Olefins in finished petroleum products
Refinery streams containing high percentages of olefins, such as coker naphtha, have a tendency to polymerize and form gums that can cause problems in storage and transportation systems, so these streams usually are hydrotreated to saturate the olefins
Olefins in refinery feedstocks
In a refinery, olefins are an important feedstock into the alkylation unit to produce alkylate (a high-value gasoline blend stock). The olefins most commonly used in the alkylation unit are butylene and propylene, which primarily come from the FCC unit.