Ions 6 Alkali-metal Oxides

Alkali metal ion-exchanged zeolites and occluded alkali metal oxide zeolites have been investigated extensively and applied as basic catalysts for a variety of organic transformations (1,41,221,222). Zeolites modified with alkaline earth compounds have been applied much less frequently as base catalysts for organic reactions. 

The symmetry between cations and anions in the bond valence model can best be seen in the compounds of the alkali metals and alkaline earths where the cation valences are similar to those of the anions. Binary compounds such as NaCl (18189), CsCl (22173), and ZnO (67454) are invariant under the interchange of the cations and anions since both kinds of ions occupy equivalent sites. For compounds such as CaF2 (29008) which crystallizes with the fluorite structure, changing the signs of ions gives the antifluorite structure adopted by the alkali metal oxides such as Na20 (60435). Although the antifluorite... 

A further possibility for side-chain alkylation of toluene is oxidative methylation with methane. Catalysts with occluded alkali metal oxides, prepared by impregnating zeolites with alkali metal hydroxides followed by calcination, usually exhibit better performance.441 Further enhancement was achieved by impregnating ion-exchanged zeolites 442 Significant improvements in stability and the yields of Cg hydrocarbons were also observed when NaX was impregnated with 13% MgO which was found to increase the amounts of active sites.443... 

SILICATES (Soluble). The most common and commercially used soluble silicates are those of sodium and potassium. Soluble silicates are systems containing varying proportions of an alkali metal or quaternary ammonium ion and silica. The soluble silicates can be produced over a wide range of stoichiometric and nonstoicluometric composition and are distinguished by the ratio of silica to alkali. This ratio is generally expressed as the weight percent ratio of silica to alkali-metal oxide (SiOj/MjO). Particularly with lithium and quaternary ammonium silicates, the molar ratio is used. 

When an alkali metal oxide is treated with water, it reacts with the water to form hydroxide ions. What concentration of hydroxide ions is present if 0.250 mol of solid Li20 is treated with water and the final volume is... 

Even though most of the simple MO oxides have the halide structures where the metal ions are octahedrally coordinated by the oxygen ions there are a few MO oxides where the metal ions are tetrahedrally coordinated (26). The alkali metal oxides, Li20, Na20, K2O and Rb20 possess the anti-fluorite structure with oxygen ions considered as close-packed and cations occupying all of the tetrahedral sites. 

An improvement effected by alkali metal oxide additives is also reported on HjP04-ZrSi02 [22] and zirconium phosphate [23, 24]. The addition of alkali metal ions, therefore, appears to be effective in several respects. Maintaining the alkali metal ions on the surface in humid... 

It is desirable from an energy utihzation viewpoint to minimize the quantity of alkah metal ions which must be removed from the solution. For this reason, a practical minimum weight ratio of sihca to alkali metal oxide in the nucleating solution is about 2.5 1. On the other hand, if the ratio of silica to alkali metal oxide (M2O) is too... 

Conducting polymers can be mixed with or electrochemically deposited onto transition metal oxides to achieve better performances as electrode materials. However, the wrapping of conducting polymers on metal oxides may reduce the effective contact area between metal oxides and electrolytes. This will further impede insertion of alkali ions into metal oxides and result in poor rate performance with low specific capacitance. A rational strategy is to use conducting polymers as active electrode materials directly and optimize their structures. To this end, a hierarchically nanostructured conductive polymer hydrogel was synthesized by a facile interfacial polymerization (Shi et al., 2014). 

Originally, emphasis was placed on the apparent similarities between the electronic and structural properties of the hydrogen-containing phases and those of the well known alkali-metal oxide bronzes in which alkali-metal ions reside in cavities in the parent-oxide matrix. This approach is justifiable in the case of the electronic properties, since the two classes of compound share a common redox insertion process... 

---