Abstract: A process for upgrading a hydrocarbon feed to produce light olefins, includes contacting the hydrocarbon feed with steam in the presence of a cracking catalyst in a steam catalytic cracking reactor at reaction conditions sufficient to cause at least a portion of the hydrocarbons in the hydrocarbon feed to undergo one or more cracking reactions to produce a steam catalytic cracking effluent comprising ethylene, propylene, or both, wherein the process is capable of being transitioned between an ethylene-selective mode and a propylene-selective mode; determining whether to produce ethylene or propylene; when producing ethylene, then operating the process in ethylene-selective mode comprises producing more ethylene than propylene; or when producing propylene, then operating the process in propylene-selective mode comprises producing more propylene than ethylene.