Zeolites sodium form

The monomer-loaded zeolite samples display dramatic color changes from white to different hues of blue and green when (a) aniline in different acidic zeolite forms is treated with the oxidant, or when (b) pyrrole or thiophene monomers are admitted into Cu(II)/Fe(III)-containing zeolites Y or MOR from the vapor phase or from hexane (or other hydrocarbon) solutions (Table 1). These color changes correspond to those observed in bulk synthesis reactions.H l No reaction is observed with the zeolite sodium forms, indicating that the polymerizations proceed only in the presence of intfazeolite protons and/or appropriate oxidants. No polymer formation is detected in zeolite Cu(II)A (pore size 0.4 nm, smaller than pyrrole or thiophene). This is... 

Zeolites are hydrous aluminosilicates that are widely used as catalysts in the chemical process industry. Zeolite A is usually synthesized in the sodium form from aqueous solutions of sodium... 

Samples of Y faujasites were prepared by sodium exchange of a starting ultrastable Y zeolite (H form, denoted in the following as USY). Global Si/Al ratio is 16 according to X fluorescence measurements framework Si/Al is 21 as measured by 29Si MAS NMR. 

To prepare alkali- or alkaline earth-modified zeolites or mesoporous moleeular sieves, identieal general methodologies are used. Thus, alkaline earth eation-exehanged zeolites are prepared by exehange of the zeolite in the sodium form in aqueous solution of alkaline earth metal salts, followed by washing and ealeination. Alkaline earth metal oxides loaded in zeolites are also prepared by impregnation of alkaline earth metal salts sueh as nitrates, aeetates, or ethoxides followed by ealeination (70,215,216). 

Decationated zeolites. We start by considering decationated zeolites since they do not contain any metal ions extrinsic to the silica-alumina framework. This type of zeolite is obtained by pretreating, above 350°C, a NH4Y zeolite prepared by exchanging the sodium form of a Y-type zeolite with ammonium ions. Ammonia is evolved leaving a decationated or HY zeolite ... 

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. 

McDaniel and Maher (159-161) were the first to report that upon thermal treatment of NH4-Y, under a particular set of conditions, thermal stability of the zeolite is considerably increased. The product retains crystallinity at temperatures in excess of 1000°C, while the decomposition of the sodium form of the zeolite takes place at ca. 800°C. This process is known as ultrastabilization. Ultrastable zeolite Y is very well suited as a catalyst for hydrocracking reactions—much more so than the as-prepared zeolite, which is too acidic and has insufficient thermal stability. 

This requires a second zeolite tank that has a zeolite resin in the hydrogen form in addition to the usual tank with the resin in the sodium form. The two tanks are operated in parallel. In one tank, calcium and magnesium ions are replaced by hydrogen ions. The effluent from this tank with the resin in hydrogen form is on the acid side and has a lower total-solids content. The total flow can be proportioned between the two tanks to produce an effluent with any desired alkalinity as well as excellent hardness removal. When the hydrogen resin is exhausted, it is regenerated with acid. 

Ward measured the o-xylene isomerization activities of Na, Mg, RE, and H—Y zeolites and found the rare earth form to be intermediate in activity between the magnesium and hydrogen forms as shown in Table IX (212). The sodium form was essentially inactive. He interpreted the activity relationship RE—Y > Mg—Y to result from the formation of two acidic structural hydroxyl groups per trivalent rare earth cation. The formation of acidic structure hydroxyl groups by exchange of sodium ions with protons in the rare earth solution, as proposed by Bolton (218), may also account for the greater activity of the rare earth-exchanged zeolite. 

Phase equilibrium was accomplished by weighing suitable quantities of the sodium form of the zeolite into 125 ml polycarbonate bottles which contained 50 ml of the salt solution. 

It should be noted that zeolites will form from reactant gels with very low water contents ) although reaction rates are low. Also, the conversion of the zeolite chabazite in the absence of added water to give a range of other more compact framework structures has been reported. Particularly relevant was the conversion of a silicaceous sodium-form of chabazite to nosean (sodalite) at ca. 300°C. 1 )... 

The oxidation of CO is widely used as a test reaction for oxidation catalysts because of its simplicity. Thus, there is quite an extensive literature on CO oxidation using various zeolite catalysts. The parent (sodium forms) of zeolites show very little oxidation activity as might be expected and therefore the majority of the studies have concentrated on transition metal ion-exchanged forms. 

Sodium softeners are used to treated RO influent water to remove soluble hardness (calcium, magnesium, barium, and strontium) that can form scale on RO membranes. Once known as sodium zeolite softeners, zeolites have been replaced with synthetic plastic resin beads. For sodium softeners, these resin beads are strongly acidic cation (SAC) polystyrene resin in the sodium form. The active group is benzene sulfonic acid, in the sodium, not free acid, form. Figure 8.12 shows styrene-divinylbenzene gel cation resin. Equation 8.4 shows the softening reaction for calcium exchange ... 

The selective adsorbent CaA is prepared in the sodium form (the detergent zeolite NaA) and subsequently partially exchanged with Ca(II). 

