fluid catalytic cracking
Catalysis from A to Z · 2020
Catalytic cracking is a process in which hot, powdered catalyst is in timately mixed with a hot petroleum -derived feedstock, then transported through a turbulent reaction zone with a reactant residence time of 1 -5 seconds.It has enabled refineries to produce a treme ndous amount of high -octane number gasoline from high -boiling stocks using catalysts.It progresses through a carbocation to produce active species on acidic catalytic sites.This process involves acidic catalysts like zeolite in the breaking up of long carbon chains of n-alkanes into shorter chains alkanes like iso-alkanes, cycloalkanes, and aromatics .Other products like Liquefied Petroleum Gas (LNG), cycle oils, and olefin -rich light hydrocarbons (C3, C4) are also produced.The olefin-rich light hydrocarbons are used as petrochemical feedstock, and as reactants in alkylation and polymerization reactions.Refining shale crude oil presents a very dif ficult challenge because of its very low hydrogen to carbon ratios .The production of good quality gasoline, kerosene, and diesel are very poor due to high levels o f heavier components such as asphaltene and Sulphur-containing species.Many petroleum refin eries combine two methods in order to convert and refine this heavy crude oil: conventional fluidized catalytic cracking followed by residue fluidized catalytic cra cking, allowing heavy oils with high viscosity to be processed and refined .