Basal distance

The diffusion of Li+ in the octahedral cavities of the Na+montmorillonite allows to control the density of the pillars of the Zr pillared montmorillonite. The solids, stable up to 300°C, have larger surface area basal distancy than the pure Zir montmorillonite. The distance between the pillars increases while the interaction strength between the pillars and the clay layer decreases. 

The formation conditions, the composition (Ni0 Al203 = 4-14) and the characteristic basal distance d = 0.8 nm of the phase agree with another model of layer packing a continuous brucite layer is a leading layer while bayerite layer possesses discrete structure, i.e., it is not tightly packed with Al cations. 

The molecular and electronic structures of (CpM)4(//2-E)6 and (CpM)4(/x2-E)3(//3-E)3 (E = O, Se) for titanium as well as group 5 and 6 transition metals have been compared using extended Hiickel molecular orbital calculations. The conclusions indicate that the M4(/x2-0)3(/x3-0)3 structure cannot exist unless the M4-tetrahedron is severely distorted by lengthening of the M(apical)-M(basal) distance. The M4(/x2-Se)3(/x3-Se)3 structure can exist with a small distortion. The M4(/x2-E)6 structure is preferred over M4(//2-E)3(//3-E)3 when M-E multiple bonding is important, that is, when E = O. There is little M-M interaction in any of the cluster orbitals.830... 

The XRD patterns of zirconium sulfate pillared clays obtained after 90 hours of intercalation with different zirconium acetate concentrations using 0.5 as sulfate to Zr ratio and the same clay concentration as used earlier are presented in Fig. 5. The diffraction data show the appearance of two first order reflections. The first one is at 23.4 A for the lowest zirconium concentration and appears as a shoulder at the same distance for 0.05 mol/L concentration. The second reflection is observed at approximately 12.3 A for the lowest concentration and at 13.7 A for 0.1 mol/L zirconium acetate. The first one results from the intercalation of sulfated zirconium species. Those species are more voluminous than the non sulfated one which gives a distance spacing at only 19.6 A. The better intercalation of sulfated zirconium species at low Zr concentration is probably due to the slow progress of polycondensation reactions. This process reduces the number of different zirconium species and gives a better cristallinity of the solid. Table 2 summarizes the textural properties of samples prepared with different zirconium concentrations. The decrease of the surface area with the decrease of the Zr concentration is probably due to the increase of the sodium clay layers by comparison with the intercalated layers. The microporous volume increases when the Zr concentration decreases. The higher microporosity is due to the important basal distance of this sample. 

In addition, i reflects an adjustment for the misfit between the tetrahedral sheet and the octahedral sheet (the regression coefficient, r, of x vs. the difference between mean basal tetrahedral edges and mean octahedral triads is r = 0.92). Furthermore, as the mean <0-0> basal distance decreases, the tetrahedral cation moves away from the basal oxygen-atom plane. Thus, x increases in value (Fig. 7). The deviation of the parameters for clintonite and kinoshitalite from the trend for true micas further suggests that there is a significant influence of the interlayer cation on the value of x. 

Table 5 gives the basal distances and the surface areas of Al-pillared saponites prepared at pH = 4.8 (process 1) and heated to SOO C at 36" /h, then to 750X at 90°/h and kept for 4 hours at this temperature. 

Layered crystalline titanates (CT) [Anthony and Dosch, U.S. Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum(III) acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetraethyl orthosilicate or aluminum(III) acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane can directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT are higher than those of commercial catalysts (Shell324 and AmocatlC). The silicon and aluminum contents of the pillared CT, used as supports, have considerable effects on the catalytic activities and physical properties of the supports. 

The metal co-ordination in the pyridine oxide complexes (78) and (79) shows interesting differences. In (78) the metal adopts a distorted square-pyramidal configuration. The apical Cu-CI distance of 2.354(3) A is longer than the corresponding basal distance of 2.258(3) A, and the terminal Cu-O bond of 1.925(5) A is shorter than those involved in the bridging unit. The basal O3CI unit is planar to 0.2 A, with the metal displaced from it by 0.44 A. The crystal structure of (79) contains two independent... 

X-ray diffraction (XRD) measurements were taken on a Philips PW-1830 diffractometer, Cu Ka radiation (1 = 0.154 mn) being used at 40 kV and 25 mA between 20= 1-15°. The basal distances, di, were calculated from the first (001) Bragg reflections through the PW 1877 automated powder diffraction software. 

In the case of ZnO/hectorite nanocomposites similar X-ray diffractograms were observed (Fig. 5) with basal distances in the range 4.0. 5 nm. The amount of salicylic acid decomposed increased with increasing ZnO content (46.2-70.8%) (Fig. 6, Table 1). The maximal specific amount of salicylic acid removed after 1 h as 168 jumol g ZnO can be found at 41 wt% ZnO content in hectorite. 

XRD spectra recorded for Sn02/montmorillonite nanocomposites are presented in Fig. 7. The figure demonstrates that intercalation of nanoparticles among the silicate layers indeed occurred, as the peak intensity of the basal spacing characteristic of montmorillonite gradually decreases and, in the presence of Sn02, thevalues of the basal distances fall in the range fl L = 2.7-6.6 nm. Nanocomposites with hectorite are shown in Fig. 8 intercalation of nanoparticles is amply... 

FIG. 25 Basal distance (dj) and enthalpy of displacement at different volume fractions of toluene (( )2 ) in the interfacial layer in ethanol (l)-toluene (2) mixtures on hexadecylam-monium vermiculite. 

The most important argument for the siUcate layers intercalation by protonated adducts was revealed by XRD analysis, which gives the value of the basal distance between silicate layers as shown in Fig. 3. From Fig. 3, one may observe that the basal distance of modified montmorillonite is always higher than of unmodified clay. The modification directed that aU the new protonated adducts were successively intercalated between the silicate layers during the cationic exchange process. 

The intercalation of clay exhibits high basal distances (18-25 A) at 20 = 8.8 due to long hydrophobic (polymeric) chains, which include 14-18 carbon atoms, while the basal distance of unmodified montmorillonite is only 11.2 A at 20 = 8.7 (Basara et al. 2005). 

FIG. 28 Schematic representation of the hydrophobic vermiculite at different basal distances (a) monolayer, (b) bridging , (c) bilayer orientation. 

In the particular case of montmorillonite, XRD is used mainly to determine the basal distance, which is calculated applying Braggs equation ... 

MtNanofil 116 and the OMt with different content of surfactant (ethyl hexadecyl dimethyl ammonium, C16). It can be observed that as the content of C16 increases (from 20 to 100% of the CEC) in the OMt the position of the dgg peak displaces towards lower angles (0). Therefore, the basal distance increases. 

TABLE 2 Basal Distances d ) of Intercalated Clays and Particle Diameters (dave) of Pd° Clays... 

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