Ion exchange alkaline earth

Kwak, J.H., Szanyi, J. and Peden, C.H.F. (2004) Non-thermal plasma-assisted NOx reduction over alkali and alkaline earth ion exchanged Y, FAU zeolites, Catal. Today 89, 135—41. 

Sherry, H.S. (1968) The ion-exchange properties of zeolites. IV. Alkaline earth ion exchange in the synthetic zeolites linde X and Y./. Phys. Chem., 72 (12), 4086-4094. 

Kraikul, N., Rangsunvigit, P., and Kulprathipanja, S. (2005) Study on the adsorption of 1,5-1, 5- and 2,5-dimethyl-naphthalene on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites. Adsorption, 12, 317. 

Ward, J.W. (1968) The nature of active sites on zeolites. 111. The alkali and alkaline earth ion-exchanged forms. 

Efficient oxidation of alkanes with molecular oxygen can be attained using N-hydroxyphthalimide combined with Co(acac) (n = 2,3).1121 According to a new concept, photocatalyzed selective oxidation of small hydrocarbons at room temperature is carried out over alkali or alkaline-earth ion-exchanged zeolites.1122... 

Catalytic activity measurements. Alkali metal ion X and Y zeolites show no activity for hydrocarbon conversions involving carbonium ion intermediates. Ward (210) showed that the decomposition of cumene to benzene and propylene did not occur over Na—Y zeolite at 260°C, whereas extensive conversion took place with H—Y and alkaline earth ion-exchanged forms. Similarly, isomerization of o-xylene at 250°C did... 

The spectra of alkaline earth ion-exchanged samples, with the exception of the barium form (211), have hydroxyl absorption bands at 3645 and 3540 cm-1, similar to those found in H—Y zeolite. The barium form behaves like the alkali-exchanged zeolites. The similarity of the spectra of the alkaline earth forms with that of the hydrogen form suggests that the acidic hydroxyls are associated with the same structural features (151). Band frequencies in the region of 3600 to 3560 cm-1 vary with the cations and are thought to result from hydroxyl groups associated with the divalent cations (211). They are weakly acidic or inaccessible to adsorbate molecules since the band intensity is not affected by adsorption of pyridine (209). 

A large body of information has been published on polyvalent ion exchange in zeolites. Examples of alkaline earth ion exchange in zeolites include studies on ion exchange of Na-A (5),... 

Alkaline Earth Ion Exchange of Zeolites X and Y. In recent years, alkaline earth ion exchange in zeolites X and Y has been studied thoroughly. In 1966, Barrer, Rees, and Shamsuzzoha reported on alkaline earth ion exchange in zeolite X at 25°C (12), and in 1968, Barrer, Davies, and Rees reported on exchange in zeolite Y at 25°C (6). In 1968, Sherry reported on alkaline earth ion exchange in zeolites X and Y over the temperature range of 5° to 50°C (54). 

Aromatic systems have always attracted considerable attention. Eremenko et al. [107,108], choosing naphthalene and naphthylamine as probe molecules in alkah metal and alkaline earth ion-exchanged faujasites, investigated the formation of donor-acceptor complexes and the oxidation of naphthalene using luminescence and DR spectra. Naphthalene adsorbed from hexane solution in... 

Being endowed with more degrees of vibrational freedom the use of triatomic probes should in principle enlarge the information on interaction. Extending the interaction calculations to linear triatomics like CO2 and N2O in partly alkaline earth ion-exchanged zeolites A stable sorption sites were found between adjacent SI cations due to the enlarged dimension of these molecules. 

The catalytic activity for the aniline formation from chlorobenzene and ammonia of the Y zeolites with various cations was studied at 395° C (Table I). It is clear that the transition metal-exchanged zeolites have the catalytic activity for the reaction, while alkali metal and alkaline earth metal zeolites do not. The fact that alkaline earth metal-exchanged zeolites usually have high activity for carbonium ion-type reactions denies the possibility that Bronsted acid sites are responsible for the reaction. Thus, catalytic activity of zeolites for this reaction may be caused by the... 

In contrast with the observed behavior of the alkaline earth forms, addition of water to dehydroxylated rare earth ion-exchanged Y zeolite did not result in formation of new structural hydroxyl groups (2/7). This is consistent with Bolton s interpretation that a significant fraction of the structural hydroxyl groups are formed by exchange with protons in solution rather than by hydrolysis of the rare earth ion. 

Formation of intrinsic colloids in natural waters can be excluded for radioisotopes of elements of groups 0, I and VII, and the probability that they may be formed is small for radioisotopes of elements of other groups as long as the concentration of the elements is low. In general, formation of carrier colloids by interaction of radionuclides with colloids already present in natural waters is most probable. Thus, clay particles have a high affinity for heavy alkali and alkaline-earth ions, which are bound by ion exchange. This leads to the formation of carrier colloids with Cs, Ra and °Sr. Formation of radiocolloids with hydrolysing species has already been discussed (section 13.4). 

For the samples studied, no pyridine adsorbed on Lewis acid sites was detected, indicating that the zeolite had not been partially dehy-droxylated to form such sites. The band reflecting pyridine-cation interaction was detected only after about 16 alkaline earth ions had been introduced into the unit cell. It grew steadily in intensity as more divalent ions were introduced into the structure. In Figure 1, the intensity of the pyridinium ion band, expressed as absorbance/sample mass, is plotted as a function of the per cent exchange by divalent ion. The concentration of acid sites is a function of the degree of exchange. 

J. W. Ward It was previously shown (Ward, /. Catalysis 1968, 11, 251, Nature of Active Sites on Zeolites VI) that alkaline earth ions stabilized the hydrogen-Y zeolite. Examination of the infrared spectra, unit cell constant, ion exchange capacity, thermal analysis data, and other properties indicates that this material is not the so-called ultra-stable zeolite. 

Divalent Ion-Hydrogen Ion Selectivities. Selectivity coefficients determined at equivalent ionic fractions of 0.5 for the alkaline earth ions, Co2" ", and Zn " " are listed in Table II along with corresponding polymer water contents (7). Again, the normal order of selectivities is seen for the alkaline earth ions for a low charge density exchange site environment. The order of standard hydration free energies for these cations is Zn2" " > Co2" "... 

Mg2" " > Ca2" " > Sr2" " > Ba2" " which is the inverse order of exchange selectivities. The spread in selectivities for the alkaline earth ion series is much smaller compared to that of the alkali metal ions however. The values for the normal form of Nafion in Table II are similar to those of a 4% divinylbenzene cross-linked polystyrene sulfonate resin Mg2" ", 2.23 Ca2" ", 3.14 Sr2" ", 3.56 Ba2" ", 5.66 (12). Resins of 8% and 16% cross-linking have a much larger spread than do these values thus the enhancement in... 

T. Sata, Modification of properties of ion-exchange membranes, Doctoral Thesis, 1975, p.10 V Svetlicic and Z. Ronrad, Study of the electrical resistance of alkaline earth ions in cation exchange membranes, J. Membr. Sci., 1979, 5, 129-134. 

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