Para-Xylene CAS 106-42-3

What is Para-Xylene?

Para-xylene is the C8 aromatic isomer with methyl groups on opposite ring carbons. It is a clear flammable liquid boiling at 138 °C, but it freezes at 13.3 °C, so in cool weather it is handled as a heated product.

Its symmetry is its value. Oxidising both methyl groups gives terephthalic acid, a linear rigid diacid that packs into highly crystalline polyester chains. Nothing else gives polyester its strength and barrier properties the same way.

More than 98% of global para-xylene goes to purified terephthalic acid or dimethyl terephthalate, and from there to PET bottle resin, polyester fibre and film. The product is effectively a single-chain commodity.

Why Para-Xylene specifically

• Symmetric 1,4 structure. Oxidation gives the linear terephthalic acid that makes polyester crystalline and strong.
• The polyester chain. PX, PTA and PET form the largest single aromatic value chain in the industry.
• Fibre-grade purity. 99.7% minimum with tight isomer limits, because contaminants end up in the polymer.
• Separable only by adsorption or crystallisation. Boiling within a degree of meta-xylene, it requires dedicated separation technology.

How Para-Xylene is Manufactured

Para-xylene is produced in integrated aromatics complexes, where separation and isomerisation run as a closed loop.

• Mixed xylene feed. Reformate and pyrolysis gasoline supply a C8 cut containing about 20% para-xylene.
• Adsorptive separation. Simulated moving bed units on zeolite adsorbent recover para-xylene at 99.7% or better in a single pass.
• Crystallisation. The alternative route exploits the 13 °C freezing point, chilling the stream and separating PX crystals.
• Isomerisation. The raffinate, now depleted in para, is isomerised back to equilibrium and recycled to the separation unit.
• Transalkylation. Toluene and C9 aromatics are converted to additional xylenes to raise complex capacity.
• Finishing. Rerun distillation and guard beds deliver fibre grade with sulphur and nitrogen in the low ppm range.

Typical Commercial Specification

Figures below are representative of commercial fibre-grade para-xylene. Tell us whether the downstream unit is PTA or DMT and we will advise on the limits you should specify.

Physical & Chemical Properties

Behaviour in the process

Para-xylene is chemically unremarkable but logistically distinctive because of its freezing point:

• Freezes at 13.3 °C. Tanks, lines and ISO tanks need heating or tracing in any climate with a cool season.
• Crystallises cleanly. The same property that complicates logistics is exploited industrially to purify it.
• Oxidises at both methyl groups. Sequential oxidation under cobalt-manganese-bromide catalysis gives terephthalic acid.
• Static accumulation. Low conductivity means charge builds during splash filling; bonding and earthing are essential.

Para-Xylene and Alternative Polyester Feedstocks

Para-xylene is bought for one chain, and the alternatives are further down that chain rather than beside it.

Stated plainly: there is no substitute for para-xylene in the polyester chain. The commercial choice is whether to buy PX and oxidise it, or buy PTA and skip the oxidation step entirely.

Industries We Supply Para-Xylene To

Para-xylene goes to a narrow set of very large customers, and the specification barely varies between them.

Where Para-Xylene is Used

Para-xylene consumption is almost entirely the polyester chain, through terephthalic acid.

In PTA manufacture

Para-xylene is oxidised with air in acetic acid solvent over a cobalt-manganese-bromide catalyst at about 190 °C. Crude terephthalic acid precipitates and is then hydrogenated and recrystallised to remove 4-carboxybenzaldehyde. Feed isomer purity matters because meta and ortho carry-over give soluble isophthalic and phthalic acids that end up in the polymer.

Logistics and heating

Because PX freezes at 13.3 °C, bulk logistics use heated or steam-traced tanks and lines. A cargo allowed to solidify can be recovered by heating, but partial freezing in a tank can create a solid plug at the suction, so heating is designed in rather than added later.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with the full isomer breakdown and freezing point reported because both confirm fibre grade.

