Reforming (or Aromatization)

  • Reforming means rearrangement of molecules without much affecting the average molecular weight of feed which is generally naphtha of gasoline boiling range.

  • The main reaction in the reforming process is dehydrogenation of naphthenes to produce aromatics.

  • Catalytic reforming is a process of upgrading low octane naphtha to a high-octane reformate by enriching it with aromatics and branched paraffins.

  • It is a highly endothermic process requiring large amounts of energy. The process can be operated in two modes: a high severity mode to produce mainly aromatics (80–90 vol%) and a middle severity mode to produce high octane gasoline (70% aromatics content).

  • Benzene, toluene, xylenes (BTX), and ethylbenzene are obtained mainly from the catalytic reforming of heavy naphtha. Reformates are the main source for extracting \(\ce{C6}\)–\(\ce{C8}\) aromatics used for petrochemicals. Catalytic reforming typically leads to a BTX mixture containing 50–55% toluene, 30–35% xylenes, but only about 10–15% benzene—the product most in demand for chemical production. Toluene and the xylenes, on the other hand, have been favored for raising the octane number of unleaded gasoline, and they are less toxic than benzene.

  • Reformer Feed:

    • Feeds are characterized by the Watson characterization factor (\(K\)). A characterization factor of 12.5 or greater indicates a hydrocarbon compound predominantly paraffinic in nature. Lower values of this factor indicate hydrocarbons with more naphthenic or aromatic components. Highly aromatic hydrocarbons exhibit values of 10.0 or less; therefore, the Watson characterization factor provides a means of determining the paraffinicity of a crude oil.

    • Naphthenic feeds give a much higher yield than paraffinic feeds. The main feed comes from hydrotreated heavy naphtha, and some feed comes from hydrotreated coker naphtha.

  • The dehydrogenation reactions are the most important reactions in reforming. Catalytic reformers produce more hydrogen than they consume.

  • Platforming: The name comes from the fact that this catalytic reforming process uses \(\ce{Al2O3}\) catalyst containing 0.25% platinum.