Zeolite Y exchange

Mochida et al. studied the oxidation of propylene by molecular oxygen over zeolite Y exchanged with Cu2+ [12-15]. The oxidation products obtained at different feed gas compositions are listed in Table 1. 

Introduction of aluminium into a zeolite lattice broadens the lattice modes, but also introduces additional bands in the Raman spectra at low frequencies due to cation vibrations, completely analogous to the far infrared bands described in section 3.3. Figure 18 shows, for example, Raman spectra taken from the work of Bremard and Le Maire [53] of zeolite Y exchanged with different alkali metal cations. The arrows indicate bands assigned to translational modes of the cations these move to lower frequency as the mass of the cations increases, just as in the far infared spectra. 

The characteristic curves of zeolites Y exchanged with alkaline cations are shown in Figure 8. In these cases, the same concentration of cations exists in the zeolite but with quite different polarising power (i.e., ratio between charge and cation radius). It is observed that by increasing the polarising power of the cations (i.e., from K to Li ), which results in an increase of the acidity of the zeolites, the negative deviation of the characteristic curve starts at lower adsorption potentials. 

Simple gas molecules have been used to probe the electrostatic fields in zeolite Y exchanged with univalent and divalent cations (49). The large electric field which should be present near the polyvalent cations was not observed, and the heats of adsorption measured indicate that the field was obscured by strongly bound OH or O ions on the cation. 

Fig. 43. Xe NMR chemical shifts as a function of the number of xenon atoms per gram of powder material adsorbed on zeolites Y exchanged with various cations [288]...

The first generation of zeolite FCC catalyst involved the use of zeolite Y exchanged with trivalent rare earth ions and was activated by calcination according to Eq. 3. 

Metallic palladium on zeolite gives PhNCO fi om nitrobenzene with 35 % selectivity in dichlorobenzene at 240 °C and 200 atm [29], It has also been reported that zeolite Y exchanged with palladium (II), alone or in the presence of pyridine, gives PhNCO from nitrobenzene at 220-240 °C and 250 atm [30]. At... 

Similar films are obtained from powdered molecular sieves loaded with organic molecules Zeolite Y microparticles embedded into a polystyrene film and loaded with appropriately sized transition metal complexes allow selective electron exchange reactions between trapped and mobile species in the film... 

Zeolite Y samples with Si/Al = 2.5 modified with Na+, Ca2+, Mg2+ or Zn2+ ions were used in the present study for propene adsorption at room temperature. Ca (42 % of ion exchange) and Mg (35% of ion exchange) samples were prepared by multiple ion... 

Solid-state ion exchange dynamics of cadmium in zeolite Y... 

The high temperature XRPD technique can be used to investigate the dynamics of solid-state ion exchange of zeolites. Data suggest that the rate of Cd2+ ion transport in the zeolite Y micropores controls the rate of the solid-state ion exchange. 

Figure 1. High-resolution electron micrograph and corresponding optical transform (inset) of an x-ray amorphous zeolite-Y specimen that has undergone ion-exchange with a solution containing U022+ ions. The microcrystalline regions are rendered visible by the locally ordered U022+ ions. ( See text.)...

Na - K - Co exchange in Y zeolite. Heterovalent exchange reactions in zeolites generally show an even more pronounced dependency on loading (116-118). Rees (116) observed variations of the selectivity coefficient by a factor 1000 for the Na-Ca and Na-llg exchange in zeolite A at 25 °C. An+exajnple of e treipe variations is shown in fig. 9 for the K -Co and Na -Co selectivities in zeolite Y at 45 °C (117). The exchange... 

In 1962 Mobil Oil introduced the use of synthetic zeolite X as a hydrocarbon cracking catalyst In 1969 Grace described the first modification chemistry based on steaming zeolite Y to form an ultrastable Y. In 1967-1969 Mobil Oil reported the synthesis of the high silica zeolites beta and ZSM-5. In 1974 Henkel introduced zeolite A in detergents as a replacement for the environmentally suspect phosphates. By 2008 industry-wide approximately 367 0001 of zeolite Y were in use in catalytic cracking [22]. In 1977 Union Carbide introduced zeolites for ion-exchange separations. 

FAU type zeolites exchanged with many different cations (Na, K, Ba, Cu, Ni, Li, Rb, Sr, Cs, etc.) have been extensively studied. The unit cell contents of hydrated FAU type zeolite can be represented as M,j(H20)y [A Sii92 0384] -FAU, where x is the number of A1 atoms per unit cell and M is a monovalent cation (or one-half of a divalent cation, etc.). The number of A1 atoms per cell can vary from 96 to less than 4 (Si/Al ratios of 1 to more than 50). Zeolite X refers to zeolites with between 96 and 77 A1 atoms per cell (Si/Al ratios between 1 and 1.5) and Zeolite Y refers to zeolites with less than 76 A1 atoms per cell (Si/Al ratios higher than 1.5). 

Synthetic zeolites and other molecular sieves are important products to a number of companies in the catalysis and adsorption areas and numerous applications, both emerging and well-established, are encouraging the industrial synthesis of the materials. There are currently no more than a few dozen crystalline microporous structures that are widely manufactured for commercial use, in comparison to the hundreds of structures that have been made in the laboratory. See Chapter 2 for details on zeolite structures. The highest volume zeolites manufactured are two of the earliest-discovered materials zeolite A (used extensively as ion exchangers in powdered laundry detergents) and zeolite Y (used in catalytic cracking of gas oil). 

The synthesis of phthallocyanines in zeolite Y has been the subject of several publications [52-58]. The different procedures are represented in Scheme 3. In principle, dicyanobenzene is reacted under inert conditions with transition metal zeolites. The latter can be prepared either via ion exchange, or via carbonyl or metallocene impregnation. 

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