Dimethyl Terephthalate CAS 120-61-6
Chelora Chemicals supplies high-purity dimethyl terephthalate to polyester, PBT and specialty resin producers worldwide, in flake and molten form. Every consignment leaves with a batch-specific COA covering purity, acid number, colour and metals, the current SDS and full export documentation.
Also known as: DMT · Dimethyl 1,4-benzenedicarboxylate · Terephthalic acid dimethyl ester · Methyl terephthalate
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Price, lead time and a sample COA for Dimethyl Terephthalate, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (purity, acid number, colour, metals)
- Safety Data Sheet (SDS)
- Transport and export documents
- Third-party inspection on request
- Certificate of origin
What is Dimethyl Terephthalate?
Dimethyl terephthalate is the dimethyl ester of terephthalic acid, C₁₀H₁₀O₄, a white crystalline solid melting at about 141 °C and traded as flake or molten liquid.
It was the original route into polyester, because terephthalic acid could not be purified economically until the hydrogenation process was developed. DMT could be distilled, which made it the practical monomer for decades.
PTA has since displaced it on most new capacity, but DMT remains in use for existing ester-interchange plants, for PBT and for specialty polyesters where the ester route gives better control.
Unlike PTA, DMT melts and can be distilled, which makes it easier to purify and to handle in liquid form, at the cost of a methanol recovery loop in the polymerisation plant.
Why Dimethyl Terephthalate specifically
- Distillable. Unlike terephthalic acid, DMT can be purified by distillation, which is why it came first historically.
- Melts at 141 °C. Handled as a liquid in heated systems, simplifying metering compared with a slurry.
- Ester interchange chemistry. Transesterification with glycols gives controlled polyester formation and releases methanol for recovery.
- Specialty polyester routes. Preferred for some copolyesters and PBT grades where reaction control matters.
How Dimethyl Terephthalate is Manufactured
DMT is made by oxidising and esterifying para-xylene in an integrated sequence, then purifying by distillation and crystallisation.
- Para-xylene feed. High-purity PX is the starting material, as for PTA.
- Oxidation. PX is oxidised with air over a cobalt catalyst to p-toluic acid.
- Esterification. p-Toluic acid is esterified with methanol to methyl p-toluate.
- Second oxidation. The methyl ester is oxidised further to monomethyl terephthalate.
- Second esterification. Esterification with methanol gives crude DMT, with the Witten-Hercules process cycling through these stages.
- Distillation and crystallisation. Crude DMT is distilled and recrystallised from methanol to reach polymer grade.
Typical Commercial Specification
Figures below are representative of commercial polymer-grade DMT. Tell us whether the material goes to polyester or PBT and we will advise on the limits you should specify.
| Parameter | Typical Value |
|---|---|
| Appearance | White crystalline flakes or clear colourless molten liquid |
| DMT purity | 99.9% min by weight |
| Acid number | 0.03 mg KOH/g max |
| Saponification number | 576 to 578 mg KOH/g |
| Colour (APHA, molten) | 10 max |
| Monomethyl terephthalate | To grade, typically 50 ppm max |
| Methyl p-toluate | To grade, typically 50 ppm max |
| Iron | To grade, typically 0.5 ppm max |
| Ash | To grade, typically 20 ppm max |
| Crystallisation point | 140.4 °C min |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₁₀H₁₀O₄ |
| Molecular weight | 194.18 g/mol |
| Appearance | White crystalline flakes; clear liquid above 141 °C |
| Melting point | 140.6 °C |
| Boiling point | 288 °C |
| Flash point | About 153 °C (closed cup) |
| Density | 1.075 g/cm³ at 150 °C (molten) |
| Solubility in water | Practically insoluble |
| Solubility in organics | Soluble in hot methanol, esters and aromatics |
| Sublimation | Sublimes readily below the melting point |
| Dust explosion | Combustible dust requiring ignition control |
| Incompatibilities | Strong oxidisers, strong acids and bases |
Behaviour in the process
DMT's melting and subliming behaviour drives most of its handling requirements:
- Sublimes below melting point. Vapour deposits as crystals in cool parts of vent lines and headspaces, which can block them over time.
- Solidifies at 141 °C. Molten handling needs well-traced systems at higher temperature than most molten products.
- Releases methanol on transesterification. The polymerisation plant needs a methanol recovery loop, which PTA plants do not.
- Combustible dust in flake form. Fines generated in handling form explosible clouds; control ignition sources.
