o-Xylene for Phthalic Anhydride Production | Aure Chemical
o-Xylene, chemically known as 1,2-dimethylbenzene and identified by CAS number 95-47-6, is an established industrial feedstock for the production of phthalic anhydride. Phthalic anhydride serves as an important intermediate in the manufacture of plasticizers, alkyd resins, unsaturated polyester resins and related chemical systems used across coatings, plastics and construction materials. For phthalic anhydride producers and procurement teams, successful sourcing of this aromatic feedstock depends on more than price alone. Feedstock specification, batch-to-batch consistency, packaging options, logistics arrangements and formal plant qualification all influence process reliability and final product quality. Understanding the relationship between o-Xylene and the broader family of xylene isomers helps buyers evaluate material suitability against the approved requirements of their specific oxidation unit.
Why is o-Xylene used to produce phthalic anhydride? The two adjacent methyl groups on the aromatic ring of o-Xylene can be oxidized under controlled catalytic conditions to form the corresponding ortho-dicarboxylic functionality. Industrial vapor-phase oxidation with air converts the molecule into phthalic anhydride, making o-Xylene a chemically suitable and widely established aromatic feedstock for this intermediate.
What Is o-Xylene?
o-Xylene is the ortho isomer of dimethylbenzene. Its molecular formula is C8H10, and its approximate molecular weight is 106.17 g/mol. The two methyl groups occupy adjacent positions on the benzene ring, known as the 1,2-positions. This arrangement distinguishes it from m-Xylene, or 1,3-dimethylbenzene, and p-Xylene, or 1,4-dimethylbenzene. Commercial o-Xylene is generally supplied as a clear, colorless liquid with a characteristic aromatic odor.
Mixed xylenes, by contrast, may contain variable proportions of all three xylene isomers together with ethylbenzene. A product described simply as “xylene” is therefore not automatically equivalent to o-Xylene CAS 95-47-6. Accurate CAS identification in every request for quotation helps ensure that the supplier evaluates the correct isomer against the buyer’s approved specification rather than a general aromatic solvent grade.
Why o-Xylene Is Used as a Phthalic Anhydride Feedstock
The adjacent placement of the two methyl groups allows them to be oxidized to the ortho-phthalic structure. Under industrial conditions, this conversion is commonly carried out through vapor-phase catalytic oxidation with air, with phthalic anhydride recovered as the principal intended product.
The route has been practiced commercially for decades and is an established process configuration for plants designed to use o-Xylene feedstock. Suitability for continuous industrial operation depends on the specific plant design, catalyst system and formal feedstock qualification procedure. Not every phthalic anhydride unit is configured for o-Xylene, as some installations are designed around naphthalene or another approved feedstock. Feedstock selection remains a plant-specific engineering and commercial decision rather than a universal preference.
How Phthalic Anhydride Is Produced from o-Xylene
Industrial production generally follows a sequence of feed preparation, catalytic oxidation, product recovery and purification. Exact operating conditions are determined by the licensed process technology and the individual plant’s design basis. The description below is therefore a general overview and not an operating instruction.
Feed preparation and quality control. Incoming o-Xylene is checked against the plant’s approved specification before being introduced into the production system.
Controlled introduction of o-Xylene and air. The liquid feedstock is vaporized and introduced with air under conditions controlled by the plant’s process and safety systems.
Vapor-phase catalytic oxidation. The feed mixture contacts an oxidation catalyst, commonly a vanadium-based system in plants using multitubular fixed-bed reactors. The oxidation reaction is strongly exothermic.
Heat removal or energy recovery. Heat generated by the oxidation is removed through the plant’s heat-management system. Depending on the licensed process, part of this energy may be recovered for steam generation or other plant use.
Cooling and product recovery. The reactor effluent is cooled, and phthalic anhydride is recovered through a plant-specific condensation or collection system.
Purification of crude phthalic anhydride. The recovered crude product undergoes the purification steps required by the licensed process and the final product specification.
