Abstract

The Fluid Catalytic Cracking (FCC) unit remains the primary hydrocarbon conversion unit in the modern petroleum refinery. The ability to convert a variety of feed types (eg, gas oils, cracked gas oils, deasphalted gas oils, atmospheric/vacuum resids) into lighter, more valuable products makes the FCC process extremely versatile and more importantly, profitable.

The profitability of an FCC unit depends largely on the type of feed being processed and the FCC catalyst employed. Up until the early 1960s, amorphous silica/alumina catalysts were used to crack vacuum gas oils. As feedstocks have become heavier and the level of contaminant metals has increased, more sophisticated catalysts have been introduced that contain special metals trapping technologies. Zeolite and matrix technologies have evolved to maximize conversion of difficult feeds to valuable transportation fuels and light olefins.

Increasingly stringent environmental regulations have also changed the objective function of the modern refinery. In addition to the classical goals of optimizing FCC yields for high gasoline selectivity, minimum dry gas production, high octane number, or good bottoms cracking, today's refiner must also reduce gaseous pollutants that originate in the FCCU regenerator as well as produce gasoline with low levels of contaminants, notably sulfur. This has presented opportunities for catalyst manufacturers to develop additives that enable the refiner to reduce emissions of SO_x and NO_x from the FCCU regenerator and catalysts and additives that produce cleaner transportation fuels.