M41S materials synthesis

Synthesis of M41S mesoporous materials was attempted using MFI type zeolite as sources of silica and aluminum, that is, dissolution of MFI zeolite in an alkaline solution and successive precipitation of dissolved aluminosilicate species with a surfactant, cethyltrimethylammonium bromide (CTAB). Pure phase of M41S was obtained when the filtrate of alkali-treated slurry was mixed with CTAB and crystallized at 293K. The M41S materials obtained in this method showed a catalytic activity originated from Bronsted acid site of the parent MFI zeolite. This method enables us to obtain a new type of mesoporous materials, which have both characteristics of zeolitic and mesoporous materials a strong Bronsted acidity and mesopores with a uniform size. 

Ordered Mesoporous Molecular Sieves (M41S Materials), 283 Synthesis Pathways for Ordered Mesoporous Materials, 284 Ordered Mesoporous Silica, 288 Fimetionalization of Mesoporous Materials, 296 Nonsdiceous Mesostructured and Mesoporous Materials, 302 Morphology, 309... 

Keywords Structure-Directed Synthesis / Mesoporous Materials / Mesostructured Materials / Trialkoxysilanes / M41S Materials... 

The key aspect of the LCT mechanism is that the liquid crystalline mesophases or micelles act as templates rather than individual single molecules or ions. Accordingly, the final product is an inorganic (e.g., silicate) skeleton that contains voids, mimicking the shape of the surfactant mesophases. This mechanism, first proposed by researchers at the Mobil Corporation for the synthesis of M41S materials, is based on similarities between liquid-crystalline surfactant assemblies and the resulting mesoporous solid product. The whole process can be described by two possible mechanistic pathways, which are represented schematically in Fig. 4. 

In case of post synthesis, many research groups have used porous materials (M41S) as support. The pore surface of M41S materials has a number of silanol groups which present as ideal anchor groups. For example, Belkacemi et al. [53] studied mono, di-, and tri-ammonium-functionalized mesoporous SBA-15 silica for the adsorption of monovalent phosphate anions from aqueous solutions via post-synthesis grafting. 

Vartuli J C, Roth W J, Beck J S, McCullen S B and Kresge C T 1998 The synthesis and properties of M41S and related mesoporous materials Moiecuiar Sieves Science and Technoiogy vol 1, ed FI G Karge and J Weitkamp (Berlin Springer) pp 97-119... 

MCM-50 consists of stacks of silica and surfactant layers. Obviously, no pores are formed upon removal of the surfactant layers. The silica layers contact each other resulting in a nonporous silica. It is noteworthy to mention that materials of M41S type were probably already synthesized by Sylvania Electric Products in 1971 [32], However, at that time the high ordering of the materials was not realized [33], M41S-type materials are synthesized under basic reaction conditions. Scientists from the University of Santa Barbara developed an alternative synthesis procedure under acidic conditions. They also used alkyltrimethyl ammonium as the surfactant. The porous silica materials obtained (e.g., hexagonal SBA-3 Santa BArbara [SBA]) had thicker pore walls but smaller pore diameters. Furthermore, they developed materials with novel pore topologies, e g., the cubic SBA-1 with spherical pores. 

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