This paper is concerned with the problem of proportional-integral tracking control of a two-stage chemical reactor system subject to time-delays, disturbances, uncertainties and input quantization. In this work, an improved equivalent-input-disturbance estimator is incorporated to the proportional-integral tracking control system to compensate the disturbances in the addressed model. Moreover, to minimize the communication congestion in the control networks, the quantized control input signals is considered while designing the controller. Further, a robust stability condition for the addressed system is established in the form of linear matrix inequalities by employing asymmetric Lyapunov-Krasovskii functional together with Jensen's integral inequalities. Moreover, in accordance with the derived conditions, the control and observer gain matrices are determined. Finally, a numerical example is provided to demonstrate the validity of the proposed control scheme.