Synthetic Petrol

SYNTHETIC PETROL

The gasoline, obtained from the fractional distillation of crude petroleum oil, is called straight run petrol. As the use of gasoline is increased, the amount of straight run gasoline is not enough to meet the requirement of the present community. Hence, we are in need of finding out a method of synthesizing petrol.

1. Hydrogenation of coal (or) Manufacture of synthetic petrol

Coal contains about 4.5% hydrogen compared to about 18% in petroleum. So, coal is a hydrogen deficient compound.

If coal is heated with hydrogen to high temperature under high pressure, it is converted to gasoline. The preparation of liquid fuels from solid coal is called hydrogenation of coal (or) synthetic petrol.

An important method, available for the hydrogenation of coal is Bergius process (or direct method).

Bergius process (or) (direct method)

In this process, (fig. 5.3) the finely powdered coal is made into a paste with heavy oil and a catalyst powder (tin or nickel oleate) is mixed with it. The paste is pumped along with hydrogen gas into the converter, where the paste is heated to 400 - 450°C under a pressure of 200 – 250 atm.

During this process hydrogen combines with coal to form saturated higher hydrocarbons, which undergo further decomposition at higher temperature to yield mixture of lower hydrocarbons. The mixture is led to a condenser, where the crude oil is obtained.

The crude oil is then fractionated to yield

(i) Gasoline (ii) Middle oil (iii) Heavy oil.

The middle oil is further hydrogenated in vapour phase to yield more gasoline. The heavy oil is recycled for making paste with fresh coal dust. The yield of gasoline is about 60% of the coal used.