Homogenous chemical promotion

Ultrasound is known for its capacity to promote heterogeneous reactions (Ley and Low, 1989) mainly through greatly increased mass transport, interfacial cleaning and thermal effects. In addition, homogeneous chemical reactions have been reported to be modified (Suslick et ai, 1983 Luche, 1990 Colarusso and Serpone, 1996) for example the sonochemical generation of radical species in aqueous media is important in environmental detoxification (Kotronarou et al., 1991 Serpone et al., 1994). 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

The electrochemical oxidation of monomers such as pyrrole,2-5 thiophene,6-9 aniline,10-13 etc., or their derivatives, initiates a polymerization process at the electrode/electrolyte interface that promotes the formation of a polymeric film that adheres to the electrode. A similar homogeneous polymerization process can be initiated by chemical oxidation or chemical polymerization.14-21 Some monomers can be polymerized as well by electrochemical or chemical reduction. 

The first step in the CSD process is solution preparation, which involves reagent selection (chemical precursors) and solvent choice.1,5-12,16 During solution preparation, other chemical modifiers may also be added to the solution to facilitate or limit chemical reactivity. Also during this stage of the process, identification of appropriate reaction conditions to promote other desired changes in precursor nature or solution characteristics is also considered. The goal for solution preparation is to develop a homogeneous solution of the necessary cation species that may later be applied to a substrate. 

Supercritical CO2 at temperatures of 31-50 °C and pressures of about 10 MPa is now widely used as a nontoxic extractant of excess fats from foodstuffs and in decaffeinating coffee, but its largest scale future use is likely to be the enhancement of recovery of oil that cannot be extracted from wells by conventional techniques. Supercritical CO2 is finding increasing favor as a solvent for chemical syntheses, for example, in the radical-promoted polymerization of fluoroacrylic monomers in homogeneous solution, for which ozone layer-destroying chlorofluorocarbons had been the only effective solvents previously.210... 

There is evidence in the literature that many of these transition metal derivatives, when chemically bonded or grafted onto an inorganic oxide surface, possess catalytic activity for olefin reactions far greater than that observed when the organometallic compound is used in a homogeneous manner (26). In some examples, catalytic activity was promoted when the original compound had none (3, 27). 

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