Selective adsorption of p-CNB and o-CNB in silica-coating HZSM-5 zeolite

• Modified zeolite significantly improved p-selectivity from p- and o-CNB mixture.
• Silica layer only dispersed on external surface and pore mouth of HZSM-5 zeolite.
• Modification of zeolite with TOES finely narrowed of pore opening of the zeolite.

HZSM-5 zeolite was modified by chemical liquid deposition (CLD) using TEOS as silylation agent. Meanwhile, selective adsorption of p-chloronitrobenzene (p-CNB) was investigated with modified zeolite from an aqueous mixture of p-CNB and o-CNB. Results show that the modification of HZSM-5 zeolite significantly improved p-CNB selectivity compared to that of parent zeolite. As a result, 98.8% p-CNB and 94.3% o-CNB can be recovered from the mixture in modified zeolite at 300 K on the basis of the larger differences in adsorption capacity and diffusivity between p-CNB and o-CNB. The enhanced p-CNB selectivity in modified zeolite can be mainly attributed to the slight regulation in pore size of zeolite channel.

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