Carbon oxides reduction

Nucleic acid pathways (Mg, Zn, Fe/S, B12 or Fe20) P-carbon oxidation/reduction (flavin, Fe)... 

The feasibility of performing the water-carbon oxidation-reduction reaction in combination with the C02 absorption by CaO in a single reactor has been confirmed in experiments.1112 The underlying concept of the HyPr-RING process involves two reactors a main... 

Synthesis of fats P-carbon oxidation/reduction (flavin, Fe)... 

These often heterogenous reactions take place between different types of phases solid-liquid-gas. There is a whole hst of possible reactions dissociatiort, volatilization, reduction, notably by carbon, oxidation-reduction, formation of new compounds. 

Although essentially inert m acid-base reactions alkanes do participate m oxidation-reduction reactions as the compound that undergoes oxidation Burning m air (combus tion) IS the best known and most important example Combustion of hydrocarbons is exothermic and gives carbon dioxide and water as the products... 

As we have just seen the reaction of alkanes with oxygen to give carbon dioxide and water IS called combustion A more fundamental classification of reaction types places it m the oxidation—reduction category To understand why let s review some principles of oxidation-reduction beginning with the oxidation number (also known as oxidation state)... 

Combustion of alkanes is an example of oxidation-reduction Although It IS possible to calculate oxidation numbers of carbon m organic mole cules It IS more convenient to regard oxidation of an organic substance as an increase m its oxygen content or a decrease m its hydrogen content... 

The ready reversibility of this reaction is essential to the role that qumones play in cellular respiration the process by which an organism uses molecular oxygen to convert Its food to carbon dioxide water and energy Electrons are not transferred directly from the substrate molecule to oxygen but instead are transferred by way of an electron trans port chain involving a succession of oxidation-reduction reactions A key component of this electron transport chain is the substance known as ubiquinone or coenzyme Q... 

Aldehydes can undergo an intermolecular oxidation—reduction (Canni22aro reaction) in the presence of base to produce an alcohol and a carboxyUc acid salt. Any aldehyde is capable of participating in such a reaction, however, it is more common for those containing no protons on the alpha carbon, for example... 

The iron carbide process is alow temperature, gas-based, fluidized-bed process. Sized iron oxide fines (0.1—1.0 mm) are preheated in cyclones or a rotary kiln to 500°C and reduced to iron carbide in a single-stage, fluidized-bed reactor system at about 590°C in a process gas consisting primarily of methane, hydrogen, and some carbon monoxide. Reduction time is up to 18 hours owing to the low reduction temperature and slow rate of carburization. The product has the consistency of sand, is very britde, and contains approximately 6% carbon, mostly in the form of Ee C. 

In the electrothermic part of the furnace, electrical energy introduced via three carbon electrodes, keeps the bath molten and completes the lead oxide reduction. Fumes generated in the electrothermic section are oxidized in a post-combustion chamber by adding ambient air, before the vapor is cooled, dedusted, and released to the atmosphere. 

Refining Processes. AH the reduction processes yield an impure metal containing some of the minor elements present in the concentrate, eg, cadmium in 2inc, or some elements introduced during the smelting process, eg, carbon in pig iron. These impurities must be removed from the cmde metal in order to meet specifications for use. Refining operations may be classified according to the kind of phases involved in the process, ie, separation of a vapor from a Hquid or soHd, separation of a soHd from a Hquid, or transfer between two Hquid phases. In addition, they may be characterized by whether or not they involve oxidation—reduction reactions. 

Carbon dioxide generated by the fermentation process must be removed to help maintain the pH of the solution at pH 7.6—8.0. Carbon dioxide also inhibits the activity of the bacteria. The oxidation reduction potential is kept at 100—200 mV. The ideal temperature in the reactor varies with different strains in the bacteria but generally is 25—35°C. 

More recent research provides reversible oxidation-reduction potential data (17). These allow the derivation of better stmcture-activity relationships in both photographic sensitization and other systems where electron-transfer sensitizers are important (see Dyes, sensitizing). Data for an extensive series of cyanine dyes are pubflshed, as obtained by second harmonic a-c voltammetry (17). A recent "quantitative stmcture-activity relationship" (QSAR) (34) shows that Brooker deviations for the heterocycHc nuclei (discussed above) can provide estimates of the oxidation potentials within 0.05 V. An oxidation potential plus a dye s absorption energy provide reduction potential estimates. Different regression equations were used for dyes with one-, three-, five-methine carbons in the chromophore. Also noted in Ref. 34 are previous correlations relating Brooker deviations for many heterocycHc nuclei to the piC (for protonation/decolorization) for carbocyanine dyes the piC is thus inversely related to oxidation potential values. 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

Verify that reaction (23) is an oxidation-reduction reaction and that the oxidation number change of carbon is balanced by the oxidation number change of the sulfur. 

N204 also forms expl mixts with incompletely halogenated hydrocarbons, NGu, carbon disulfide, etc (Ref 33). The effect of spontaneous decompn by oxidation-reduction reactions when N204 is mixed with a number of fuels (hydrazine, gasoline, liq paraffin, etc) has resulted in its extensive use in liq propint rocket engines (Refs 12, 22, 27 35)... 

Two of the study systems, Lake Michigan and Pond 3513, exhibit cyclic behavior in their concentrations of Pu(V) (Figure 2 and 3). The cycle in Lake Michigan seems to be closely coupled with the formation in the summer and dissolution in the winter of calcium carbonate and silica particles, which are related to primary production cycles in the lake(25). The experimental knowledge that both Pu(IV) and Pu(V) adsorb on calcium carbonate precipitates(20) confirms the importance of carbonate formation in the reduction of plutonium concentrations in late summer. Whether oxidation-reduction is important in this process has not been determined. 

The pc-Au/propylene carbonate (PC) + NaC104 interface has been studied by Nguyen Van Huong.481 A flame-annealed (02 + H2) pc-Au sphere was used. Before each experiment the pc-Au electrode was cleaned in an NaC104 aqueous solution by a few potential cycles involving oxidation-reduction of the surface until the i,E and C,E curves exhibited stable character. The C,E curves were recorded in the interval 15 150... 

Biocatalysts have received great attention in these last few years. Due to their capacity to perform asymmetric transformations under mild conditions [78], they have been useful tools for synthesizing optically active organic molecules. They promote a variety of chemical transformations, including the syntheses of esters and amides and oxidations, reductions, eliminations and carbon carbon forming. Little is known about biocatalyst-promoted Diels Alder reactions. 

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