DMT and Polyester Feedstock Alternatives
DMT competes directly with PTA, and the choice is normally fixed by the plant design rather than made fresh each time.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| Polymer-grade DMT | 99.9%+, low acid number | Ester-interchange polyester plants, PBT and specialty polyesters |
| Purified terephthalic acid | The direct acid route, CAS 100-21-0 | Nearly all modern PET capacity; higher yield, no methanol loop |
| Isophthalic acid | Meta isomer, CAS 121-91-5 | Copolymer modifier for clarity and toughness |
| Dimethyl isophthalate | Ester of the meta isomer | Specialty copolyester and resin applications |
| 1,4-Butanediol | The PBT co-monomer, CAS 110-63-4 | Bought alongside DMT for PBT production |
Stated plainly: if you are building new polyester capacity, PTA is the right feedstock. DMT makes sense where the plant is already designed for ester interchange, or where PBT and specialty polyesters benefit from the controlled transesterification route.
Industries We Supply Dimethyl Terephthalate To
DMT serves a smaller and more specialised customer base than PTA, concentrated in engineering resins and specialty polyesters.
Where Dimethyl Terephthalate is Used
PBT and specialty polyesters now account for a growing share of DMT demand as commodity PET has moved to PTA.
In PBT manufacture
DMT is transesterified with 1,4-butanediol over a titanium catalyst, releasing methanol which is recovered, then polycondensed under vacuum. The ester route gives better control of the early reaction stages than direct esterification with the acid, which is one reason PBT producers have stayed with DMT.
Handling molten DMT
Molten DMT is held above 150 °C in traced and lagged systems under nitrogen. The product sublimes readily, so vapour deposits crystals in cool vent lines and headspaces, and those lines need periodic attention. Flake supply avoids that but requires remelting at the consumer's plant.
Need a specific grade, purity and packing format?
Tell us the grade, whether you take flake or molten product and the acid number your catalyst needs, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with acid number and colour reported alongside purity because both affect transesterification and polymer appearance.
- DMT purity and saponification number — confirming identity and ester content.
- Acid number — the key control for ester-interchange catalyst performance.
- Colour in the molten state — by APHA, predicting polymer appearance.
- Monomethyl terephthalate and methyl p-toluate — reported as the characteristic process impurities.
- Iron and ash — measured in ppm because metals affect polymer colour.
- Crystallisation point — confirming purity independently of chromatography.
Common Process Problems & Likely Causes
When DMT causes trouble, it is usually acid number, colour, sublimation deposits or moisture. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Ester interchange slow or incomplete | Acid number above specification interfering with catalyst | Acid number figure on the COA |
| Yellow colour in the polymer | Colour bodies or metals in the DMT | APHA colour and iron results |
| Blocked vent lines or headspace deposits | Sublimation and recrystallisation in cool sections | Line tracing and vent design |
| Solid plug in molten transfer lines | Temperature falling below 141 °C | Tracing, lagging and heating system integrity |
| Methanol recovery load variable | Purity or impurity profile shifting | Purity and impurity figures against the previous COA |
| Dust during flake handling | Attrition in conveying and bag emptying | Enclosed transfer, extraction and earthing |
Packaging, Storage & Shipping
- Standard packing. 25 kg bags and jumbo bags for flake; heated ISO tank containers and road tankers for molten product.
- Temperature control. Hold molten DMT above 150 °C. Below 141 °C it solidifies and plugs lines.
- Nitrogen blanketing. Standard for molten storage to prevent oxidation and colour development.
- Sublimation management. Vent lines and headspaces need tracing or periodic cleaning because DMT sublimes and redeposits.
- Dust control. Flake handling generates combustible dust; use earthed, enclosed conveying with extraction.
- Material compatibility. Stainless steel for molten service; carbon steel contributes iron and colour.
- Shelf life. Typically 24 months for sealed flake in dry storage; molten product should be used promptly.
- Transport classification. Not classified as dangerous goods; molten shipments are declared as elevated temperature cargo.
Hazards & Safe Handling
DMT has low toxicity and is not classified as dangerous goods. The practical hazards are combustible dust from flake handling and thermal burns from molten product.
- Low toxicity. DMT is not classified as hazardous to health in most jurisdictions and is handled routinely at scale.
- Combustible dust. Flake fines form explosible clouds. Earthing, enclosed conveying and extraction are required.
- Hot liquid. Molten DMT above 150 °C causes severe thermal burns and solidifies on skin, worsening the injury.
- Mild irritation. Dust can irritate eyes and the respiratory tract; use goggles and dust masks during bag handling.
