Xylenes are an important petrochemical produced by catalytic reforming and also by coal carbonisation in the manufacture of coke fuel. They also occur in crude oil in concentrations of about 0.5–1%, depending on the source. Small quantities occur in gasoline and aircraft fuels.
Xylenes are produced mainly as part of the BTX aromatics (benzene, toluene, and xylenes) extracted from the product of catalytic reforming known as reformate. The xylene mixture is a slightly greasy, colorless liquid commonly encountered as a solvent.