Description

Xylene, also known as dimethylbenzene, is an aromatic hydrocarbon with the chemical formula (CH₃)₂C₆H₄. It exists in three isomeric forms: ortho-xylene (o-xylene), meta-xylene (m-xylene), and para-xylene (p-xylene), differentiated by the positions of the two methyl groups on the benzene ring. Xylene is a colorless, sweet-smelling liquid that is highly flammable. Its versatility as a solvent makes it invaluable in various industrial applications.

History

Xylol was first isolated in 1850 by Auguste Cahours, a French chemist, from wood tar. The name “Xylol” comes from the Greek word “Xylol,” meaning wood, reflecting its original source. Initially derived from coal tar, xylene’s significance grew with the development of petroleum refining and the petrochemical industry. By the mid-20th century, xylene became a critical industrial solvent and chemical intermediate, especially as the demand for synthetic fibers, plastics, and other petrochemical products increased.

Properties

Chemical Formula: C₈H₁₀

Molecular Weight: 106.16 g/mol

Density: 0.864 g/cm³ (at 20°C)

Boiling Points:

• o-Xylene: 144.4°C
• m-Xylene: 139.1°C
• p-Xylene: 138.4°C

Melting Points:

• o-Xylene: -25.2°C
• m-Xylene: -47.9°C
• p-Xylene: 13.2°C

Solubility: Xylol is insoluble in water but soluble in many organic solvents such as ethanol, ether, acetone, and benzene.

Vapor Pressure: Approximately 8-9 mmHg at 20°C

Flash Point: 25-30°C (closed cup)

Viscosity: 0.6 cP at 20°C

Refractive Index: 1.4972

Various Grades

1. Technical Grade:

Suitable for industrial applications where high purity is not critical. This grade is commonly used in paints, coatings, and adhesives.

2. Reagent Grade:

Used in laboratories and research where higher purity is required. This grade ensures minimal impurities for accurate and reliable results in scientific experiments.

3. Pharmaceutical Grade:

The highest purity level, used in medical and pharmaceutical applications. This grade is necessary for ensuring safety and efficacy in drugs and medical formulations.

4. Mixed Xylene:

A mixture of the three isomers (o-Xylol, m-xylene, and p-Xylol) typically used in general-purpose applications, especially as a solvent in the chemical industry.

Application and uses

Industrial Applications

1. Solvent in Paints and Coatings:

– Xylol is a crucial solvent in the formulation of paints, varnishes, lacquers, and stains. Its ability to dissolve various substances makes it ideal for creating smooth, consistent coatings. It also helps control the drying and curing times of these products.

2. Printing Industry:

– In the printing industry, Xylol is used in the production of printing inks and for cleaning printing presses and other equipment. Its solvent properties help dissolve ink residues and other materials.

3. Adhesives and Sealants:

– Xylol is utilized in the formulation of adhesives and sealants, where it helps to dissolve and mix the adhesive components. It also aids in the application process by adjusting the viscosity and improving the spreadability.

 Chemical Intermediates

1. Terephthalic Acid and Dimethyl Terephthalate:

– Xylol is a precursor in the production of terephthalic acid (TPA) and dimethyl terephthalate (DMT), both of which are essential for manufacturing polyethylene terephthalate (PET). PET is widely used in producing plastic bottles, synthetic fibers, and packaging materials.

2. Isophthalic Acid:

– Isophthalic acid, derived from Xylol , is used to produce high-performance polymers and resins. These materials are employed in coatings, adhesives, and various composite materials for enhanced durability and resistance to chemicals and heat.

 Laboratory and Medical Uses

1. Histology and Pathology:

– In medical laboratories, Xylol is used in histology for tissue processing, staining, and slide preparation. It clears tissues by dissolving paraffin wax, making it easier to slice thin sections for microscopic examination.

2. Cleaning Agent:

– Xylene is an effective cleaning agent for laboratory equipment and glassware. It removes organic residues, oils, and greases, ensuring that the apparatus is clean and ready for use in subsequent experiments.

 Energy and Fuel

1. Gasoline Additive:

– Xylene is added to gasoline to enhance its octane rating, which improves engine performance and reduces knocking. This application is critical in the automotive and aviation industries, where high-performance fuels are required.

 Miscellaneous Uses

1. Leather Processing:

– In the leather industry, Xylol is used as a solvent in tanning and finishing processes. It helps dissolve dyes and other chemicals, ensuring uniform application and enhancing the leather’s quality.

2. Rubber and Plastics:

– Xylol is used in the manufacture and processing of rubber and plastics. It serves as a solvent and a processing aid, helping to produce flexible, durable materials with various applications, from automotive parts to household goods.

3. Cleaning and Degreasing:

– Xylene is a powerful degreaser used in various industries to clean machinery, tools, and equipment. Its solvent properties effectively dissolve grease, oils, and other contaminants.

Specialty Applications

1. Electronics:

– Xylene is used in the electronics industry for cleaning circuit boards and other components. It removes flux residues and other contaminants, ensuring the reliability and performance of electronic devices.

2. Textiles:

– In the textile industry, xylene is used in dyeing and printing processes. It helps to dissolve dyes and other chemicals, ensuring even application and vibrant colors.

3. Pharmaceuticals:

– Pharmaceutical-grade xylene is used in drug formulation and manufacturing processes. Its high purity ensures that it meets the stringent requirements for medical applications.

By leveraging xylene’s solvent properties and chemical reactivity, industries can achieve high-quality results in a wide range of applications. However, it is essential to handle xylene with care, adhering to safety guidelines to mitigate health and environmental risks.

packing

Bulk Transport:

For large industrial operations, xylene is transported in tank trucks, railcars, or ISO containers.

Drums:

Commonly available in 55-gallon steel drums, which are suitable for medium-scale usage in various industries.

Cans:

Smaller quantities are packed in 1-gallon or 5-gallon metal cans, making them manageable for smaller businesses and laboratories.

Bottles:

Laboratory-grade xylene is often packed in glass or high-density polyethylene (HDPE) bottles, available in various sizes to meet the needs of scientific research and medical applications.

 

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