Cracking (gasoline)

Cracking is defined as "the decomposition of bigger hydrocarbon molecules into simpler low boiling hydrocarbons of lower molecular weight"

C₁₀ H₂₂-------Cracking----------- C₅H₁₂        +        C₅H₁₀

Decane                                      n-pentane          Pentene

B.Pt. 174^oC                            B.Pt. 36^oC

Thermal cracking 

Heavy oil ------------------High Temp------Olefins + Parafins

Higher Hydrocarbons                                Lower Hydrocarbons

Liquids Phase thermal cracking 

Heavy oil (gas Oil) -------475-53^oC (100Kg/Cm² Pressure) ------- Products----- Fractionating Column

then we get 50-60% gasoline.

Vapour phase thermal Cracking

Heavy oil ---------vaporised -----------600-650 ^oC (cracked 10-20Kg/ Cm² Pressure------readily vaporised------ Product

Petrol obtained from vapour phase cracking has better anti knocking properties but poor stability than petrol from liquid –phase cracking.