Abstract:

In order to achieve high para-xylene (PX) selectivity, pulse test was employed to evaluate the performance of BaX-type zeolite, the influences of the framework SiO2/Al2O3 molar ratio of X zeolite, Na+ exchange ratio and water content on the PX selectivity were investigated systematically. It was found that with the increasing of the framework SiO2/Al2O3 molar ratio from 2.01 to 2.53, the separation factors of PX to meta-xylene (βP/M) and ortho-xylene (βP/O) increased firstly, and then decreased. The two separation factors reached the highest point within the framework SiO2/Al2O3 molar ratio of 2.20-2.40. The separation factor of PX to ethylbenzene (βP/E) exhibited alinearly decreased trend with the increase of the framework SiO2/Al2O3 molar ratio. All of βP/M, βP/O and βP/E increased with the increase of Na+ exchange ratio, and maintained stable when Na+ exchange ratio was higher than 94.3%. As the water content in the BaX zeolite increased from 2.0% to 8.2%, βP/M, βP/O and βP/E increased firstly and then decreased, with the highest points in the water content range of 4.0-5.0%. The separation factor of PX to para-diethyl benzene (βPX/PDEB) in PX-PDEB binary mixture was also studied using static adsorption equilibrium experiment.The result showed that βPX/PDEBvaried with the changing of PX concentration in PX-PDEB mixture, and theX zeolite with high SiO2/Al2O3 molar ratio favored a small changing range of βPX/PDEB, the value of which was very close to 1.

Key words: adsorptive separation, selectivity, aromatics, para-xylene