PETROLEUM (SagerNet app & files)
Petroleum means “rock oil ” in Latin. It occurs as dark viscous liquid under earth crust. It is mixture of gascous, liquid and solid alkanes (containing one to forty carbon atoms per molecule), alkenes, cycloalkanes and aromatic hydrocarbons.
It is generally believed that petroleum was formed from the remains of living organisms i.e plants and animals which lived in the warm inland seas millions of years ago. The chemical effects of pressure, heat and bacteria have anverted these remains into petroleum. Petroleum is extracted by drilling deep holes into the ground. In Pakistan, the important petroleum reseves are in pathway areas of Punjab, and badin and Hyderabad in Sind.
FRACTIONAL DISTILLATION OF PETROLEUM
Crude petroleum is separated into several groups of products by fractional distillation during which different fractions are obtained due to difference in boiling points.
The petroleum is heated to above 400°C in an electric furnace. The resulting vapour is then carriedd by pipes to fractionating column. The column is ddivided into several compartments. Each compartment is maintained within specific range of temperature, a little cooler than the one below. As the petroleum vapour ascend the column, it conddenses and separates out into several fractions..
Natural gas is an important source of roganic compounds especially in the gaseous state. It is mixture of hydrocarbons which are found in porous rocks in the earth crust usually associated with petroleum deposits. It consists of mainly methane. However, it may contain other components. In Pakistan, huge deposits of natural gas are found at Sui in Baluchistan and is known as Sui Gac..
In the interval combustion engine, a mixture of petrol vapours and air is highly compressed before ignition. Ordinary petrol tends to explod before the piston head reaches the stroke. The premature explosion causes “Knoch” and therefore loss of powe. Knock is a sharp metallic sound produced in the internal combustion-engine.
The fuel knock in the engine can be prevented by adding tetrathyl lelad Pb(C2Hs), to the petrol used for the
engine. Such petrol is said to “premium petrol”. Value o fuel (petrol) is expressed in terms of octane number. Pb(CzHs)4 increases octane number of gasoline and moderates the explosion in the engine. It is generally believed that open chain alkanes have low value of octane number and cause more fuel knock. In presence of a catalyst, open chain molecules are rearranged or reformed to branchedd chain molecules. e.g.
hcat H3C-CH2CH2-CH2-CH2-CH2CH3 Catalyst
CRACKING OF PETROLEUM
Thermal decomposition of organic compounds of larger molecules into smaller molecules at higher temperature and pressure in presence of a catalyst. This process also known as pyrolysis.
The term “Cracking” is applied to the thermal and chemical decomposition of higher hydrocarbons with the production of lower hydrocarbons. The process is extensively employed in the manufacture of petrol from less volatile fuel oils such as Kerosene oil and fuel oil. For example, hexadecane (C16H34) is not volatile engough to be used as motor fuel. On heating to dull red hot the molecule may undergo a rupture as:
C16H34 => C3H18+C8H16+C6H14+C10H20
n-hexa-decane a n-octane +1-octene+n-hexane +1-Decene
All the products boil below 200°C and are quite suitable for use as motor fuel. The process of Cracking takes place between 500-800°C. Cracking of n-butane of n-butane.