Synthesis sepiolite

Laboratory synthesis of aluminum-free sepiolite (Siffert, 1962 ... 

Wollast, et al., 1968) at 1 atmosphere, 25°C, demonstrates the inherent stability of this mineral at surface conditions. These experimental studies establish the necessity of an alkaline solution (pH 8) and sili v on-centration in aqueous solution controlled by the presence of amorphous silica (20-150 ppm). Calculations based upon laboratory synthesis data suggest that sepiolite could form in equilibrium with quartz (i.e., 10 ppm... 

The conditions necessary for artificial synthesis of smectites suggest the kind of natural environment in which these minerals will be found. This environment is alkaline as a result of restricted drainage and/or evaporative salt accumulation (see Chapter 8), so that the normally mobile alkaline and alkaline earth ions (Na, K, Ca, Mg) accumulate, along with silica. Neoformation of smectites from Na-rich saline water, and possibly illites from more K-rich water, is favored under these conditions. Other very silica-rich silicate minerals, such as attapulgites, sepiolites, and zeolites, are also known to fomi under these conditions. Less alkaline conditions may be necessary for Fe and Al-rich (dioctahedral) smectite formation, and a reducing environment may assist crystallization. 

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. 

From the results of the AAS experiments, we can conclude that most sepiolite structure is destroyed during the catalyst synthesis due to the loss of constitutional water. Thus, we may assume that the support in Ni/Sep catalysts is basically made up mostly of a 3Si02.2Mg0 amorphous mixture. However, X-Ray and TEM experiments indicate that a smaller portion of sepiolite structure remains undamaged. Thus, in Fig. 1 we can see metal particles supported on the typical noddies constituting the sepiolite structure. 

Femandez-Saavedra R, Aranda P, Ruiz-Hitzky E (2004) Templated synthesis of carbon nanofibers fiom polyacrylonitiile using sepiolite. Adv Funct Mater 14 77-82... 

Shafiq M, Yasin T, Saeed S (2012) Synthesis and characterization of linear low-density polyethylene/sepiolite nanocomposites. J Appl Polym Sci 123 1718-1723... 

Zhang FQ, Guo ZJ, Gao H, Li YC, Ren L, Shi L, Wang LX (2005) Synthesis and properties of sepiolite/poly (acrylic acid-co-acrylamide) nanocomposites. Polym Bull 55 419-428... 

In the chapter Dispersion of Inorganic Nanoparticles in Polymer Matrices Challenges and Solutions, the synthesis, properties, and applications of nanoparticles their surface modification and preparation of polymer-inorganic nanocomposites are reviewed in detail. The chapter Recent Advances on Fibrous Clay-Based Nanocomposites reviews recent results on nanocomposite materials derived from the fibrous clay silicates sepiolite and palygorskite and combined with diverse types of polymers, from typical thermoplastics to biopolymers such as polysaccharides, proteins, lipids, and nucleic acids. The chapter Nanohybrid Materials by Electrospinning highlights recent progress and current issues in the production of... 

Kitayama reported that Mn -exchanged sepiolite can be a selective catalyst for the synthesis of butadiene from ethanol.Butadiene can be produced also from alkali cation containig hectrite. ... 

B. Eren, G. Erdogan, Eco-friendly and efficient synthesis of benzimidazole derivatives using iron oxide modified sepiolite catalyst, Reac. Kinet. Mech. Cat. 107 (2012) 333-344. 

Figure 1. One pot synthesis route used for the synthesis of sepiolite supported CuOx-apphed for the production of scalable pelletised catalysts.

---