Zeolites potassium form

We have studied the potassium form of zeolite L (batch 385-386), the same zeolite enriched with sodium and cesium ions (NaL and CsL), and a sample of potassium L-zeolite (sample A). Both zeolites were experimental batches. The chemical composition of dehydrated zeolites is given in Table I. 

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. 

Barrer and Hinds [43] recorded the first observation of hysteresis created by cation exchange in a zeolite. The sodium form of analcime has one water molecule per cation in its framework, whereas the potassium form is anhydrous in its homoionic form. This K form is another phase, lcucite, and the hysteresis is a consequence of the co-existence of the two phases within the solid. Lcucite is now classified as a zeolite. 

A LSX zeolite sample was studied under its as-made form and its fully exchanged potassium form. Upon dehydration, a lowering of the symmetry is observable at room temperature. This phenomenon was confirmed by MAS NMR spectroscopy. The structure reveals for the first time a simultaneous occupancy of sites 1 and T by potassium cations. This is due to a shift of site 1 from the centre of the D6R unit. wide line NMR spectroscopy confirms the Rietveld analysis, especially the absence of ions on site I in the as-made Na72,K24-LSX sample. 

Another versatile approach to the synthesis of valuable products is outlined in [203], The authors performed tandem reactions leading to substituted cyclopropanes using basic potassium form of Y zeolite ... 

It is highly probable that lattice vacancies created by removal of silicon may be filled up in the same way and under similar conditions as those remaining after release of aluminum. Thus, recrystallization of the desilicated products to particles with well-ordered crystal structure but traversed by nanopores is obviously effected by water steam present as reaction product of the dehydroxy-lation of hydroxyl nests . After the desihcation process, the zeolite is in the sodium (or potassium) form and this is known to be highly resistant towards hydrothermal effects. Therefore, it is to be expected that steaming represents the most effective method for the stabilization of desilicated zeolites avoiding the risk of concurrent dealumination. 

Anilines are converted into nitrosoarenes ArNO by the action of hydrogen peroxide in the presence of [Mo(0)(02)2(H20) (HMPA)]224, whereas catalysis of the reaction by titanium silicate and zeolites results in the formation of azoxybenzenes ArN (0)=NAr225. Azo compounds ArN=NAr are formed in 42-99% yields by the phase-transfer assisted potassium permanganate oxidation of primary aromatic amines in aqueous benzene containing a little tetrabutylammonium bromide226. The reaction of arylamines with chromyl chloride gives solid adducts which, on hydrolysis, yield mixtures of azo compounds, p-benzoquinone and p-benzoquinone anils 234227. 

A wide variety of zeolites are known to form in saline lakes where the species present is dependent upon the chemistry of the solutions. Rapid zeolite formation is aided by the existence of the volcanic glass and high water salinities. Potassium feldspar occurs with the common alkali zeolites (Hay and Moiola, 1963 Hay, 1964 Hay, 1966 Sheppard and Gude, 1969, 1971), however, albite is not evident as a diagenetic mineral in saline lakes. 

In each of the different parageneses outlined here, the instability of a mineral can be denoted by its replacement with one or usually several minerals. The rocks in these facies are typified by multi-phase assemblages which can be placed in the K-Na-Al-Si system. This is typical of systems where the major chemical components are inert and where their masses determine the phases formed. The assumptions made in the analysis up to this point have been that all phases are stable under the variation of intensive variables of the system. This means that at constant P-T the minerals are stable over the range of pH s encountered in the various environments. This is probably true for most sedimentary basins, deep-sea deposits and buried sedimentary sequences. The assemblage albite-potassium feldspar-mixed layered-illite montmorillonite and albite-mixed layered illite montmorillonite-kaolinite represent the end of zeolite facies as found in carbonates and sedimentary rocks (Bates and Strahl,... 

Physicochemical properties of L zeolites and of clinoptilolite were studied by adsorption, chromatographic, spectral, and ther-mogravimetric methods. The sodium form of L zeolite is characterized by better adsorption with respect to water and benzene vapor and by higher retention volumes of C C hydrocarbons and CO than potassium and cesium forms. The activation energy of dehydration determined by the thermogravimetric method decreases on going from the sodium to cesium form of L zeolite. When calcium is replaced by potassium ions in clinoptilolite, the latter shows a decreased adsorption with respect to water vapor. The infrared spectra of the L zeolite at different levels of hydration show the existence of several types of water with different bond characters and arrangements in the lattice. 

Potassium, sodium, and cesium forms of the L zeolite were studied by the thermogravimetric method. There is an endothermal effect on the initial potassium zeolite KL-DTA curve within 50°-300°C caused by the loss of adsorbed water. Most of the water (15.1%) is lost in this narrow... 

The nature of the exchanged ion in a zeolite determines the amount of equilibrated adsorbed water, decreasing from 16.3% for NaL to 12.5% for CsL. Activation energies of the dehydration process were calculated for these zeolites by the method given in Ref. 25. Their values for sodium, potassium, and cesium forms are 4.52, 2.31, and 1.85 kcal/mole. The results show that the smaller the cation radius is (i.e., the stronger its field), the higher the activation energy is. 

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. 

Zeolites, also known as molecular sieves, are important alternative builders for powdered laundry detergents and replaced phosphate salts that were banned for legislative reasons. Zeolites exist in the form of calcium, sodium, magnesium, potassium, and barium salts. 

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