Mineral zeolite

This is the first monograph that was devoted to structure, chemistry and use of zeolites. It reviews zeolite synthesis to 1973, gives a detailed structural description of synthetic and mineral zeolites, illustrates their physical properties and describes applications. 

Chemical potentials for the constituents of minerals are defined in a similar manner. All minerals contain substitutional impurities that affect their chemical properties. Impurities range from trace substitutions, as might be found in quartz, to widely varying fractions of the end-members of solid solutions series. Solid solutions of geologic significance include clay minerals, zeolites, and plagioclase feldspars, which are important components in most geochemical models. 

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of aqueous species onto sediment surfaces (e.g., Zhu and Anderson, 2002). Because of their large surface areas and high reactivities (e.g., Davis and Kent, 1990), many components of a sediment - especially clay minerals, zeolites, metal oxides and oxyhydroxides, and organic matter - can sorb considerable masses. 

In general, zeolites are crystalline aluminosilicates with microporous channels and/or cages in their structures. The first zeolitic minerals were discovered in 1756 by the Swedish mineralogist Cronstedt [3], Upon heating of the minerals, he observed the release of steam from the crystals and called this new class of minerals zeolites (Greek zeos = to boil, lithos = stone). Currently, about 160 different zeolite structure topologies are known [4] and many of them are found in natural zeolites. However, for catalytic applications only a small number of synthetic zeolites are used. Natural zeolites typically have many impurities and are therefore of limited use for catalytic applications. Synthetic zeolites can be obtained with exactly defined compositions, and desired particle sizes and shapes can be obtained by controlling the crystallization process. 

From the clay mineral-zeolite associations found at low temperatures, it is apparent that kaolinite as well as potassium mica occur rarely with alkali zeolites. Such assemblages are known for highly alkaline waters in continental lakes (Hay, 1966 Sheppard and Gude, 1969) where montmoril-lonite is nevertheless the predominant clay mineral. At higher temperatures, where most alkali zeolites become unstable but analcite persists, mont-morillonite will be present up to 100°C and a mixed layered mineral above this temperature. 

Mineral Surfaces. Organic matter is chemically adsorbed (deriva-tized) at the surfaces of clay minerals, zeolites, and related minerals (105) and is at times protected, concentrated, and degraded by contact with the solid surfaces. For example, porphyrins are protected (106), as are optically active amino acids by montmorillonite (107). This may result in part from the position of the organic matter in lattice spaces, as shown by Stevenson and Cheng (108) for proteinaceous substances keyed into hexagonal holes on interlamellar surfaces of expanding lattice clays, or from the fact that there are ordered structures at solid-water interfaces (109). 

Weiss, A., "Organic Derivatives of Clay Minerals, Zeolites and Related... 

Synthetic and mineral zeolites of primary importance are listed in Table I. 

Fig. I Structure of the mineral zeolite chabu/ite is depicted by packing model, tell, and skeletal model, right. The silicon and aluminum atoms lie at ihe corners ol die framework depicted hy solid lines. In this figure die solid lines do nut depict chciniej bonds. Oxygen atoms lie near rhe midpoint ol the lines connecting Irainewnrk corners. Cation sites are shown m three vJillereni toeanons referred io as sues I. II, and III. Courtesy nl Sriewilii Atmoi. im...

Mineralogically the sediments of the laminite series consist of carbonates (mainly dolomite and calcite), various clay minerals, zeolites, opal, quartz and rare gypsum (8). The occurrence of gypsum, based on our X-ray diffraction (XRD) data, is restricted to the marl unit. Deposition, according to Jankowski (8), occurred in a periodically evaporitic, stagnant lake. The high bitumen concentrations most probably were responsible for the preservation of unusual minerals such as Mg-rich calcites (up to 25% Mg 9) and bituminous smectites (Muller, G., University of Heidelberg, personal communication, 1989). 

The literature of supported transition metal complexes has been thoroughly reviewed. In this article, the chemistry of supported complexes is covered in general terms by class of solid support these include metal oxides, clay minerals, zeolites, polymers, and ion-exchange resins. 

Another state-of-the-art detection system contains a surface acoustic wave (SAW) device, which is based on a piezoelectric crystal whose resonant frequency is sensitive to tiny changes in its mass—it can sense a change of 10-1° g/cm2. In one use of this device as a detector it was coated with a thin film of zeolite, a silicate mineral. Zeolite has intricate passages of a very uniform size. Thus it can act as a molecular sieve, allowing only molecules of a certain size to pass through onto the detector, where their accumulation changes the mass and therefore alters the detector frequency. This sensor has been used to detect amounts of methyl alcohol (CH3OH) as low as 10 9 g. 

The history of crystalline gas adsorbents is old and starts with the mineral zeolite. Nowadays, there are successful synthetic techniques for the production of zeolites and zeotypes with controlled diameter pores. Moreover, processes able to produce porosity in pure organic and metal-organic skeletons have been developed. Typical compounds suitable for the topics of this chapter are shown in Fig. 3.4.6. They possess inner accessible spaces for gaseous guests to generate a gas inclusion state... 

Inorganic ion exchangers include both naturally occurring materials such as mineral zeolites (sodalite and clinoptilolite), the greensands, and clays (themontmorillonite group) and synthetic materials such as gel zeolites, the hydrous oxides of polyvalent metal (hydrated zirconium oxide) and the insoluble salts of polybasic acids with polyvalent metals (zirconium phosphate). 

