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Pillar permanent

Relevant to Ae grafting reaction, Ae anionic species can be monofunctional or bifunctional. For monofunctional species, each permanent pillar is bonded wi A only one sheet of Ae structure, and swelling properties by intercalation of neutral species remain possible. For bifunctional species of appropriate geometry, it is possible to consider the grafting on two adjacent sheets Ae compound is no longer lamellar, and tridimensional material similar for example to zeolites could be obtained. [Pg.147]

Some hydroxylated lamellar compounds present such graftings and can be considered as permanently pillared compounds ... [Pg.147]

Aim of the work. As opposed to the more studied nonpermanent pillars, we will focus our interest here on the creation of permanent pillars. The feasibility of the grafting of pillars on the hydroxylated layers in accordance with a well-defined geometry has not yet been proved for anionic clays. Therefore a systematic study seems to us necessary to acquire a better knowledge of the interactions between the anions and the hydroxylated backbone of the anionic clays. So, we will consider the present study as a very preliminary work intended to lead to a better understanding of the conditions of permanent-pillaring, as well as the characterization of the chemical nds involved in these transformations. [Pg.148]

The intercalation of alkylammonium cations in clays, specifically tetraalkylammonium, was carried out by Barrer and MacLeod. The idea of maintaining the clays permanently expanded by intercalating strong inorganic pillars was advanced later [132], In Figure 2.25, a schematic representation of a PILC is shown. [Pg.80]

As we have already seen, swelling is the direct result of the interlayer sorption of polar molecules by smectites. The generation of an internal area of about 800 m2 g-1 by the sorption of water vapour is associated with the development of an interlayer width of at least 0.6 run, but the expanded structure lacks thermal stability. It is perhaps surprising that the work of Barrer on the sorption properties of expanded smectites, described in the previous section, did not immediately attract more attention. Twenty years were to elapse before the first successful attempts to produce stable permanently expanded smectites by the introduction of inorganic pillars were made by Vaughan et al. (1974) and Brindley and Sempels (1977). [Pg.373]

The strengthening work necessary at Tunnel Quarry consisted of the repair of existing pillars and the provision of further permanent works to ensure that the overhead cover was adequately supported. It was considered at the time that the roof was so sound and the overhead cover so deep that there was no danger of it breaking up imder bombing attack, but there was some doubt that it was sufficiently supported as a mass. Colonel Minnis noted to the War Office Tunnel Quarry Committee that ... [Pg.187]

M. Before pillaring, the solution is stirred for 3 h at 25 °C. The pillaring process consists in slowly adding the Na-montmorillonite (4 g.l i) to the hydrolyzed or partially hydrolyzed titanium solution (10 mmoles Ti/g day). After 12 h under permanent stirring at 25 °C, the pillared clay is washed and centrifuged (5000 rpm for 5 mn). The pillared montmorillonite is then dried and caldned at 500 °C. [Pg.300]

Clays are layered minerals with space between the layers where they can adsorb positive and negative ions as well as water molecules. Clays undergo exchange interactions of adsorbed ions with the outside too. Although clays are very useful for many applications, they have one main disadvantage i.e. lack of permanent porosity. To overcome this problem, researchers are looking for a way to prop and support the clay layers with molecular pillars. Most of the clays can swell and thus increase the space between their layers to accommodate the adsorbed water and ionic species. These clays are employed in the pillaring process. [Pg.82]

Pillared clays, layered silicates whose sheets have been permanently propped open by thermally stable molecular props, were used as templates to load various organic precursors.The pore diameters of resulting carbon materials range from 8 to 22 A, and the mass fractal dimension varies from 2.5 to 2.9, which are accessible to lithium ions when the intercalation process takes place in a lithium secondary battery. An approach to pyrolyse aromatic hydrocarbons such as pyrene within a pillared clay was also reported, in which the pillared clay serves two functions.It acts as the inorganic template around which the carbon can be formed, and it also functions as an acid catalyst to promote condensation of the aromatics similar to the Scholl reaction. The resulting carbon materials have pore sizes from 15 to 50... [Pg.230]

The construction of the pillars is illustrated in Fig.9. For an automatic TMS which is installed permanently, or at least for longer periods, a continuous tilting control by means of 2 biaxial tiltmeters is advantageous. [Pg.150]

The percentage of coal that is removed may also be determined by the need to protect the mine workings from overhead water. For example, when mining operations are carried out below the sea (such as, as has already been mentioned, in the North Sea off the coast from Sunderland in North East England), only narrow working places may be allowed with large protective pillars of coal being left permanently between the rooms. [Pg.142]

In the early nineties, clays once more have come to the attention of researchers because thermally and hydrothermally stable expanded materials have been synthesized by interlayering 2 1 clay minerals with oligomeric molecules and colloidal particles derived from the hydrolysis of polyvalent cations. On heating, these inorganic polymers (or colloidal particles) form pillars that permanently prop open the clay layers generating high surface area solids enclosing cavities available to sorption and catalysis. [Pg.387]


See other pages where Pillar permanent is mentioned: [Pg.147]    [Pg.155]    [Pg.162]    [Pg.147]    [Pg.155]    [Pg.162]    [Pg.147]    [Pg.155]    [Pg.162]    [Pg.147]    [Pg.155]    [Pg.162]    [Pg.253]    [Pg.177]    [Pg.52]    [Pg.502]    [Pg.426]    [Pg.304]    [Pg.781]    [Pg.1772]    [Pg.1772]    [Pg.617]    [Pg.133]    [Pg.25]    [Pg.214]    [Pg.1771]    [Pg.1771]    [Pg.125]    [Pg.134]    [Pg.1146]    [Pg.439]    [Pg.283]    [Pg.57]    [Pg.734]    [Pg.58]    [Pg.58]   
See also in sourсe #XX -- [ Pg.147 ]

See also in sourсe #XX -- [ Pg.147 ]




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