This paper focuses on non-isothermal plug flow reactors with fast and slow reactions. These processes are modeled by first order hyperbolic partial differential equations with-large and small parameters, which results in stiffness and multi-scale behavior. Through a combination of the method of characteristics and singular perturbation techniques, a model reduction method is developed for obtaining a non-stiff representation of the dominant dynamics of these systems. The application of the method and the advantages of using the reduced models for model-based control are illustrated through a case study. (c) 2008 Elsevier Ltd. All rights reserved.