Montmorillonite prepared from

An interesting approach was adopted by Annabi-Bergaya et al. (1979), who determined methanol and isopropanol desorption isotherms on a series of charge-deficient Ca-montmorillonites (prepared from Na- and Li-saturated montmorillonite). Each desorption isotherm was determined after a surface cleaning process with the particular alcohol in order to prevent the irreversible collapse of the interlamellar space. The adsorbent was exposed to the alcohol vapour atp/p° = 0.9 and the stepwise mass... 

The structural parameters of cation-exchanged montmorillonites prepared from calcium-montmorillonite (Istenmezeje) are listed in Table 2.3. As seen in Table 2.3, the basal pacing of monovalent montmorillonite is approximately 1.25 nm, and the water content is approximately 1%. It means that there is one layer of water in the interlayer space. For bivalent montmorillonite, both basal spacing (>1.5 nm) and water content (>10%) are higher, showing two layers of water molecules in the interlayer space. The basal spacing of Pb-montmorillonite is 1.254 nm, which is similar to the value characteristic of monovalent montmorillonite (1.241 nm). However, it does not mean that lead is sorbed on the surface of montmorillonite as monovalent cation since the other parameters that are determined by the distance between the layers (hydration entropy, charge/ion radius value, water content in the interlayer space) lie between the values for bivalent and monovalent cations (Foldvari et al. 1998). 

The Structural Parameters of Cation-Exchanged Montmorillonites Prepared from Calcium-Montmorillonite (Istenmezeje, Hungary)... 

The decrease of Vm and Ki values for the adsorption of benzene on the cetylpyridi-nium montmorillonite prepared from the heated Li-form (samples 5, 6) relative to the modified material based on initial Li-montmorillonite (sample 7) can be explained by the closing of the interlayer gaps of the thermoprocessed mineral. This prevents most active sites of the external surface, the micropores on side faces, from taking part in the adsorption-separation processes. 

PZC/IEP of Na-Montmorillonite Prepared from MX-80 Bentonite from American Colloid... 

Na-Montmorillonite Prepared from Bentonite from Almeria, Spain... 

Fig. 2. X-ray diffraction patterns of La/Al-, Ce/Al-, and RE/Al-pillared montmorillonites prepared from solutions autoclaved at 120 C for 12-96 h.

FIG. 12 X-ray diffraction patterns of poly(dimethylsiloxane)-clay nanocomposites prepared from dimethyl ditallowammonium-exchanged montmorillonite as a function of the weight ratio of water to silicate. (From Ref. 67.)... 

Poly(styrene-fc-butadiene) copolymer-clay nanocomposites were prepared from dioctadecyldimethyl ammonium-exchanged MMT via direct melt intercalation [91]. While the identical mixing of copolymer with pristine montmorillonite showed no intercalation, the organoclay expanded from 41 to 46 A, indicating a monolayer intercalation. The nanocomposites showed an increase in storage modulus with increasing loading. In addition, the Tg for the polystyrene block domain increased with clay content, whereas the polybutadiene block Tg remained nearly constant. 

Experiments were carried out using isotopically labelled methanol (97% 0) and ethanol (98% purchased from MSD Isotopes. Anhydrous isobutanol was purchased from Aldrich Chemical Co., Inc. and contained the natural abimdances of orygen isotopes, i.e. 99.8% and 0.2% O. Nafion-H was obtained fi om C. G. Processing, Inc. and Amberlyst resins were provided by Rohm and Haas. The 2SM-5 zeolite was provided by Mobil Research Development Corp. H-Mordenite, montmorillonite K-10, and silica-alumina 980 were obtained firom Norton, Aldrich, and Davison, respectively. y-AIumina was prepared from Catapal-B fi om Vista. 

Vaccari (1983,1999) has given a state-of-the-art account of the preparation and catalytic properties of cationic and anionic clays. Some examples of industrial importance have also been reported. Clays exhibit many desirable features, such as low cost, wide range of preparation variables, ease of set-up and wOrk-up, high selectivity, and environmental friendliness. Cationic clays are widespread in nature, whereas anionic clays are rarely found in nature, but they can be synthesized cheaply. Cationic clays are prepared from the minerals but industrial anionic clays are generally synthetic. Smectite clays exhibit both Brpnsted and Lewis acid sites on the edges of the crystals. Hammet s acidity function values are as follows Na -montmorillonite (M), -3 to t- 1.5 NH4VM -3 to 1.5 H M -8.2 to -5.6 acid activated clay less than -8.2. Laporte also has a synthetic version of cationic clays, Laponite. The acid... 

The original epoxidation with titanium-tartrate is homogeneous, but it can be carried out heterogeneously without diminishing enantioselectivity by using titanium-pillared montmorillonite catalyst (Ti-PILC) prepared from titanium isopropoxide, (+)-DAT, and Na+-montmorillonite.38 Due to the limited spacing of Ti-PILC, the epoxidation becomes slower as the allylic alcohol gets bulkier. 

Al203-montmorillonite complexes were prepared according to the procedure described by Sterte and Otterstedt (19). The samples used in this study were prepared from untreated aluminum chlorohydrate and from aluminum chlorohydrate hydro thermally treated at 120° and l O C (catalyst designations Ml, M2 and M3). The catalysts were air dried and ground in a ball mill. The fraction 0-100 microns was separated and steamed in a muffle furnace at 750°C for 18 hrs. As a reference, a sample containing 20 % REY in a kaolin-binder matrix was prepared and treated in the same manner (catalyst M ). 

