TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The process further comprises: subjecting at least a portion of the process stream comprising C4+ hydrocarbons substantially free of diolefinic hydrocarbons to at least one further hydrocarbon processing step comprising olefin cracking, metathesis and alkylation processing; splitting at least a portion of the first depropanizer process stream in a C3 hydrocarbon splitter to form a first C3 hydrocarbon splitter product stream comprising propylene and a second C3 hydrocarbon splitter product stream comprising propane; compressing the first deethanizer process stream prior to the demethanizing or prior to the converting of a portion of acetylene. The process comprises: separating the hydrocarbon effluent in a separation system comprising a main column section and a compression section, where the main column section passes a main column vapor stream to the compression section to form at least one separator liquid stream and a separator vapor stream, the separator liquid stream comprises C4+ hydrocarbons, and the separator vapor stream comprises C4- hydrocarbons; and combining the separator liquid stream with second depropanizer process stream. The contacting step comprises contacting the heavy hydrocarbon feedstock with a blended catalyst comprising regenerated catalyst and coked catalyst in a fluidized reactor zone at hydrocarbon cracking reaction conditions to produce a cracked stream containing hydrocarbon products including light olefins. The separator liquid stream and second depropanizer process stream each comprises C4+ diolefin hydrocarbons and the treating of at least a portion of the separator liquid stream and a portion of the second depropanizer process stream in a single downstream processing unit comprises: introducing the separator liquid stream and the second depropanizer process stream into a hydrogenation unit to hydrogenate at least a portion of C4+ diolefin hydrocarbons of the separator liquid stream and the second depropanizer process stream to form a process stream comprising C4+ hydrocarbons substantially free of diolefinic hydrocarbons. The C3- hydrocarbons of the first depropanizer process stream further comprises C3- diolefinhydrocarbons, the process further comprises hydrogenating at least a portion of C3 diolefin hydrocarbons to form additional propylene prior to the splitting in the C3 hydrocarbon splitter. The second depropanizer process stream comprises C4+ hydrocarbons comprising 4-7C olefins, and the process further comprises cracking at least a portion of the 4-7C olefins to form a cracked olefin effluent comprising C2 and C3 olefins. The first deethanizer process stream further comprises: acetylene, and the process further comprises: subsequent to the compressing, converting at least a portion of acetylene to form a first deethanizer process stream enriched in ethylene; and a acetylene and where, prior to the demethanizing, the process further comprises converting at least a portion of acetylene to form a first deethanizer process stream enriched in ethylene. EXAMPLE - None given.