For the optimal reactor design, the knowledge of the optimal reaction route is crucial. Model-based methods are superior since in complex reactions the intuitive identification of the optimal reaction route is mostly impossible. Using the hydro-formylation of long chain olefins as an example, an optimal control-based method is presented which considers the possible recycling of chemical components in early stages of the design process. Thereby, not only the optimal reaction concept can be identified, but also requirements for the downstream separation processes can be derived.