The process in which higher hydrocarbon (heavy oil) having higher boiling point is converted into lower hydrocarbon (heavy oil ) having higher boiling point is converted into lower hydrocarbon (petrol)having lower boiling point in the presence of hydrogen gas and catalysts like alumina or aluminum silicate comparatively at low temperature and pressure is called like hydro catalytical cracking.
The terms which determine the yield of the product of catalytic cracking process with respect to the starting material used is called activity of catalytic.
The terms which measure the ability of the catalyst to accelerate the desired reactions and suppresses the rate of unwanted reaction is called selectivity of the catalyst.
Ageing of the catalyst
Ageing of the catalyst during catalytic, the activity and selectivity of the catalytic gradually decrease the age of catalyst decrease. This is due to the deposition of carbon particles (formed in cracking) on the surface of catalytic. This process is called ageing of the catalyst when the carbon particles deposited on the surface of the catalyst is burnt in presence of air about 6000C, the activity and selectivity of the catalyst increase.