Why More PET Factories Switch from Antimony Acetate to ATG Catalyst

For PET and polyester producers, catalyst selection is no longer a small raw-material decision. It affects esterification stability, polycondensation rate, color tone, acetaldehyde formation, chip quality, filter life, maintenance frequency, and ultimately the cost per ton of polymer. As PET plants run larger continuous lines, tighter intrinsic viscosity control, lower haze, and fewer shutdowns have become more important than simply choosing the lowest-priced antimony source.

This is why more PET factories switch from antimony acetate to ATG catalyst, commonly known as antimony glycolate or antimony ethylene glycolate. Both systems provide antimony as an active polycondensation catalyst, but their behavior in ethylene glycol systems is different. Antimony acetate introduces acetate groups and may release acetic acid during processing, while ATG catalyst is designed to be more compatible with the glycol-rich PET reaction environment.

For procurement managers, the question is not only “Which catalyst is cheaper per kilogram?” The more useful question is: which catalyst gives stable polymerization, better operability, lower side reactions, and consistent product quality under the plant’s actual process conditions?

1. PET Catalyst Selection Is Moving Toward Process Stability

From catalyst activity to total plant performance

In PET production, antimony-based catalysts remain widely used because they provide a practical balance of activity, cost, color performance, and industrial familiarity. Antimony trioxide, antimony acetate, and ATG catalyst are all used in different process routes. However, modern PET plants are increasingly focused on operational stability rather than catalyst activity alone.

A high-volume PET line may operate continuously for weeks or months. Even small changes in catalyst solubility, feeding accuracy, acidity, metal dispersion, or impurity profile can influence polymer color, intrinsic viscosity, end-group concentration, and downstream spinning or bottle-grade performance. When the catalyst system creates fewer process disturbances, the value appears in fewer corrective adjustments, lower off-spec generation, and improved production continuity.

Antimony acetate has historically been used because it is relatively reactive and can be dissolved or dispersed into the reaction system. But the acetate group is not neutral in PET chemistry. Under heat and vacuum, acetate-containing species may contribute to acidity, volatility, and by-product formation. In contrast, ATG catalyst is already coordinated with glycol groups, making it more chemically aligned with ethylene glycol-based esterification and polycondensation systems.

Why this matters in continuous PET plants

In a typical PET process, purified terephthalic acid or dimethyl terephthalate reacts with ethylene glycol, followed by pre-polycondensation and final polycondensation under high temperature and vacuum. Catalyst behavior must remain predictable across several demanding conditions: high temperature, low pressure, changing viscosity, and continuous removal of ethylene glycol and volatile by-products.

When catalyst dispersion is inconsistent, antimony may not distribute uniformly in the melt. This can lead to local reaction differences, color variation, metal precipitation, or deposits in transfer lines and filters. In fiber-grade PET, these issues may affect spinning pack pressure rise and filament breakage. In bottle-grade PET, they may influence haze, yellowness, acetaldehyde control, and resin consistency.

ATG catalyst is often selected because it can provide a cleaner, more uniform introduction of antimony into the PET reaction system. For plants optimizing for long operating cycles and stable quality, this compatibility is a practical reason for switching.

2. Antimony Acetate vs. ATG Catalyst: Technical Comparison

The difference between antimony acetate and ATG catalyst is not simply a change in chemical name. It changes how the catalyst enters the reaction system, how it interacts with ethylene glycol, and what secondary components may be introduced into the process.

Parameter	Antimony Acetate	ATG Catalyst	Practical Impact in PET Production
Main chemical form	Antimony acetate compound	Antimony glycolate / antimony ethylene glycolate type catalyst	ATG is more compatible with glycol-based PET reaction media
Functional group introduced	Acetate group	Glycolate group	ATG reduces acetate-related acidity and volatile by-products
Typical use stage	Esterification or polycondensation catalyst addition	Polycondensation catalyst addition, often in EG solution or slurry system	ATG can support more stable feeding and dispersion
Solubility and compatibility	Requires careful dissolution and handling	Designed for ethylene glycol compatibility	Better compatibility helps reduce deposits and feeding variation
Potential by-products	Acetic acid and acetate-related volatiles may be concerns	Lower acetate contribution	Can support lower corrosion risk and cleaner vacuum operation
Color control	Depends strongly on purity, dosage, and process control	Often preferred for stable L/b color performance	Useful for fiber-grade and bottle-grade PET requiring consistent appearance
Process stability	Can be effective but sensitive to impurity and acidity control	Generally selected for smoother catalyst introduction	Helps plants reduce batch-to-batch or shift-to-shift variation

Acetate-related concerns

One of the main technical reasons PET factories evaluate alternatives to antimony acetate is the presence of acetate chemistry. Acetic acid formation or acetate-related volatiles may contribute to corrosion, odor, vacuum system load, and end-group variation. These effects depend on the plant design, catalyst dosage, residence time, vacuum efficiency, and stabilizer package, but they are real considerations in large-scale production.

