Binary metal oxides acid-base properties

Tentative Summary of the Acid-Base Properties of Binary Metal Oxides... 

Ai and associates reported that for several oxidation reactions catalyzed by binary and ternary metal oxide catalysts, the catalytic activity and selectivity are correlated with the acid-base properties of the catalysts. The correlations were explained... 

Bulk and supported mixed oxide compositions, from binary metal oxides to quaternary metal oxides, consist in general of large crystalline phases possessing low surface area values (typically from 1 to 10m g ). Examples of oxides of this type of catalytic relevance are V-Nb-0, Mo-Nb-O, Co-Ti-0, Ni-Ti-0, etc. The acid-base properties of mixed metal oxides have been found to change with the nature of the constituents and their relative concentrations, preparation (co-precipitation and sol-gel synthesis among are the most popular methods used), and pre-treatments procedures. Appropriately choosing the mentioned variables, mixed oxides can be used to prepare catalysts with the desired-acid-base characteristics. 

From practical and theoretical points of view concerning binary metal oxides, it is interesting to And oxide combinations having well defined and mnable acid or basic properties. On a catalytic oxide surface, the acid or basic sites can be either too strong causing some irreversible adsorption of the substrate species or the sites can be too weak to activate the substrate species. Therefore, the possibility to regulate the acid-base strength, besides the acid site amount of the oxide surfaces, appears a necessary tool for catalytic purposes. 

This work is devoted to the synthesis of Zr02 by various methods, the synthesis of zirconium-containing pentasils and Zr02 - -zeolite based binary carriers. These materials were used as carriers of transition metal oxides (chromium, cobalt) and their catalytic properties were characterized in the selective reduction of NO by methane and propane-butane mixture, the acidic properties of the samples were investigated by thermoprogrammed desorption and IR-spectroscopy methods. 

From a general point of view, at ambient pressure and temperature, all electrooxidations of short-chain aliphatic alcohols (in acid) require the presence of the expensive precious metal Pt. However, as is well known, Pt is readily poisoned by CO-like intermediate species formed during methanol oxidation at low temperatures. It has been found that Pt-based binary or ternary catalysts, Pt-Mi, Pt-Mi-M2 (M = Ru, Sn, etc.) can improve the reaction kinetics of methanol electrooxidation based on the bifunctional effect (promoted mechanism by the second metal) [17,19,22,24,26] and/or on the tuned electronic properties of Pt (the intrinsic mechanism) [28,29,36]. The bifunctional effect is illustrated in the following equations ... 

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