Quality confirmation before downstream use. Finished phthalic anhydride is analyzed against the applicable product specification before storage, transfer or use in downstream manufacturing.
Because the oxidation reaction is highly exothermic, catalyst performance, heat management and process control are specific to each plant. Buyers evaluating o-Xylene feedstock should therefore focus on material that meets the plant’s qualified specification rather than relying on generic process parameters.
Why o-Xylene Feedstock Quality Matters
Feedstock qualification is based on the buyer’s approved specification rather than a universal internet standard. Parameters reviewed by phthalic anhydride producers may include o-Xylene assay, residual m-Xylene and p-Xylene, ethylbenzene, non-aromatic impurities, water, color, nonvolatile residue and catalyst-sensitive trace impurities where relevant. Analytical methods and acceptance limits should be defined in the purchase specification, quality agreement or plant qualification documentation.
Batch-to-batch consistency is also important. Unexpected changes in impurity profile, analytical results or source characteristics should be communicated and evaluated against the plant’s approved feedstock specification and qualification requirements. Buyers preparing an inquiry may consult the xylene specifications and procurement checklist for the main technical and commercial information normally required during supplier evaluation.
| Quality parameter | Why a phthalic anhydride producer may review it | How it should be confirmed |
|---|---|---|
| o-Xylene assay | Determines the proportion of the feed available for the intended oxidation reaction and may affect plant performance under process-specific conditions | Current COA and agreed specification |
| m-Xylene and p-Xylene content | May influence oxidation behavior, impurity formation and final product quality depending on the process | Gas-chromatographic analysis and agreed limits |
| Ethylbenzene | May affect oxidation chemistry and should remain within the plant’s approved impurity profile | Agreed specification and analytical method |
| Non-aromatic impurities | May affect catalyst performance, process stability or product appearance depending on their identity and concentration | Supplier specification, analytical data or pre-shipment sample |
| Water | May affect feed handling and must remain within the plant’s approved feedstock specification | Karl Fischer or another agreed analytical method |
| Color | Provides a general appearance and quality-control indicator; acceptance should follow the agreed specification | Visual or instrumental measurement stated on the COA |
| Nonvolatile residue | May indicate the presence of higher-boiling or nonvolatile impurities requiring evaluation | Agreed test method and specification |
| Sulfur or other catalyst-sensitive trace impurities | May affect catalyst performance depending on the catalyst system and plant-specific impurity limits | Plant qualification, quality agreement or additional analysis where required |
Current o-Xylene specifications and supply information, including representative product documentation where available, can be reviewed on the Aure Chemical product page. The applicable specification must still be confirmed for each source, batch and purchase requirement.
o-Xylene Compared with Mixed Xylenes
Mixed xylenes contain o-Xylene together with m-Xylene, p-Xylene and ethylbenzene in proportions that vary according to the refining or petrochemical source. A material sold simply as “xylene” or “mixed xylenes” is therefore not chemically identical to o-Xylene CAS 95-47-6.
Phthalic anhydride producers operating o-Xylene-based units normally require a defined ortho-isomer assay and a controlled impurity profile. Substitution with mixed xylenes without formal plant review and approval may change oxidation behavior, impurity distribution or final product quality. Acceptance of any alternative aromatic stream remains subject to the plant’s licensed process, catalyst system and approved feedstock specification.
o-Xylene and Naphthalene as Phthalic Anhydride Feedstocks
Both o-Xylene and naphthalene have historically been used as industrial feedstocks for phthalic anhydride. The selection between them depends on plant configuration, catalyst system, impurity-management capability, raw-material availability and local economics.