• Para-xylene purity — by gas chromatography, the primary grade measure.
• Meta, ortho and ethylbenzene content — reported because each gives a different acid on oxidation.
• Freezing point — the classic confirmation of isomer purity.
• Non-aromatics — measured because they are inerts that build up in the oxidation loop.
• Total sulphur — reported in ppm because it affects oxidation catalyst performance.
• Colour and water content — confirming freedom from contamination and moisture pick-up.

Common Process Problems & Likely Causes

When para-xylene causes trouble, it is usually isomer carry-over, sulphur or freezing in transit. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. ISO tank containers, road tankers and bulk parcel cargoes, heated or steam traced.
• Temperature control. Keep above 15 °C at all times. Para-xylene solidifies at 13.3 °C and a frozen plug at the tank suction is the classic logistics failure.
• Storage. Heated, earthed and bunded flammable-liquid tankage with nitrogen blanketing where colour matters.
• Static control. Bond and earth all equipment and use bottom filling.
• Material compatibility. Carbon steel and stainless steel are standard; stainless is preferred where colour specification is tight.
• Segregation. Keep apart from oxidisers, acids and halogens.
• Shelf life. Indefinite in sealed, dry, heated storage. Colour and water are the practical checks.
• Transport classification. UN 1307, xylenes, Class 3 flammable liquid, packing group III.

Hazards & Safe Handling

Para-xylene is a flammable liquid with irritant and central nervous system effects, classified in line with the other xylene isomers. It is not a carcinogen, but vapour control and ignition control are both required.

• Flammability. Flash point about 27 °C with a flammable range of roughly 1.1 to 7.0%. Control ignition sources and bond transfer equipment.
• Health classification. Harmful by inhalation and skin contact, skin irritant, and may cause organ damage through prolonged exposure.
• Occupational exposure. Typical limits are around 50 to 100 ppm as an 8-hour average; confirm the limit in your jurisdiction.
• Hot surfaces. Heated storage and traced lines present a burn risk at sampling and drain points.
• Aspiration hazard. Swallowing and aspirating liquid can cause chemical pneumonitis. Never induce vomiting.
• Heavy vapour. Vapour pools at low points. Ventilate and monitor at low level.
• Environment. Harmful to aquatic life; prevent entry to drains and watercourses.

Regulatory & Compliance Notes

Para-xylene is regulated in line with the xylene isomer group, with additional documentation where the chain ends in food packaging. The notes below are orientation rather than legal advice.

• GHS classification. Flammable liquid Category 3, acute toxicity Category 4, skin irritant Category 2, STOT RE Category 2 and aspiration hazard.
• REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
• Dangerous goods transport. UN 1307, Class 3, PG III. ADR, IMDG, IATA and DOT rules apply, with heating requirements noted on the transport document.
• Food contact chains. Where the PET goes to beverage packaging, additional purity and food-contact documentation is normally required down the chain.
• Quality agreements. PTA producers commonly expect documented isomer, sulphur and non-aromatics limits with change control.

We Supply Para-Xylene Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Para-Xylene 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 single heated ISO tank 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 Para-Xylene from Chelora

We are an independent sourcing and supply partner. For para-xylene that means settling three things at enquiry: the isomer purity and sulphur ceiling, the heated logistics route into your tankage, and the volume and lead time against a market supplied by a limited number of complexes.

• Documentation on every lot. Batch-specific COA (GC isomer purity, sulphur, colour), 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 single heated ISO tank through to full bulk shipments on contract supply.
• Grade matching. Fibre grade to the isomer, sulphur and non-aromatics limits your oxidation unit requires.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related products. Purified Terephthalic Acid, Mono Ethylene Glycol, Mixed Xylenes and other feedstocks alongside Para-Xylene 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.

Related Products

Buyers of para-xylene often source other polyester chain products alongside it — PTA, MEG and PET resin are commonly bought on the same programme.