5.1 Cracking Hydrocarbons

Large Hydrocarbon molecules can be broken down into smaller molecules by a process called cracking.

CRACKING

·         Heating a mixture of hydrocarbon vapours and steam to very high temperatures.

·         Passing hydrocarbon vapours over hot catalyst

During cracking thermal decomposition reaction produce a mixture of smaller molecules.

·         Alkanes – saturated hydrocarbons with general formula CnH2n+2. (Useful fuels)

·         Alkenes – unsaturated hydrocarbons, contain fewer hydrogen atoms with same number of carbon atoms, with general formula CnH2n. Have double bonds making them more reactive.

C10H22  à 800  C + catalyst à  C5H12 + C3H6 + C2H4

Decane  -------------------à  Pentane +Propene + Ethene