Sepiolite thermal

Effect on rheological properties sepiolite thermal treatment 81... 

In this paper, XPS and Raman spectroscopy have been used to study the chemical state and location of Ni and V contaminants. The effects of thermal and hydrothermal treatments on catalyst surface properties, and the role of sepiolite in promoting metals tolerance has been observed and reported. 

Differential thermal analysis (DTA) data was obtained using a DuPont 1090 thermal analyzer using 0.04 SCF/h of air as purging gas and heating rates of 10°C/min. All powder diffraction measurements were obtained with a Siemens D-500 diffractometer at a scan rate of l°/min using monochromatic Cu-K radiation. The preparation of DFCC mixtures containing sepiolite hSs been described elsewhere (4). 

High pressure studies using natural sepiolite and palygorskite (Frank-Kameneckiji and Klockova, 1969) indicate that these minerals can contain variable quantities of silica because they exsolve quartz while retaining their basic structural and mineral identity. These experiments also demonstrate that the natural minerals are compositionally intermediate between talc or montmorillonite and quartz. These latter phases are formed upon the thermal breakdown of sepiolite and palygorskite under conditions of 1 and 2Kb total pressure. Both sepiolite and palygorskite appear to remain stable in sequences of buried rocks, at least up to the depth where fully expandable dioctahedral montmorillonite disappears (Millot, 1964). 

Figure 43. Phase diagram of phyllosilicates found above the thermal stabilities of sepiolite and palygorskite in the system Si-R -R. ...

As a parenthesis, Figure 42 shows the system Si-R -R as it appears above the thermal stability limits of sepiolite and palygorskite. This is based upon the experiments of Velde (1973) in the Mg-Al-Si-H20 system at 2Kb pressure and temperatures above 200°C, and the experiments at high pressure of Frank-Kameneckiji and Klockova (1969) on natural sepiolite. 

Currently, a wide range of technological applications is based on the sorptive and catalytic properties of sepiolite [2], Sepiolite is increasingly being used as a decolorizing agent [3], as a catalyst or catalyst carrier [4-6], and as odorant adsorbents in environmental applications [7-9], Several papers have appeared recently that examine the structural, textural and sorptive properties of untreated sepiolite [10-12] and of sepiolite subjected previously to acid and/or thermal treatment [13-16], Sepiolite has also been used recently as... 

Sepiolite (SepSp-1) was obtained from the Source Clay Mineral Repository (University of Missouri) and was used without additional purification. Thermal treatment was carried out for 19-20 hours under air in a baffle furnace, using 0. l-0.2g sepiolite that had been gently ground in a mortar and passed through a 100-mesh sieve. The vials containing dried sepiolite were transferred into capped bottles containing a few milliliters of acetone (acetone-d6 for the broad line 2H NMR experiments) and then remained in contact with the acetone vapor at room temperature for 4 days. 

The hydrothermal stability of the SA1 sample has been compared with that of the original SMg in Figure 6. The X-Ray diffraction pattern of an A1 sepiolite before (a) and after (b) steaming at 700aC, 100% steam and a natural sepiolite (SMg) also steamed at 7000C (c). The results indicate that after this thermal treatment an important fraction of the aluminic sepiolite remains unalterated, while the natural sample is completely folded. The folding of the sepiolite is shown by the disappearance of the (1,10) reflexion at 7.2, 20, and the appearance of a new reflexion at 8.9, 20 (16). Moreover, the adsorption of pyridine shows the presence of a residual Bronsted acidity in the SA1 after the hydrothermal treatment which is approximately 30% of the untreated sample. 

The selection of the more suitable nature for a porous support was based in the criteria of thermal and thermo dynamical stability (AG 0, chemically inert support) in the sulfurization step. The melting temperatures of 1000 C or higher, are required because zinc ferrite phase is prepared about 950 C. One representative material from each of the aforementioned categories has been selected for the preparation of every supported sorbent Coimnereial sepiolite (Tolsa, S.A., Spain), USY zeolite (Zeolyst Ine., U.K.), and Zr02, m.p. 2500°C,... 

Sepiolite was subjected to a thermal treatment which removes crystallization water at 500 C and constitution water at 850°C. When these changes occur, they are accompanied by crystal folding which introduce substantial changes in the structure and interaction capabilities of sepiolite. Treated and untreated sepiolites were used in the preparation of a polyurethane adhesive to determine if the modification impacts the properties of the adhesive such as its interaction with polymer essential for its performance in adhesive. Figure 19.1 shows the effect of treatment... 

Hubbard, B., Kuang, W., Moser, A., Facey, G.A., and Detellier, C. 2003. Structural study of Maya blue Textural, thermal and solid-state multinuclear magnetic resonance characterization of the palygroskite-indigo and sepiolite-indigo adducts. Clays and Minerals 51,318-326. 

S. Mir, T. Yasin, P.J. Halley, H.M. Siddiqi, O. Ozdemir, A. Nguyen, Thermal and rheological effects of sepiolite in linear low-density polyethylene/starch blend. J. Appl. Polym. Sci. 127, 1330-1337 (2013)... 

Tartaglione et al. [62] have recently studied the thermal behavior of melt-compounded PP/sepiolite composites (3 wt% loading) and the effect of the clay surface modification. In inert atmosphere, the catalytic activity of sepiolite on PP pyrolysis was confirmed, except for the begiiming of the degradation process (less than 20% of mass loss) where the presence of the clay improved the polymer stability (Figure 12.21a). This was explained by the adsorption of PP volatile products by the sepiolite external surface and internal zeolitic channels. 

Acosta, J. L., Ojeda, M. C., Morales, E., and Linares, A. 1986. Morphological, structural, and interfacial changes produced in composites on the basis of polypropylene and surface-treated sepiolite with organic-acids. 2. Thermal properties, loumal of Avolied Polymer Science 31 1869-1878. 

Tartaglione, G., Tabuani, D., Camino, G., and Moisio, M. 2008. PP and PBT composites filled with sepiolite Morphology and thermal behavior. Composites Science and Technology 68 451M60. 

The incorporation of 5 % organically modified sepiolite, which is a microcrystalline-hydrated magnesium silicate, in a bisphenol A-based epoxy resin has no significant effect over the thermal stability of the epoxy resin, due to the poor dispersion of the clay and poor diffusion of the resin between fibres [69]. The effect of attapulgite (magnesium aluminium phyllosilicate) over the thermal properties of hyperbranched polyimides was studied. The presence of this silicate in the nanocomposites significantly improved the thermal stability of the neat polyimide [70]. 

Nohales, A., Solar, L., Porcar, I., Vallo, C.I., Gomez, C.M. Morphology, flexural, and thermal properties of sepiolite modified epoxy resins with different curing agents. Eur. Polym. J. 42, 3093-3101 (2006)... 

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