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Thank you.

Hello,

the zeolites Y must be activated by acid treatment followed by calcination at 300°C -400 ° C, and therefore you will have a rigid and stable zeolite.

The idea of ultrastable HY is to work in temperatures above those of coque removal in FCC units. Some people treat with water vapour in calcination temperatures range. Some of crystalinity will be lost, but with a higher stability. Some people try to remove Al2O3 after that treatment. Try read some Patents (ep.espacenet.com) and Chemical Abstracts if you have access.

The activation of Y-zeolite by acid treatment (Halima) is nonsense, by this way you can only destruct the zeolite structure. USY must be prepared from ammoniun form of Y (NH4Y) by thermal treatment in hydrothermal conditions (presence of steam) at the temperature of 550-800 °C. Such conditions can be achieved by treatment of NH4Y with 100% steam or diluted steam in dynamic conditions, or in deep-bed treatment (static conditions) - see: Lovas et al.: Alkylation...., Appl. Cat. 475, 341-346, 2014. The term of USY is connected with the development of stable Y-zeolite FCC catalyst, that must be stable at high temperatures (550-800 °C) in the presence if steam.

Activation of y zeolite at low concentration acid treatment does not destroy the y zeolite structure, this is confirmed by XRD analysis; followed by moderate calcination strengthens and stabilizes the y zeolite cistalline network.

Yes, Halima, but the question was how po prepare Ultrastable zeolite Y. For the increase the stability of Y-zeolite to the level "Ultrastable" its structure must be quite strongly dealuminated, by wery low acid concentration it can be prepared only H-form of Y-zeolite with very small dealumination, and, as you mentioned, it is necessary to calcine it very carefully to keep the crystallinity. Ultrastable Y-zeolite must by prepared by hydrothermal treatment at the temperatures above 500 °C - at this condition a hydrolysis of framework aluminumum occurs creating extra-framework Al-species (EFAL), and Al-vacancies in framework are partially replaced by Si-atoms. Then, EFAL species could be partially extracted by mineral acid - its concentration can be even higher, because after hydrothermal dealumination in e.g. deep-bed conditions at 550-750 °C the dealuminated structure of USY is strong enough to be stable against acid treatment. There are also another methods how to dealuminate the structure of Y-zeolite - slow extraction by H4EDTA-acid, but the hydrothermal steaming is the most used method for the prepartation of Ultrastable Y-zeolite. Method you propose is suitable for H-form of Y-zeolite preparation, but without higher stability.

thank you for your contribution, I hope that our discussion will be beneficial for Rujito