This paper is concerned with a short analysis of the semi-global stabilization obtained using a linear high and low gain feedback approach for the study of controllability of isothermal and non-isothermal reactors. The control of chemical reactors and principally the analysis of stability are very important in the chemical industry since that is the first step for the industrial automation of the reactors. The importance of this method is the relation between the slow and the fast time scales. Furthermore, a procedure involving a control law with a single tunable gain parameter allows achievement of local asymptotic stability for ally initial condition in some a priori given bounded set.