Silicates calcination steps

Fig. 77. Schematic drawing of the liquid-crystal templating mechanism. Hexagonal arrays of cylindrical micelles form (possibly mediated by the presence of silicate ions), with the polar groups of the surfactants (light grey) to the outside. Silicate species (dark grey) then occupy the spaces between the cylinders. The final calcination step burns off the original organic material, leaving hollow cylinders of inorganic material [473]...

Ti-silicate materials were prepared utilising automated robotic equipment. The preparation required three steps (1) gel synthesis, (2) material crystallization under hydrothermal conditions, and (3) post-synthesis treatment that includes at least one of calcination, organic extraction and silylation. 

The Phillips catalyst is usually made by impregnating a chromium compound onto a porous, high-surface-area silicate carrier and then calcining in dry air at 500-900° C (14) (Fig. 1). This latter step is an activation that converts the chromium into a hexavalent surface chromate or perhaps dichromate ester. Because each chromium atom is individually attached to the... 

Figure 2. SEM representing the steps of the formation of nanofibers of [Pt(NH3)4](HC03)2, acting as templating units for the condensation of silicate monomers forming the Si02 nanotubes original salt (a), after re-precipitation in ethanol and after addition TEOS and calcination. The bars represent 4 pm.

In an attempt to upgrade the siliceous bauxites and other aluminous materials, such as clay where the alumina usually is in the form of complex silicates, Skow and Conley (Si 9) considered the removal of the silica by caustic digestion. Prior to leaching, the aluminuous materials were calcined at 970°C, resulting in an optimal removal of silica with little loss in alumina content in the subsequent leaching step. The desilication step is necessary prior to using the raw materials as feed to the standard Bayer process (E3). The pilot plant operation to extract alumina from an anorthosite ore has been reported by St. Clair et al. (S24). 

Silica support modification in the case of catalyst B was perfi)rmed as reported earlier by Beguin et al. [22], prior to the catalyst preparation, by means of a non-aqueous slurry phase impregnation step using Tetra Ethoxy Ortho Silicate (TEOS) as precursor. TEOS dissolved in dry ethanol was used as impregnation solution. The alumina powder was added and after impregnation, the slurry was dried at 60°C under vacuum for 6 hours. The dried modified support was calcined in air at 500°C for 2 hours [4], The silica level was found to be 2.5 Si atoms/nm fresh support. 

A step forward for this type of cleaning was reported in US Patent (5,077,070, 1991) by Robert Regutti. In this invention, an adsorbent comprised of calcined metal oxide and silicate agglomerate was used to treat used frying oil. Reduction in free fatty acids, color and odor were reported along with improved taste of the treated oil. The invention also makes reference to the reduction of soap. The author also believed that the other impurities present in the frying oil were reduced. However, the patent does not report any specific results with objective data to fully support the benefit of this treatment process. 

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