Liquid microporous mixed oxide catalysts

The activity exhibited by the pretreated G-66A catalyst could be attributed to the presence of a CuVCu redox couple in a spinel matrix. This is also in agreement with previous studies where catalytic activity of mixed oxide catalysts with a spinel structure in the phenol oxidation was found to be higher than that of the pure oxides [11, 12]. On the other hand, the specific catalytic activity of molecular sieves is limited by the concentration of isolated redox centres located in the microporous voids or in the fiamework. Although molecular sieves have a much lower concentration of metals (Table 1), they show fairly good activity for liquid-... 

Abstract. Nanocarbon materials and method of their production, developed by TMSpetsmash Ltd. (Kyiv, Ukraine), are reviewed. Multiwall carbon nanotubes with surface area 200-500 m2/g are produced in industrial scale with use of CVD method. Ethylene is used as a source of carbon and Fe-Mo-Al- mixed oxides as catalysts. Fumed silica is used as a pseudo-liquid diluent in order to decrease aggregation of nanotubes and bulk density of the products. Porous carbon nanofibers with surface area near 300-500 m2/g are produced from acetylene with use of (Fe, Co, Sn)/C/Al203-Si02 catalysts prepared mechanochemically. High surface area microporous nanocarbon materials were prepared by activation of carbon nanofibers. Effective surface area of these nanomaterials reaches 4000-6000 m2/g (by argon desorption method). Such materials are prospective for electrochemical applications. Methods of catalysts synthesis for CVD of nanocarbon materials and mechanisms of catalytic CVD are discussed. 

Sol-gel chemistry (Chapter 5) is a preparation method, which can easily be adapted to synthesis robots. The application of this method to high-throughput catalysis was first described by the group of Maier, who prepared amorphous microporous mixed-metal oxides in small cavities of a carrier slate plate [95, 96]. Libraries of doped Ti02, Sn02, and WO3 have been prepared in larger amounts in sets of HPLC flasks [97]. The robot-assisted sol-gel preparation has been applied to mixed-metal oxide catalysts of various composition and the catalysts have been tested for several reactions in gas phases as well as in liquid phase (see Table 11.3). 

The most efficient catalysts in liquid-phase oxidation of organic compoimds were crystalline mked oxides [1]. They are ionic mixed oxides or mixed oxides containing oxides supported on oxides. In the latter case, the catalytic activity of the oxide support is increased by adding one or more metal components or is obtained by immobilization of metal oxides on inactive oxide support. Metal ions were isomorphously substituted in framework positions of molecular sieves, for example, zeolites, silicalites, silica, aluminosilicate, aluminophosphates, silico-aluminophosphates, and so on, via hydrothermal synthesis or postsynthesis modification. Among these many mixed oxides with crystalline microporous or mesoporous structure, perovskites were also used as catalysts in liquid-phase oxidation. 

Palazzi C., Oliva L., Signoretto M., Strukul G., Catal J. Microporous zirconia-silica mixed oxides made by sol-gel as catalysts for the liquid-phase oxidation of olefins with hydrogen peroxide. J. Catal. 2000 194 286-293... 

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