Benzene is the fundamental building block of aromatic compounds. It, and the methylbenzenes (toluene and the xylenes), are manufactured from fractions obtained from the distillation of oil and are used as intermediates in the production of a very wide range of chemicals as well as in petrol. They are amongst the most important organic chemicals.
Four chemical processes contribute to industrial benzene production: catalytic reforming, toluene hydrodealkylation, toluene disproportionation, and steam cracking. According to the ATSDR Toxicological Profile for benzene, between 1978 and 1981, catalytic reformats accounted for approximately 44–50% of the total U.S benzene production.
Until World War II, most benzene was produced as a by-product of coke production (or "coke-oven light oil") in the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing polymers industry, necessitated the production of benzene from petroleum. Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal.