Copper -montmorillonite

Adenine and adenosine were converted into hypoxanthine and inosine respectively on a copper-montmorillonite support, adsorption being accompanied by oxidation <91N121>. 7-Benzyl-2-iso-butyryl-3-methylguanine lost the 3-methyl group when heated in toluene with 2-3-5-tri-0-ace-tylribosyl bromide <85Mi 711-05). 

A typical titration curve is shown in Figure 2.3 for copper-montmorillonite. 

FIGURE 2.3 Potentiometric titration curve of copper-montmorillonite in 0.1 mol dm-3 NaC104 solution, m = 50 mg, V = 20 cm3 (upper left). Vs are the experimental points, line is the plotted curve by the surface complexation model. The concentration of surface sites—lower left interlayer cations upper right silanol sites lower right aluminol sites (Nagy and Konya 2004). 

In Figure 2.16 the sorbed quantity of valine is shown on calcium-, zinc-, and copper-montmorillonite. 

FIGURE 2.17 The quantity of sorbed valine in the interlayer space and on the silanol sites of copper-montmorillonite, and the concentration of valine species in the solution m = 100 mg, V=20 cm3, c0= le-3 mol dm-3, T = 20°C. The right y-axis shows the concentration of HVal, all other species are labeled on the left y-axis. 

As a conclusion, we can say that the interlayer cations have an important role in the valine sorption mechanism. The total quantity of the adsorbed valine increases in the following order calcium-montmorillonite < copper-montmorillonite < zinc-montmorillonite. This order can be explained by the cumulative effect of the affinity of cations to the layer charges (Table 2.2) and the stability constants of metal ion-valine complexes in the solution (Table 2.11). 

The first examples of cationic exchange of bis(oxazoline)-metal complexes used clays as supports [49,50]. Cu(II) complexes of ligands ent-6a, 6b, and 6c (Fig. 15) were supported on three different clays laponite (a synthetic clay), bentonite, and montmorillonite KIO. The influence of the copper salt from which the initial complexes were prepared, as well as that of the solvent used in the cationic exchange, was analyzed. 

Bis(oxazoline)-copper complexes supported on clays were investigated as heterogeneous catalysts in the cyclopropanation reaction (37, 38). Optimal results were obtained from chloride-derived complexes in nitroethane as reaction medium. Laponite clay was found to provide higher selectivities than montmorillonite or bentonite. In every case, the heterogeneous reaction afforded increased amounts of the cis cyclopropane relative to the homogeneous reaction. 

Cruz M, Kaiser A, Rowxhat PG, et al. 1974. Absorption and transformation of HCN on the surface of copper and calcium montmorillonite. Clays Clay Mineral 22 417-425. 

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. 

Chlorpyrifos is stable to hydrolysis in the pH range of 5-6 (Mortland and Raman, 1967). However, in the presence of a Cu(lf) salt (i.e., cupric chloride) or when present as the exchangeable Cu(II) cation in montmorillonite clays, chlorpyrifos is completely hydrolyzed via first-order kinetics in <24 h at 20 °C. It was suggested that chlorpyrifos decomposition in the presence of Cu(II) was a result of coordination of molecules to the copper atom with subsequent cleavage of the side chain containing the phosphorus atom forming 3,5,6-trichloro-2-pyridinol and 0,0-ethyl-0-phosphorothioate (Mortland and Raman, 1967). 

Soil. In soils, phosmet is rapidly hydrolyzed to phthalimide (Camazano and Martin, 1980 S nchez-Camazano and S nchez-Martin, 1983). The rate of hydrolysis is greater in the presence of various montmorillonite clays and chloride salts. The calculated hydrolysis half-lives of phosmet in the presence of calcium, barium, copper, magnesium, and nickel montmorillonite clays were 0.084, 0.665, 10.025, 16.926, and 28.738 d, respectively. Similarly, the half-lives of phosmet in the presence of copper, calcium, magnesium, and barium chlorides were <0.020, 5.731, 10.680, and 12.242 d, respectively. In comparison, the hydrolysis of phosmet in a neutral water solution was 46.210 d (Sanchez-Camazano and S nchez-Martin, 1983). 

To elevate p-selectivity in nitration of toluene is another important task. Commercial production of p-nitrotoluene up to now leads with twofold amount to the unwanted o-isomer. This stems from the statistical percentage of o m p nitration (63 3 34). Delaude et al. (1993) enumerate such a relative distribution of the unpaired electron densities in the toluene cation-radical—ipso 1/3, ortho 1/12, meta 1/12, and para 1/3. As seen, the para position is the one favored for nitration by the attack of NO (or NO2 ) radical. A procednre was described (Delande et al. 1993) that used montmorillonite clay supported copper (cupric) nitrate (claycop) in the presence of acetic anhydride (to remove excess humidity) and with carbon tetrachloride as a medinm, at room temperature. Nitrotoluene was isolated almost quantitatively with 23 1 76 ratio of ortho/meta/para mononitrotoluene. 

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. 

Zeolite channels have provided sites for silver [555, 556], silicon [557], and selenium [558, 559] clusters copper clusters have been generated between the layers of montmorillonite [560] and copper, platinum, and palladium clusters were formed in silicon dioxide matrices [561]. 

FOURNIER (R.O.), 1965. Montmorillonite pseudomorphic after plagioclase in a porphyry copper deposit. Amer. Min. 50, 771-7. 

Addition of alkynes to imines generated in situ can lead to quinolines when the reaction is conducted in the presence of copper chloride [126] or montmorillonite clay doped with copper bromide [127]. In the latter case, the reaction was performed under solvent-free conditions and was microwave assisted (Scheme 8.57). 

Serdyuchenko (1933), McConnell (1954), and Ross (1960) have reported analyses of Cr-rich clays ranges from 1 to 15% (Table XL1). Some of the clays are formed by ground water alteration of serpentine and probably volcanic material. It is questionable if any of the samples are pure. McConnell s (1954) material has a lath-shaped morphology. Chukhrov and Anosov (1950) described a copper-bearing (20.96%) montmorillonite from the oxidized zone of weathered sulfide ores (Table XLI). Spangenberg (1938) described a nickel-rich montmorillonite. 

Chukhrov, F. V. and Anosov, F. Ya., 1950. Medmontite, a copper-bearing montmorillonite mincraL... 

Microwave irradiation considerably improved the reaction speed and yields of 2,4-disubstituted quinolines in a MCR of aldehydes, anilines and alkynes [111]. The cyclocondensation was catalyzed by montmorillonite clay doped with copper bromide and was completed within 3-5 minutes (pulsed irradiation technique—1 min with 20 s off interval), when performed in a household microwave oven. Oil-bath heating at 80 °C for 3-6 hours was necessary to achieve comparable yields of quinolines (71-90%) (Scheme 42). 

Simulation of the ESEM pattern for Cu2+-doped Mg-montmorillonite leads to a coordination number of six and a Cu2+-D distance of 0.29 nm [41]. X-ray diffraction shows that the smectite layers are about 1.04 nm apart when the ESR lineshape becomes isotropic with a single peak. This large basal-plane spacing and the ESEM data suggest a diffuse-layer Cu(H20)g+ species that tumbles sluggishly. Copper-doped Mg-hectorite whose layers are about 0.54 nm apart yields an ESR spectrum like those for beidellite and montmorillonite at low relative humidity, whereas with the layers 1.04 nm apart, the spectrum is again isotropic [39]. Figure 8 illustrates the three Cu2+ surface complexes that appear successively as a smectite... 

The acid-base properties of calcium-, copper-, zinc-, and manganese-montmoril-lonites produced from calcium-montmorillonite were studied by potentiometric titration (Nagy and Konya 2004 Nagy et al. 2004). The neutralization reactions of Cu, Zn, and Mn ions can be described by Equations 2.6-2.8 ... 

The results of potentiometric titration, the number of edge sites, and intrinsic stability constants of the protonation and deprotonation reactions of calcium-, copper-, zinc-, manganese(II)-montmorillonites, and KSF montmorillonite are shown in Table 2.4. As a comparison, some similar data for other montmoril-lonites are also listed. 

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