Although the title of this book, Perspectives in Molecular Sieve Science, avoids the zeolite definition controversy, a large majority of the research reported here centers on traditional zeolites. Only three of the 39 chapters comprising the book deal with materials that are clearly nonzeolitic Two cover clay-type derivatives, and one deals with carbon molecular sieves. Not surprisingly, interest in these materials lies in their possible use as catalysts. Only four chapters present work on mineral zeolites and three on aluminum phosphate-type molecular sieves. Two of those chapters are by workers from Union Carbide, the laboratory that did the pioneering work in this field. It is surprising that other workers have not submitted papers on the aluminum phosphates, but perhaps this situation indicates that although much activity may be underway, laboratories hesitate to publish until patent positions are established in this potentially lucrative area. Union Carbide s synthetic faujasites (zeolites X and Y) and zeolite A receive the most attention, while ZSM-5-class materials are accorded more attention than zeolite A alone. This reflects the important roles that zeolites X and Y and ZSM-5 materials have already played as catalysts. 

Still another special problem in CEC and ESP determinations occurs for soils of high pH containing significant amounts of the slightly soluble zeolite minerals. Zeolites such as analcime and leucine contain replaceable monovalent cations in their crystal lattices. These structural cations are readily displaced by other monovalent cations, but not by divalent cations. If a monovalent cation is used as the index or... 

The object of this study was to apply mid-infrared spectroscopy to zeolite structural problems with the ultimate hope of using infrared, a relatively rapid and readily available analytical method, as a tool to characterize the framework structure and perhaps to detect the presence of the polyhedral building units present in zeolite frameworks. The mid-infrared region of the spectrum was used (1300 to 200 cm"1) since that region contains the fundamental vibrations of the framework (Si,Al) 04 tetrahedra and should reflect the framework structure. Infrared data in similar spectral regions have been published for many mineral zeolites (30) and a few synthetic zeolites (23, 49, 50). There is an extensive literature on infrared spectra of silica, silicates, and aluminosilicates (17). However, no systematic study of the infrared characteristics of zeolite frameworks as related to their crystal structure has appeared. 

The B zeolites have been called, at various times, phillipsite-like, harmotome-like, Na-P-like, and gismondine-like phases. This nomenclature has arisen by comparison with the x-ray diffraction patterns of mineral zeolite specimens. Since the B zeolites first were identified, however, the structures of phillipsite, harmotome, and gismondine have been determined, and a structure was proposed by Barrer (2), based on x-ray powder diffraction data, for Na-Pl, the equivalent of cubic Linde Bi. 

The following discussion attempts to explain the previous confusion of describing the B zeolite structures in terms of mineral zeolites by showing similarities among structures of the mineral phases and x-ray powder patterns of the mineral and synthetic phases. 

X-ray diffraction patterns of the mineral zeolites phillipsite, harmo-tome, and gismondine are shown in Figure 2 and Table IV. The Sylvania Sea Mount phillipsite is a deep-sea specimen on decomposed basalt obtained from the Scripps Institute, La Jolla, Calif. The Nidda, Germany, and Rome, Italy, phillipsites are from igneous rocks. The Nidda x-ray pattern checks in all major peaks with the ASTM card (13-455) for a phillipsite from the same locality, and is from the Harvard Museum collection (No. 102839). The Rome, Italy, specimen came from Ward s, Rochester, N. Y. 

The Linde Type B zeolites have been correlated with synthetic phases produced by Barrer (2) and Taylor and Roy (13) on the basis of x-ray powder diffraction data. The powder patterns of the B zeolites also show similarity with those of the mineral zeolites phillipsite, harmotome, and gismondine. 

Determination of the structural relationships between the Linde Type B zeolites and the related mineral zeolites by comparison of x-ray powder data would be greatly aided if powder data were available on the same specimen on which structure determinations were made. 

W. C. Beard I agree that we should accept Steinfink s structure determination as that of a real phillipsite and that the practice be extended to cover the other zeolites for which structures have been determined. For practical identification of powder x-ray diffraction patterns, I would suggest using calculated powder diffraction patterns from the structure data as carried out by D. K. Smith (Ref. 9). I plan to do this for the three mineral zeolites discussed in this paper. 

Experimental work by others indicates that the activity ratio of alkali ions to hydrogen ions and the activity of silica are the major chemical parameters of the pore water that control whether clay minerals, zeolites, or feldspars will form at conditions that approximate surface temperatures and pressures (35, 52, 53). The formation of zeolites and feldspars is favored over clay minerals by relatively high alkali ion to hydrogen ion activity ratios and by relatively high silica activities. 

Zeolite deposits that formed by the above mechanism commonly show a vertical zonation of authigenic silicate minerals similar to that in the John Day Formation. Tertiary tuffs at the Nevada Test Site in southern Nevada were altered after burial by subsurface water (59), but the authigenic mineral zonation is more complex than that in the John Day Formation. The upper zone consists of unaltered glass with local concentrations of chabazite or clay minerals. Zeolitic tuff continues downward for as much as 6000 feet. A zone rich in clinoptilolite underlies the zone of unaltered glass and is succeeded downward by zones rich in mordenite and analcime, respectively. 

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