Zeolite Y encapsulates

FIGURE 11.18. EPR spectra of (i) Cu(salen) and (ii) Cu(5-Cl-salen) at 77 K (a) neat polycrystalline sample, (b) frozen CHas/CHsCN (3 1) solution, (c) frozen DMF solution and (d) zeolite-Y-encapsulated complexes. Dotted line (e) is a blown-up trace of curve (d). 

Figure 5.28 Triple catalytic system involving zeolite Y-encapsulated [Co(tetra-tert-butylsalophen)] to reoxidize hydroquinone for the Pd-catalyzed aerobic 1,4-oxidation of 1,3-dienes. (Redrawn from De Vos et al. [165].)...

The same holds for t-BuOOH and Fe phthalocyanines encapsulated in zeolites or adsorbed on carbon black (121, 124). On the other hand, hydroperoxides have been detected as products in the oxidation of ds-pinane by t-BuOOH in the presence of zeolite Y-encapsulated FePc (133). This is irrefutable evidence of trapping of a radical by dissolved O2. Superior hydroperoxide yields are obtained with FePc in zeolite NaY in comparison with the homogeneous reaction, particularly at subambient temperature ... 

The encapsulation of catalytically active species into porous solids is one of the possible strategies of particular interest. Thus, Bessel and Rolison (1997b,c) compared the electrocatalytic effect of zeolite Y-encapsulated Co(salen) (salen = N,N -bis(salicylidene)ethylenediamine) on the reaction between benzyl chloride and carbon dioxide in tetrahydrofuran/hexamethylphosphoramide, with that exerted by the same complex in solution. Using a large surface area reticulated vitreous carbon electrode immersed into suspensions of Co(salen) NaY in solutions of the reagents, the effective electrocatalytic turnover is ca. 3000 times that of homogeneous Co(salen) under comparable conditions. Remarkably, coulometric experiments indicated that only... 

Table 1. Comparison of the IR amide modes of (de)protonated bpen Me complexes (top) and zeolite Y encapsulated bpR Mn" complexes (bottom).

The linear SALEM ligand is mixed with dry zeolite in inert atmosphere and heated in mild conditions (393 K) till development of a bright color. In this way the preparation of zeolite Y encapsulated Co(ll) (38,39), Mn(ll) (40), Pd(ll) (42) and Rh(lll)SALEM (41) has been reported. The necessary purification of the material is done via soxhiet extraction with acetonitrile and dichloromethane. The linear SALEM ligand, which possesses 2 ionizable protons, easily enters the supercages of zeolite Y, is loosing the protons to the zeolite upon coordination with a bivalent exchangeable metal ion (reaction VIII). 

Maurya, M., Chandrakar, A. andChand, S. (2007). Zeolite-Y Encapsulated Metal Complexes of Oxovanadium(VI), Copper(ll) and Nickel(II) as Catalyst for the Oxidation of Styrene, Cyclohexane and Methyl Phenyl Sulfide, J. Mol Catal A Chem., 274, pp. 192-201. 

In addition, iron(II) complexes of tetraaza macrocyclic ligands 17-20 were encapsulated within the nanopores of zeolite-Y and were used as catalysts for the oxidation of styrene with molecular oxygen under mild conditions (Scheme 9) [57]. 

Another approach involved encapsulation of a bulky guanidine, N,N,N-tricyclohexyl-guanidine, in the super-cages of hydrophobic zeolite Y (Sercheli et ai, 1997). The resulting ship-in-a-bottle guanidine catalysed the aldol reaction of benzaldehyde with acetone to give 4-phenyl-4-hydroxybutan-2-one. 

Iron N,N -bis(2-pyridinecarboxamide) complexes encaged in zeolite Y were used for the partial oxidation of alkanes.99 Epoxidation with manganese N,N -bis(2-pyridinecarboxamide) complexes encapsulated in zeolite Y was also reported.100... 

Figure 2. Scanning electron microscopy of (a) zeolite X-chitosan, (b) zeolite Y-chitosan and (c) mordenite-chitosan composites prepared by encapsulation of zeolites during the gelling of chitosan.

Figure 4. (a) Adsorption-desorption isotherms of N2 at -196°C of 80°C-outgassed (empty squares) chitosan, (filled trangles) zeolite X-chitosan composite from in-situ zeolite synthesis and (empty triangles) zeolite Y-chitosan composite from encapsulation of the zeolite in the gelling chitosan. (b) Scanning electron micrographs of a calcined zeolite-chitosan bead prepared by zeolitisation of a silica-chitosan composite. 

Alvaro, M., Ferrer, B., Fornes, V., Garcia, H. and Scaiano, J.C. (2002). Bipyridinium macroring encapsulated within zeolite Y supercages. Preparation and intrazeolitic photochemistry of a common electron acceptor component of rotaxanes and catenanes. J. Phys. Chem. B 106, 6815-6820... 

Ray, S. and Vasudevan, S. (2003). Encapsulation of cobalt phthalocyanine in zeolite-Y evidence for nonplanar geometry. Inorg. Chem. 42, 1711-1719... 

Sanjuan, A., Alvaro, M., Aguirre, G., Garcia, H. and Scaiano, J.C. (1998). Intrazeolite photochemistry. 21. 2,4,6-Triphenylpyrylium encapsulated inside zeolite Y supercages as heterogeneous photocatalyst for the generation of hydroxyl radical. J. Am. Chem. Soc. 120, 7351-7352... 

S. Chavan, D.Srinivas, and R. Ratnasamy, Structure and catalytic properties of dimeric copper(II) acetato complexes encapsulated in zeolite-Y, J. Catal. 192, 286-295 (2000). 

The synthetic route followed in the encapsulation of [Ru(bpy)3] + in ZeoliteY is referred as ship-in-a-bottle synthesis due to non-extractability of the [Ru(bpy)3] complex, once encapsulation has taken place within the cages of the zeolite Y. Nanoparticles of TiO was then introduced through TiClj in ethylene glycol mixture under argon, with sintering at 200°C. A schematic diagram of the synthesis is shown in Fig. 16.1 [1]. 

Synthesis of zeolite Y in the presence of Gd(III) complexes of 18-crown-6 resulted not only in the encapsulation of the complex but the complex also served as a template for EMT polytype zeolite Y (Fig. 22b) (86). Feijen et al. described how the two different polytypes (the cubic FAU and the hexagonal EMT) can be formed (87). In the absence of an organic template, the FAU structure will form. If Na" "-18-crown-6 is present, it can be absorbed on the surface of the growing zeolite layer. This will influence the interconnection of the layers and, therefore, in the presence of this crown ether, the formation of the EMT framework may be favored. The difference between the pore window sizes is that in the EMT there are two different types 7.3 x 7.3 A in the [001] direction and 7.5 x 6.5 A perpendicular to the [001] direction. (The FAU has pore windows with 7.4 x 7.4 A in the [111] direction.)... 

A series of zeolite-Y hosts containing different proton concentrations has been used for MTO encapsulation [80], and the resulting materials were studied for 1-hexene metathesis. The MTO molecule was activated by intra-zeolite protons, and simultaneously blocks their isomerisation activity. The ability to tune intra-zeolite acidity and the doping levels of the intact MTO precatalyst permits control over selectivity in the metathesis reaction. 

Domenech A, Formentrn P, Garcia H, Sabater MJ (2000) Combined electrochemical and epr studies of manganese schiff base complexes encapsulated within the cavities of zeolite Y. Eur J Inorg Chem 1339-1344. 

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