Montmorillonite crystalline structure

The problem with limited selectivity includes some of the minerals which are problems for XRD illite, muscovite, smectites and mixed-layer clays. Poor crystallinity creates problems with both XRD and FTIR. The IR spectrum of an amorphous material lacks sharp distinguishing features but retains spectral intensity in the regions typical of its composition. The X-ray diffraction pattern shows low intensity relative to well-defined crystalline structures. The major problem for IR is selectivity for XRD it is sensitivity. In an interlaboratory FTIR comparison (7), two laboratories gave similar results for kaolinite, calcite, and illite, but substantially different results for montmorillonite and quartz. 

Kellogg Chlorine Process. The Kellogg process uses 1% nitrosylsulfuric acid [7782-78-7] catalyst and a dissimilar material containing a day desiccant having a reversible water content of 0.5 wt% and a crystalline structure stable to at least 760°C (72,73). Montmorillonite [1318-93-0] is the desired clay desiccant. It absorbs water as it forms, shifting the equilibrium of equation 28 to the right. The basic reaction is carried out on a fluidized bed in which the solids run countercurrent to the gaseous reactants at a temperature of 400—500°C and pressures of 300—1200 kPa (3—12 atm). Nitrosylsulfuric acid catalyst is fed into the top of the stripper column where it reacts with HQ to form nitrosyl chloride which then reacts with 02 in the oxidizer to produce Clg. 

Figure 8.1 Crystalline structure of montmorillonite (MMT) clay. (Reproduced with permission of Elsevier Ltd.)...

In mineralogy, the term clay is used for a variety of polycrystaUine materials that are well described in clay science, mineralogy properties, and characterization textbooks [2-5]. Clays can be present in fibrous, tubular, lath shaped, and planar geometries. In this chapter, however, our focus will be mainly on the planar clay varieties called smectites that include montmorillonites, the most commonly used clay for the produchon of polyolefin-clay nanocomposites. In this section, we wiU focus on clay characteristics that are relevant to catalyst supporting and particle break-up during polymerization clay chemistry, crystalline structure, and geometry. 

The nylon-6/inorganic hybrids show dramatic enhancements in their mechanical and thermal properties upon addition of a minute amount (2-10 wt.%) of montmorillonite (MMT), a nanometer thin mica-type layered silicate with a surface area of about 750 mig. This was later attributed to a filler-stabilized 7 crystalline phase of nylon-6 formed at the silicate surface.PVA/layered-silicate nanocomposites also possess such filler-induced property enhancements, which were also attributed to the existence of a non-bulk-like crystalline structure promoted when Na montmorillonite (MMT) is added to PVA. ... 

MgO was necessary to form montmorillonite from a variety of starting materials. When Mg was not present, analcite wasformed and all the A1 was presumably tetrahedrally coordinated. When CaO was added to the starting material, rather than MgO, tober-morite was formed and A1 did not enter into any crystalline silicate structure. Although Hawkins and Roy (1963) and Keller (1964) believe the role of Mg is to precipitate the Si, it is possible that its major contribution is, in some manner, assisting the A1 in assuming six-fold coordination under conditions where it would normally take four-fold coordination. 

Applications. Numerous uses of x-ray analysis were reported for filled systems. They include orientation of talc particles in extruded thennoplastics, particle size deteimination in nanocomposites, crystallinity of talc nucleated PP, crystallinity of polymerization filled PE, diffraction pattern of filled PVA, structure of nanocomposites based on montmorillonite, degree of filler mixing, structural characteristics of fillers, structure of carbon black filled rubber, the effect of apatite concentration on the structure of wood pulp, and graphite as template. " This list shows the versatility of the method in applications to filled systems. 

XAFS data, showing the formation of Ni-Al LDH phases on soil components, are shown in Figure 3.5 and Table 3.1. Radial structure functions (RSFs), collected from XAFS analyses, for Ni sorption on pyrophyllite, kaolinite, gibbsite, and montmorillonite were compared to the spectra of crystalline Ni(OH)2 and takovite. All spectra showed a peak at R 0.18 nm, which represents the first... 

The montmorillonite structure of the starting material was converted by the alkaline treatment into a mixture of zeolitic products and crystalline minerals. There was a remarkable influence of the nature of the medium (sea or distilled water) on the crystallization process. The zeolitic products synthesized in sea water showed higher crystallinity and less heterogeneity than their counterparts synthesized in distilled water. 

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