Silicates, derivative difference

Cheng and coworkers at Taiwan University1611 have discussed the silica- and alumina-pillared derivatives of four layered silicates with different charge density and thickness, as well as related synthetic problems. Here, this system will be presented as a typical example. In general, its synthesis includes three steps. 

NEt4]Br and silver oxalate (molar ratio 1 2 3)), was first described in 1969, and ca. 25 years later the crystal structures of the derivatives 26 and 27 were reported/ In the meantime, various tris[oxalato(2-)] silicates with different cations were describedP As shown by crystal structure analyses, the Si coordination polyhedra of 26 27 28 " (synthesis Scheme 24.2 structure Figure 24.3), and 29 " are distorted octahedra. 

Nitrogenated macrocycles based on the cationic form of hemin can also be intercalated in layer silicates. Thus, different porphyrin derivatives, such as phenyl- and pyridyl-porphyrins, metalloporphyrins, chlorophylin, and related ma-... 

Layered silicates, derived from smectite clays, are commonly used as fillers for polymeric materials for ma ny different applications as their chemistries have been extensively studied [22 ]. Polymer-layered silicate nanocomposites have shown improvements in mechanical, thermal, optical, physicochemical, and barrier properties as well as fire resistance compared to pure polymers or conventional composites (composed of micron-sized particles) [5,12]. 

Reservoir rocks are either of clastic or carbonate composition. The former are composed of silicates, usually sandstone, the latter of biogenetically derived detritus, such as coral or shell fragments. There are some important differences between the two rock types which affect the quality of the reservoir and its interaction with fluids which flow through them. 

Subsequently, Goncalves cl al.97 reported the acetylation of glycerol with acetic acid performed over different solid acids, including montmorillonite K-10 and such acid zeolites as HZSM-5 and HUSY. Among the siliceous porous materials examined, montmorillonite K-10 gave the best performance, with 96% conversion into the mono-, di- and tri-acetylated derivatives. When zeolites were used, the conversion was lower than with the other catalysts, giving a 30% conversion for HZSM-5 and only 14% for HUSY. However, selectivity for the primary monoacetylated product,... 

There are significant differences in the 142Nd and e182W values obtained for the different types of Martian meteorites (Fig. 9.15). These variations indicate that the meteorites were derived from distinct mantle reservoirs that were established early in the history of Mars. Modeling based on s l42Nd and e182W indicates that differentiation of the silicate mantle could have taken place contemporaneously with core formation or could have been... 

---