Para-Xylene
The polyester isomer. Almost all para-xylene is oxidised to purified terephthalic acid for PET resin, polyester fibre and film.
Molecular Structure
What is Para-Xylene?
Para-xylene is the 1,4-disubstituted xylene isomer, with methyl groups on opposite ring carbons. It boils at 138.4 °C and — unusually for an aromatic liquid — freezes at 13.2 °C, so it solidifies in cool ambient conditions.
That high freezing point comes from the isomer's symmetry: the linear 1,4 geometry packs efficiently into a crystal lattice. The same symmetry is the reason p-xylene is worth separating at all, because oxidation gives terephthalic acid, a rigid linear diacid that forms highly crystalline, drawable polyester chains.
Because p-xylene and m-xylene boil within 1 °C of each other, separation uses adsorptive processes such as simulated moving-bed adsorption, or low-temperature crystallisation exploiting the freezing-point gap. Well over 95% of world p-xylene goes on to purified terephthalic acid.
Chelora supplies PTA-grade para-xylene at ≥99.7 wt% with a freezing point of at least 13.0 °C, and controlled m-xylene, ethylbenzene and toluene. Heated and insulated transport arranged where ambient conditions require it.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
Para substitution places the methyl groups directly opposite each other. That linear geometry survives oxidation into terephthalic acid, and it is what allows polyester chains to crystallise and be drawn into fibre.
Skeletal structure — methyls at C-1 and C-4 (para)
Structural Identity
- IUPAC Name1,4-Dimethylbenzene
- Molecular FormulaC₈H₁₀
- Molecular Weight106.17 g/mol
- Hybridisationsp² ring, sp³ methyl carbons
- Substitution pattern1,4-disubstituted (para)
- Bond lengths1.39 Å ring C–C; 1.50 Å C–CH₃
- GeometryPlanar ring, linear D₂ₕ substitution
- Isomer separationAdsorptive separation or crystallisation
- Freezing point13.2 °C — used as a purity indicator
- CAS Number106-42-3
- InChI KeyURLKBWYHVLBVBO-UHFFFAOYSA-N
Product Specifications
Chelora supplies Para-Xylene in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Para-Xylene (p-xylene) |
|---|---|
| CAS Number | 106-42-3 |
| Molecular formula | C₈H₁₀ |
| Molecular weight | 106.17 g/mol |
| Purity (PTA grade) | ≥ 99.70 wt% |
| Purity (high-purity grade) | ≥ 99.90 wt% |
| Freezing point | ≥ 13.0 °C |
| m-Xylene (max) | ≤ 0.20 wt% |
| o-Xylene (max) | ≤ 0.05 wt% |
| Ethylbenzene (max) | ≤ 0.20 wt% |
| Toluene (max) | ≤ 0.05 wt% |
| Non-aromatics (max) | ≤ 0.10 wt% |
| Total sulfur (max) | ≤ 1.0 ppm wt |
| Water (max) | ≤ 200 ppm wt |
| Colour | ≤ 10 Pt-Co (Hazen) |
| Density | 0.858 – 0.864 g/cm³ at 20 °C |
| Flash point | 27 °C (closed cup) |
| Autoignition temperature | 528 °C |
| Flammable limits | 1.1 – 7.0% v/v in air |
| UN Number | UN 1307 |
| IMDG / ADR Class | Class 3 (Flammable Liquid), PG III |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Para-Xylene.
Purified Terephthalic Acid
Liquid-phase air oxidation in acetic acid over a cobalt–manganese–bromide catalyst gives crude terephthalic acid, hydrogenated and crystallised to PTA. This route takes almost all world p-xylene.
PET Bottle & Packaging Resin
PTA polycondensed with mono-ethylene glycol gives PET resin for beverage bottles, thermoformed packaging and sheet — the fastest-growing polyester outlet.
Polyester Fibre
Polyester staple and filament made from PTA and MEG is the largest single textile fibre by volume, covering apparel, home textiles and industrial yarn.
PET Film & DMT Route
Biaxially oriented PET film for packaging, electrical insulation and imaging, plus the older dimethyl terephthalate route still operated in some film and fibre plants.
Engineering Polyesters
Terephthalate units go into PBT and PTT engineering resins for automotive and electrical parts, and terephthaloyl chloride into para-aramid fibre.
Parylene & Specialities
Di-p-xylylene from p-xylene is vapour-deposited as parylene conformal coating for electronics, medical devices and implants, alongside solvent and intermediate uses.
Why source Para-Xylene through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
PTA grade and high-purity grade available. Isomer distribution, ethylbenzene and freezing point can be specified to match your oxidation unit.
