Mixed Xylene (MX) refers to a mixture of three isomers of xylene: ortho-xylene (o-xylene), meta-xylene (m-xylene), and para-xylene (p-xylene), in varying proportions. Xylene is an aromatic hydrocarbon with the chemical formula C₆H₆(CH₃)₂. It is widely used as a solvent in various industrial applications and is often a by-product of petroleum refining and catalytic reforming of crude oil. The specific composition of mixed xylene can vary depending on the source and refining process.
Properties of Mixed Xylene:
- Molecular Formula: C₆H₆(CH₃)₂ (for each isomer)
- Boiling Point: 138°C to 144°C (depending on isomer composition)
- Melting Point: -47°C to -25°C
- Density: 0.865 g/cm³ (at 25°C)
- Flash Point: 22°C (72°F) – flammable
- Solubility: Slightly soluble in water but highly soluble in organic solvents like acetone, ethanol, ether, and other hydrocarbons.
Key Uses of Mixed Xylene:
Solvent:
Mixed xylene is widely used as a solvent in products like paint thinners, lacquers, varnishes, cleaning agents, and adhesives. It is particularly valued for its ability to dissolve oils, greases, and resins. It is also used in printing inks, coatings, and rubber formulations.
Chemical Intermediate:
- Para-xylene: A significant portion of mixed xylene is converted into para-xylene through isomer separation, which is crucial for the production of terephthalic acid (TPA), a precursor to polyester fibers and plastics (e.g., PET bottles).
- Meta-xylene: Used in the production of phthalic anhydride, which is used in manufacturing plasticizers and resins.
- Ortho-xylene: Another isomer is used to make phthalic anhydride, which is used in alkyd resins and plastics.
Fuel Additive:
Like toluene, mixed xylene is also used in fuel as an octane booster to improve the performance of gasoline.
Petrochemical Production:
Mixed xylene is an important feedstock for the production of isomers like para-xylene, ortho-xylene, and meta-xylene, which are further processed to make products such as plasticizers, resins, solvents, and synthetic fibers.
Extraction Solvent:
Mixed xylene is used as an extraction solvent in petroleum refining to separate aromatic compounds from non-aromatics.