Benzene and its homologues toluene and xylene are mainly obtained from coal tar fractionation and cracking petroleum. The three are colorless, transparent and aromatic liquids with strong volatility. Industrial use of the three boiling points to separate them. But under normal circumstances, it is difficult to completely separate these three. Therefore, general industrial benzene contains a considerable amount of toluene and xylene, and industrial toluene also contains a considerable amount of benzene. Therefore, in the production environment air, benzene, toluene, and xylene are often present at the same time. Coal tar fractionation and petroleum cracking can be connected to Chemicalbook benzene, toluene, and xylene; these three are mainly used as organic solvents and chemical raw materials. Benzene can be contacted in rubber, paint, spray paint, pharmaceuticals, synthetic fibers (polyester), dyes, pesticides, artificial leather production and printing industry. Toluene is less toxic than benzene. In recent years, it has been widely used to replace benzene as a solvent for rubber and resin and as a diluent for paints, spray paints, inks, etc. It is also used in explosives, pharmaceuticals and other chemical production. Xylene is less toxic than toluene and is used as a solvent for paints, pesticides, and substitutes for benzene and toluene.