Previously, the attainable region has been constructed for systems where th
e rate vector is uniquely defined. In this paper we extend the attainable r
egion approach to situations where the rate vector depends on a control par
ameter, such as temperature. In these cases, the rate vector can take on a
range of values, depending on the value of the control parameter. Arguments
based on the geometry of the boundary of the attainable region are used to
derive equations that describe the optimal control policies. These conditi
ons are applied to various examples and both the optimal reactor structures
as well as optimal operating and control policies are derived by looking a
t the structures that make up the boundary of the attainable region. In par
ticular, an example is given where the optimal reactor structure has a reac
tor with simultaneous side stream addition and temperature control.