Mixed oxides textural properties

Sol-gel process allows excellent control of the synthesised mixed oxide textural properties, such as surface area and pore volume. Within the sol-gel process, relative precursor reactivity can be used to control homogeneity [2]. 

Catalyst characterization - Characterization of mixed metal oxides was performed by atomic emission spectroscopy with inductively coupled plasma atomisation (ICP-AES) on a CE Instraments Sorptomatic 1990. NH3-TPD was nsed for the characterization of acid site distribntion. SZ (0.3 g) was heated up to 600°C using He (30 ml min ) to remove adsorbed components. Then, the sample was cooled at room temperatnre and satnrated for 2 h with 100 ml min of 8200 ppm NH3 in He as carrier gas. Snbseqnently, the system was flashed with He at a flowrate of 30 ml min for 2 h. The temperatnre was ramped np to 600°C at a rate of 10°C min. A TCD was used to measure the NH3 desorption profile. Textural properties were established from the N2 adsorption isotherm. Snrface area was calcnlated nsing the BET equation and the pore size was calcnlated nsing the BJH method. The resnlts given in Table 33.4 are in good agreement with varions literature data. 

New Fe-Mo-Ti mixed oxides prepared via the sol-gel method comparison of the textural properties with solids obtained by impregnation... 

The aim of this work is to develop new Fe-Mo containing mixed oxides highly dispersed in a titania matrix, prepared by the sol-gel method, and to compare these materials to those of iron molybdate prepared by conventional methods (i.e. impregnation). Here, we report the preparation of sol-gel derived iron molybdenum titanium mixed oxides. The bulk composition and the textural properties of these materials are investigated by elemental chemical analysis and N2 adsorption, respectively. 

Nitrogen adsorption-desorption isotherms of the the mixed oxides obtained by the impregnation and sol-gel methods exhibit very different shapes, showing the great influence of the preparation method on their textural properties (Figs. 1 and 2). 

Mixed porous oxides can be divided into two main classes (similar to nanooxides) with mixed oxides synthesized simultaneously or matrix oxides (host oxides) modified by grafting of another oxide (guest oxide) using CVD, PVD, precipitation, or other methods. Clearly, the properties of the materials with the same gross composition but from different classes can be strongly different. Many of regularities found for mixed nanooxides can be true for porous oxides. However, the difference in the textural organization of these materials can play an important role, especially for... 

In many catalytic systems, the performance is known to depend not only on the inherent catalytic activity of the active phase, but also on the textural and physicochemical properties of the support. In the attempt to obtain better catalysts the use of some new supports, such as Ti-A1 mixed oxides, has been tried with promising results in some reaction systems such as hydrodesulfurization reactions. In this case, greater catalytic activities have been found due to the role of the support [1,2]. 

In this work we report the preparation of alumina modified by zirconia or titania using a precipitation technique. The objective was to obtain mixed oxide supports for wdiich we could asses the resulting structural and textural properties, and their thermal stability. Al303-Ti02 and AljOj -ZrOj at several compositions were characterized by TGA, DTA, XRD, Nj adsorption and CCI4 adsorption. 

For better comprehension, the textural properties from our previous study of the synthesized LDHs (ZnAl-LDH) and calcined mixed oxides (C-ZnAl) were obtained by low-temperature nitrogen adsorption and the changes in the surface area values and pore size distribution before and after thermal treatment are presented in Table 20.3 and... 

The introduction of isovalent and aliovalent elements into a ceria lattice can induce important modifications of its textural, structural and redox properties and this can deeply affect its catalytic properties. " Ceria-zirconia still represents the best example showing how the incorporation of an isovalent element like Zr into the ceria structure can enhance the thermal, redox and catalytic properties. " The state-of-the-art material for oxygen storage in TWC is in fact appropriate amounts of zirconia-modified ceria mixed oxides including small amounts of other rare-earth elements, which are added to further enhance the redox and textural features of ceria. ... 

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