Cracking is a process by which heavy hydrocarbons in petroleum are broken down into lighter molecules and isomerized, by high
temperatures or catalysis. It yields branched-chain alkanes and alkenes of high octane rating for gasoline, and
also simple gaseous alkenes for chemical synthesis.
|Catalytic cracker. The feedstock
of long-chain hydrocarbons (1) is mixed with hot catalyst (2) and
vaporized. The vapor/powder mixture is carried to the reactor where
the cracking reactions occur. Cyclones (3) extract the cracked hydrocarbon
vapor and pass it to the fractionating column where it is fractionated,
yielding petroleum gases and gasoline (4), light gas oil (5), medium
gas oil (6), and heavy gas oil (7). Spent catalyst meanwhile is mixed
with steam (8) and carried in a current of hot air (9) to the catalyst
regenerator where it is cleaned and recycled (10. Waste gases are
drawn off (11) and vented.