Silica mesoporous materials preparation

Time-resolved in situ Small Angle Neutron Scattering (SANS) investigations have provided direct experimental evidence for the initial steps in the formation of the SBA-15 mesoporous material, prepared using the non-ionic tri-block copolymer Pluronic 123 and TEOS as silica precursor. Upon time, three steps take place during the cooperative self-assembly of the Pluronic micelles and the silica species. First, the hydrolysis of TEOS is completed, without modifications of the Pluronic spherical micelles. Then, when silica species begin to interact with the micelles, a transformation from spherical to cylindrical micelles takes place before the precipitation of the ordered SBA-15 material. Lastly, the precipitation occurs and hybrid cylindrical micelles assemble into the two-dimensional hexagonal structure of SBA-15. 

SEM micrographs of the mesoporous materials prepared from C 6TMAB-HN03-TE0S-H20 composition, with and without the addition of PEO-6000 polymer, are shown in Fig. 1. In the absence of this polymer additive, mesoporous silica with gyroidal particulate morphology (Fig. 1 A) was formed even under the shear flow conditions. On the other hand, the addition of this polymer promotes the formation of mesoporous silica materials with millimeter-sized, rope-... 

Impregnated Mesoporous Materials are prepared as following a certain amount (see notation) of alkali, alkaline earth or/and rare earth salt is added to 5 g of pure silica or aluminosilica mesoporous material, prepared (with cetyltrimethylammonium bromide) as previously described [4] and 50 g of methanol. The mixture is agitated at ambient temperature during 2 hours, the solvent is then rapidly evaporated under vacuum and the solid is calcined under air at 450°C overnight at a heating rate of l°C/min. Notation ... 

The possible compositions for the walls of the ordered mesoporous materials go beyond the field of inorganic chemistry, and materials with hybrid organosilica walls have been prepared [81-84], Some mesoporous benzene-silica hybrids are stable at a temperature higher than 500 °C [84], Mesoporous materials prepared from polysilazanes and nonionic surfactants can be activated to form silicon carbonilride ceramics, which retain an ordered mesoporosity up to 1500 °C [85],... 

Not surprisingly other cationic surfactants and the alternative surfactant systems listed in Table 1 were also able to generate the three basic structures. The cubic MCM-48 type was most difficult to synthesize and consequently quite rare. Other types of surfactants and/or alternative media (acidic or neutral) allowed preparation and recognition of additional structural kinds of mesoporous materials (which could also be correlated with certain g values). More than 20 types of silica mesoporous materials are listed in a recent compilation as unique in terms of structure and/or method of assembly [18]. Several new cubic structures... 

The second case study. This involves all silica micro- and mesoporous SBA-15 materials. SBA-15 materials are prepared using triblock copolymers as structure-directing templates. Typically, calcined SBA-15 displays pore sizes between 50 and 90 A and specific surface areas of 600-700 m g with pore volumes of 0.8-1.2cm g h Application of the Fenton concept to mesoporous materials looks simpler since mass transfer would be much less limited. However, it is not straightforward because hydrolysis can take place in the aqueous phase. 

The parent siliceous materials of the SBA-15 and MLV types were synthesised after typical procedures [2], The carbon replicas were prepared via polymerisation, catalysed by ferric chloride, of pyrrole introduced into the mesopores of matrices [3]. The products were characterised by the nitrogen adsorption, TEM, and thermal analysis (DTG, DTA). The nitrogen content in carbons was determined using elemental analysis, XPS, and EDX, while the Si and Fe contents, with XPS. The replicas of SBA-15 and MLV-0.75 are denoted as CMK-3Nx and OCM-.Nx, respectively, were x refers to the number of g of FeCl3 per 1 g of silica used for preparations. 

The synthetic procedure for preparing the MCM-41 mesoporous materials is based on the delayed-neutralization process reported in our previous paper.[l 1] The silica source is sodium... 

The silica forms of MCM-41, MCM-48, KIT-1, HMS, and SBA-1 were prepared by hydrothermal synthesis following the methods reported in the literature [1,2,3,4,7]. The calcined mesoporous materials were slurried in absolute isopropyl alcohol solution containing TIPOT (10wt%) with magnetic stirring at room temperature for 3h. The solid products obtained were then washed with absolute isopropyl alcohol, dried and calcined in air at 823K... 

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

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