In the process of refining oil, fractions rich in aromatics are obtained from refining (reforming) of gasoline and from cracking processes in olefin manufacture. This reformate gasoline and pyrolysis or cracked gasoline represent valuable sources of aromatics.

Reformate gasoline is formed both from paraffinic crude oils, which comprise more than 50% branched and unbranched alkanes, and from naphthalenic oils, which are mainly cycloalkanes. Distillation of both types of crude oil gives lowoctane fractions which must be reformed before being used as gasoline. This reforming process is a special type of catalytic modification using bifunctional catalysts containing an acidic component such as Al₂O₃^.SiO₂ and a hydrogenation-dehydro-genation component, e. g., platinum in the Platforming process or the bimetallic system platinumhhenium in the Rheniforming process (Chevron catalyst). The addition of rhenium increases catalyst stability by preventing sintering processes and thus maintaining the metal dispersivity. In a more recent development made by Exxon, multimetal cluster catalysts of undisclosed composition exhibit substantially higher activity. They are already being used commercially.

At reforming conditions of 450-550 °C and 15-70 bar, alkyl-cyclopentanes, for example, are isomerized to substituted cyclohexanes, which are then aromatized by the dehydrogenative component of the catalyst. Ring-forming dehydrogenations of alkanes to cycloalkanes and isomerizations of n-alkanes to isoalkanes also take place.

Distillation of the reformed crude product leads to a fraction rich in aromatics, which, due to the level of higher boiling aromatics, is especially suitable for the production of toluene and xylene isomers.

Pyrolysis gasoline comes from the steam cracking of naphtha for the production of ethylene, propene, and higher olefins. Its relatively high benzene content makes it one of the leading feed-stocks for benzene.

While reformate gasoline can be used directly for the production of aromatics, cracked gasoline and crude benzene from coke plants must first be freed from polymerizable mono- and diolefins by hydrogenation. S, N, and O compounds are also removed by this hydrogenation, which is usually done in two stages. A typical commercial process is the IFP process, which uses Pd and Ni-W catalysts. Other processes use CoO-MoO₃/Al₂O₃ catalysts at 300-400°C and 20-40 bar.

If one neglects the effect on the aromatic distribution arising from different reforming or cracking conditions (two-step) and the boiling point ranges of the naphtha cuts, a simplified picture of the distribution is obtained: