This paper presents an optimisation-based method for the screening and conceptual design of processes with heterogeneous catalytic reactors. The method follows a multi-level approach to process synthesis to establish performance targets and identify high-performance designs. At each level, process superstructures are optimised to explore performance limits of the system and to guide the understanding of the relationships between individual design features and process performance. This enables the design engineer to explore trade-offs between performance and structural complexity in a coordinated manner. The method leads to a number of potential design candidates that provide the design engineers with insight into the performance gains that can be expected by increasing design complexity. The method has been developed and implemented for heterogeneously catalysed gas-phase reaction systems and is illustrated with an example in styrene production. (C) 2010 Elsevier B.V. All rights reserved.