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Y4.10.1

Hydrothermal Synthesis of Mechanically Strong Porous Composites of MeOx/Al2O3/Altype. Sergey F. Tikhov, Vladislav A. Sadykov, Yulia V. Potapova, Ivan V. Yudaev, Olga B. Lapina, Sergey V. Tsybulya, Aleksey N. Salanov, Aleksandr I. Titkov. Boreskov Institute of Catalysis SB RAS, pr.Lavrentieva, 5, 630090, Novosibirsk, Russia. ABSTRACT The impact of powdered oxides of Mg, Ca, La, Ti, Al or their nitrate salts on the properties of MeOx/Al2O3/Al composites obtained via the hydrothermal treatment (HTT) of Al-based blends put in a closed space of the die allowing the free water vapor access has been studied. Additives were found to affect the process of aluminum oxidation mainly through variation of the density of formed aluminum hydroxide layer. In some cases, incorporation of dopant cations into the structure of alumina formed after calcination of composite in air was revealed by 27Al MAS NMR. Variation of the Al oxidation degree and associated change of the solid phase volume in a closed die caused by dopants affects also the pore structure and texture of composites determining the mechanical strength of produced monoliths. The processes of the redistribution of soluble additives between the solid phase and autoclave solutions were revealed and their consequences are considered. INTRODUCTION The low-temperature oxidation of aluminum powder placed in a special die and subjected to the action of the liquid water or its vapor at temperatures and pressures exceeding those corresponding to the normal boiling point of water is known to produce powdered materials promising as catalyst supports and adsorbents due to their high porosity, thermal conductivity and crushing strength [1, 2]. This method permits to obtain Al2O3/Al composites as monolithic materials of various shapes. The hydrothermal oxidation of Al powder blended with some MeOx additives results in their encapsulation in the Al2O3/Al matrix. This appears to be a promising procedure for the preparation of shaped catalysts through the encapsulation of powdered active components [2, 3]. The hydrothermal oxidation of Al in an autoclave filled by solutions of metal (Me) nitrates permits to obtain composites with varied textural and structural properties. This work aims at developing approaches for controlling the structure and texture of such cermets as catalytic supports by adding some oxides (Ca, Mg, La, and Ti) to Al powder before HTT or via transfer of salts dissolved in the water in an autoclave. EXPERIMENTAL As starting materials, Al0 powder (commercial PA-4 grade) as well as oxide powders (MgO, CaO, TiO2, "La2O3") prepared through the thermal decomposition of corresponding metal nitrates at 7000C and commercial γ-Al2O3 (A-1 type) oxide were used. According to XRD data, in the sample of titanium oxide, the rutile phase dominates, though an admixture of the anatase phase was detected as well. MgO, CaO and Al2O3 exhibit typical diffraction patterns of the cubic structures of these oxide phases. In the case of “La2O3”, due to comparatively low temperature of