Abstract: A method of treating a hydrocarbon stream comprising cyclopentadiene (CPD) and one or more diolefins, the method comprising: providing a hydrocarbon stream comprising an initial CPD concentration, an initial target diolefin concentration, and an initial secondary diolefin concentration; subjecting the hydrocarbon stream to preseparation conditions effective to separate (a) a crude target diolefin feedstock having a decreased concentration of CPD and an increased target diolefin concentration, and (b) a CPD dimerization feedstock having a decreased target diolefin concentration and an increased CPD concentration that is 1.5 or more times the initial CPD concentration; subjecting the CPD dimerization feedstock to CPD dimerization conditions effective to produce a raw DCPD stream comprising 20 wt. % or more DCPD; and, separating a high purity DCPD product stream comprising 90 wt. % or more DCPD from the raw DCPD stream.