Two-step multiobjective synthesis of sustainable chemical processes

This paper presents the development of a two-step multiobjective approach for the superstructural synthesis of sustainable chemical processes by means of mixed integer nonlinear programming methods. The first step is the usual economy-based synthesis. It is performed on a superstructure of technological and economic alternatives for identifying the best economic solution for use as a reference solution during the second step. The second step is sustainable multiobjective synthesis in which the superstructure is extended using sustainable alternatives. The economic and environmental criteria are identified for the multiobjective optimisation in order to generate sets of Pareto optimal solutions. The experiences gained by means of the two-step synthesis approach indicate that solutions can be obtained that have improved in both, often conflicting, criteria. This approach is illustrated using a well-known process of toluene hydrodealkylation.