Surfactant stabilizer synthesis templating

Nanocrystals, anatase Nanocrystals, offretite Nanoemulsion template Nanoparticles agglomerates, MFI Nanoparticles, Au Nanoparticles, Fe203 in MCM-41 Nanoparticles, Sn02 Nanoparticles, surfactant stabilized Nanoparticles, Zr02 in SBA-15 Nanoscopic precursor particles Nanoslabs, silicalite-1 Nanowires in FSM-16 Nanowires, Se in MFI Naphtha isomerisation Naphthalene isopropylation Naphthalene alkylation 25-0-03 25-P-Naphthene ring opening S-Naproxen synthesis... 

Ordered mesoporous materials of compositions other than silica or silica-alumina are also accessible. Employing the micelle templating route, several oxidic mesostructures have been made. Unfortunately, the pores of many such materials collapse upon template removal by calcination. The oxides in the pore walls are often not very well condensed or suffer from reciystallization of the oxides. In some cases, even changes of the oxidation state of the metals may play a role. Stabilization of the pore walls in post-synthesis results in a material that is rather stable toward calcination. By post-synthetic treatment with phosphoric acid, stable alumina, titania, and zirconia mesophases were obtained (see [27] and references therein). The phosphoric acid results in further condensation of the pore walls and the materials can be calcined with preservation of the pore system. Not only mesoporous oxidic materials but also phosphates, sulfides, and selenides can be obtained by surfactant templating. These materials have pore systems similar to OMS materials. 

In this presentation, several synthesis parameters have been investigated in order to improve the thermal stability of the Ti-Zr containing phosphorus-free mesoporous oxides by using either single surfactant, i.e., cetyltrimethylammonlum bromide (CTAB) or mixed surfactants, i.e., CTAB and dodecylamine (DDA) as the templating agent under hydrothermal conditions. 

High quality HMS was repeatedly and reproducibly prepared by a novel extraction procedure to remove the primary amine template using acidified water. This very efficient extraction (100%) does not affect the physical properties of the resulting mesostructure. Compared to the ethanol-extracted HMS, no subsequent calcination step is required to remove the surface ethoxy groups produced during the ethanol extraction. Moreover, the recovered surfactant can be easily re-used in a fresh synthesis. Furthermore, an improved hydrothermal stability was observed after using the acidified water extraction procedure. 

Oxides Compared to silica-based networks, nonsiliceous ordered meso-poious materials have attracted less attention, due to the relative difficulty of applying the same synthesis principles to non-sihcate species and their lower stability (227). Nonsiliceous framework compositions are more susceptible to redox reactions, hydrolysis, or phase transformations to the thermodynamically preferred denser crystalline phases. Template removal has been a major issue and calcination often resulted in the collapse of the mesostracture. This was the case for mesostractured surfactant composites of mngsten oxide, molybdenum oxide, and antimony oxide, and meso-structured materials based on vanadia that were obtained at early stages. Because of their poor thermal stability, none of these mesostructures were obtained as template-free mesoporous solids (85, 228, 229). 

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