- Sublimed deposits. Crystalline deposits in vents and headspaces can block relief paths; inspect regularly.
- PPE. Gloves, eye protection and dust mask for flake handling; heat-resistant gloves and face shield for molten work.
- Environment. Low aquatic toxicity and poorly soluble; contain spills as a housekeeping matter.
Regulatory & Compliance Notes
DMT is unregulated for transport, with food contact documentation required down the chain. The notes below are orientation rather than legal advice.
- GHS classification. Not classified as hazardous in most jurisdictions; some classifications apply mild irritation.
- Transport. Not classified as dangerous goods. Molten shipments are declared as elevated temperature substances.
- Food contact. Polyester for food packaging requires compliance documentation, which traces back to monomer purity.
- Dust explosion regulation. Flake handling systems fall under ATEX, NFPA or equivalent combustible dust requirements.
- REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
- Quality agreements. Polyester and PBT producers commonly expect documented acid number, colour and metals limits with change control.
We Supply Dimethyl Terephthalate Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Dimethyl Terephthalate from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
- Flexible volumes. From a pallet of bagged flake up to repeat bulk shipments on a supply contract.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Dimethyl Terephthalate from Chelora
We are an independent sourcing and supply partner. For DMT that means settling three things at enquiry: flake or molten supply, the acid number and colour your catalyst and polymer require, and the lead time, because DMT comes from a smaller producer base than PTA.
- Documentation on every lot. Batch-specific COA (purity, acid number, colour, metals), plus SDS and the full transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. From a pallet of bagged flake through to full bulk shipments on contract supply.
- Grade matching. Polymer grade in flake or molten form, to the acid number, colour and metals limits your transesterification requires.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. Purified Terephthalic Acid, Mono Ethylene Glycol, Para-Xylene and other feedstocks alongside Dimethyl Terephthalate from one supplier.
How ordering works
- Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
- We quote. Price, lead time, packing format and a sample COA, normally within one working day.
- Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.
Dimethyl Terephthalate — Common Questions
The questions our technical desk is asked most often about Dimethyl Terephthalate. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of dimethyl terephthalate?
The CAS number for DMT is 120-61-6, and its EC number is 204-411-8. Its molecular formula is C₁₀H₁₀O₄ with a molecular weight of 194.18 g/mol, and it is classified under HS code 2917.37.
What is DMT used for?
For polyester production in ester-interchange plants, PBT engineering resin, copolyester elastomers, specialty polyester films and powder coating resins.
Do you supply DMT worldwide?
Yes. Chelora Chemicals supplies and exports DMT worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India, in flake and molten form.
Why did PTA replace DMT in polyester?
Because direct esterification with terephthalic acid avoids the methanol recovery loop, gives higher yield per tonne and reduces capital cost. DMT came first only because terephthalic acid could not be purified economically until the hydrogenation process was developed.
How is DMT manufactured?
By the Witten-Hercules process: para-xylene is oxidised to p-toluic acid, esterified with methanol, oxidised again to monomethyl terephthalate and esterified again, with the crude DMT purified by distillation and recrystallisation.
Why is acid number specified so tightly?
Because free acid interferes with the ester-interchange catalyst and shifts the reaction balance in transesterification. It is a tiny fraction of the material but has a disproportionate effect on polymerisation.
Is DMT hazardous?
No, in chemical terms it is benign and not classified as dangerous goods. The practical hazards are combustible dust from flake handling and thermal burns from molten product above 150 °C.
Should I buy flake or molten DMT?
Molten suits plants with heated receiving facilities and avoids remelting energy; flake suits smaller consumers and longer supply chains. Molten systems need attention to sublimation deposits in vent lines.
Why does DMT block vent lines?
Because it sublimes readily below its melting point, so vapour from molten storage recrystallises in any cool section of a vent or headspace. Tracing and periodic cleaning are part of normal operation.
Is DMT still used for PBT?
Yes, widely. The ester-interchange route gives better control of the early reaction stages with 1,4-butanediol, which is why PBT producers have largely stayed with DMT rather than moving to PTA.
How should DMT be stored?
Flake in sealed bags in dry warehousing; molten product above 150 °C in nitrogen-blanketed, traced stainless tanks with attention to sublimation in vent lines.
What packing sizes and order quantities are available?
25 kg bags and jumbo bags for flake, and heated ISO tank containers or road tankers for molten product. Orders run from a pallet of bagged flake up to repeat bulk shipments on contract supply.
Ready to source Dimethyl Terephthalate?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.