Solid-state Ion Exchange In Zeolites Research Articles

ChemInform Abstract: Introduction of Cations into Zeolites by Solid-State Reaction

Abstract A brief review is given of early observations of cation incorporation into zeolites through solid-state reaction. The general procedure and techniques suitable for investigation of solid-state ion exchange in zeolites are described. Results of systematic studies on introduction of alkaline, alkaline earth, rare earth, transition metal and noble metal cations into hydrogen, ammonium and sodium forms of zeolites are reported. In these studies, halides or oxides of the in-going cations are preferentially employed. Particular attention is paid to the stoichiometry of the solid-state ion exchange. It is shown that in several cases a one-step solid-state reaction leads to a 100% cation incorporation, whereas such a high degree of exchange is difficult to obtain by conventional methods. As is illustrated by a few selected examples, solid-state ion exchange might be an interesting way to prepare active acid and bifunctional catalysts.

Échange ionique dans les zéolites par la méthode sèche. Mise en évidence de l'influence de quelques paramètres

There is only very little data on solid-state ion exchange in zeolites reported in the literature so far. These studies concern principally alkaline and alkaline earth metals. We can obtain, high exchanged zeolites with transition metals, between 30 and 50% exchange. It was shown that, both low temperature and high-temperature exchange processes occured. It was the aim of the present study to elucidate whether in principle, higher degrees of exchange can be obtained by solid-state reaction than by conventional ion exchange in salt solution, and result in catalysts more active. We also study, the influence of some parameters, such as, temperature, inert gas flow, time of exchange and the proportion of salt, on the degree of exchange. Chlorides of cobalt and iron were tested.

An FT-Raman study of solid-state ion exchange in zeolites

This work describes the first application of FT-Raman spectroscopy to the investigation of solid-state ion exchange. The contact-induced ion exchange between the following zeolites was examined: Li-exchanged zeolite A (Li-A) and zeolite Y (Na-Y), Li-A and zeolite X (Na-X), Li-A and Ca-exchanged zeolite A (Ca-A). The solid-state ion exchange between zeolite Y (Na-Y, NH 4-exchanged Y) and metal salts (LiCl and CaCl 2) was also studied. The results were verified by powder X-ray diffraction. They are also in good agreement with those obtained from other techniques. The study demonstrates that FT-Raman spectroscopy is a useful tool for the study of ion exchange of zeolites in the solid-state.

Solid-state ion exchange in zeolites: Part 8. Interaction of lanthanum(III) chloride with zeolites under anhydrous conditions

Interaction of lanthanum(III) chloride with hydrogen forms of ferrierite, mordenite, zeolite L, and faujasite, under completely anhydrous conditions, is described. The course of the interaction has been studied by in situ i.r. and XRD techniques. No evidence of interaction between LaCl3 and small-pore H-ferrierite was found. The other three structures investigated do interact with LaCl3 even under the complete exclusion of water or water vapor from the surroundings. Plausible mechanisms of the solid-state ion exchange in zeolites are also discussed.

Far Infrared Spectroscopy — a New Powerful Tool for the Investigation of Solid-State Ion Exchange in Zeolites

Article Far Infrared Spectroscopy — a New Powerful Tool for the Investigation of Solid-State Ion Exchange in Zeolites was published on February 1, 1995 in the journal Zeitschrift für Physikalische Chemie (volume 189, issue 2).

FTIR study of the kinetics of solid-state ion exchange in zeolites using pyridine as a probe

