Iron montmorillonite

Nontronite apparently forms under the same general environmental conditions as the low-iron montmorillonites. It is formed by hydrothermal alteration and as vein fillings. It is commonly formed by both the hydrothermal alteration and surface weathering of basalt. Nontronite is the dominant clay in some soils (Ross and Hendricks, 1945). Arrhenius (1963) found that much of the authigenic montmoril-lonite in the pelagic muds of the Pacific Ocean has a relatively high iron content. 

Banin, A., Margulies, L. Chen, Y. (1985) Iron montmorillonite A spectral analog of Martian soil. Proc. 15th Lunar Planet. Sci. Conf., J. Geophys. Res., 90, C771-4. 

It is well known that Fe(II) ions are easily oxidized and hydrolyzed in the presence of oxygen and water, so the preparation of iron-montmorillonite is problematic. In aqueous suspension or in any Fe salt (either Fe(II) or Fe(III) salt) in the presence of air, iron(III) oxyhydroxides or oxides are formed (e.g., Berry et al. 1986 Drame 2005 Green-Pedersen and Pind 2000 Izumi et al. 2005 Kong et al. 2005 Kozai et al. 2001 Oliveira et al. 2003 Pillai and Sahle-Demessie 2003 Shrigadi et al. 2003). 

P-Amino esters Iron montmorillonits. shows good catalytic activities for the synthesis of /3-amino esters from silyl ketene acetals and aldimines. 

Carbonyl compounds can be reduced efficiently in hydrosilylation reactions with an inorganic solid acid or base catalyst present [108, 109]. Iron montmorillonite catalyses hydrosilylation reactions most effectively (e.g. equation 4.21) [108], while sodium montmorillonite is completely inactive. 

AldolCondensations. Cation-exchanged montmorillonites accelerate the aldol condensation of silyl enol ethers with acetals and aldehydes. Similarly, the aldol reaction of silyl ketene acetals with electrophiles is catalyzed by solid-acid catalysts. Neither report discussed the use of iron montmorillonite for these reactions however, some reactivity is anticipated. 

Miscellaneous Reactions. The coupling of silyl ketene acetals (enolsilanes) with pyridine derivatives bearing an electron-withdrawing substituent, namely cyano, in the meta position is catalyzed by iron montmorillonite and other similar solid-acid catalysts (eq 16). ... 

Some work has also been achieved with heterogeneous catalysis. These catalysts include Amberlyst-15, Nafion-H, montmorillonite KSF clay, ferrihydrite silica gel aerogels containing 11-13% iron, silica sulfuric acid, and zeolites. ... 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

The first indication of a possible connection between geological processes occurring at the boundaries between tectonic plates of the mid-oceanic ridges and the biogenesis problem was provided by J. B. Corliss (1981). He considered the hydrothermal conditions to be ideal reactors for abiotic synthesis these ideal conditions were the water temperature gradients, the pH, and the concentrations of solutes in the hot springs. The presence of certain minerals which could act as catalysts, such as montmorillonite, clay minerals, iron oxide, sulphides etc., was also very important. The initial model presented for the hydrothermal synthesis of biomolecules (Corliss, 1981) was modified, particularly by Russell (1989) and Wachtershauser (see Sect. 7.3). 

A facile method for the oxidation of alcohols to carbonyl compounds has been reported by Varma et al. using montmorillonite K 10 clay-supported iron(III) nitrate (clayfen) under solvent-free conditions [100], This MW-expedited reaction presumably proceeds via the intermediacy of nitrosonium ions. Interestingly, no carboxylic acids are formed in the oxidation of primary alcohols. The simple solvent-free experimental procedure involves mixing of neat substrates with clayfen and a brief exposure of the reaction mixture to irradiation in a MW oven for 15-60 s. This rapid, ma-nipulatively simple, inexpensive and selective procedure avoids the use of excess solvents and toxic oxidants (Scheme 6.30) [100]. Solid state use of clayfen has afforded higher yields and the amounts used are half of that used by Laszlo et al. [17,19]. 

Fig. 2. Diagram showing the intercalation of compact quaternary ammonium cations, such as trimethylphenylammonium (TMPA) into different smectites, giving rise to type I organoclays with a basal spacing of about 1.5 nm. SWa is a high-charge nontronite (iron-rich smectite) and SAz is a high-charge montmorillonite, while SAC is a low-charge montmorillonite. After Jaynes and Boyd (1991b).

The first cracking catalysts were acid-leached montmorillonite clays. The acid leach was to remove various metal impurities, principally iron, copper, and nickel, that could exert adverse effects on the cracking performance of a catalyst. The catalysts were first used in fixed- and moving-bed reactor systems in the form of shaped pellets. Later, with the development of the fluid catalytic cracking process, clay catalysts were made in the form of a ground, sized powder. Clay catalysts are relatively inexpensive and have been used extensively for many years. 

Montmorillonite An iron-rich clay mineral that has a very high cation exchange capacity. Unlike the other clay minerals, a significant amount of sedimentary montmorillonite is hydrothermal in origin. 

Layered clay silicates, generally from the intermediate-grained montmorillonite kaolin clay, are often used as filler in plastics and in the production of pottery and other ceramic items. These silicates consist of the silicate sheets held together mostly by the sodium cation with lesser amounts of other metal ions, such as iron, copper, nickel, etc. There are several approaches to open these silicate layers. 

M.C. (1991) Relationship between zinc and phosphate adsorption on montmorillonite and an iron oxyhydroxide. Aust. J. Soil Res. 29 239-247... 

Iron-exchanged Montmorillonite as an Efficient Acid Catalyst in Liquid-Phase Organic Synthesis... 

Iron exchanged Montmorillonite as Catalyst for Organic Synthesis 373... 

Windblown Surface Dust Quartz Calcite Oxides of iron Clay minerals Montmorillonite Illite 1-10 pm 30% globally... 

If the cation introduced by ion exchange is capable of multiple valence, the clay may serve as a catalyst for oxidation or reduction reactions. For example, montmorillonite treated with iron(III) nitrate is so reactive that it has to be stored under an inert atmosphere the clay catalyzes reactions of the nitrate ion, such as oxidation of secondary alcohols to ketones (via nitrite ester intermediates) and organic hydrazides to azides, and the nitration of phenols. 

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