synthetic petrol

The petrol obtained artificially from coal as a mixture of alkanes resembling petroleum like aliphatic hydrocarbon fuels is called synthetic petrol.
Synthetic petrol is manufactured either from coal or from natural gas or from petroleum fraction.Crude oil residues and other residue rich in carbon can be converted into petrol such petrol, too can be called synthetic.

In the process it took 4 tons of coal to produce 1 ton of petrol, pressure up to 700 atm and temperatures of 410° - 460°C being employed. The coal was dried, pulverizing and mixed with heavy oil to form thick slurry. Catalysts were added, and about 70,000 cu. Ft. of hydrogen gas per ton of coal was forced in. the hydrogen was produced from coal and water, the carbon monoxide formed in this process being utilized as fuel gas or converted.

Two important methods for producing synthetic petrol are the Fischer-Tropsch process and the Bergius process. These processes were developed in Germany during World War II, when its petroleum supplies were cut off. Germany produced considerable amounts of fuel from coal by the above processes during that period.


Bergius process
In this process, powdered coal is mixed with heavy oil and heated with hydrogen under high pressure (200-250 atm) at about 748 K in presence of iron oxide as catalyst.
The vapours on condensation give a liquid resembling crude oil. This is called synthetic petroleum, which on fractional distillation gives petrol (gasoline).

Fischer-Tropsch process
In this process, a mixture of water gas and hydrogen under pressure (5-10 atm) is passed over a cobalt catalyst at 450 - 475 K. The water gas required is obtained by passing steam over red-hot coke.
C (red hot) + H2O(g) CO + H2water gas