Propylene is the second most widely product in the world after ethylene. The amount of propylene produced by steam cracking processes as the first source of ethylene and propylene production is limited. New methods of propylene production (dehydrogenation of propane, conversion of methanol to olefins, conversion of methanol to propylene, etc.) can supply some of its growing demands. The intermediate conversion processes of olefins can meet part of the market demand by converting some of the lighter or heavier olefins from thermal cracking furnaces and by increasing the amount of propylene product. In this paper, we study the technology and economics of several catalytic cracking processes of C4 to C8 carbon olefins. The processes investigated in this report for the catalytic conversion of the by-product of heavier olefins to propylene include Omega, OCP, Superflex, Propylur, and MOI processes.