Sepiolite properties

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. 

Choudhury et al. [86] have studied the effect of polymer-solvent and clay-solvent interaction on the mechanical properties of the HNBR/sepiolite nanocomposites. They chose nine different sets of solvent composition and found that chloroform/methyl ethyl ketone (Qi/MEK) (i.e., HNBR dissolved in Ch and sepio-lite dissolved in MEK) is the best solvent combination for improvement in mechanical properties. XRD, AFM, , and UV-vis spectroscopy studies show that the dispersion of clay is best in the Ch/MEK solvent combination and hence polymer-filler interaction is also the highest. images shown in Fig. 14a, b clearly elucidate the aforementioned phenomena. Consequently, the tensile strength and modulus are found to be higher (5.89 MPa and 1.50 MPa, respectively) for the Ch/MEK system due to the minimum difference in interaction parameter of HNBR-solvent (xab) and sepiolite-solvent (Xcd)- Choudhury et al. have also studied the effect of different nanoclays [NA, , 15A, and sepiolite (SP)] and nanosilica (Aerosil 300) on the mechanical properties of HNBR [36]. The tensile... 

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... 

In our case, we have modified the sepiolite in order to improve the textural characteristics, while removing the Mg2+ ions of the border and introducing other cations which can give acid properties to this material. In the present work, the acidity, stability and textural properties of modified sepiolites are presented, and its implications in gasoil cracking and vanadium trapping have been studied. 

The fibrous structure of sepiolite is composed of talc-like ribbons with two sheets of tetrahedral silica units linked by oxygen atoms to a central octahedral sheet of magnesium. It has needle-shaped particles with chaimels oriented along the fibers which can absorb liquids. Sepiolite has three kinds of water hygroscopic water, crystallization water, and constitution water. The ciystallization water is removed at 500°C and constitution water is removed at 850°C at which point physical properties change brought about by ciystal folding of sepiolite. ... 

Effect on rheological properties sepiolite thennal treatment 81... 

Special considerations sepiolite treatment below 550°C does not alter the properties which modify the rheological properties of adhesives filler presence may affect adliesion (see Figure 8.54) rubber particles are hygroscopic and can absorb 1.4% moisture with the rate of 0.01% per minute (similar to carbon black) " ... 

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... 

Alkan, M.. Demirbas, O., and Dogan, M., Electrokinetic properties of sepiolite suspensions in differncl electrolyte media, J. Colloid Inter/. Sci., 281,240, 2005. 

The aim of the present work was to study the activity of Pt/titania/sepiolite monolithic catalysts prepared with different kinds of titania, in the reduction of NOx with propylene under oxidising conditions. The influence of the source of titania, titania content, heat treatment, presence of water vapour in the gas exhaust and area velocity on the activity, and on the structure and properties of the catalysts were investigated. 

The results of this study have been divided into four sections. In the first, the influence of the titania nature and sepiolite content on the catalysts activities were studied. The second deals with the influence of the heat pretreatment on both the textural properties of the support and activity of the catalysts. The phase distribution of platinum on the titania-sepiolite supports... 

To study the influence of the titania used in the support preparation on the properties of the catalyst, five different commercial titanias produced in industrial scale were used to prepare catalysts with 0.1 wt.% Pt supported on sepiolite/titania, 50 50, wt/wt, monoliths heat treated at 500°C. 

Table 2 summarises the main textural properties of the five titania-sepiolite, 50 50, wt/wt, supports (named after the titania type used in their preparation). The BET sur ce area gives the total surface area, while the MIP sur ce area is due to pores larger than 7 nm in diameter. Thus, the differences between both areas were due to narrow mesopores of less than 7 nm diameter. Characteristic mesopores of the sepiolite [12] were detected for A, B and E, which also showed a bimodal MIP pore size distribution. 

The results presented in this study on Pt-titania-sepiolite monolithic catalysts indicated that their activity in the reduction of nitrogen oxides with propene in the presence of 10% oxygen was strongly affected by the properties of the titania selected for the support s preparation. Thus, different industrially produced titanias had different textural properties, and these differences affected the textural properties of the titania-sepiolite monoliths (MIP total pore volume, MIP surface area, MIP pore size distribution and BET surface area) and the NOx... 

Sepiolite/ Palygorskite Phyllosilicates Marine sediments, arid soils, high Si and Mg levels R Moderately high CEC.15 surface area, and sorptive properties... 

This new single-step synthesis unites the simplicity of preparation and lower production costs, with the outstanding properties of the final catalysts. By the single-step procedure proposed here, deposition of dispersed nanoparticles of noble metals on ceramic supports with customised textural properties and shape was achieved. Noble metals including platinum, palladium, rhodium, ruthenium, iridium, etc. and metal oxides including copper, iron, nickel, chromimn, cerium oxides, etc on sepiolite or its mixtures with alumina, titania, zirconia or other refractory oxides have been also studied. 

Liquid-phase selective hydrogenation of ethyl linolate to ethyl oleate has been carried out on nickel catalysts supported on sepiolite as well as on several different supports. The influence of metal loading and Ni-Cu alloying has been studied as well. The results indicate that catalytic activity and selectivity correlate closely with some textural and/or acid-base properties of the support and selectivity increases with metal loading. Furthermore, as a general rule, Ni-Cu alloying improves in selectivity. 

Increasing attention is now on solid catalysts possessing both basic and shape selective properties to perform selective base-catalyzed fine organic chemical reactions [1-9]. Exchanged alkali zeolite demonstrated both these characters, however recent results show that these catalysts possess much less activity than sepiolites or hydrotalcites [10,11]. 

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