Chemical processing of petroleum

The three main processes in the petroleum refinery are cracking, combining and reforming. Crude oil on initial distillation yields only less than 20% petrol which is very less and not economical. In cracking, higher molar mass hydrocarbons break down to lighter hydrocarbons. Three types of cracking mechanisms exist. They are thermal cracking, catalytic cracking and hydrocracking. In thermal cracking, heavy oil feed stock is subjected to high pressure and temperature in the absence of air. Efficiency of this method is very poor and there is no control over the products of cracking. This method is not used nowadays. In catalytic cracking, vapourised feed stock is made to undergo cracking by coming into contact with a solid catalyst in a finely powdered state. Since we carry out this crcking under low temperatures and pressures, this method is now used. Another advantage is that we can fine control the end products. Reforming is a process involving modification of molecular structure by heat, pressure and catalyst and thus producing high octane petrol and petrochemical feedstock.