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Tunable mesoporosity was successfully generated by introducing Fe cations into the framework of NaY as starting points, and then by sequential ammonium ion exchange and steaming deferrization–dealumination treatment. Accordingly, the pore diameter and volume of mesopores depended on the content of framework Fe. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), N 2 physisorption, TEM, DSC, Py-IR, and 27 Al MAS NMR. The results show that the mesopore volumes of the Fe-induced mesoporous ultra-stable Y (USY Fe ) zeolites, which prepared via sequential deferrization-dealumination by steaming, are all higher than 0.21 cm 3 g −1 with an additional thermal stability. The highest one reaches 0.23 cm 3 g −1 , over 53% of enhancement compared to USY (0.15 cm 3 g −1 ) without deteriorating acidity. Furthermore, the most probable mesopore distributions can be finely tuned, typically in the range of 9–17 nm. In addition, it is found that large mesopores (8–50 nm) are surprisingly boosted with the increase in the Fe content used for the preparation of USY Fe samples. In the catalytic cracking of adsorbate molecule of 1,3,5-triisopropylbenzene, the mesopores-enriched zeolites exhibit higher activity and lower deactivation tendency than USY with time on stream. The results demonstrated that the mesoporous material originating from the modification of zeolite with the pre-set Fe sites aided the diffusion into and out of the micropores via mesopores, and thus produced a positive influence on the catalytic performance. [ABSTRACT FROM AUTHOR]

Realumination of dealuminated HZSM-5 zeolites by acid treatment has always been controversial and puzzling. Through characterizations of XRD, nitrogen adsorption, NH 3 -TPD, IR, XPS and 27Al MAS NMR, this work confirmed realumination of dealuminated HZSM-5 zeolites could indeed be achieved after treated with HCl solution. And it was found mainly a portion of the penta-coordinated extra-framework aluminia (EFAl) were reinserted into the framework during the process of realumination. Moreover, the characterizations of ICP-AES and UV–Vis-DRS of Co2+-exchanged zeolites indicated the realumination capacity was closely related to the distribution of framework Al (Al F). Realumination was more likely achieved when there was lower content of Al pairs and less Al F located in the channel intersections in HZSM-5. Finally, realuminated zeolites exhibited a higher conversion of n -octane due to its more Brønsted acid sites than dealuminated HZSM-5 in catalytic cracking reaction. The significantly lower content of Al pairs in realuminated zeolites compared to parent HZSM-5 inhibits the hydride transfer process to a certain extent, resulting in a higher selectivity of propylene. [Display omitted] • Realumination of dealuminated HZSM-5 zeolites achieved by treatment with the aq HCl solution. • A portion of the penta-coordinated EFAl reinserted into the framework during realumination. • Realumination capacity is strongly dependent on the distribution of Al F in HZSM-5 zeolites. • Fewer Al pairs and more Al F located in the straight and sinusoidal channels are easier for realumination. [ABSTRACT FROM AUTHOR]