Catalytic Reforming
Gasoline has a number of specifications that must be satisfied to provide high performance for today's motor vehicles. Octane, however, is the most widely recognized specification. The octane number is generally reported as the average of Research Octane Number (RON) and Motor Octane Number (MON), (R+M)/2. MON is the more severe test, so for a given fuel RON is always higher than MON.
Unfortunately, heavy naphtha from atmospheric distillation, which forms a significant percentage of the gasoline blend, has an octane rating of around 50 (R+M)/2. Octane demand for gasoline ranges from upper-80 to mid 90 (R+M)/2. Catalytic Reforming is the workhorse for octane upgrade in today's modern refinery. Molecules are reformed into structures that increase the percentage of high octane components while reducing the percentage of low octane components.
In short, Catalytic Reforming converts straight chain and saturated molecules into unsaturated cyclic and aromatic compounds. In doing so, it liberates a significant amount of hydrogen that may be used in desulfurization and saturation reactions elsewhere in the refinery. In addition to hydrogen and reformate, some light ends are removed to meet vapor pressure requirements. Catalytic Reforming creates a density increase (i.e., finished product volume is significantly less than feed volume) that creates a volumetric loss to refining operations.
Reforming uses platinum catalyst. Sulfur poisons the catalyst; therefore, virtually all sulfur must be removed prior to reforming. Temperature is used to control produced octane. The unit is operated at temperatures between 925-975˚F (500-525˚C) and pressures between 100-300 psi (7-25 bar). Reformer octane is generally controlled between 90 and 95 (R+M)/2 depending on gasoline blending demands. As a result of very high reactor temperatures, coke forms on the catalyst, which reduces activity. Coke must either be removed continuously (Continuous Catalyst Regeneration CCR Units) or periodically (Semi-regenerative Units) to maintain performance.