| Consideration | o-Xylene-based route | Naphthalene-based route | Buyer or plant action |
|---|---|---|---|
| Feedstock identity | C8 aromatic isomer | C10 fused-ring aromatic hydrocarbon | Confirm the licensed process and approved feedstock |
| Plant configuration | Commonly associated with fixed-bed oxidation systems designed for o-Xylene | May use fixed-bed or fluid-bed configurations depending on the process | Review existing reactor and recovery equipment |
| Catalyst system | Commonly uses vanadium-based oxidation catalysts formulated for o-Xylene | May use a different vanadium-based formulation suited to naphthalene feed | Confirm requirements with the process licensor and catalyst supplier |
| Impurity profile | Requires control of isomer distribution and other aromatic or non-aromatic impurities | Impurity considerations may include sulfur and other source-dependent components | Approve a feedstock-specific quality specification |
| Raw-material availability | Generally associated with petrochemical aromatic streams | May originate from coal-tar processing or petrochemical sources | Evaluate local availability, consistency and commercial terms |
An existing naphthalene-based plant should not be assumed to accept o-Xylene without engineering review, catalyst evaluation and formal qualification. Feedstock selection is an engineering and commercial decision based on the plant’s licensed technology, equipment design, catalyst system, approved specification and local raw-material economics.
Main Downstream Uses of Phthalic Anhydride
o-Xylene is normally supplied to a phthalic anhydride producer rather than directly to every downstream user. The value chain proceeds from o-Xylene to phthalic anhydride and then to a range of intermediate and finished materials.
Established downstream categories include plasticizer production, particularly phthalate esters used in flexible polymer systems; alkyd resins used in coatings; unsaturated polyester and related resin systems; and other specialty chemical intermediates. Feedstock quality is only one of several factors that influence downstream product performance. Catalyst condition, process control, purification efficiency and the downstream manufacturer’s formulation also affect final quality.
Other Industrial Applications of o-Xylene
Although phthalic anhydride production is a major industrial use of high-purity o-Xylene, the isomer may also be evaluated for certain solvent, formulation or chemical-synthesis applications depending on the required grade and customer process. Buyers assessing solvent-related uses should review the separate guide to o-Xylene industrial solvent applications, as suitability must be confirmed against the intended formulation and applicable regulatory requirements.
Related Feedstock Pathways for Other Xylene Isomers
The three principal xylene isomers support different major chemical value chains. o-Xylene is associated primarily with phthalic anhydride, while m-Xylene is associated primarily with isophthalic acid. Buyers evaluating the meta isomer can refer to the guide on m-Xylene for isophthalic acid production.
p-Xylene is principally associated with purified terephthalic acid and dimethyl terephthalate, which are important intermediates in PET and polyester production. Further information is available in the application guide covering p-Xylene for PTA and DMT production.
Packaging and Transportation Considerations
Industrial quantities of o-Xylene may be evaluated for supply in steel drums where appropriate, road tankers, buyer-provided ISO tanks, supplier-arranged ISO tanks or other bulk arrangements where operationally feasible. Actual availability depends on the approved source, product specification, quantity, packaging, loading location, destination, equipment availability, carrier acceptance and dangerous-goods regulations.
In Aure Chemical’s usual operating model, buyer-provided ISO tanks may be considered for certain FCA or FOB arrangements. Where Aure Chemical is requested to arrange the ISO tank and ocean freight, CFR or CIF terms may be evaluated. Incoterms alone do not determine tank ownership or leasing responsibility, and all arrangements remain subject to operational confirmation.
Loading quantity depends on the tank design, product density, permitted filling ratio and applicable transport requirements. A single universal loading figure should therefore not be assumed. Further practical guidance is available in the article on bulk xylene packaging and ISO tank transportation. The current safety data sheet, carrier requirements and applicable regulations take precedence over general information presented on this page.
Information Required for an o-Xylene RFQ
A clear request for quotation allows the supplier to evaluate technical, commercial and logistical feasibility accurately. Buyers should normally provide the following information:
Product name, stated as o-Xylene or ortho-Xylene.
CAS number 95-47-6.
Required assay or complete specification.
Intended use in phthalic anhydride production.
Initial trial quantity, if applicable.
Regular order quantity.
Estimated annual demand.
Preferred packaging.
