade DOTP and premium DOTP both meet this standard.

Step 8 — Finished DOTP and MEG: Two Products, Zero Waste

Purified DOTP is cooled, given a final filtration, and transferred to finished-product storage tanks. The group's combined annual capacity reaches 300,000 tons—150,000 tons at the Changxing facility and 150,000 tons at the Wan Sheng facility. Packaging options span the full range of global logistics needs: flexitanks for bulk liquid shipment, IBC totes for mid-volume orders, plastic and galvanized iron drums for smaller quantities, and ISO tank containers for temperature-controlled transport.

The co-produced MEG is refined to premium grade (purity >99.5%) and sold as an independent product. This is what makes our process a true circular economy: every input becomes a saleable product, and nothing is wasted. For a deeper exploration of this closed-loop model, see our article on circular economy DOTP production.

Quality Parameters Buyers Should Verify

When evaluating DOTP from any plasticizer manufacturer, verify these specifications against your application requirements. The table below shows the thresholds our process achieves.

For MEG by-product sourcing, key specifications include purity (>99.5% for premium grade), water content, and color—aligned with antifreeze and coolant formulation requirements. Each batch of both products is tested against 15+ parameters under our ISO 9001-certified quality management system before release.

Capacity and Credentials

Shandong Changxing Plastic Additives operates two production bases sharing the same 8-step process route:

• Changxing facility —150,000 t/yr DOTP, mature PET-recycling process line with decades of operational experience
• Wan Sheng facility —150,000 t/yr DOTP, continuous esterification with full DCS automation and advanced distillation towers
• MEG co-production —refined to premium grade, available for joint DOTP+MEG sourcing contracts
• Packaging flexibility —flexitanks, IBC totes, plastic drums, galvanized iron drums, ISO tank containers

4× ISO

9001 / 14001 / 45001 / 50001

31

Granted patents

Little Giant

National SRDI enterprise

Gazelle

Shandong Province certified

Our technical team—supported by the Shandong Provincial Enterprise Technology Center and Academician Workstation—offers formulation guidance, compatibility testing, and custom product development for buyers transitioning from phthalate to non-phthalate plasticizers. We have completed 60+ R&D projects and can help you optimize your PVC compounds for DOTP.