In carbon production, the primary materials used as binders and impregnants are coal tar and resins. Small amounts of coal tar and anthracene oil are sometimes used to temper the coal tar. Coal tar is derived from coal, a byproduct of the coking industry. During high-temperature dry distillation of coal, the pyrolysis reaction produces not only coke and coke oven gas, but also 30 to 45 kg of coal tar per ton of dry coal.
Coal tar is a complex mixture of highly aromatic hydrocarbons, the majority of which are polycyclic and condensed-ring compounds with or without side chains, and heterocyclic compounds containing oxygen, sulfur, and nitrogen. It also contains small amounts of aliphatic hydrocarbons, cycloalkanes, and unsaturated hydrocarbons. Coal tar is a product of the coal tar distillation process.
Coal tar is a black solid at room temperature with no fixed melting point. It is a complex mixture composed primarily of polycyclic aromatic hydrocarbons with three or more rings, as well as heterocyclic compounds containing oxygen, nitrogen, and sulfur, and small amounts of high-molecular-weight carbon substances. Coal tar pitch contains numerous compounds, with over 70 identified. Its relative molecular mass ranges from 170 to 2000, and its elemental composition is: C 92% to 93%, H 3.5% to 4.5%, with the remainder being N, O, and S.
When studying tar pitch, coal tar pitch is often extracted using different solvents to separate its components. The resulting components vary depending on the solvent combination used. In recent years, a commonly used method has been to use toluene and quinoline as solvents to obtain toluene-insoluble and quinoline-insoluble fractions.