Whether the buyer can provide an ISO tank.
Destination country.
Destination port or delivery point.
Required Incoterm.
Required documents, such as COA, SDS or certificate of origin.
Target shipment schedule.
Proposed payment method.
Importer and end-user details where compliance review is required.
General end-use confirmation helps the supplier assess product suitability, compliance requirements, logistics constraints and source qualification. Detailed confidential operating data are not normally required during the initial quotation stage.
Evaluating o-Xylene Supply with Aure Chemical
Aure Chemical works with qualified Chinese producers and supply partners to evaluate o-Xylene requirements for international industrial buyers. Supply feasibility is reviewed according to the requested specification, quantity, packaging, loading arrangement, destination and current market availability.
Aure Chemical may assist with source evaluation, representative certificate-of-analysis review, safety-data-sheet provision, packaging confirmation, export-document coordination, dangerous-goods logistics evaluation and discussion of FOB, CFR or CIF terms where operationally feasible. Pre-shipment communication may also be coordinated to align documentation and logistics with the buyer’s confirmed requirements.
Industrial purchasers can use the o-Xylene CAS 95-47-6 product page to review available product information and submit the specification, quantity, packaging and destination required for a formal supply evaluation.
Frequently Asked Questions
Why is o-Xylene used to produce phthalic anhydride?
The adjacent methyl groups of o-Xylene can be oxidized under catalytic conditions to form the ortho-dicarboxylic structure associated with phthalic anhydride. This chemical relationship and the availability of qualified petrochemical feedstock have made o-Xylene an established raw material for plants designed around vapor-phase oxidation.
What is the CAS number of o-Xylene?
The Chemical Abstracts Service registry number for o-Xylene is 95-47-6. Stating this CAS number in an inquiry helps distinguish the ortho isomer from mixed xylenes, m-Xylene, p-Xylene and other aromatic solvent products.
Is o-Xylene the same as mixed xylene?
No. Mixed xylenes contain variable proportions of o-Xylene, m-Xylene, p-Xylene and ethylbenzene. o-Xylene CAS 95-47-6 refers specifically to the ortho isomer. Phthalic anhydride plants designed for o-Xylene normally require a defined assay and impurity profile that mixed xylenes may not meet without formal review and qualification.
How is o-Xylene converted into phthalic anhydride?
Industrial conversion is generally carried out through vapor-phase catalytic oxidation with air. The reaction mixture contacts an oxidation catalyst in a plant-specific reactor system, after which the reaction products are cooled, recovered and purified. Exact operating conditions depend on the licensed technology and individual plant design.
Can naphthalene also be used to produce phthalic anhydride?
Yes. Both o-Xylene and naphthalene have been used commercially as phthalic anhydride feedstocks. The appropriate choice depends on reactor design, catalyst system, recovery equipment, feedstock specification, raw-material availability and local economics. Switching between the two normally requires engineering review and formal requalification.
Which o-Xylene specification is required for phthalic anhydride production?
There is no single universal specification for every plant. Each producer should define an approved feedstock specification covering assay, residual isomers, ethylbenzene, water and other relevant impurities according to its catalyst system, licensed process and product-quality requirements.
Can o-Xylene be shipped in an ISO tank?
ISO tank shipment may be evaluated where operationally feasible. Arrangements can involve a buyer-provided or supplier-arranged tank, subject to source capability, quantity, destination, equipment availability, carrier acceptance and dangerous-goods requirements. The exact arrangement must be confirmed before quotation and loading.
What information is needed for an o-Xylene quotation?
Buyers should provide the product name and CAS number, required specification, quantity, estimated annual demand, preferred packaging, destination, Incoterm, required documents and target shipment schedule. End-use and importer information may also be requested for compliance and logistics review.
Industrial buyers evaluating o-Xylene for phthalic anhydride production may provide Aure Chemical with the required specification, quantity, packaging, destination, Incoterm and shipment schedule for a supply-feasibility review.