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• A process to make P containing Y zeolite more stable. • P is incorporated into the framework by P for Si(4Al) isomorphous substitution. • Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. • The P species in DPY zeolite are more difficult to loss than usual P modify. • The distribution of P species in DPY zeolite is more uniform. It's a dream to make zeolites more stable so as to keep the activity and stability of the catalyst. Phosphorus modification is an effective method, however, the known post-modification predominantly presents as non-framework P, and the P-loss is a big trouble in application. We have discovered that in the reaction of PCl 3 or SiCl 4 + PCl 3 with NaY zeolite, a portion of P enters the framework of the zeolite, forming a PO 4 -AlO 4 structure. Further investigations revealed that P cannot be incorporated into the framework through P for Al isomorphous substitution, but rather through isomorphous substitution with Si(4Al). PCl 3 exhibits two effects in reaction: at lower quantities, it mainly undergoes isomorphous substitution with Si(4Al); at higher quantities, it leads to zeolite dealumination generating aluminum vacancies, which disrupt the zeolite framework or promotes Si for Al isomorphous substitution. After hydrothermal aging at 800 °C for 4 h, the stable presence of framework PO 4 -AlO 4 implies that the weakest site Si(4Al) becomes the more stable site P(4Al) in the Y zeolite framework. Compared with the JPY (prepared by impregnating (NH 4) 2 HPO 4 solution to high silica Y zeolite) sample, after 10 cycles of hydrothermal and water washing treatment, the P 2 O 5 loss rate of DPY (prepared by SiCl 4 + PCl 3 with NaY) zeolite ranged from 0.4 % to 3.5 %, significantly lower compared to the range of 18.7 % to 25.9 % observed in the JPY sample. This indicates that in DPY zeolite, the interaction between P and the zeolite is stronger and less prone to loss. Moreover, P is more uniformly distributed on the surface and bulk phase of DPY than JPY sample. [ABSTRACT FROM AUTHOR]

Abstract: NaY/kaolin composite microspheres were synthesized by an in situ method using calcined kaolin microspheres as raw material. By mixing the modified NaY/kaolin composite microspheres and additive microspheres containing ZSM-5, a novel fluid catalytic cracking (FCC) catalyst for maximizing propylene yield in FCC unit was prepared. The catalyst was characterized by X-ray diffraction (XRD), temperature-programmed desorption of ammonium (NH3-TPD), and N2 adsorption–desorption techniques and tested in a bench FCC unit. The characterization results indicated that the catalyst has more meso- and macro-pores and more acid sites than the reference catalyst and thus can increase propylene yield by 1.27%. [Copyright &y& Elsevier]

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]

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]