Zeolite lithium-exchanged

Fig. 7.28 INS spectra (INlBeF, ILL) of liiran at 5 K and futan adsorbed by lithium exchanged zeolite X, Li93,iNa2,4Al95.5Si97,50384 at 20 K. One molecule of fiiran per supercage. The out-of-plane bending modes near 750 and 870 cm of solid fiiian are shifted to ca 780 and 890 cm in the zeolite. Reproduced from [120] with permission from Elsevier.

Figure 2. Lithium isotope separation effected during ion exchange with synthetic zeolite (Taylor and Urey 1938). As has been demonstrated repeatedly since that study, in both natural and synthetic experiments, Li is fixed more effectively in the exchanger than Li.

Ultramarines are zeolites, though lattice paths are restricted by 0.4 nm diameter channels. The sodium ions can be exchanged for other metal ions (e.g., silver, potassium, lithium, copper). Although this produces marked color change, none of the products have commercial value. 

Selective absorption of durene from heavy gasoline (bp 150—225°C) is possible using a version of UOP s Sorbex technology where the X zeolite is made selective for durene by replacing the exchangeable sodium cations with lithium ions (16). 

The condensation of benzaldehyde with ethyl cyanoacetate, ethyl malonate and ethyl acetoacetate were carried out with high rates and selectivity promoted by lithium-, sodium, potassium-, and caesium-exchanged X and Y zeolites and on sodium-Germanium substituted faujasite. 

NaX and NaY zeolites (Union Carbide) were exchanged by lithium, potassium, and caesium in a 1 M solution of the corresponding metal chloride at 80°C for 60 min, using a liquid to solid ratio of 10. The samples were then filtered and washed free of chlorides. After drying, the zeolite was pelletized, crushed, and sieved to different particle sizes. 

Influence of Ethanol. Three different amorphous aluminosilicate solids of Si/Al ratios 1.33, 1.48 and 4.28 were synthesized by mixing sodium silicate and aluminate solutions of various concentrations. These solids were extensively ion-exchanged with LiCl and NaCl solutions. The lithium and sodium containing solids (2g) were then mixed with 50 mL of 1JJ LiOH and NaOH, respectively. The hydroxide solutions contained 0%, 10%, 25%, 50% and 75% ethanol (volume by volume). These samples were then heated to 90-95 C, and formation of zeolites was monitored by powder diffraction. In one experiment, the lithium aluminosilicate solid was reacted in the NaOH system. 

The similarity in the adsorption behavior of krypton on the three kinds of mica surfaces suggests that the adsorption here is primarily due to dispersion forces, with very little contribution from ion-induced dipole forces. The results of Barrer and Stuart (1) for the adsorption of argon on various ion-exchanged forms of faujasite are similar. They found that while calcium, strontium, and lithium faujasite—i.e., the materials containing cations with greater polarizing power—did show heat effects correlatable with ion-induced dipole interactions, no such effects were observed with sodium, potassium, or barium zeolites. With the latter materials, they also concluded that the adsorbed argon possessed appreciable mobility. 

In 1989, Chao [2] reported that LiLSX (lithium ion-exchanged low silica X zeolite, having a Si/Al ratio close to I.O) showed an unexpected high capacitiy and selectivity for nitrogen over oxygen. He found a Li exchange threshold value in LiNaLSX at about 2/3. Below... 

Dimerizations of aryldiazomethanes to 1,2-diarylethylenes were reported to be catalyzed by cerium(IV) ammonium nitrate (4J), lithium bromide (42), copper(II) salts (43), and rhodium(II) acetate (44) and to be induced by photolysis (45). Catalysis of copper ion-exchanged zeolite (CuNaY) was compared with reactions of copper salts supported on AI2O3 and a homogeneous catalyst, Cu(C104)2, for the dimerization [Eq. (11)] of aryldiazomethane (Table XIII) (-/6). 

Whereas parent. Mo-free D-NH4Y zeolite shows, in the t.p.d. spectrum, the presence of two maxima (630 and 820 K) and a shoulder at 520-S50 K, similar to those described by Neuber et al.[lS], Li, Na and K exchanged samples indicate only two distinct peaks one above 800 K and a second one located between 500 K (for potassium) and 630 K (for lithium). For caesium exchanged zeolite the t.p.d. resembles that of D-NH4Y but with 5-fold lower intensity. 

Recent work in Versailles and Santa Barbara has led to the synthesis of several nanoporous nickel(II) phosphates. A zeolitic nickel(II) phosphate, VSB-1 (Versailles/Santa Barbara-1), was prepared under simple hydrothermal conditions [22] and has a unidimensional pore system delineated by 24 NiO and PO4 poly-hedra with a free diameter of approximately 0.9 nm (Figure 18.7). It becomes microporous on calcination in air at 350 °C, yielding BET surface areas up to 160 m g and is stable in air to approximately 500 °C. The surface area appears low compared with aluminosilicate zeolites, but the density of VSB-1 is twice that of a zeolite and the channel walls are particularly thick. VSB-1 can be prepared in both ammonium and potassium forms, and exhibits ion-exchange properties that lead, for example, to the formation of the lithium and sodium derivatives. Other cations (e.g. Mn, Fe, Co, and Zn) can be substituted for Ni in VSB-1, up to a level as high as 30 atomic%. The parent compound shows canted antiferromagnetic order at Tn = 10.5 K with 6 = —71 K on doping with Fe, Tn increases to 20 K and 6 decreases to —108 K. 

Some other materials are AIPO4 [293, 302], AIP04-Ti0 [294], magnesium phosphates [26], alkali-exchanged zeolites [148, 286], hydrotalcite-like materials [295], lithium aluminaies and HAIO2 [202]... 

The original Fries procedure has been modified extensively to occur under either UV irradiation (Photo-Fries Rearrangement) or anionic lithiation or lithium-bromo exchange (anionic ortho-Fries rearrangement). Other modifications include the application of microwaves,electron beam, BF3-H20, Y zeolite,zinc powder, Bi(OTf)3, and solid acid catalyst as the promoters. 

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