Organically modified silica processes

On the basis of the sol-gel process, much more attention has been paid to silicate-containing Class II hybrids, also referred to as organically modified silicas, ormosils. In this section, the synthesis of some of the most characteristic ormosils for bone and dental applications are described. 

Note 1 Organically modified silicas can be obtained by sol-gel processing. 

Related and Modified Reagents. In addition to the standard reagent, a polymer-supported perruthenate (PSP) compound has been described. i Recent work has also examined the doping of organically modified silicas (ormosils) with TPAP via a sol-gel process, 7 which enhances the general versatility and reusability of TPAP catalysts. The use of supercritical carbon dioxide as a solvent has also been investigated. TPAP has also found use as a convenient source of ruthenium in mthenium-catalyzed hypochlorite oxidations. ... 

Hay J.N., Porter D., Raval H.M. A versatile route to organically-modified silicas and porous sihcas via the non-hydrolytic sol-gel process. J. Mater. Chem. 2000 10 1811-1818 Hay J.N., Raval H.M. Synthesis of organic-inorganic hybrids via the non-hydrolytic sol-gel process. Chem. Mater. 2001 13 3396-3403... 

Co-containing POMs have been found to be among the most efficient catalysts for homogeneous aerobic oxidation and co-oxidation processes [91-93]. This prompted many researchers to design solid Co-POM-containing materials [78,94-100]. Thus, various Co-POMs have been deposited on cotton cloth [94] and silica [100], datively [95] or electrostatically [96,97] bonded to NH2-modified silica surfaces (vide infra) as well as intercalated in LDHs [78,98,99]. The resulting materials were successfully used for aerobic oxidation of aldehydes, alkenes, alkanes, alcohols and some other organic substrates. 

To reduce the cost of the AD process immobilization of the chiral Cinchona alkaloid-derived ligands has attracted attention, too. Several approaches to address this problem have been reported [51]. The chiral ligand has been attached to solid supports comprising organic polymers or modified silica. After comple-... 

Sol-gel matrices can also provide a chemical surrounding that favors enzymatic reactions. Lipases act on ester bonds and are able to hydrolyze fats and oils into fatty acids and glycerol. These are interphase-active enzymes with lipophilic domains and the catalytic times reaction occurs at the water-lipid interface. Entrapped lipases can be almost 100 times more active when a chemically modified silica matrix is used. The cohydrolysis of Si(OMe)4 and RSi(OMe)3 precursors provides alkyl groups that offer a lipophihc environment that can interact with the active site of Upases and increase their catalytic activity. Such entrapped lipases are now commercially available and offer new possibilities for organic syntheses, food industry, and oil processing. ... 

Since the degree of adsorption to reverse phase silica gel is proportional to the lipophilicity of the compounds being chromatographed, mobile phases used are usually aqueous. An organic modifier such as methanol, acetonitrile, or tetrahydroftiran is used and its concentration increased during the development process. The pH of the aqueous phase can also be controlled. A common application involves the use of a small percentage of trifluoroacetic acid (TEA), usually in the 0.01-0.1% range. 

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