a) contacting heavy residue feed stock with hot adsorbent, said adsorbent being lifted with steam from a riser bottom from such contact, to make the heavy residue feed, free from all contaminants;

b) contacting the feed depleted of contaminants with the catalyst at an intermediate location of the riser to cause catalytic cracking reaction;

c) transporting the vapor products, the spent catalyst and the coked adsorbent mixture to the riser top pneumatically;

d) separating the catalyst and the adsorbent from product hydrocarbon vapors in a riser termination device;

e) separating the spent catalyst and coked adsorbent in a stripper cum separator located below the reactor, at a low temperature, as two distinct layers of spent catalyst and coked adsorbent depending upon the particle size, density and differences in their minimum fluidization velocity, by using steam, so that heavier particles of coked adsorbent are settled at the bottom of the stripper cum separator and the lighter particles of spent catalyst are settled at the intermediate location of the stripper cum separator and all the strippable interstitial hydrocarbons are stripped off from the cracking catalyst and adsorbent mixture in said stripper cum separator;

f) introducing the coked adsorbent into adsorbent regenerator for partial or complete removal of coke by using air or oxygen containing gas for reactivation;

g) transporting the reactivated adsorbent into the riser;

h) transporting portion or full of coked adsorbent into the riser without reactivation;

i) introducing the spent catalyst into catalyst regenerator for partial or complete regeneration of catalyst using air, oxygen or oxygen containing gases; and

j) transporting the regenerated catalyst into the riser.