The molecular weight distribution (MWD) of linear polymers was controlled based on on-line reaction calorimetry. A method to estimate the MWD from reaction calorimetry when chain transfer to a chain-transfer agent is the main termination event was developed and its robustness assessed by simulation. Following this method, the desired final MWD was decomposed in a series of instantaneous MWDs to be produced at different stages of the process. An optimization algorithm was used to calculate the set-point trajectories to produce the desired MWD in a minimum time. A nonlinear model based controller was used to track these trajectories. The control scheme was validated by preparing polystyrene latexes of widely different predefined MWD.

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A high-gain nonlinear cascade state estimator is presented in this work and used to monitor conversion and polymer composition in an emulsion copolymerization process. The advantage of this cascade observer is that it requires neither occasional online samples nor prior knowledge of the dependence of the overall heat-transfer coefficient with the solids content of latex. A simple test is used to ensure that the results are robust to process noise and to rapid changes in conditions during the semibatch phase. Applications of this technique are presented in both laboratory-scale and industrial pilot-scale reactors.

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