In the oil business, catalytic cracking is a crucial procedure whereby petroleum vapour flows over a bed of low-density catalyst, causing the heavier fractions to "break," generating lighter, more valuable products. The process by which the high-boiling point, high-molecular weight hydrocarbon fractions of petroleum (crude oils) are transformed into gasoline, olefinic gases, and other petroleum products is known as fluid catalytic cracking (FCC). Thermal cracking, which was once the primary method for breaking down petroleum hydrocarbons, has been largely replaced by catalytic cracking, which yields more high-octane gasoline and by-product gases with higher concentrations of carbon-carbon double bonds (also known as olefins), which have higher economic value than those produced by thermal cracking.