Zeolite with mixed cations

In the case of propene the frequency shift of the p6 fundamental obeys a nearly linear relationship with respect to the charge/radius ratio for alkali and alkaline earth cations, whereas for transition metal ions larger redshifts are observed [125]. In zeolites with mixed cation occupation such as MgNaA, ZnNaA and CoNaA propene molecules adsorbed near the divalent ions can be distinguished by their frequencies between 1607-1624 cm from those in front of the Na ions at 1636 cm which indicates the adsorbate molecules to remain localized during an infrared event. 

The use of surfactant-modified zeolite (SMZ) as a permeable barrier sorbent may offer several unique advantages when dealing with mixed contaminant plumes. Zeolites are hydrated aluminosilicate minerals characterized by cage-like structures, high internal and external surface areas, and high cation exchange capacities. Both natural and synthetic zeolites find use in industry as sorbents, soil amendments, ion exchangers,... 

Effects of cation sites can be best illustrated with the important system of N2/O2 on type X zeolites. Na/X (or 13X) has been used commercially for air separation since the 1970 s. Li/LSX is the best sorbent commercially available today (Chao, 1989). Mixed-cation AgLi/LSX (with 1-3% Ag cations) has been shown to be even better than Li/LSX (Yang and Hutson, 1998 Hutson, Rege, and Yang, 1999). 

In this study we report that the sodium-23 MASNMR spectra of Na cations in dehydrated Na-Y and mixed cation Y zeolites can be observed at 96 MHz. Using MAS rates in excess of 5 KHz reveals structure to the spectrum which can be associated with lines arising from cations sites in the different Y zeolites cages. However, it is estimated that only about 70 to 80% of the Na atoms present in the zeolite may be observable by NMR under these conditions. As an example of the sodium-23 MASNMR spectra obtainable from the dehydrated Y zeolites, the spectra of a Na-Y and the three mixed cation Y zeolites are presented in Figure 3. For the (NH, Na), (Ca,Na) and (La,Na)-Y zeolites, the degrees of cation exchange were 56, 58, and 65%, respectively. In contrast to the NMR spectra of the hydrated Y zeolites presented in Figure... 

It is also possible to prepare crystalline electrides in which a trapped electron acts in effect as the anion. The bnUc of the excess electron density in electrides resides in the X-ray empty cavities and in the intercoimecting chaimels. Stmctures of electri-dides [Li(2,l,l-crypt)]+ e [K(2,2,2-crypt)]+ e , [Rb(2,2,2-crypt)]+ e, [Cs(18-crown-6)2]+ e, [Cs(15-crown-5)2]" e and mixed-sandwich electride [Cs(18-crown-6)(15-crown-5)+e ]6 18-crown-6 are known. Silica-zeolites with pore diameters of vA have been used to prepare silica-based electrides. The potassium species contains weakly bound electron pairs which appear to be delocalized, whereas the cesium species have optical and magnetic properties indicative of electron locahzation in cavities with little interaction between the electrons or between them and the cation. The structural model of the stable cesium electride synthesized by intercalating cesium in zeohte ITQ-4 has been coirfirmed by the atomic pair distribution function (PDF) analysis. The synthetic methods, structures, spectroscopic properties, and magnetic behavior of some electrides have been reviewed. Theoretical study on structural and electronic properties of inorganic electrides has also been addressed recently. ... 

Commercially available zeolite A and X from Zeolites and Allied Products Mumbai India was used as the starting material without any further purification. For exchanging with transition and rare earth metal ions, the zeolite was mixed with 0.1M aqueous solution of the specific cation and refluxed at 80 C for 4 hours. The zeolite was filtered and washed with distilled water until the washings were free from ions and used for the adsorption measurements after diying. The percentage of ion exchange was determined by Atomic Adsorption Spectroscopy after acid digesting the sample. 

Nickel tetracarbonyl and nickel complexes with mixed carbonyl and alkylphosphine ligands in zeolite Y have been studied with EXAFS, NMR, and FTIR spectroscopies (85,240-242). The loading of Ni(CO>4 in dehydrated zeolite X can be as high as 28 wt%, corresponding to 2.75 Ni(CO>4 molecules per supercages. The IR spectrum of Ni(CO>4 was found to be affected by the cations inside the zeolite supercages. The spectrum of... 

A typical hydrothermal zeolite synthesis can be summarized as follows Amorphous precursors containing silica and alumina are mixed together with a cation source, usually in alkaline media. This aqueous reaction mixture is then... 

The cation exchange capacity of a zeolitic product can be determined by mixing 1.066 g of powder sample with 9 ml of CH3COONa solution in a mechanical shaker for 5 min. The mixture was centrifuged until a clear supernatant is obtained and later it is decanted. The similar process can be repeated for another two times to ensure that all cations in the zeohte have been replaced with Na". The Na" laden zeolites were mixed with 9 ml of 99 % isopropyl alcohol and shaken in a... 

Until recent work by Zhen et al. [ 149,150], there has been little evidence for the formation of mixed metal clusters in zeolites. Through single crystal XRD, they studied the reaction of zinc vapour with Cd-X and Tl-X (FAU) and identified a unique range of possible cadmium-zinc and thallium-zinc clusters. Some evidence has also been presented that the reaction of various alkali metals with zeolites containing the cations of a different metal may result in the formation of mixed metal clusters [68, 71, 151], but, for the most part, these products remain poorly characterized. 

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