What are xylenes?
Xylenes are extracted or distilled from reformate, a stream derived from the refining of high-octane motor gasoline. They can also be produced from toluene using the disproportionation process. They are colourless, sweet-smelling liquids that are very flammable. Xylenes occur as three isomers, each having two methyl groups attached to a basic benzene hydrocarbon ring. The type of isomer is distinguished by the position of the methyl groups on the ring. Para-xylene has the methyl groups attached on opposite sides of the ring, ortho-xylene has the two methyl groups next to each other, while meta-xylene has them positioned with one carbon in between the two groups. Shell chemicals companies primarily supply xylenes as a mixed stream, although various processes can be used to separate and/or convert the isomers.