ATG catalyst reduces this concern because it introduces antimony in a glycolate form rather than an acetate form. For plants already using ethylene glycol as a major reactant and carrier medium, this is a more natural fit. The catalyst can be prepared into a stable EG-based feed system, helping the process team improve dosing accuracy and reduce undissolved particles.

Color and haze performance

PET color is commonly monitored through CIE L*, a*, and b* values. Higher L* indicates brightness, while b* is often watched closely because positive b* indicates yellow tone. Antimony catalyst type, oxidation state, impurity profile, phosphorous stabilizer, cobalt toner, residence time, and thermal history all influence final color.

ATG catalyst is not a standalone solution for every color issue, but it can support more consistent color control because of improved compatibility and cleaner catalyst dispersion. For producers of polyester filament, film, and bottle resin, stable color reduces the need for corrective toner adjustments and helps maintain downstream customer specifications.

3. Quality Parameters PET Producers Should Check Before Switching

Antimony content and active dosage

When comparing antimony acetate and ATG catalyst, plants should calculate dosage based on active antimony content, not only product mass. Antimony acetate typically contains about 40% antimony by mass depending on purity and hydration state. ATG catalyst specifications vary by supplier and grade, so procurement and process teams should confirm the exact antimony content, moisture, insoluble matter, and recommended feed concentration.

For many PET processes, antimony in the final polymer is commonly controlled in the range of roughly 150-300 ppm Sb, depending on resin grade, reaction design, and required polycondensation rate. The correct dosage should be validated through plant trials, intrinsic viscosity build rate, color, acetaldehyde, and carboxyl end-group data rather than by direct one-to-one mass replacement.

Intrinsic viscosity and polycondensation rate

Intrinsic viscosity is one of the most important PET quality indicators. Fiber-grade PET may target different IV ranges than bottle-grade resin, and solid-state polycondensation adds another layer of control for high-IV applications. Catalyst activity directly affects the rate of molecular weight growth during melt polycondensation.

ATG catalyst can help maintain stable IV development because it disperses well in glycol-based systems and provides active antimony in a form suitable for PET polycondensation. During a switch, the plant should compare final IV, IV deviation, melt viscosity trend, vacuum load, esterification completion, and residence time. A successful switch should not only match the target IV but also reduce variability around that target.

Acetaldehyde and thermal degradation

For bottle-grade PET, acetaldehyde is a critical performance parameter because it can affect beverage taste. Catalyst type is only one factor; temperature, residence time, moisture, stabilizers, melt handling, and solid-state polycondensation also matter. However, a more stable catalyst system can help reduce unnecessary thermal stress and process fluctuations.

Plants may evaluate acetaldehyde using headspace gas chromatography methods, while IV is commonly measured according to solution viscosity methods such as ASTM D4603 or equivalent internal procedures. Color can be measured using spectrophotometer-based CIE L*a*b* methods, and polymer thermal properties may be monitored by DSC methods such as ASTM D3418.

Moisture, insoluble matter, and impurities

For catalyst procurement, low moisture and low insoluble matter are essential. Moisture can influence esterification balance and hydrolysis risk, while insoluble particles can affect filterability and spinning performance. Trace metals such as iron may influence color and degradation. Chloride, sulfate, sodium, and other ionic impurities should be controlled according to the plant’s internal specification.

Recommended Control Item	Why It Matters	Common Test or Management Approach
Antimony content	Determines active catalyst dosage and cost per ton of PET	Supplier certificate of analysis, ICP or titration verification
Moisture	Excess moisture may affect hydrolysis and process consistency	Karl Fischer moisture testing
Insoluble matter	Can increase filtration load and spinning pack pressure	Filtration test, residue analysis
Iron and heavy metal impurities	May influence color, degradation, and customer compliance	ICP-OES or ICP-MS analysis
Color of catalyst solution	Indicates consistency and possible contamination	Visual check, spectrophotometer measurement
Batch consistency	Reduces line adjustments and quality drift	COA trend review and incoming QC

4. Standards and Compliance Considerations

ISO management systems for stable supply

For PET factories, catalyst quality is not only a laboratory issue. It also depends on manufacturing control, environmental management, traceability, packaging, and supplier responsiveness. ISO 9001 is relevant because it reflects a structured quality management system, including production control, corrective actions, and customer feedback handling. ISO 14001 is relevant for environmental management, especially for antimony chemical production where wastewater, emissions, and waste handling must be controlled responsibly.

Haihui Antimony, Luoyang Haihui New Materials Co., Ltd., has been producing antimony-based materials since 2000 in Luoyang, China. Its background in antimony trioxide, sodium pyroantimonate, sodium metaantimonate, and PET catalyst chemistry gives it a broad technical base for controlling antimony purity, particle behavior, and batch stability. The company operates under ISO 9001 and ISO 14001 systems and serves industrial customers including Sinopec, Xinyi Glass, Rongsheng, Tongkun, and Shenghong.

ASTM methods used in PET evaluation

Although catalyst products may have their own enterprise specifications, PET producers often use ASTM or equivalent internal standards to evaluate polymer performance after the catalyst is introduced. Commonly referenced methods include ASTM D4603 for intrinsic viscosity of PET, ASTM D3418 for thermal transitions by differential scanning calorimetry, and ASTM D1003 for haze and luminous transmittance of transparent plastics where applicable to sheets, films, or molded articles.

