Abstract:
Crystallization has been used for the separation of chlonitrobenzenes (CNBs), which are isomeric substances (o-, m-, and p-CNB) and important intermediates in chemical productions. In the experiments, a liquid mixture of m- and p-CNB was cooled to its crystallization temperature, and the solid composition was determined by gas chromatography. The crystallization with the addition of KY zeolite results in the crystal formation, not the amorphous solid as in the case, where this is only m-and p-CNB. The eutectic composition is 65.5 w t% m-CNB, which is about 3 w t% m-CNB higher in the m-CNB composition than the amorphous solid composition, 62.9 w t% m-CNB, from the system with only m-and p-CNB. In addition, the new eutectic temperature is about 4 ℃ lower, 18.5 ℃ compared to 22.5 ℃. The same behavior can also be observed when the KY zeolite is changed to other zeolites, BaX and NaX zeolites, or amorphous materials, activated carbon and silica gel. It can be seen that m-CNB selectivity on the solid materials has more and less as the same behavior. Effects of a solid material may only play a role as impurity rather than having any role on the adsorption. It may be explained that the added materials may act as impurity in the form of seeding and change the boundary between the stable zone and metastable zone.