The samples used in this study were both natural and synthetic varieties of mordenite and are listed in Table I. Each material contained more than 95% pure zeolite with the remainder being amorphous material as measured by x-ray diffractometry. Before being used in experimentation, each sample was exchanged to the sodium form. 

Series of zeolite-supported iron-containing catalysts with weight percent iron (% Fe) varying from 1 to 17% Fe have been prepared from Fe3(CO) 2 and the synthetic zeolites ZSM-5, mordenite and 13X by an extraction technique. The zeolites ZSM-5 and mordenite were used in the acid form, 13X in the sodium form. 

The charge distribution in sodium forms of faujasites was investigated by Beran and Dubsky (102, 103). A fragment of the potential surface corresponding to the localization of Na+ ion near two four-membered windows of X- and Y-type zeolites (S, sites) was calculated, and the estimated activation energy for the ion migration between two equivalent positions was found to be 5 kcal/mol. 

Effect of H and Al content. MOR and MFI zeolites have been primarily studied. Sodium forms exhibit very low activity in comparison with H-forms (76). The catalytic activity is a strong function of the degree of proton exchange, i.e. with the acidity of the catalyst (76). One should therefore expect that SCR activity be dependent on the Al content. Andersson et al. (77) found the activity proportional to Al content on a series of acid-leached H-MOR samples with Si/Al ratio from 16.5.3 to 9.9. Eng et al. (78) do not observe any correlation in their study on H-MFI and H-MOR. But they found that a minimum exists for Al content below which the SCR activity is negligible (Si/Al = 10 and 35 for MOR and MFI respectively). More recently, Stevenson et al. (75) reported that H-MFI catalysts of varying Si/Al ratios from 12 to 350 exhibited the highest activity at the lowest Si/Al ratio. 

Composition of the liquid products was determined by gas chromatography, using a 100m capillary column with squalane. gas products were analyzed over vaseline oil. The catalysts were prepared by the Ion exchange of the sodium form of zeolite Y with metal cations (3). 

Sodium forms of zeolites X and Y are known to be Inactive for alkylation. Calcium Introduction (catalyst 1) has resulted In a catalyst with some activity. Selectivity of the sample was not high about 57% of the alkylate were octanes with a ratio of TfV to DW of 2 1. The yield and quality of the alkylate were Improved, If Na" " cations were replaced with cations of rare-earth elements (catalysts 2 and 3). Product yield for catalysts 2 and 3 were 86.0% and 77.5% respectively with a TMP content In C0-fractionof about 85%. Unfortunately the stabilities of these two catalysts were rather low In both cases, and alkylates yields and quality declined after 3 or 4 runs. For example the percentage of unsaturated hydrocarbons In the hydrocarbon product for catalyst 3 Increased from 18 up to 30%, and TMP concentration decreased to 35% after several runs. Catalyst 4 has proved to be the most active and stable catalyst and the yields and quality of alkylates obtained over It have been the same even after many reaction-regeneration cycles. Further Increase of calcium content In the catalyst (catalyst 5) deteriorated Its catalytic properties. 

Dimerization presumably takes place on the transition metal-containing sites, and alkylation on the acidic sites of zeolltic surface. The sodium form of zeolite exchanged with transition metal cations Is capable of dimerization (and further polymerization), but does not practically exhibit alkylating capacity. This explains the composition of the product obtained from ethylene and Isobutane over this catalyst (Table V, column 3). 

In order to avoid such an undesirable effect drying agents, such as ethylortho-formate or boric anhydride 01 the calcined sodium form of a synthetic zeolite, can he added to the reaction mixture (21 ]. Moreover the negative influence of water on the activity and productivity of the catalytic system is also related to (he deactivation of the copper redox system. Indeed, in dr> alcohol, the real copper oxidant species is titc alkoxide Cu(OK)CI which is readily formed via the reaction ... 

Detergency. The largest-scale industrial production of zeolites is that devoted to the production of the sodium form of zeolite A (LTA) for use in the detergent industry. This uses currently in excess of 0.5 million metric toimes per annum worldwide. Zeolite A (NaA) is added to washing powders and other household detergents or cleansing powders as a water softener (described by the detergent industry as a builder). It... 

A methane molecule, in contrast to that of carbon monoxide, has no dipole and quadrupole moment. For lithium and sodium forms of a zeolite, the following order of elution is characteristic methane-carbon monoxide (Figure 4). 

G. Tsitsishvili Interaction of LP with molecules of unsaturated hydrocarbons and CO is very sensitive to the presence of water molecules in a zeolite and to column temperature increase. On a zeolite containing hydrophilic lithium cations, with most of the substitutions corresponding to Li" in open positions Sn and Sm, the adsorption heat of the studied compounds is lower than with the sodium form. In lithium forms with a high percentage of lithium ions, the Li" in nonhydrated positions influence adsorbate molecules, causing an increase of adsorption heat in comparison with NaX zeolite. Migration of Li" ions from Si to other positions is also possible. 

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