Phthalic Anhydride
The aromatic dicarboxylic anhydride supplied by Chelora Chemicals — the essential feedstock for PVC plasticiser, unsaturated polyester resin and alkyd coating manufacture — exported from Indonesia as molten liquid or flaked solid with full batch documentation on every shipment.
What Phthalic Anhydride is, and why buyers source it
A working overview of the compound's chemistry, its role as a reactive aromatic anhydride, and the grades Chelora Chemicals keeps in regular supply.
Phthalic anhydride is the cyclic anhydride of a benzene ring carrying two adjacent carboxylic acid groups (ortho-phthalic acid). The ring-fused five-membered anhydride is readily opened by alcohols, giving two distinct esterification steps — a mono-ester followed by a slower diester — a stepwise reactivity that plasticiser and polyester producers exploit directly.
At room temperature it is a white, crystalline, needle-like solid or flake with a mild aromatic odour, soluble in many organic solvents and slowly hydrolysed by water to phthalic acid. It is commonly shipped and handled as a molten liquid above its 131 °C melting point for large-scale continuous processing, and requires dry, moisture-controlled storage and transport.
Where it fits in the synthesis chain
Phthalic anhydride's largest use is esterification with branched alcohols such as 2-ethylhexanol to make di(2-ethylhexyl) phthalate (DEHP/DOP) and related phthalate plasticisers for flexible PVC. It is also condensed with glycols and other diacids, alongside maleic anhydride, to make unsaturated polyester resins, and reacted with glycols and fatty acids in alkyd resin cooking for solvent-borne and industrial coatings.
Grade we supply
Chelora Chemicals offers Phthalic Anhydride in flake and molten-liquid form (99.8%+ assay) suitable for plasticiser, unsaturated polyester resin and alkyd coating manufacture, supplied with a batch-wise certificate of analysis.
How Phthalic Anhydride is made
An overview of the production route for orientation purposes. Our manufacturing partners' own process parameters and in-process controls are proprietary and are not disclosed beyond what is needed to interpret the certificate of analysis.
Phthalic anhydride is manufactured by the catalytic gas-phase oxidation of ortho-xylene (the dominant modern route) or, in older plants, naphthalene, with air over a vanadium pentoxide catalyst in a fixed- or fluidised-bed reactor: C₈H₁₀ + 3 O₂ → C₈H₄O₃ + 3 H₂O. The crude anhydride is then recovered, purified by distillation, and either cast into flake or kept molten for bulk shipment.
Why ortho-xylene oxidation is the standard process
Oxidising ortho-xylene, whose two methyl groups are already positioned correctly on the ring, converts a widely available BTX aromatic directly into phthalic anhydride in a single catalytic step with good selectivity, which is why it has displaced the older naphthalene-oxidation route and is now the dominant commercial process used worldwide.
Industries and processes that use it
Phthalic Anhydride is consumed across plasticiser, composites and coatings manufacture, where its stepwise ring-opening esterification chemistry is the main draw. The fields below account for most of the demand we see through our export desk.
Phthalate Plasticisers (DOP/DEHP)
Esterified with 2-ethylhexanol to make di(2-ethylhexyl) phthalate and related phthalate plasticisers used to soften flexible PVC in cable, film and flooring applications.
Unsaturated Polyester Resins (UPR)
Condensed with glycols alongside maleic anhydride to adjust the rigidity and chemical resistance of unsaturated polyester resins for composites and gelcoats.
Alkyd & Coating Resins
Cooked with glycols and fatty acids to make alkyd resins, the backbone of many solvent-borne architectural and industrial coating formulations.
Dyes, Pigments & Pharmaceutical Intermediates
Used as a starting material for phthalein dyes, phthalocyanine pigments and selected pharmaceutical and agrochemical intermediates.
How the molecule is typically carried forward
The ring-fused anhydride's stepwise esterification chemistry governs almost all of this molecule's further reaction chemistry. Reaction classes below account for most of the ways Phthalic Anhydride is converted into a finished product or intermediate.
Mono-Esterification
The anhydride ring opens readily with one equivalent of alcohol to form the mono-ester, the fast first step in both plasticiser and alkyd-resin synthesis.
Di-Esterification
A second, slower esterification under acid or metal catalysis converts the mono-ester to the full diester, completing plasticiser synthesis such as DEHP/DOP.
Polyesterification
Condensed with glycols and other diacids, releasing water, to build unsaturated polyester or alkyd resin backbones for composites and coatings.
Catalytic Gas-Phase Oxidation (Upstream)
Ortho-xylene and air react over a vanadium pentoxide catalyst to form phthalic anhydride itself, the dominant industrial route in the whole chain.
