Organic templating

In zeolite synthesis (ref. 2) an aqueous mixture containing a silicon source, an aluminum source, an alkali source (usually NaOH) is autoclaved and subjected to hydrothermal treatment. Hydrated Na-ions are then filling the pore system in the as-synthesized zeolite. In the case of relatively high Si/Al zeolites an organic template is required which is usually a tetraalkylammonium compound, applied as the bromide or the hydroxide. 

Thermal treatments can be applied to modify the properties of a material, for example, dealumination and optimization of crystalHne phases. These techniques do not require oxidants. Oxidative thermal treatments are generally employed to activate molecular sieves, by removing the organic templates employed during synthesis. This is one of the key steps when preparing porous catalysts or adsorbents. In air-atmosphere calcination, the templates are typically combusted between 400... 

We discuss here a combined process including detemplation and Fe incorporation by ion-exchange in the zeolite framework [147]. To achieve this, oxidants to decompose the organic template and Fe-cations for exchange are needed. Both requirements are in harmony with Fenton chemistry. The OH radicals can oxidize the template and the Fe-cations be exchanged simultaneously. 

Third Concept in Catalyst Design. Fenton Detemplation. Mild Organic Template Removal in Micro- and Mesoporous Molecular Sieves... 

Role of Organic Templates and Drawbacks Associated to Calcination... 

The organic templating approach was first introduced by Barrer and Deimy... 

The approach consists of a liquid-phase oxidation using OH Fenton radicals from H2O2 for detemplation [148-150]. The radicals oxidize the organic template into CO2 and H2O while the porosity of the material is developed. The proof-of-principle of this concept is discussed for two case studies. 

Controlled and selective combustion of components via thermal or chemical routes Calcination. Thermal detemplation of organic templates in micro- and mesoporous materials. Chemical detemplation protocols. Solution combustion synthesis... 

Abstract A review of the thermolytic molecular precursor (TMP) method for the generation of multi-component oxide materials is presented. Various adaptations of the TMP method that allow for the preparation of a wide range of materials are described. Further, the generation of isolated catalytic centers (via grafting techniques) and mesoporous materials (via use of organic templates) is simimarized. The implications for syntheses of new catalysts, catalyst supports, nanoparticles, mesoporous oxides, and other novel materials are discussed. 

In order to prepare functional particles, it is important to control the size of metal particles accurately. To achieve such size controlled synthesis of metal particles, inorganic or organic templates are useful to suppress the growth of metal particles. 

Traditional methods for fabricating nano-scaled arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of self-organizing templates. Due to their intrinsic ability to adopt complex and flexible conformations, proteins have been used to control the size and shape, and also to form ordered two-dimensional arrays of nanopartides. The following examples focus on the use of helical protein templates, such as gelatin and collagen, and protein cages such as ferritin-based molecules. 

Keywords AlP04-5, hydrothermal synthesis, organic template, FT-Raman, XRD. 

Fig. 2 shows the XRD patterns of the as-synthesized AIPO4-5 obtained using MCHA, TEA, TP A, and TEAOH templates. Strong reflections due to AlP04-5 phase at around 2 theta = 7.43, 14.89, 19.74, 20.97, 22.38, and 25.94° [7] were observed with all organic templates. Furthermore, pure AlP04-5 phase was obtained. This ensures the ability of all templates used here to form AlP04-5 under this synthesis conditions. 

Figure 2 XRD pattern of the as-synthesized AlP04-5 using MCHA, TEA, TP A, and TEAOH organic templates. Reflections due to A1P04-5 are marked by ( ).

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