This invention relates to processes and systems for converting acyclic hydrocarbons to alkenes, cyclic hydrocarbons and/or aromatics, for example converting acyclic C5 hydrocarbons to cyclopentadiene in a reactor system. The process includes contacting a feedstock comprising acyclic hydrocarbons with a catalyst material in at least one reaction zone to convert at least a portion of the acyclic hydrocarbons to a first effluent comprising alkenes, cyclic hydrocarbons and/or aromatics. A co-feed comprising H2, C1-C4 alkanes and/or C1-C4 alkenes may also be provided to the at least one reaction zone.