Abstract:
Crystallization has been used for the separation of chloronitrobenzene or CNBs, which are isomeric (o-, m- and p-CNB) and important intermediates in chemical productions. The effect of feed composition on the m- and p-CNB crystallization was first studied. The experiment was carried out with 61.0, 62.9, and 65.0 wt% m-CNB in the feed. The liquid mixture was cooled to its crystallization temperature and the precipitate composition was determined by a gas chromatograph. The results reveal that the crtstallization of m- and p-CNB at the eutectic composition (62.9 wt% m-CNB in the feed) provides opaque precipitates with the CNB composition close to that of the feed at 23.0 °C. Above the eutectic composition (65.0 wt% m-CNB in the feed), the precipitates appear in a transparent form with the composition being rich in m-CNB, while the p-CNB enriched-precipitates are observed for the composition below the eutectic composition (61.0 wt% m-CNB in the feed) The effect of FAU zeolites (NaX, NaY, CaX, CaY, and BaX) on their precipitate composition was then investigated. The result shows that the FAU zeolites significantly affect the precipitate composition, especially the precipitates in the feed above the eutectic composition, the composition of which is shifted from being rich in m-CNB to p-CNB. Moreover, the precipitate composition in the feed below the eutectic composition is affected by the cation, type of the zeolite and the position of the precipitates more that in the feed at and above the eutectic composition. Zeolite selectivity type of adsorbent, and adsorbent structure also affect the precipitate composition but they do not shift the precipitate composition from being rich in one component to the other.