Phthalic Anhydride against other amines we supply
Buyers sourcing Phthalic Anhydride for plasticiser, composites or coatings manufacture often need a related anhydride or aromatic-chemistry intermediate. A quick reference to what else is on our regular supply list.
| Product | CAS Number | Category | Notes |
|---|---|---|---|
| Phthalic Anhydride | 85-44-9 | Aromatic dicarboxylic anhydride | The product on this page — the feedstock for phthalate plasticisers, UPR and alkyd resins. |
| Maleic Anhydride | 108-31-6 | Unsaturated dicarboxylic anhydride | The related unsaturated anhydride used alongside phthalic anhydride in alkyd and UPR resins — see its product page. |
| Ortho-Xylene | 95-47-6 | BTX aromatic isomer | The starting material for phthalic anhydride synthesis — see its product page. |
| Mono Ethylene Glycol | 107-21-1 | Diol / polyester comonomer | A common glycol comonomer condensed with phthalic anhydride in alkyd and polyester resins — see its product page. |
Exact physical constants and purity specifications are confirmed per batch on the certificate of analysis — treat the notes above as a sourcing guide, not a specification sheet, for products other than Phthalic Anhydride.
Safety classification at a glance
Based on GHS classification as commonly listed for this substance. This is a summary for orientation only — always work from the current safety data sheet supplied with your specific batch.
Causes skin irritation.
Causes serious eye damage.
May cause respiratory irritation.
May cause allergy or asthma symptoms or breathing difficulties if inhaled.
Chemical-resistant gloves, splash goggles and respiratory protection against dust/fume are mandatory for routine handling.
Keep reasonably dry; prolonged contact with moisture slowly generates phthalic acid.
Repeated exposure can cause respiratory sensitisation; good ventilation and dust/fume control are recommended.
Warning — GHS05 corrosive, GHS07 irritant and GHS08 respiratory-sensitiser pictograms apply.
This compound causes skin irritation and serious eye damage, and may cause respiratory irritation, allergy or asthma symptoms or breathing difficulties if inhaled, including through sensitisation on repeated exposure. It must be handled only with chemical-resistant gloves, splash-proof eye protection, and respiratory protection against dust or fume. Full first-aid, storage, spill and PPE guidance is in the MSDS issued with every shipment, and must be read in full and followed without exception before this material is handled.
Keeping it on spec between delivery and use
General storage guidance for this grade. Site-specific storage rules, segregation requirements and re-test intervals should follow your own EHS procedures and the MSDS issued with your batch.
Store in a dry, sealed area away from strong moisture exposure and oxidizing agents. The molten-liquid grade must be kept in a heated, insulated tank above its 131 °C melting point to prevent solidification in transfer lines. Only trained personnel using proper PPE and dust/fume control should handle this material. If a batch is held past its retest date, re-check assay and colour before use.
How it ships from Indonesia
Standard packing and export terms for this product. Confirm exact figures against your order — they vary slightly by destination and quantity.
What travels with every batch
Specification is agreed before the purchase order, not discovered on arrival. Every shipment of Phthalic Anhydride leaves with a documented, checkable paper trail.
Certificate of Analysis
Batch-wise assay (by titration/GC), colour and relevant physical constants, issued against the agreed specification so your QC team can check it, not just file it.
Safety Data Sheet
GHS-format SDS in English covering hazard classification, handling, storage, first-aid and spill response for the exact grade of Phthalic Anhydride shipped.
Technical Data Sheet
Reference physical and chemical properties, recommended storage and typical applications, for internal circulation to your process or R&D teams.
Certificate of Origin
Confirms Indonesian origin for customs clearance and any preferential-duty claim at your destination port.
Dangerous Goods Declaration
UN packing group, classification and shipper's declaration prepared ahead of loading so documentation never holds up customs.
Third-Party Inspection
Independent pre-shipment inspection and re-sampling can be arranged on request, at your cost, for buyers who require it as a matter of policy.
Frequently asked questions
What buyers most often ask our sales desk about this grade.
01What is Phthalic Anhydride used for?+
02What is the CAS number of Phthalic Anhydride?+
03How is Phthalic Anhydride made?+
04What grades does Chelora Chemicals supply?+
05Why does esterification of Phthalic Anhydride happen in two steps?+
06Is Phthalic Anhydride hazardous?+
07What packing options are available?+
08How long does delivery take?+
09Can I get a sample before placing a bulk order?+
10Do you supply Ortho-Xylene and Maleic Anhydride as well?+
Need Phthalic Anhydride on spec, on time?
Send us your required purity, quantity, packing preference and destination port. Our desk quotes most enquiries within one working day.