Mixed xylene, also called mixed xylenes or xylol, is a commercial mixture of three xylene isomers: ortho-xylene, meta-xylene, and para-xylene. It also contains a certain amount of ethylbenzene.
Unlike purified o-xylene, m-xylene, or p-xylene, mixed xylene is supplied as a blend and is widely used as an aromatic solvent. It is also used as a feedstock in petrochemical processing and as a component in some fuel formulations.
Most commercial mixed xylene comes from petroleum refining, particularly catalytic reforming of naphtha. Pyrolysis gasoline is another source.
The term "xylene" is often used for mixed xylene in the solvent market. In technical or petrochemical applications, however, it may refer to a specific xylene isomer. The CAS number is therefore useful when confirming exactly which material is being offered.
Chemical Identity of Mixed Xylene
CAS Number, Chemical Formula and Molecular Weight
Mixed xylene has CAS Number 1330-20-7. Its molecular formula is C₈H₁₀, and its molecular weight is approximately 106.17 g/mol.
Common commercial names include:
- Mixed xylene
- Mixed xylenes
- Xylene
- Xylol
- Dimethylbenzene
These names are widely used in the chemical and solvent markets, but they do not always guarantee an identical specification. Commercial grades can differ in total xylene content, isomer distribution, ethylbenzene content, and other impurities.
For bulk purchases, the product specification is more important than the name alone.
Is Mixed Xylene the Same as Xylene?
In the industrial solvent market, "xylene" often means mixed xylene. The material is normally a mixture of the three xylene isomers rather than one purified compound.
The situation is different when discussing individual petrochemical products. For example, p-xylene refers specifically to para-xylene, while o-xylene and m-xylene refer to the other two isomers.
A simple way to distinguish them is by CAS number:
- Mixed xylene: CAS 1330-20-7
- o-Xylene: CAS 95-47-6
- m-Xylene: CAS 108-38-3
- p-Xylene: CAS 106-42-3
If a quotation only states "xylene," the TDS or SDS should be checked before the product is compared with another supplier's material.
Composition of Mixed Xylene
Typical Isomer Ratio and Ethylbenzene Content
There is no single isomer ratio that applies to every mixed xylene product. The composition varies with the refinery, feedstock, processing conditions, and commercial grade.
A typical industrial mixed xylene may contain approximately:
| Component | Typical Range |
|---|---|
| Meta-xylene | 40–65% |
| Ortho-xylene | 20–25% |
| Para-xylene | 15–20% |
| Ethylbenzene | 10–20% |
These numbers are only a general indication. Actual commercial specifications can fall outside these ranges.
For solvent applications, the exact isomer distribution may not be critical. For petrochemical processing, it can have a much greater impact on the value and suitability of the material.
The COA for an individual batch provides the most useful information when the exact composition matters.
Where Does Mixed Xylene Come From?
The main industrial source of mixed xylene is catalytic reforming of petroleum naphtha.
In a refinery, naphtha is processed over a catalyst at elevated temperature. The process converts suitable hydrocarbons into aromatic compounds such as benzene, toluene, and xylenes. The resulting reformate can then be processed to recover mixed xylene.
Another source is pyrolysis gasoline, which is produced during the manufacture of olefins such as ethylene. Pyrolysis gasoline contains several aromatic hydrocarbons and can be processed to recover xylenes.
Xylene was also historically recovered from coal tar, but petroleum-based production is much more important in today's commercial market.
The Three Xylene Isomers Explained
Ortho-Xylene, Meta-Xylene and Para-Xylene
The three xylene isomers have the same molecular formula, C₈H₁₀. The difference is the position of the two methyl groups attached to the benzene ring.
- o-Xylene: The methyl groups are next to each other.
- m-Xylene: The methyl groups have one carbon atom between them.
- p-Xylene: The methyl groups are opposite each other.
This small structural difference gives the three isomers different physical properties and different downstream uses.
What Is Para-Xylene Used For?
Para-xylene is an important petrochemical feedstock. Its largest application is the production of terephthalic acid and related intermediates used in polyester fiber and PET resin manufacturing.
As a result, p-xylene has strong demand from the polyester, plastics, and packaging industries.
What Is Ortho-Xylene Used For?
Ortho-xylene is primarily used to produce phthalic anhydride.
Phthalic anhydride is an intermediate used in products such as plasticizers, alkyd resins, unsaturated polyester resins, coatings, and other chemical materials.
What Is Meta-Xylene Used For?
Meta-xylene is used in several specialty chemical processes where the meta-isomer is required. Its downstream market is smaller than that of para-xylene, particularly because p-xylene has a much larger role in polyester production.
Why Is Mixed Xylene Sold as a Blend?
The three xylene isomers have relatively close boiling points, which makes their separation more complicated than ordinary fractional distillation.
For solvent users, separating the isomers often provides little practical benefit. Mixed xylene already offers the aromatic solvency needed for many formulations and is generally more economical than buying a highly purified individual isomer.
This is why mixed xylene is common in products such as paints, coatings, printing inks, adhesives, and industrial cleaning solvents.
