Transition metal ions mesoporous molecular sieves

Jhung, S.H., Lee, J.H., and Chang, J. (2008) Crystal size control of transition metal ion-incorporated aluminophos-phate molecular sieves effect of ramping rate in the syntheses. Micropor. Mesopor. Mater., 112, 178-185. 

The use of microporous solid catalysts such as zeolites and related molecular sieves has an additional benefit in organic synthesis. The highly precise organization and discrimination between molecules by molecular sieves endows them with shape-selective properties [12] reminiscent of enzyme catalysis. The scope of molecular sieve catalysis has been considerably extended by the discovery of ordered mesoporous materials of the M41S type by Mobil scientists [13,14]. Furthermore, the incorporation of transition metal ions and complexes into molecular sieves extends their catalytic scope to redox reactions and a variety of other transition metal-catalyzed processes [15,16]. 

P-07 - Photoionization of N-alkylphenothiazines in transition-metal-ion modified mesoporous silica SBA-15 molecular sieves... 

The most widely used industrial routes to propylene oxide (PO) are based on the chlorohydrin process or hydroperoxide methods. Much attention has also been directed to processes performed in the presence of hydrogen peroxide in the liquid phase with a TS-1 molecular sieve as the catalyst, iron complexes accommodated in amorphous SBA-15 and MCM-41 modified with alkaline metal salts, and SBA-3 mesoporous molecular sieves doped with transition metal ions (Fe, V, Nb, and Ta). 

The development of mesoporous materials with more or less ordered and different connected pore systems has opened new access to large pore high surface area zeotype molecular sieves. These silicate materials could be attractive catalysts and catalyst supports provided that they are stable and can be modified with catalytic active sites [1]. The incorporation of aluminum into framework sites of the walls is necessary for the establishment of Bronsted acidity [2] which is an essential precondition for a variety of catalytic hydrocarbon reactions [3], Furthermore, ion exchange positions allow anchoring of cationic transition metal complexes and catalyst precursors which are attractive redox catalytic systems for fine chemicals [4]. The subject of this paper is the examination of the influence of calcination procedures, of soft hydrothermal treatment and of the Al content on the stability of the framework aluminum in substituted MCM-41. The impact on the Bronsted acidity is studied. 

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