The main fractionator offgas is sent to what is called a " gas recovery unit " where it is separated into butanes and butylenes, propane and propylene, and lower molecular weight gases ( hydrogen, methane, ethylene and ethane ).
32.
The catalyst-hydrocarbon mixture flows upward through the riser for a few seconds, and then the mixture is separated via fractionator for separation into fuel gas, LPG, gasoline, naphtha, light cycle oils used in diesel and jet fuel, and heavy fuel oil.
33.
For example, the crude oil fractionator produces an overhead fraction called " naphtha " which becomes a gasoline component after it is further processed through a catalytic hydrodesulfurizer to remove sulfur and a catalytic reformer to reform its hydrocarbon molecules into more complex molecules with a higher octane rating value.
