A hierarchical control structure that comprises regulatory and coordination control layers is designed for a reactor/separator process with recycle. At the regulatory control layer, the process is divided into subunits on the basis of the controlled group unit approach. In defining inventory controls for the subunits, Luyben's rule ( fixing one of the flows on the recycle path) is employed to reduce dynamic interaction between subunits. The higher level coordination control layer is designed on the basis of the time-scale separation principle, which slowly manipulates the recycle flow between the subunits. A control structure that results in a wider operation range and small dynamic interaction is proposed, and its control performance is compared with that of a conventional control structure through simulations.