In situ chemical reactions

Another approach to dealing with the nonelectrochemically active nature of most amino acids is to generate, in situ, chemical reactions at the electrode surfaces to produce electrochem-ically active products for detection. Related to this concept, is the online use of immobilized enzymes (142) to react with amino acids. A by-product of this reaction is hydrogen peroxide, which is then quantified by amperometric detection. 

A specific attention has been paid to the mechanochemical generation of X in unsaturated elastomers, EPDM, ABS, PVC and polyolefins [243, 252]. This synthetical approach exploits processing operations producing free radicals. In situ chemical reactions can be performed during some important industrial processes like mastication of rubber and extrusion, mixing or reaction injection molding of plastics. 

In-situ chemical reactions such as oxygen initiated reactions, e.g., aldehydes to acids... 

The first fundamental examinations with polycondensates like polyanoides and polycarbonates were carried out in an interdisciplinary cooperation between chemists and engineers as published in [33-35] by use of fast in situ chemical reactions at high melt temperature. It is well known that the gross kinetical reaction rate decreases very fast with decreasing temperature. 

The desired compatibilization can be obtained by different methods such as the addition of a third component (copolymer or functional polymer) or by inducing in situ chemical reactions (reactive blending) among blend components, leading to the modification of the polymer interfaces and tailoring the blend phase structure and the final properties. The final properties of a blend will be determined not only by the components properties but also by the phase morphology and the interface adhesion, both of which determine the stress transfer within the blend and its end-use applications. 

Other forces, like 7C-interactions, are also of value. Benzene, or fused rings, contribute to stronger lateral interactions, and, by these means, the aliphatic chains can be shortened, or even eliminated in some cases. For such "in situ" chemical reactions, the drawbacks are that the syntheses are more difficult, and that the aromatic rings are more reactive than the inert aliphatic chains. 

In the alkaline flood process, the surfactant is generated by the in situ chemical reaction between the alkali of the aqueous phase and the organic acids of the oil phase The surface-active reaction products can adsorb onto the rock surface to alter the wettability of the reservoir rock and/or can adsorb onto the oil-water interface to lower the interfacial tension. At these lowered tensions (1-10 dyne/cm), surface or shear-driven forces promote the formation of stable oil-in-water emulsions or unstable water-in-oil emulsions the nature of the emulsion phase depends on the pH, temperature, and electrolyte type and concentration. These different paths of the surface-active reaction products have created different recovery mechanisms of alkaline flooding. The four alkaline recovery mechanisms which have been cited in the recent literature are (i) Emulsification and Entrainment, (ii) Emulsification and Entrapment, (iii) Wettability Reversal from Oil-to Water-Wet, and (iv) Wettability Reversal from Water- to Oil-Wet. These four mechanisms are similar in that alkaline flooding enhances the recovery of acidic oil by two-stage processes. 

The pressure history of the secondary alkaline flood reflects the formation of a secondary oil bank behind the immiscible phase oil bank. This secondary oil bank results in an overall recovery which is above that obtained by secondary waterflooding or by secondary caustic flooding with an univalent ion of high electrolyte concentration. The concentration history of the fractional water production during the secondary calcium hydroxide flood represents the total consumption of the hydroxyl ion. This consumption curve is made up of consumption due to adsorption of the silica surfaces and consumption due to the in situ chemical reaction which forms the more oil-soluble, surface-active salt, calcium oleate. 

Alkaline Floods. Alkaline floods, typically using sodium hydroxide, generate surface active products by an in-situ chemical reaction between the injected alkali and the organic acids of the crude. Four possible mechanisms [95] are responsible for the recovery of oil by alkaline floods (1) emulsification and entrainment, (2) emulsification and entrapment, (3) wettability reversal from oil-wet to water-wet, and (4) wettability reversal from water-wet to oil-wet. One example in the literature of wettability alteration by alkali [96] was reported for an offshore field in the Gulf of Mexico fhat had a low recovery factor from primary production. The wettability of this reservoir was found, using the... 

Dallas, M. S. J. (1970). In situ chemical reactions on thin layers in the identification of organic compounds. J. Chromatogr. 48 193-199. 

Primary particles, such as road dust, salt (sea-) spray from the oceans and cement dust do not change form after emission, whereas a substantial fraction of mass of the secondary particles, such as photochemically produced sulfates and photochemical smog, is formed by in situ chemical reactions involving gases. 

NMR spectroscopy is routinely used in today s organic synthesis laboratories to identify and structurally characterize reaction products. Yet despite the enormous structural information content of NMR and the availability of a variety of high-pressure NMR techniques (3-13), it is little used for studying in situ chemical reactions and solvent effects on chemical reactions in supercritical media. 

Real-Time Atomic-Level Observations of In Situ Chemical Reactions and Transformations Utilizing High-Resolution Electron Microscopy, Z. Kang and L. Eyring, Metall. Trans. A, 22,1323-1329 (1991). 

Another microstructural feature of these composites is that a-Al203 formed through the in-situ chemical reactions between A1 and Ti02 in the fine Al/ Ti02 composite particles at high temperatures would tend to develop a three-... 

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