Isothermal Seeded Semicontinuous Reactive Crystallization of Crude Terephthalic Acid Crystals

In the reactive crystallization of terephthalic acid (TA) by liquid-phase oxidation of p-xylene (PX), four simultaneous physicochemical processes occurred, including the oxidation of PX to TA, the nucleation of TA from solution, the growth of TA crystals, and the incorporation of impurity 4-carboxybenzaldehyde (4-CBA). In this work, by using the experimental technique of seeded semicontinuous reactive crystallization, the growth of TA crystals and the incorporation of impurity 4-CBA were studied. The effects of supersaturation and temperatures on the crystallization kinetics were experimentally examined. A detailed semicontinuous reactor model including chemical reactions, TA growth, and 4-CBA incorporation was developed. The model was solved numerically to optimize the model parameters for crystallization kinetics. The effect of temperatures on the growth rate and the incorporation rate was studied and correlated. The correlated results agreed with the experimental results satisfactory. The obtained crystallization kinetics can be used as essential data to predict the growth of TA crystals and the incorporation of impurity 4-CBA.