Cracking
Plastics can be converted into crude oil or directly petrol by cracking. Cracking is the process of breaking the bonds. This long chain molecules of plastics on cracking get converted into short chain molecules of oil. This chain length determines the quality and properties of the oil. Cracking is broadly categorised as
- Thermal Cracking
- Catalytic Cracking
- Hydro-Cracking (not much used, and hence is not explained here)
Thermal Cracking:
Thermal cracking is the process involving heating of the plastic to a elevated temperature; say about 450-900 C. The the energy from this heat first loosens the bonds and the plastic melts. On further heating, the energy from the heat increases the bond energy and causes the material to crack (breaking of bond). And thus plastics get converted into oil.
Video of thermal cracking of plastics
Catalytic Cracking:
Catalytic Cracking is the advancement in thermal cracking by addition of catalyst. This catalyst do not take part in reaction but increase the rate of reaction and thus decreases the thermal energy required for cracking.
Catalyst also help in giving low molecular weight distribution products i.e. they help in giving specific products.
