Ultrastable Y zeolite

Samples of Y faujasites were prepared by sodium exchange of a starting ultrastable Y zeolite (H form, denoted in the following as USY). Global Si/Al ratio is 16 according to X fluorescence measurements framework Si/Al is 21 as measured by 29Si MAS NMR. 

An example of such thermal dealumination is the formation of ultra-stable Y zeolites (USY zeolites). McDaniel and Maher (6) reported the preparation of two types of ultrastable Y zeolites (a) one type prepared by the hydrothermal... 

C. Hydrothermal and chemical treatment Reaction of ultrastable Y zeolites with ... 

It has already been mentioned that the formation of ultrastable Y zeolites has been related to the expulsion of A1 from the framework into the zeolite cages in the presence of steam (8,9), and the filling of framework vacancies by silicon atoms (11,12). This results in a smaller unit cell size and lower ion- exchange capacity (6). It also results in a shift of X-ray diffraction peaks to higher 20 values. Ultrastable Y zeolites prepared with two calcination steps (USY-B) have a more silicious framework than those prepared with a single calcination step (USY-A). Furthermore, since fewer aluminum atoms are left in the USY-B framework, its unit cell size and ion-exchange capacity are also lower and most of the nonframework aluminum is in neutral form (18). 

Stability. Ultrastable Y zeolites, prepared by the hydrothermal treatment of ammonium Y zeolites, have considerable thermal and hydrothermal stability (6) The high... 

Infrared spectra. The infrared spectra of ultrastable Y zeolites have been investigated by Ward (10), Jacobs and Uytterhoeven (50,53), Scherzer and Bass (51) and Peri (52). 

A fairly large number of patents has been issued describing the application of aluminum-deficient Y zeolites in different areas of catalysis. Ultrastable Y zeolites have been used in the preparation of catalysts applied in hydrocarbon cracking, e.g. (94,95) hydrocracking, e.g. (96,97) hydrotreating, e.g. (98) and disproportionation, e.g. (99). 

Pater, J.P.G., Jacobs, P.A., and Martens, J.A. (1998) 1-Hexene oligomerization in liquid, vapor and supercritical phases over beidellite and ultrastable Y zeolite catalysts. J. Catal., 179, 477. 

Catrinescu, C Neamtu, M Yediler, A Macoveanu, M Kettrup, A. Catalytic wet peroxide oxidation of an azo dye. Reactive Yellow 84, over Fe-exchanged ultrastable Y zeolite. Environmental Engineering and Management Journal, 2002 1, 177-186. 

Tetrahedral and Octahedral Extraframework Aluminum in Ultrastable Y Zeolites... 

Different procedures can be used in practice to activate the zeolite, and the choice of a particular method will depend on the catalytic characteristics desired. If the main objective is to prepare a very active cracking catalyst, then a considerable percentage of the sodium is exchanged by rare earth cations. On the other hand, if the main purpose is to obtain gasoline with a high RON, ultrastable Y zeolites (USY) with very low Na content are prepared. Then a small amount of rare earth cations is exchanged, but a controlled steam deactivation step has to be introduced in the activation procedure to obtain a controlled dealumination of the zeolite. This procedure achieves a high thermal and hydrothermal stability of the zeolite, provided that silicon is inserted in the vacancies left by extraction of A1 from the framework (1). The commercial catalysts so obtained have framework Si/Al ratios in the... 

Faced with the need of obtaining more transportation fuels from a barrel of crude, Ashland developed the Reduced Crude Conversion Process (RCC ). To support this development, a residuum or reduced crude cracking catalyst was developed and over 1,000 tons were produced and employed in commercial operation. The catalyst possessed a large pore volume, dual pore structure, an Ultrastable Y zeolite with an acidic matrix equal in acidity to the acidity of the zeolite, and was partially treated with rare earth to enhance cracking activity and to resist vanadium poisoning. 

This work has shown that such a catalyst must possess very high cracking activity that is stable in the presence of steam and high temperature, but must have good selectivity as well. This has been achieved by employing Ultrastable Y zeolite, partially enhanced in activity by addition of a small amount of rare earth, both in the zeolite and in the matrix. 

The most widely used zeolite in petroleum refining so far is Y zeolite. Currently, REUSY zeolite is the main active component of RFCC catalysts. However, in the course of hydrothermal preparation of ultrastable Y zeolite, nonframework aluminum debris formed by dealumination could block the channels thus influencing the ion-exchange ratio of rare earth as well as the accessibility of active sites [2],... 

Recently, RIPP has developed a proprietary method to modify the properties of ultrastable Y zeolite via a treatment for cleaning its pores (CP) [3], which include the selective removal of nonframework aluminum from zeolite pores by a novel acid treatment at optimized pH and temperature conditions. 

Zeolites are crystalline aluminosilicates with a regular pore structure. These materials have been used in major catalytic processes for a number of years. The application using the largest quantities of zeolites is FCC [102]. The zeolites with significant cracking activity are dealuminated Y zeolites that exhibit greatly increased hydrothermal stability, and are accordingly called ultrastable Y zeolites (USY), ZSM-5 (alternatively known as MFI), mordenite, offretite, and erionite [103]. 

Epoxidation of olefins over Mo containing Y zeolites was studied by Lunsford et al. [86-90]. Molybdenum introduced in ultrastable Y zeolite through reaction with Mo(C0)g or M0CI5, shows a high initial activity for epoxidation of propylene with t-butyl hydroperoxide as oxidant and 1,2-dichloroethane as solvent [88]. The reaction is proposed to proceed via the formation of a Mo +-t-butyl hydroperoxide complex and subsequent oxygen transfer from the complex to propylene. The catalyst suffers however from fast deactivation caused by intrazeolitic polymerization of propylene oxide and resulting blocking of the active sites. 

Influence of Superacid Sites in Ultrastable Y Zeolites on Gas Oil Cracking... 

CATALYST PREPARATION ZSM-5 was prepared according to procedures discussed in the literature (8.9) and identified as such by X-ray diffraction analysis. Ultrastable Y zeolite was obtained from the... 

In general, we have outlined how the conversion of isobutane on sohd acid catalysts takes place according to well-established carbenium ion transition state chemistry. The difficulty with using isobutane conversion as a probe of catalyst performance is that many combinations of oligomcrization// -scission processes with isomerization steps are possible, resulting in a wide variety of adsorbed species and observable reaction products. For example, the following products are observed from isobutane conversion in the presence of ultrastable Y zeolite at temperatures near 520 K (where the reaction is initiated by the addition of isobutylene to the feed) ... 

Reaction Conditions and Products Observed for Isobutane Conversion on Ultrastable Y Zeolite at Low (523-573 K) and High (733-773K) Temperaturesa... 

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