Ortho-Xylene CAS 95-47-6

What is Ortho-Xylene?

Ortho-xylene is the C8 aromatic isomer with two methyl groups on adjacent ring carbons. It is a clear, flammable liquid boiling at about 144 °C, the highest-boiling of the three xylene isomers, which is what makes it separable by distillation.

That separability is its commercial advantage. Para- and meta-xylene boil within a degree of each other and require crystallisation or adsorption to separate, while ortho-xylene can be taken off a column, so it is the cheapest isomer to isolate.

Almost all ortho-xylene goes to one product: phthalic anhydride, made by catalytic air oxidation over vanadium pentoxide. Phthalic anhydride then goes to plasticisers, unsaturated polyester resins and alkyd paints.

A smaller volume serves as a high-boiling aromatic solvent and as the starting point for phthalonitrile, phthalimide and specialty intermediates.

Why Ortho-Xylene specifically

• Adjacent methyl groups. The ortho arrangement is what allows clean cyclisation to the five-membered anhydride ring on oxidation.
• Separable by distillation. A 5 °C boiling point gap from the other isomers makes recovery economical without crystallisation.
• The phthalic anhydride route. Modern PA plants run on ortho-xylene rather than naphthalene, and the feed purity sets the catalyst life.
• A high-boiling solvent. Where a slow-evaporating aromatic is wanted, ortho-xylene outlasts the mixed isomers.

How Ortho-Xylene is Manufactured

Ortho-xylene is separated from the mixed xylene stream by distillation, in the same aromatics complexes that produce para-xylene.

• Aromatics extraction. The C8 cut is recovered from reformate or pyrolysis gasoline and freed of non-aromatics.
• Xylene splitter. A high-efficiency distillation column takes ortho-xylene off the bottom, exploiting its 5 °C boiling point advantage.
• Rerun column. A second column removes C9 aromatics and heavy ends to reach 98.5% or better.
• Isomerisation credit. In integrated complexes, ortho-xylene recovery competes with recycling the stream to the isomerisation unit for more para-xylene.
• Toluene disproportionation. Selective disproportionation units supply additional xylenes where reformate is insufficient.
• Finishing. Clay treatment or guard beds remove sulphur and nitrogen species that would poison the oxidation catalyst.

Typical Commercial Specification

Figures below are representative of commercial phthalic-grade ortho-xylene. Tell us your oxidation catalyst and we will advise on the sulphur and nitrogen limits you should specify.

Physical & Chemical Properties

Behaviour in the process

Ortho-xylene handles like the other xylenes, with a few differences that follow from its higher boiling point:

• Highest boiling xylene isomer. At 144 °C it evaporates more slowly than mixed xylene, useful in high-bake coatings.
• Stays liquid in cold weather. Freezing at −25 °C, it has none of the crystallisation problems of para-rich streams.
• Oxidises cleanly. The adjacent methyl groups oxidise to the anhydride in a single vapour-phase pass over vanadium catalyst.
• Static accumulation. Low conductivity means charge builds during splash filling; bonding and earthing are essential.

Ortho-Xylene and Alternative Feedstocks

Ortho-xylene is bought almost entirely for oxidation, and the only real alternative is the older naphthalene route.

Stated plainly: for phthalic anhydride, ortho-xylene has displaced naphthalene on almost all modern lines because it gives higher yield per tonne and a cleaner product. Switching back is a plant decision, not a purchasing one.

Industries We Supply Ortho-Xylene To

Most ortho-xylene goes to a single reaction in a phthalic anhydride plant, but the solvent and specialty markets take meaningful volume too.

Where Ortho-Xylene is Used

Ortho-xylene is overwhelmingly an oxidation feedstock. Solvent and specialty uses are secondary but steady.

