In this work, the optimal petroleum refinery topology is formulated as a conceptual process synthesis problem using the superstructure optimization approach. We begin with the development of a state-task network (STN)-based superstructure representation that is sufficiently rich to encompass all possible topology alternatives of a conventional oil refinery. Subsequently, a biobjective mixed-integer linear program (MILP) of maximization of profit and minimization of environmental impacts is formulated according to the constructed superstructure. Then, based on a given set of fixed amounts of desired products with available crude oil, the model is solved to generate an optimal topology. The proposed optimization framework also incorporates principles from life cycle analysis (LCA) to account for potential environmental impacts. A numerical example is illustrated to implement the modeling approach. Copyright © 2010 Taylor & Francis Group, LLC.