For color, many plants use CIE L*a*b* measurements under controlled illumination and observer settings. For flame-retardant polyester applications, UL 94 may become relevant when PET is compounded with flame retardants and antimony trioxide synergists, although UL 94 is not a PET catalyst standard. The key point is that catalyst switching should be evaluated through the standards that matter to the final application, not only by the catalyst certificate of analysis.

Regulatory and customer audits

Global PET supply chains increasingly require documentation on heavy metals, restricted substances, environmental management, and product traceability. Antimony catalysts must be handled with appropriate occupational hygiene and environmental controls. Buyers may request safety data sheets, certificates of analysis, ISO certificates, REACH-related information, RoHS-related declarations for applicable downstream uses, or food-contact supporting documentation depending on the resin application and jurisdiction.

For bottle-grade PET, catalyst selection should also align with the customer’s food-contact compliance framework. For fiber-grade PET, downstream requirements may focus more on spinnability, color, dyeing behavior, and consistency. For film and engineering polyester applications, haze, thermal stability, and additive compatibility may be more important.

5. Practical Steps for Switching from Antimony Acetate to ATG Catalyst

Start with a controlled plant trial

A switch from antimony acetate to ATG catalyst should be managed as a process optimization project. The first step is to calculate equivalent active antimony dosage, then choose a conservative trial range based on supplier recommendation and the plant’s historical catalyst level. A laboratory or pilot trial can narrow the dosage window before full-line validation.

During plant trials, production teams should monitor esterification endpoint, pre-polycondensation behavior, final polycondensation time, vacuum stability, IV build rate, melt pressure, filter pressure, color, DEG content, carboxyl end groups, acetaldehyde, and final chip appearance. For fiber-grade PET, spinning performance and pack pressure rise should be included. For bottle-grade PET, acetaldehyde generation and solid-state polycondensation behavior should be evaluated carefully.

Review the feed preparation system

ATG catalyst is often introduced through an ethylene glycol-based solution or slurry. The feed preparation system should be checked for tank agitation, filtration, dosing pump accuracy, storage stability, and line cleanliness. If the previous antimony acetate system used different solvent conditions or feed concentration, the plant may need to adjust preparation temperature, mixing time, or filtration mesh.

Good catalyst feeding practice reduces variation. Even a high-quality catalyst can perform poorly if it is added through an unstable slurry, inaccurate pump, blocked strainer, or contaminated day tank. For this reason, many PET producers treat catalyst switching as both a raw-material change and a process-control improvement.

Evaluate cost by polymer output, not catalyst price only

ATG catalyst may not always look cheaper when compared by purchase price per kilogram. The correct comparison is cost per ton of qualified PET, including catalyst dosage, reaction efficiency, off-spec rate, filter replacement, downtime, maintenance, color correction, and customer claims. If ATG improves stability, reduces acetate-related issues, or helps maintain tighter quality control, the economic value can exceed the difference in unit catalyst price.

Procurement teams should therefore work with process engineers instead of making a decision based only on quotation sheets. The best supplier comparison includes technical service, batch consistency, logistics reliability, documentation, and the supplier’s ability to support troubleshooting during the transition.

Work with a supplier that understands antimony chemistry

ATG catalyst quality depends on antimony source control, reaction process, purification, impurity management, and packaging. A supplier with a narrow product focus may provide a commodity material, but PET plants often benefit from a partner that understands multiple antimony applications and downstream industrial requirements.

Haihui Antimony has more than 25 years of experience in antimony new materials and holds 60 patents, including 10 invention patents. As a national high-tech enterprise and national “Little Giant” specialized enterprise, Haihui’s technical background supports consistent manufacturing and application communication for PET, glass, ceramics, flame-retardant, and petroleum refining customers. For PET producers considering ATG catalyst, this experience can help shorten the trial period and reduce avoidable process uncertainty.

Conclusion: ATG Catalyst Fits the Direction of Modern PET Production

More PET factories switch from antimony acetate to ATG catalyst because the industry is moving toward cleaner catalyst introduction, better glycol compatibility, lower acetate-related concerns, and more stable polymer quality. Antimony acetate can still work in established systems, but ATG catalyst offers practical advantages for plants that want tighter IV control, improved color consistency, smoother feeding, and reduced process disturbance.

The most successful switch is based on active antimony calculation, controlled plant trials, polymer performance testing, and supplier quality review. Standards such as ISO 9001, ISO 14001, ASTM D4603, ASTM D3418, ASTM D1003, and UL 94 for relevant downstream flame-retardant applications provide useful reference points, but each PET plant should validate the catalyst under its own operating conditions and customer requirements.

If your PET or polyester plant is evaluating a move from antimony acetate to ATG catalyst, Haihui Antimony can provide technical specifications, sample support, and application discussion based on your resin grade, process route, and quality targets. Contact Haihui Antimony to request ATG catalyst data, pricing, and a technical consultation for your next PET catalyst trial.