In phthalic anhydride manufacture

Ortho-xylene is vaporised, mixed with a large excess of air and passed over a supported vanadium pentoxide catalyst at around 350 to 400 °C. The reaction is strongly exothermic and runs in a molten salt cooled tubular reactor, so feed purity matters twice over: impurities poison the catalyst and they also shift the heat release that the salt loop has to absorb.

As an industrial solvent

The 144 °C boiling point makes ortho-xylene useful where a slow, strong aromatic solvent is needed — high-bake coatings, resin thinning and agrochemical concentrates. It is normally used as part of a blend rather than alone, as the slow evaporation can trap solvent in thick films.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with sulphur and nitrogen reported alongside purity because they determine oxidation catalyst life.

• Ortho-xylene purity — by gas chromatography, the primary grade measure.
• Other xylene isomers and ethylbenzene — reported because they oxidise to different products and lower yield.
• Non-aromatics and C9 aromatics — measured as yield detractors and heat-balance variables.
• Total sulphur — measured in ppm because it poisons vanadium catalysts.
• Total nitrogen — reported for the same reason, particularly for coal-derived streams.
• Colour and appearance — confirming freedom from oxidation and rust contamination.
• Water content and distillation range — confirming the cut is on specification.

Common Process Problems & Likely Causes

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

Packaging, Storage & Shipping

• Standard packing. 200 L drums, ISO tank containers, road tankers and bulk parcels.
• Storage. Cool, well-ventilated, earthed and bunded flammable-liquid storage away from ignition sources.
• Static control. Bond and earth all equipment and use bottom filling.
• Material compatibility. Carbon steel and stainless steel are standard. Check elastomer compatibility for hoses and seals.
• Moisture control. Nitrogen blanketing or a desiccant breather where low water content is required.
• Segregation. Keep apart from oxidisers, acids and halogens.
• Shelf life. Indefinite in sealed, dry storage. Colour and water are the practical checks.
• Transport classification. UN 1307, xylenes, Class 3 flammable liquid, packing group III.

Hazards & Safe Handling

Ortho-xylene is a flammable liquid with central nervous system and irritant hazards. Its higher flash point makes it easier to handle than toluene, but vapour exposure control is still required.

• Flammability. Flash point about 32 °C and a flammable range of roughly 0.9 to 6.7%. Control ignition sources and bond all 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.
• Narcotic effects. High vapour concentrations cause dizziness, headache and impaired coordination. Ventilate enclosed spaces.
• Aspiration hazard. Swallowing and aspirating liquid can cause chemical pneumonitis. Never induce vomiting.
• Skin contact. Defats skin and causes dermatitis on repeated contact. Use chemical-resistant gloves.
• 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

Ortho-xylene is widely traded with established transport and occupational controls. The notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.

• 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 to packaging, labelling and routing.
• Downstream phthalate regulation. Some phthalate plasticisers made from PA are restricted in toys and food contact; this affects your customers rather than the ortho-xylene itself.
• VOC regulation. Solvent use in coatings is subject to VOC emission limits in most regions.
• Quality agreements. Phthalic anhydride producers commonly expect documented sulphur, nitrogen and isomer limits with change control.

We Supply Ortho-Xylene Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Ortho-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 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 Ortho-Xylene from Chelora

We are an independent sourcing and supply partner. For ortho-xylene that means settling three things at enquiry: the purity and isomer limits, the sulphur and nitrogen ceilings your oxidation catalyst tolerates, and the packing format that suits your receiving setup.

• Documentation on every lot. Batch-specific COA (GC purity, isomer content, 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 ISO tank through to full bulk shipments on contract supply.
• Grade matching. Phthalic grade or solvent grade, with the sulphur, nitrogen and isomer limits your process requires.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related products. Mixed Xylenes, Phthalic Anhydride, Para-Xylene and other feedstocks alongside Ortho-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 ortho-xylene often source other aromatics alongside it — phthalic anhydride producers typically buy mixed xylenes and plasticiser alcohols, and coatings formulators need toluene on the same programme.