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 and an inert material to convert at least a portion of the acyclic hydrocarbons to a first effluent comprising alkenes, cyclic hydrocarbons and/or aromatics. In particular, the catalyst material and the inert material have a different average diameter and/or density providing varying fluidization behavior in the reactor.