Zeolites containing

The rate of coke burning for coke deposited on a zeolite-containing catalyst has been reported to be first order with respect both to coke concentration and oxygen partial pressure (23) ... 

A typical NaY zeolite contains approximately 13 wt% Na20. To enhance activity and thermal and hydrothermal stability of NaY, the sodium level must be reduced. This is normally done by the ion exchanging of NaY with a medium containing rare earth cations and/ or hydrogen ions. Ammonium sulfate solutions are frequently employed as a source for hydrogen ions. 

The breakthrough in FCC catalyst was the use of X and Y zeolites during the early 1960s. The addition of these zeolites substantially increased catalyst activity and selectivity. Product distribution with a zeolite-containing catalyst is different from the distribution with an amorphous silica-alumina catalyst (Table 4-3). In addition, zeolites are 1,000 times more active than the amorphous silica alumina catalysts. 

These N,N-chelating hgands were then covalently grafted on a modified Y-zeolite containing supermicropores . The selectivities observed were low (up to 11% ee) but led to similar values when comparing the imsupported and zeolite-supported Cu complexes. Interestingly, however, the zeolite catalysts could be recovered and reused several times with no loss of activity. 

Most of the microporous and mesoporous compounds require the use of structure-directing molecules under hydro(solvo)thermal conditions [14, 15, 171, 172]. A serious handicap is the application of high-temperature calcination to develop their porosity. It usually results in inferior textural and acidic properties, and even full structural collapse occurs in the case of open frameworks, (proto) zeolites containing small-crystalline domains, and mesostructures. These materials can show very interesting properties if their structure could be fully maintained. A principal question is, is there any alternative to calcination. There is a manifested interest to find alternatives to calcination to show the potential of new structures. 

Figure 6.4 Features of beta zeolite after Fenton treatment, (a) Saito-Foley adsorption pore-size distribution from Ar-physisorption for (O) parent zeolite containing the template (no porosity) ( ) Fenton-detemplated and (V) commercial NH4-form BEA.

Spectroscopy. In the methods discussed so far, the information obtained is essentially limited to the analysis of mass balances. In that re.spect they are blind methods, since they only yield macroscopic averaged information. It is also possible to study the spectrum of a suitable probe molecule adsorbed on a catalyst surface and to derive information on the type and nature of the surface sites from it. A good illustration is that of pyridine adsorbed on a zeolite containing both Lewis (L) and Brbnsted (B) acid sites. Figure 3.53 shows a typical IR ab.sorption spectrum of adsorbed pyridine. The spectrum exhibits four bands that can be assigned to adsorbed pyridine and pyridinium ions. Pyridine adsorbed on a Bronsted site forms a (protonated) pyridium ion whereas adsorption on a Lewis site only leads to the formation of a co-ordination complex. 

The NH4-Y (CBV712, ao = 24.35 A), H-Beta (CP811E-75), NH4-Beta (CP814E) zeolites were obtained from Zeolyst International. The NH4-Y and Beta zeolites were transformed to proton forms through step calcination procedure in a muffle oven. Zeolites containing 1 wt-% platinum were prepared by wet-impregnation method using hexachloroplatinic acid as the Pt-source. 

Since the initial discovery, much work has gone into improving the catalyst. The original zeolite contained small pores that limited oxidations to relatively small molecules with shapes that allowed them to move in and out of that pore system. One modification has been to isolate titanium in zeolites with larger pores so larger molecules can be oxidized. Another modification has been to incorporate other metal ions into the frameworks of different zeolites with... 

A five-line spectrum attributed to the NH2 radical has been observed by Sorokin and co-workers (105) in y-irradiated zeolites containing am-... 

The present study concerns the interaction of propene molecules with cobalt sites in CoZSM-5. The experiments of CO and NO sorption evidenced that this zeolite contained practically only Co2+ in exchange position and Co3+ in oxide form. Propene is a reactant in several reactions catalyzed by cobalt containing zeolites (like reduction of NO, amonoxidation of propene and others). 

J. Wang and A. Walcarius, Zeolite containing oxidase-based carbon paste biosensors. J. Electroanal. Chem. 404, 237-242 (1996). 

Enciforming [National Chemical reforming] A petroleum reforming process that converts pyrolysis gasoline to mixtures of propane, butane, and aromatic hydrocarbons, thereby obviating the usual hydrogenation and solvent extraction processes. The catalyst is a ZSM-5-type zeolite containing both iron and a platinum metal. Developed by the National Chemical Laboratory, Pune, India, since 1988, but not yet commercialized. 

Isomar [Isomerization of aromatics] A catalytic process for isomerizing xylene isomers and ethylbenzene into equilibrium isomer ratios. Usually combined with an isomer separation process such as Parex (1). The catalyst is a zeolite-containing alumina catalyst with platinum. Developed by UOP and widely licensed by them. It was first commercialized in 1967 by 1992, 32 plants had been commissioned and 8 others were in design or construction. See also Isolene II. 

More recently, dealumination was achieved by fluorination of zeolites at ambient temperature with a dilute fluorine-in-air stream, followed by high-temperature calcination (102). The suggested reaction mechanism involves the formation of different aluminum-fluorine compounds along with zeolites containing hydroxyl and fluorine nests. During the high-temperature calcination, it is assumed that silica insertion occurs, similar to the scheme in Figure IB. 

Pore size distribution data obtained from adsorption isotherms and from mercury porosimetric measurements show that in addition to the micropores characteristic of the parent zeolite, the DAY zeolites contain secondary pores with radii of 1.5nm (supermicropores) and lOnm (mesopores) (36,47). The secondary pores in USY-B have a radius of 5nm. It was also shown that the micropore volume of DAY amounts to about 75 percent of that of NaY (36). Due to dealumination and the formation of secondary pores, the total pore volume of DAY is considerably larger than that of NaY zeolite (0.56 vs. 0.29 cc/g). 

A high selectivity for n-hexane isomerisation over DAY zeolites containing 0.5 percent Pt has also been reported (64). 

Thin zeolite sheets offer improved mass transfer for possible rapid cycle adsorption processes. One of the first studies of zeolite as fillers in paper-making was issued to NCR in 1955, although at that time the term zeolite was more often used to describe any ion exchanger whether or not it was actually a crystalline microporous zeolite [95]. A later patent described the incorporation of micropo-rous zeolite powders in paper sheets [96]. More recently a number of patents described zeolite-containing papers in adsorption processes [97-99]. 

Most zeolite-containing products require multiple manufacturing steps, including further chemical transformation, modification, ion exchange, impregnation, forming, drying and calcination, prior to their application as adsorbents or catalysts. Selected manipulations are detailed in the next sections. 

Attrition resistant zeolite containing catalyst. US Patent 4,333,857. 

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