The objective of this paper is to introduce a systematic framework for simultaneous solution of process/product design problems related to separation. This framework is based on the recently developed property clustering approach that allows one to perform design calculations on a component-free (or composition-free) basis. Removing the composition dependency from the design problem enables the simultaneous consideration of process and product selection and optimization. The clustering concept is based on the observation that properties, unlike mass, are not conserved and consequently they cannot be tracked among process units without performing component material balances. To overcome these limitations the use of property-based clusters has been proposed. The model derivations and reformulations to cluster-based models are presented and the usage highlighted through a simple proof of concept example and a case study. (C) 2003 Elsevier B.V. All rights reserved.