The Pechmann and Knoevenagel reactions have been widely used to synthesise coumarins and developments in both have been reported. Activated phenols react rapidly with ethyl acetoacetate, propenoic acid and propynoic acid under microwave irradiation using cation-exchange resins as catalyst <99SL608>. Similarly, salicylaldehydes are converted into coumarin-3-carboxylic acids when the reaction with malonic acid is catalysed by the montmorillonite KSF <99JOC1033>. In both cases the use of a solid catalyst has environmentally friendly benefits. Methyl 3-(3-coumarinyl)propenoate 44, prepared from dimethyl glutaconate and salicylaldehyde, is a stable electron deficient diene which reacts with enamines to form benzo[c]coumarins. An inverse electron demand Diels-Alder reaction is followed by elimination of a secondary amine and aromatisation (Scheme 26) <99SL477>. 

The mica phase contains mainly K and Mg and little Ca or Na. The field IL contains both the average composition of illites (14) given by Brown (4), the analysis of illite, treated with sea water (23), and that of the illitic fraction prepared from montmorillonite according to White-... 

Clays. The variably exchanged Ca/Fe montmorillonite clays used for the iron dependence aspect of this study were prepared and analyzed using methods described in Banin sL aJL. (22) The total iron contents of the clays prepared from two parent materials having different amounts of structural iron are summarized in Table I. For the adsorbed water studies, crude SWy and its 100% Ca and Fe forms prepared in 1987 by the same method were used. 

Figure 3. Absorbance spectra of the 1985 set of MarSAMs. a) absorbance spectra of five variably Ca/Fe-exchanged materials prepared from SWy montmorillonite of nominal iron substitutions of 0, 20, 50, 80 and 100 % of the exchange capacity. b) absorbance spectra of two replicate samples of the crude parent SWy, a 100% exchanged form of SWy prepared in 1982, the crude parent Otay, and a 100% Fe-exchanged form of Otay.

The as-method was also used by Grange and his co-workers (Gil et al., 1995 Gil and Grange, 1996) for analysing nitrogen isotherms on a series of pillared clays prepared from Na-montmorillonite. Hysteresis loops of Type H4 were associated with the secondary porosity and high values of the Langmuir constant b (see Equation (4.38)) indicated microporosity. In the case of a sample of Al-PILC, the micropore capacity was estimated to contribute about 60% to the total uptake at p/p° = 0.99. 

The most important industrial example of cation exchange is the preparation of sodium-montmorillonite/bentonite from calcium bentonite. As seen in Table 2.2, calcium ions have greater affinity to the layer charge than sodium ions, so the calcium-sodium cation exchange must be performed in the presence of carbonate ions. It means that calcium-montmorillonite/bentonite is suspended in sodium carbonate solution. Calcium ions precipitate with carbonate ions, so sodium ions can occupy the interlayer space. This process is known as soda activation of bentonite. The disadvantage of soda activation is that sodium-montmorillonite is contaminated with calcium carbonate. 

The other example of the ion sorption on edge sites is the sorption of palladium ions (Nagy and Konya 2007) on montmorillonite. As known, palladium ions are hydrolyzed at such a low pH value where the lattice of clay minerals is destroyed. For this reason, during the preparation of palladium-montmorillonite, we have to avoid the hydrolysis of Pd(II) and the acidic destruction of the clay at the same time. We can do so by applying Pd(II) as positively charged complexes at neutral pH. For example, [Pd(NH3)2]2+ complexes can be prepared from metallic palladium as follows ... 

At our laboratory we have studied aluminum-oxide montmorillonite complexes prepared from ACH-solutions hydrothermally treated at temperatures up to 160 0 (9). Hydrothermal treatment of ACH at temperatures above about 120 0 yields positively charged, fibrillar boehmite in colloidal suspension (1 ). The size of the boehmite fibrils increases with increasing temperature and time of hydrothermal treatment. Ion-exchange of montmorillonite with these positively charged fibrils resulted in AMCs with... 

Even though formic anhydride is not a stable compound (see p. 723), amines can be formylated with the mixed anhydride of acetic and formic acids (HCOO-COMe) or with a mixture of formic acid and acetic anhydride. Acetamides are not formed with these reagents. Secondary amines can be acylated in the presence of a primary amine by conversion to their salts and addition of 18-crown-6. The crown ether complexes the primary ammonium salt, preventing its acylation, while the secondary ammonium salts, which do not fit easily into the cavity, are free to be acylated. Dimethyl carbonate can be used to prepare methyl carbamates in a related procedure. A-Acetylsulfonamides were prepared from acetic anhydride and a primary sulfonamide, catalyzed by Montmorillonite KlO-FeO or sulfuric acid. "... 

We could demonstrate that haemoglobin adsorbs to colloidal clay nanoparticles prepared from sodium montmorillonite and a Pt-poljrvinyl alcohol colloid onto glassy carbon electrodes [57] Hb displayed a quasi-reversible one-electron transfer process with an = - 370 mV (vs. Ag/AgCl), AEp = 130 mV and = 70 s . The linear dependence of the peak currents from the scan rate is indicative of a surface process (Fig. 2.4a). 

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