Gas oil components, coking process recycle, and heavier hydrocarbons are cracked or coked in the coking vessel by injecting an additive into the vapors of traditional coking processes in the coking vessel. The additive contains catalyst(s), seeding agent(s), excess reactant(s),
quenching agent(s), carrier(s), or any combination thereof to modify reaction
kinetics to preferentially crack or
coke these components. The
quenching effect of the additive can be effectively used to condense the highest
boiling point compounds onto the catalyst(s), thereby focusing the catalyst
exposure to these target reactants. With a catalyst to crack these highest
boiling point materials, this mechanism can effectively increase the catalyst's selectivity, thereby increasing its efficiency and reducing catalyst requirements and costs. Selective, catalytic conversion of the highest
boiling point materials in the coking process product vapors (coker recycle and / or ‘heavy
tail’ of the heavy coker gas oil) may be accomplished with an exemplary embodiment of the present invention in varying degrees. Exemplary embodiments of the present invention can also provide methods to control the (1)
coke crystalline structure and (2) the quantity and quality of volatile combustible materials (VCMs) in the resulting
coke. Pet coke from this process may have unique characteristics with substantial utility.