When a downstream process requires a particular isomer, however, the situation changes. Petrochemical producers may use additional separation processes to recover p-xylene, o-xylene, or other specific components.
Applications and Uses of Mixed Xylene
Mixed Xylene as an Industrial Solvent
Mixed xylene is widely used as an aromatic solvent because of its ability to dissolve many resins, polymers, oils, and other organic materials.
Common applications include:
- Paints and coatings
- Lacquers and varnishes
- Printing inks
- Adhesives and sealants
- Industrial cleaning
- Degreasing
- Resin processing
- Surface preparation
In solvent-based formulations, xylene can be used to adjust viscosity and help dissolve resin components. The appropriate grade depends on the formulation and the required drying and solvency characteristics.
Mixed Xylene in Paints and Coatings
Paint and coating manufacturers use mixed xylene as a solvent or thinner in a range of solvent-based systems.
It can be found in formulations based on certain acrylic, alkyd, epoxy, and polyurethane resins. The actual compatibility depends on the complete formulation, not just the resin type.
Before replacing one solvent grade with another, formulators normally compare solvency, evaporation rate, resin compatibility, and final coating performance.
Mixed Xylene in Printing Inks and Adhesives
Mixed xylene is also used in some printing ink and adhesive formulations.
Its relatively strong aromatic solvency makes it useful for dissolving certain resins and controlling formulation viscosity. The solvent blend needs to match the resin system and drying requirements of the final product.
Mixed Xylene for Cleaning and Degreasing
Mixed xylene can dissolve many oils, greases, resins, and organic residues, making it useful for certain industrial cleaning and degreasing jobs.
It may be used to clean metal components, tools, equipment, and manufacturing surfaces where an aromatic hydrocarbon solvent is appropriate.
Material compatibility and workplace requirements should be considered before using it on plastics, rubber, painted surfaces, or other sensitive materials.
Chemical Feedstock and Fuel-Related Uses
Mixed xylene is also used beyond the solvent market.
In large-scale petrochemical operations, mixed xylene can be further processed to recover individual isomers. Para-xylene is particularly valuable because of its use in polyester and PET production.
Mixed xylene can also be included in gasoline blending as an aromatic hydrocarbon. Aromatics contribute to fuel octane characteristics, although the permitted composition of gasoline varies by market and regulatory requirements.
These applications are generally associated with refineries, petrochemical producers, chemical manufacturers, and fuel blenders.
FAQ
What is the chemical formula of mixed xylene?
The molecular formula of mixed xylene is C₈H₁₀. Mixed xylene is a mixture rather than a single pure compound, so the exact proportions of its components vary by product.
What is the CAS number of mixed xylene?
The CAS number for mixed xylene is 1330-20-7.
This is different from the CAS numbers assigned to individual xylene isomers such as o-xylene, m-xylene, and p-xylene.
Is mixed xylene the same as xylene?
In many industrial solvent applications, yes. "Xylene" is commonly used as a short name for mixed xylene.
However, the term can also refer to a specific xylene isomer in technical or petrochemical applications. The CAS number and product specification should be used to confirm the material.
What is the difference between mixed xylene and pure xylene?
Mixed xylene contains several xylene isomers, while a pure xylene product is manufactured to contain predominantly one isomer.
For example, p-xylene is a specific purified isomer used extensively as a petrochemical feedstock. Mixed xylene is more commonly used where general aromatic solvent properties are required.
Does mixed xylene have a fixed composition?
No. The composition varies between suppliers and grades.
The relative amounts of o-xylene, m-xylene, p-xylene, and ethylbenzene depend on the production source and processing conditions. A supplier's specification and COA should be used when exact composition is important.
Can mixed xylene be separated into individual isomers?
Yes. Industrial plants can separate and purify the individual xylene isomers using specialized separation processes.
This is generally not practical for ordinary end users. If a specific isomer is required, purchasing that purified isomer directly is usually the better option.
What documents should I request when buying mixed xylene?
For an industrial purchase, the most useful documents are the TDS, SDS, and COA.
The TDS provides the standard specification, the SDS provides safety and handling information, and the COA shows the actual results for a particular batch.
How can I check the purity of mixed xylene?
Start with the supplier's COA and compare the reported test results with the agreed specification.
If the application requires a specific isomer distribution, check whether the COA reports the individual levels of o-xylene, m-xylene, p-xylene, and ethylbenzene rather than only total xylene content.
What industries use mixed xylene?
Mixed xylene is used in several industries, including:
- Paint and coatings
- Printing inks
- Adhesives and sealants
- Industrial cleaning
- Petrochemical processing
- Resin and polymer manufacturing
- Fuel blending
The required specification depends on the end use.
What should I compare when choosing a mixed xylene supplier?
Price is only one part of the comparison. Buyers should also look at product specification, purity, isomer composition, documentation, packaging, MOQ, loading quantity, lead time, shipping terms, and export experience.
For larger orders, it is also useful to confirm the batch specification and COA before shipment.