Separation of p-chloronitrobenzene and o-chloronitrobenzene by selective adsorption using Silicalite-1 zeolite

Silicalite-1 zeolite was used for selective adsorption and separation of p-chloronitrobenzene (p-CNB) and o-chloronitrobenzene (o-CNB). Maximum adsorption amounts of p-CNB in the zeolite are found to be approximately 4 molecules per unit cell (mol./u.c.), much higher than those of o-CNB. p-CNB molecules are considered to be located in zeolite intersections and channels. CNBs adsorption in Silicalite-1 zeolite follows pseudo-second-order kinetic model. Adsorption amounts and temperatures are the important parameters in affecting CNBs adsorption rate constants. Adsorption rate constants of p-CNB are higher than those of o-CNB in Silicalite-1 zeolite. p-CNB with a purity of 94.9% and o-CNB of 96.1% can be recovered with Silicalite-1 zeolite under an optimal separation condition investigated. Compared with Silicalite-1 zeolite, the presence of acid sites in zeolites is not only favorable for p-CNB selective adsorption from CNBs aqueous solution, but also improves the adsorption heat of p-CNB.