Kenyaite

Kendall structure Kenics mixer Ken-React KR TTS Kentucky bluegrass Kenyaite [12285-95-9]... 

Kelvin probe microscopy, 3 332 Kemira mixer-settler, 10 775 Kenaf, 11 292, 293-294 uses of, 11 299t, 300 Kendall structure, 19 204-205 Kennecott rhenium technology, 21 682 Kennecott wet chlorination plant, 22 84 Kenyaite, 22 455... 

Figure 4 presents the isothermal phase transformation diagram of the template-free syntheses in which the SiCL/Alo ratio and the time t of crytallization are varied. The Siof/Nafcr and l O/SiCL ratios are 10 and 30, respectively. The pentasil phase could only be synthesized for n = SiC /A O, =30-50 and t = 36 - 72 h. Outside of this area amorphous material, mordenite, sheet structures similar to kenyaite, quartz and crystobalite can be found. For values of n less than 25 the crytalline product is mordenite. For 30 < n < 50 a yield of 95% (related to the SiC content) ZSM-5 type, which was proved by X-ray diffraction pattern, could be found. Depending on n and the crystallization time, t, a more or less large amount of amorphous material is produced. This is shown in Figure 5. A long crystallization time causes recrystallization and is harmful to the yield of ZSM-5 products.

Bricker, O.P., 1969. Stability constants and Gibbs tree energy of formation of magadiite and kenyaite. Am. Mineral., 54 1026-1033. 

Other known mineral stmcmres of sodium siUcates include natrosiUte [56941-93-6], Na2 i2 5 [12285-88-0], Na2Sij4 029-11H2 0 kenyaite... 

Fig.l and Fig.2 show the XRD and SEM images of the products which were obtained from the mixtures with Si02/Al203 = 100 on the base of Al(OH)3 and NaF without any pretreatment (a), with stirring by magnetic bar (b) and ball-milling (c) before crystallization. As seen from these figures the pure zeolite MWW crystallized only from the mixture milled on Planet Mill. Otherwise kenyaite and MTW were the main phases. 

No pure zeolite MWW was obtained from the mixtures on the base of NaOH (Fig.3). MWW with kenyaite impurity was formed after crystallization of mixtures with Si02/Al203 = 100 for 7-10 days. Pure kenyaite was the main phase in the case of crystallization of the mixtures with Si02/Al203 = 200. The increase of the synthesis time up to 14 days leads to formation a-quartz [10]. Only slightly difference was observed between the samples crystallized with or without ball milling and without pretreatment. 

Figure 6 A conq)arison betweeen the activities of two different layered silicates, magadiite and kenyaite, as a fimction of their interlayer species. Alumina pillared kenyaite appears to have significantly more activity than a comparable pillared magadiite. This indicates a sensitivity towards the layered structure.

In order to systematically change the properties of layered silicate materials, we have investigated the possibility of isomorphous substitution of silicon by aluminum or boron. It is demonstrated that addition of horon and/or aluminum compounds to the reaction mixture leads directly to boron and aluminum containing layered materials in a hydrothermal crystallization process without further treatment. The layered materials obtained were identified as hectorite types, magadiite and kenyaite-like types. The isomorphous substitutions were proven by "B, Al, and Si solid state NMR spectroscopy. 

Figure 9.8 (A) Clayey and calcareous diatomite from northern Lake Chad. Various sedimentary layers can be seen they correspond to transition from a lacustrine environment (bottom) to a palustrine environment (top), from sub-arid to arid conditions. (Photograph courtesy of Professor A. Durand.) (B) Spherule-like crystals of kenyaite (hydrous sodium silicate) precipitated in apolyhaline interdunal ponds, Lake Chad.

Hitherto the most successful pillaring has been carried out on smectite type clays. The original research on pillaring included several series of unsuccessful experiments on mica, vermiculite and the sheet silicic acid minerals magadiite, silhydrite and kenyaite. Recently renewed attention has focused on these and other alternative sheet structures. They include rectorite, zirconium phosphates, tetrasilicic micas, hydrotalcites and silicic acids, the general structural features of which are shown in Figure 4. 

MontmoriUonite, bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sepioUte, stevensite, sauconite, sobockite, svinfordite, kenyaite... 

Kanemite, makatite, octosUicate, magadiite, kenyaite, layered organosiUcates... 

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