Coal tar pitch

Coal tar pitch (also known as coal pitch or coal tar asphalt) is an important coal chemical product. It is a black, viscous residue obtained after distilling light fractions from coal tar. At room temperature, it is a semi-solid or solid with a glossy appearance. It typically contains 92% to 94% carbon and approximately 4% to 5% hydrogen. It is mainly composed of polycyclic aromatic hydrocarbons, heterocyclic compounds, and their derivatives, and is a complex mixture of high-molecular-weight aromatic compounds.

The main raw material for coal tar pitch comes from high-temperature coal tar, a byproduct of the coking industry (approximately 3% to 4% of the dry distilled coal).

A typical production process is as follows:

1. Crude coal tar pretreatment: The tar is first dehydrated, deslagged, and its quality is homogenized.
2. Continuous or batch distillation: The tar is heated to approximately 350-400°C in a tubular heating furnace, and then fractionated under atmospheric or reduced pressure to obtain light oil, phenol oil, naphthalene oil, wash oil, anthracene oil, and other fractions.
3. Residue is pitch: The heavy residue remaining after distillation is coal tar pitch, which accounts for 50% to 60% of the total coal tar.

Based on different softening points, coal pitch is usually classified into:

• Low-temperature pitch (softening point <75℃)
• Medium-temperature pitch (softening point 75-95℃, most common)
• High-temperature pitch (softening point >95℃)

To meet the needs of high-end applications, medium-temperature pitch is often modified. The main methods include:

• Thermal polymerization (heating polymerization)
• Oxidation method (air blowing oxidation)
• Pressurized thermal polymerization, solvent extraction blending, etc.

These processes can produce high-value-added products such as modified pitch (electrode grade) and mesophase pitch (used in high-performance carbon materials).

Due to its high carbon content, excellent binding properties, high temperature resistance, and carbonization performance, coal tar pitch plays a crucial role in several fields:

• Pre-baked anodes for aluminum production, graphite electrodes, electrode paste
• Carbon bricks and magnesia-carbon bricks for steelmaking, cathode materials
• Carbon/carbon composites, carbon microspheres

• Mesophase pitch → needle coke, pitch-based carbon fibers (high modulus, high thermal conductivity)
• Isotropic coke, lithium-ion battery anode materials, supercapacitor electrodes

• Medium-temperature pitch, after blending and modification, can be used to produce heavy-duty road asphalt (50#, 70#, 90#), improving aging resistance and adhesion.
• Waterproof coatings, roofing asphalt, pipe anticorrosion coatings

• Coal briquette binder
• Industrial anticorrosive paint, road oil
• Activated carbon, spherical carbon material raw materials

In recent years, with increasing environmental protection requirements, the development of low-benzo[a]pyrene, low-toxicity environmentally friendly modified asphalt and high-end coal tar pitch-based carbon materials has become a key focus. Although coal tar pitch is classified as a Class 1 carcinogen (mainly due to polycyclic aromatic hydrocarbons), its safe application has been well controlled through deep processing and enclosed use.

As a bulk product in the downstream of the coal chemical industry chain, the level of high-value utilization of coal tar pitch directly affects the economics of the entire coal tar processing industry, and it remains irreplaceable in the fields of metallurgy, carbon materials, and new energy materials.