Incorporation during hydrothermal synthesis

Present data do not justify the attribution of this V species to a real substitutional V site in the zeolite framework, because the amount of these V sites is very low and at present the degree of incorporation of these sites in the zeolite cannot be extended. It is therefore reasonable to assume that these V sites form at defect sites, possibly hydroxyl nests, the formation of which may be enhanced by the presence of V during hydrothermal synthesis, in agreement with Rigutto and van Bekkum (5). 

Incorporation of Phthalocyanines into the Molecular Sieve Si-MCM-41 during Hydrothermal Synthesis (Section 8.2.2) [56]... 

The two most obvious and common ways to incorporate matter into zeolite pores are (i) by adsorption and diffusion from gas or liquid phase, and (ii) by ion exchange. A third, usually more difficult approach involves incorporation of species during hydrothermal synthesis. The zeolite pores can be viewed as nanometer size reaction chambers that accommodate numerous organic and inorganic molecules with enough space for chemical conversions. It follows that there is a vast potential for ingenious chemistry in these hosts. 

Pt(NH3) ions since the molecular dimensions of these metal complexes exceed the pore apertures. Platinum was incorporated during the synthesis of the zeo-hte by mixing solutions of K2PtCl4 with solutions of sodium metasiUcate and sodium aluminate in the required amounts. More recently, Davis et al. [129,130] prepared intrazeoHtic 2-5 nm ruthenium particles in NaA and CaA zeoHtes by addition of [Ru(NH3)5Cl] CI2 to the hydrothermal synthesis mix of zeolite A. This technique of metal loading has never been widely used to prepare metal clusters in zeolites but is frequently employed to substitute lattice aluminum in zeoHtes or aluminophosphates by metal ions. 

Zeolite synthesis around a metal complex was introduced by Balkus [40]. The metal complex is added to the zeolite synthesis mixture and is incorporated into the zeolite structure during the zeolite synthesis. Of course, this procedure is only applicable when the metal complex is soluble in the synthesis mixture and can withstand the hydrothermal synthesis conditions. Another requirement is that the zeolite structure-directing agent added must be removable by a milder... 

The amount of titanium incorporation has been increased from the Si/Ti ratio of 490 to that of 56 for Ti-MCM-41-Ph and from 570 to 52 for Ti-MCM-41-Me when the hydrothermal treatment at87°C was applied during the synthesis. Ti-incorporation into the framework was favored in the hydrothermal treatment. 

Niobium and titanium incorporation in a molecular sieve can be achieved either by hydrothermal synthesis (direct synthesis) or by post-synthesis modification (secondary synthesis). The grafting method has shown promise for developing active oxidation catalyst in a simple and convenient way. Recently, the grafting of metallocene complexes onto mesoporous silica has been reported as alternate route to the synthesis of an active epoxidation catalyst [21]. Further the control of active sites, the specific removal of organic material (template or surfactant) occluded within mesoporous molecular sieves during synthesis can also be important and useful to develop an active epoxidation catalyst. Thermal method is quite often used to eliminate organic species from porous materials. However, several techniques such as supercritical fluid extraction (SFE) and plasma [22], ozone treatment [23], ion exchange [24-26] are also reported. 

A novel method has been developed for hydrothermal synthesis of zeolite beta with high chromium content and low aluminum content under static conditions. The crystalline phase and spectroscopic property of this material were characterized by means of XRD, XRF, IR, UV-Vis DRS, ESR and SEM. The results revealed that part of the chromium ions were incorporated into the zeolite framework during crystallization. Using tris(acetylacetonato) chromium(III), [Cr(C5H702)3], as a chromium source, Cr/Si molar ratio can be up to 1/48 in the calcined and ion-exchanged sample. The chromium aluminosilicate exhibited a high oxidative activity in the presence of dilute H2O2. 

Various metal complexes such as metal phthalocyanines, metal salenes or Ru pyridyl complexes have been incorporated in molecular sieves such as cavity-structured zeolites (faujasites, supercages with 1.3-nm diameter), channel-structured aluminium phosphates (AIPO4-5, channel diameter 0.73 nm) and channel-structured silicates MCM-41 (channel diameter 3.2 nm) [51-53]. Different strategies were applied for the inclusion of the phthalocyanines. For example, whereas the zeolite-encaged phthalocyanines (1 R = -FI M = Co(II), Ru(II), etc.) are synthesized by the reaction of a transition metal ion-exchanged zeolite with phthalonitrile in a closed-bomb vessel [54], in the cases of AIPO4-5 and MCM-41 substituted derivatives of phthalocyanines were added to the mixture during the hydrothermal synthesis of the molecular sieve [55,56]. 

Organically modified mesoporous titanium-substituted MCM-41 materials (Ti-MCM-41-R, R= C6H5, CH3) have been synthesized. These materials show higher hydrophobicity than unmodified Ti-MCM-41. This high hydrophobicity has a strong influence on the activity improvement in the oxidation of alkenes with H202. Furthermore, hydrothermal treatment during synthesis has increased titanium incorporation. 

AFX), SAPO-18 (AEI), SSZ-39 (AEI), [Ga]SSZ-13 (CHA), ZK-5 (KFI), and STA-7 (SAV) have also been reported to exhibit the same properties [58-63], In addition, catalysts with Cu being incorporated into the small-pore zeolite matrix during the zeolite synthesis step, instead of a post ion-exchange step, have also been found to show excellent SCR activity and hydrothermal stability [63-66],... 

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