A process for producing a feed for a stream cracker. At least a portion of the C6 cyclic hydrocarbons are removed from a stream prior to it being passed into an isomerization zone. Disproportionation reaction selectivity is increased, producing valuable C3 hydrocarbons and C4 hydrocarbons. Also, a higher ring opening conversion of C5 cyclic hydrocarbons is observed. The yield may be adjusted by controlling an amount of C6 cyclic hydrocarbons passed to the isomerization zone. The catalyst in the isomerization zone is free of chloride, and the streams including effluent from the isomerization zone may be passed to a steam cracker without requiring chloride removal.