Effect of Control Design on Yield and Selectivity for the Oxidation of O-Xylene to Phthalic Anhydride Carried Out in a Tubular Type Reactor

The behavior of selectivity and yield is studied by implementing a control structure in a consecutive multiple reaction (the oxidation of o-xylene to phthalic anhydride) carried out in a tubular type reactor, whose manipulated variable is the cooling temperature. The process is characterized by a step change of − 20% in the temperature of the jacket; to make an approximation to a first order plus dead time model (FOPDT), the controls are tuned by rules (Skogestad and Grimholt in PID control in the third millennium. Springer, London, pp. 147–175, 2012 [6]). The control system is tested with two types of disturbances of 10%, one at the feed temperature and the other at the composition. Controllers response is also analyzed at the concentration of the product (phthalic anhydride) and the temperature of the jacket, obtaining that the control system is able to maintain the temperature at the desired set point, and in turn, the control system has effects on the selectivity and yield of the reaction, as it may increase or decrease in the case of the disturbance implemented.