This paper introduces the mathematical model of ammonia and urea reactors and suggested three methods for designing a special purpose controller.The first proposed method is Adaptive model predictive controller

the second is Adaptive Neural Network Model Predictive Control

and the third is Adaptive neuro-fuzzy sliding mode controller.These methods are applied to a multivariable nonlinear system as an ammonia-urea reactor system.The main target of these controllers is to achieve stabilization of the outlet concentration of ammonia and urea

a stable reaction rate

an increase in the conversion of carbon monoxide (CO) into carbon dioxide (CO

2

) to reduce the pollution effect

and an increase in the ammonia and urea productions

keeping the NH

3

/CO

2

ratio equal to 3 to reduce the unreacted CO

2

and NH

3

and the two reactors' temperature in the suitable operating ranges due to the change in reactor parameters or external disturbance.Simulation results of the three controllers are compared.Comparative analysis proves the effectiveness of the suggested Adaptive neurofuzzy sliding mode controller than the two other controllers according to exte

rnal disturbance and the change of parameters.Moreover

the suggested methods when compared with other controllers in the literature show great success in overcoming the external disturbance and the change of parameters.