Direct hydrothermal synthesis

Direct hydrothermal synthesis. Prepared using titanium isopropoxide (triethanolaminato) and TEOS as the sources of Ti and Si, respectively, and the Gemini-type surfactant 18-12-18 or cetyl-benzyl dimethylammonium chloride (CBDAC) as a template. In the grafting method, silicious MCM-48 first prepared and then the dry surface grafted with titanium isopropoxide... 

The synthesis of titanium-containing beta zeolite has been carried out by direct hydrothermal synthesis and by secondary synthesis. In the direct synthesis with aluminum salts and titanium and silicon alkoxides, it is necessary to operate in the absence of alkalies, since these cause the formation of an amorphous precipitate containing Ti02 and Si02. Evidence for the substitution... 

Data concerning various Ox-Ti-P catalysts, their chemical analyses and the concentration of the ammonium titanyl oxalate solutions used are summarized in Table 1. These results indicate that the amount of Ti retained after the treatment depends on the concentration of the ammonium titanyl oxalate solution (samples 7 and 8) and on the type of counter-cations in the Al-P sample used for the treatment (samples 4, 5 and 8). The Ti content in Ox-Ti-P samples was always low compared to Ti levels that can be obtained by direct hydrothermal synthesis. It is interesting to notice that Na and ions were completely leached out upon treatment with ammonium titanyl oxalate and that Al was partially removed. In addition, there are indications that everything being equal, higher levels of Ti may be obtained when the Na or K-form of zeolite P are used rather than the NH4- or H-form. 

Corma[7] has prepared Ti-MCM-41 by direct hydrothermal synthesis. Ti-MCM-41 is the first example of ordered mesoporous titanosilicates, and catalytic results exhibited good properties for the oxidation of bulky reactants under mild conditions. 

Mo-containing MCM-41 has been prepared by direct hydrothermal synthesis and characterized by XRD, IR, TGA and N2 adsorption measurements, Though the state of Mo in MCM-41 is not clear, they are found to be stable and active for cyclohexanol and cyclohexane oxidation reactions. Activity has been compared with that of Ti-MCM-41 and impregnated Mo on pure siliceous MCM-41. 

Iron is introduced into the framework of three different zeolite-types MFI, MTW and TON by direct hydrothermal synthesis from alkaline reaction mixtures containing iron complexes (oxalate or phosphate). The synthesis conditions for each zeolite-type and the results on the characterization of the samples by XRD, AAS, thermal analysis, SEM and Si-, C- and P-NMR spectroscopy are discussed. 

V-beta BE A V2OS Amorphous silica TEAOH Direct hydrothermal synthesis 140 °C, 20 days Chien, 1997 (61)... 

CrAPSO-11 Cr + in calcined and ion-exchanged samples Cr most probably in the P framework sites in calcined sample ESR, ESEM Preparation by direct hydrothermal synthesis or postsynthetic ion exchange (218)... 

Zhao, X. and Wang, X. (2010). Characterizations and Catalytic properties of chromium silicalite-2 prepared by direct hydrothermal synthesis and impregnation, Catal. Lett., 135, pp. 233-240. 

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