The solid-state interaction between CuCI and sodium forms of zeolites has been followed in situ as a function of reaction time by IR spectroscopy using pyridine as a probe. It was found that, upon heat-treatment of the mixtures of CuCI/Nay or CuCI/Na-mordenite at a temperature higher that 180 °C, the intensities of the bands of pyridine coordinated to Na+ cations in Zeolites decreased, while the bands of pyridine coordinated to the Cu+ cations on the cationic positions of the zeolites appeared and the intensities increased with reaction time. This phenomenon was explained as the ion exchange of copper(I) and Na+ between CuCI and the zeolites. The results indicated that the process of ion exchange between Cu+ in CuCI and Na+ in zeolites depends strongly upon the reaction temperature. A high-temperature reaction ( >300 °C), however, caused re-migration of the Cu+ cations away from their occupied cationic positions, probably to regenerate CuCI, and re-migration of Na+ cations back to those positions. Pre-activation of the CuCI/Na-mordenite samples at a temperature as high as 150 °C did not influence the ion exchange, indicating that, according to the TPD results, the zeolite-trapped water is not a prerequisite for solid-state ion exchange. The two overlapping bands at ca. 1451 and 1442 cm–1, typical of the vibrations of pyridine–Cu+ and pyridine–Na+ coordination complexes, were deconvoluted and fitted by using a mixed Gaussian–Lorentzian function. Based upon the fitting results, the integrated absorbances of the bands of pyridine–Cu+ and pyridine–Na+ were calculated as a function of reaction time for the reactions at different temperatures and were normalised, to allow a reasonable comparison, to those which would be obtained from the identical samples at a temperature of 260 °C.

Solid-state reaction as a way to transition metal cation introduction into high-silica zeolites

A detailed review is given of transition metal cation incorporation into zeolites by a solid-state reaction. The procedures and techniques suitable for investigation of solid-state ion exchange in zeolites are described. It is shown that a solid-state reaction is a promising way for introduction of one or several transition metal ions into cationic positions of high-silica zeolites. The majority of these polyvalent cations cannot be introduced into these matrices by other methods. The influence of different factors (temperature and atmosphere of calcination, Al 3+ content in zeolitic lattice, presence of either co-cations or anionic species) on cationic species stabilization is analyzed. It is shown that pentasil-based systems with discrete types of isolated transition metal cations are unique objects for studying the relationship between catalytic properties and local topography of isolated redox sites. A solid state modification of pentasils permits the preparation of active and stable catalysts both for complete oxidation of alkanes and for NO x decomposition.

Investigations of solid-state ion exchange in zeolites by far infrared spectroscopy

Far infrared spectroscopy is a new powerful tool for monitoring solid-state ion exchange in zeolites.

Preparation of bifunctional catalysts by solid-state ion exchange in zeolites

Bifunctional catalysts containing an acidic as well as a hydrogenation/dehydrogenation function were prepared by solid-state ion exchange. Preparation and properties of Pd-loaded H-ZSM-5 are described in detail. The catalytic behavior of the reduced catalysts was investigated using hydrogenation and hydroisomerisation of ethylbenzene as a test reaction. The catalytic performance of the catalysts could be significantly improved by concomitant incorporation of Ca2+. This was advantageously achieved in a two-step procedure, where first a solid-state ion exchange with CaCl2 and subsequently a second solid-state ion exchange with PdCl2 was carried out. A Ca, H-ZSM-5 with 1.5 wt-% Pd obtained via this two-step procedure and subsequent reduction in H2 exhibited high activity, long life-time and good selectivity with respect to hydrogenation and hydroisomerisation of ethylbenzene to ethylcyclohexane and dimethylcyclohexanes, respectively. Electron micrographs of the reduced catalyst showed finely dispersed palladium with maximum size of about 2.0 nm.

129Xe-NMR studies of contact-induced solid-state ion exchange in zeolites

Ion exchange in a mixture of RbNaX and NaY zeolites after different treatments was studied by 129Xe-NMR of adsorbed xenon. The presence of water greatly favours the ion-exchange process. But this latter can also occur under water-free conditions upon heating. The exchange rate (on the NMR time scale) of adsorbed xenon between different zeolite crystallites depends on the experiment temperature.

Solid-state ion exchange in zeolites: Part IV. Evidence for contact-induced ion exchange between hydrated NaY zeolite and metal chlorides

Results obtained by solid-state 23Na MAS n.m.r. spectroscopy, X-ray diffractometry, and i.r. spectroscopy show that contact-induced ion exchange occurs at ambient temperature in mechanical mixtures of, for example, LiCl, KCl, BeCl 2, or CaCl 2, and hydrated NaY zeolite.