Full Documentation
CoA, SDS, UN transport docs, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in bulk aromatic liquid logistics, including heated and insulated tanks and traced lines where ambient temperatures approach para-xylene's 13.2 °C freezing point.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Store in a bunded, well-ventilated, dedicated area away from ignition sources, heat and direct sunlight.
- Keep bulk storage and lines above 15 °C — para-xylene freezes at 13.2 °C, so heating or tracing is needed in cool conditions.
- All electrical equipment in storage and transfer areas must be ATEX/IECEx rated for the applicable zone.
- Bond and earth tanks, tankers, drums and hoses before every transfer — aromatic liquids accumulate static readily.
- Keep away from strong oxidisers, acids and halogens; use PTFE or Viton seals, as many elastomers swell in aromatics.
- Maintain a nitrogen blanket on bulk storage where the tank headspace can sit inside the flammable range.
- Fit fixed flammable-vapour detection with audible and visual alarms set below the LEL in enclosed storage and pump areas.
- Provide local exhaust ventilation at sampling, drumming and loading points, and monitor personal exposure against the OEL.
- Keep foam, dry chemical or CO₂ media available for firefighting — water jets spread the burning liquid.
Hazard Summary
Classification: Flam. Liq. 3 (H226) · Acute Tox. 4 dermal/inhalation (H312, H332) · Skin Irrit. 2 (H315) · Eye Irrit. 2 (H319) · STOT SE 3 (H335) · STOT RE 2 (H373) · Asp. Tox. 1 (H304).
Health: Causes central nervous system depression at elevated vapour concentrations, and defatting dermatitis on repeated skin contact. Aspiration into the lungs can cause chemical pneumonitis — never induce vomiting.
Exposure limits: ACGIH TLV 100 ppm 8-h TWA with a 150 ppm STEL; EU IOELV 50 ppm TWA / 100 ppm STEL with a skin notation; OSHA PEL 100 ppm TWA. Confirm the limit in force in your jurisdiction.
Flammability: Flash point 27 °C — close to ambient in warm climates. Note that tank heating used to prevent freezing must be controlled well below the flash point.
PPE minimum: Chemical splash goggles, nitrile or Viton gloves, flame-retardant antistatic clothing, and organic-vapour respiratory protection where ventilation cannot hold exposure below the limit.
Consult the full SDS for exposure limits, spill containment, emergency response, and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about Para-Xylene sourcing and specifications.
What is para-xylene used for?
Well over 95% of para-xylene is oxidised to purified terephthalic acid, which is polycondensed with mono-ethylene glycol into PET. That PET becomes polyester fibre — the largest textile fibre in the world — plus beverage bottle resin, packaging sheet and film. Smaller volumes go to PBT and PTT engineering resins, para-aramid fibre and parylene coatings.
Why does para-xylene freeze at 13 °C when the other isomers don't?
The 1,4 substitution pattern is symmetrical and linear, so p-xylene molecules pack into a crystal lattice efficiently and the melting point rises sharply — 13.2 °C, against −25.2 °C for ortho and −47.8 °C for meta. In practice that means p-xylene will solidify in an unheated tank in cool weather, so lines and vessels are traced or heated. The same property is also exploited industrially: crystallisation is one of the two commercial routes to separating p-xylene.
How is para-xylene separated from the other xylenes?
Para- and meta-xylene boil less than 1 °C apart, so distillation is not viable. The dominant commercial route is simulated moving-bed adsorption on a zeolite molecular sieve, which gives high recovery in one pass. The alternative is low-temperature crystallisation, exploiting the large freezing-point gap. Both are usually coupled to an isomerisation unit that recycles the para-depleted raffinate.
Why is freezing point specified on a para-xylene CoA?
Freezing point is an extremely sensitive purity indicator for p-xylene. Small quantities of the meta and ortho isomers or ethylbenzene depress it measurably, so a freezing point of ≥13.0 °C is a fast, robust confirmation that the material meets PTA-grade purity, and it is usually reported alongside the chromatographic assay.
What impurities matter to a PTA plant?
Meta-xylene oxidises to isophthalic acid and ortho-xylene to phthalic acid, both of which end up as colour bodies and chain-terminating impurities in the polymer. Ethylbenzene oxidises to benzoic acid, which terminates polyester chains. Non-aromatics simply burn off and cost yield, and sulfur affects catalyst performance. That is why PTA-grade specifications are tight on all four.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering purity, freezing point, isomer distribution, ethylbenzene, toluene, non-aromatics, sulfur, water and colour; a Safety Data Sheet (GHS/REACH); UN 1307 Class 3 PG III transport documentation; an origin certificate; and any destination-market certificates required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Para-Xylene grade, volume, logistics, documentation, and lead times. We respond within one business day.
