Acids, binary strong, properties

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. 

It has been established from these studies that the different catalytic properties of transition metal oxides (chromium, cobalt) on zirconium dioxide are attributed to their different acidic properties determined by TPDA and IR-spectroscopy. The most active catalyst is characterized by strong acidic Bronsted centers. The cobalt oxide deposited by precipitation on the zirconium-containing pentasils has a considerable oxidative activity in the reaction N0+02 N02, and for SCR-activity the definite surface acidity is necessary for methane activation. Among the binary systems, 10% CoO/(65% H-Zeolite - 35% Z1O2)... 

Because the binary nickel-molybdenum alloys have poor physical properties (low ductility, poor workability), other elements, for example, iron, are added to form ternary or multicomponent alloys. These are also difficult to work, but they mark an improvement over the binary alloys. Resistance of such alloys to hydrochloric and sulfuric acids is better than that of nickel, but it is not improved with respect to oxidizing media (e.g., HNO3). Since the Ni-Mo-Fe alloys have active corrosion potentials and do not, therefore, establish passive-active cells, they do not pit in the strong acid media to which they are usually exposed in practice. 

Let us consider properties of an electrol54e solute as a whole. The simplest case is that of a binary solution in which the solute is a symmetrical strong electrolyte—a substance whose formula unit has one cation and one anion that dissociate completely. This condition will be indicated by v = 2, where v is the number of ions per formula unit. The solute with v equal to 2 might be a 1 1 salt such as NaCl, a 2 2 salt such as MgS04, or a strong monoprotic acid such as HCl. 

The physical properties of the solids obtained by thermohydrolysis of TiCU in aqueous solutions are strongly influenced by the synthetic variables. In particular, acidity, presence (and nature) of anions, and titanivun concentration govern the composition and the photoreactivity of the Ti02 photocatalysts (Cheng et al., 1995 Koelsch et al., 2004). Depending on the e>q)erimental conditions, ratile or anatase, binary mixtures of anatase and rutile or anatase and brookite, or temaiy mixtures of anatase, brookite and ratile, can be obtained. Table 1 shows the crystal phase composition of some selected samples prepared under different experimental conditions. 

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