Other Oxygen Carriers

Along with the four main OCs described above, some other materials have been studied, such as cobalt and CaS04. 

Cobalt is present as C03O4, CoO and Co the thermodynamic equilibrium for C03O4 and CoO is favoured at 900 °C, and. therefore, this material can also be used for the CLOU process. The reason that cobalt is not often used is that its costs are high (even higher than that of nickel), it is toxic and the selectivity is low (87-97% for CO) in the temperature range of 800-1200 °C [9]. 

From natural anhydrite, the CaS04/CaS-oxygen carrier can be obtained, which is a low-cost material with a high oxygen capacity. Low reaction rates were measured and the thermodynamic equilibrium caused that always a small amount of CO and Hj remains unconverted [9]. Also the side reaction could occur, in which CaO and SO2 are formed. 

As alternative mixes of OCs have been used to evaluate if advantages of OCs could be combined and the drawbacks be reduced [9]. For example, the reactivity and the fuel conversion could be increased, the amount of expensive or toxic material decreased and the strength of the particles increased. Studies have been conducted with many different combinations (Cu/Fe, Cu/Ni, Fe/Ni, Co/Ni, Fe/Mn), but have not resulted in an application on a larger scale until now [9]. Perovskite structures have been proposed as well, which might also be applicable for the CLOU process in case perovskite contains Mn-Ca-O [29]. 

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The isotopic oxygen exchange reaction is a useful tool for investigating the reactivity of various oxygen species on oxide surfaces. Most studies in this area have used 02 as a source of isotopic oxygen, although other oxygen carriers such as C 02l l and have been... 

Copper is one of the twenty-seven elements known to be essential to humans (69—72) (see Mineral nutrients). The daily recommended requirement for humans is 2.5—5.0 mg (73). Copper is probably second only to iron as an oxidation catalyst and oxygen carrier in humans (74). It is present in many proteins, such as hemocyanin [9013-32-3] galactose oxidase [9028-79-9] ceruloplasmin [9031 -37-2] dopamine -hydroxylase, monoamine oxidase [9001-66-5] superoxide dismutase [9054-89-17, and phenolase (75,76). Copper aids in photosynthesis and other oxidative processes in plants. 

This review is particularly concerned with the bonding modes of the dioxygen ligand, and the factors affecting which of the various possible orientations it assumes in any particular complex. We shall therefore consider all previous work, from the earliest work on synthetic oxygen carriers, right up to the most recent studies on picket-fence and other synthetic porphyrins. All work concerned with an irreversible system will illustrate some principle appertaining to reversibility. On this basis we shall then attempt to provide a unified rationale for ... 

Roberts and Laine [25] describe a process for electrochemically transferring oxygen with the scheme shown as Fig. 11. Air or other oxygen-containing gas is drawn into the left side of the vessel. The solution contains an organic solvent such A-methyl pyrrolidine with a supporting electrolyte as tetrabutyl ammonium tetrafluroborate. The carrier, one of the two Schiflf bases shown as Fig. 12, is dissolved to about 3 volume percent. 

One approach to compartmentalize hemoglobin is to encapsulate hemoglobin in biodegradable polymer-PEG-polylactide (30). These nanocapsules have a diameter of 80-150 nm and contain superoxide dismutase, catalase, carbonic anhydrase, and other enzymes of Embden-Meyerhof pathway that are needed for long-term function of an oxygen carrier (31,32). The polylactide capsules are metabolized in vivo to water and carbon... 

Spatial separation of hemoglobin confers many desirable properties to the LEH. Yet, like other hemoglobin-based oxygen carriers, it is not a complete resuscitation fluid for hypovolemic shock. Intervention in severe hemorrhage... 

The two most important metalloprotein, other than hemoglobin and myoglobin are hemerythrins and hemocyanin which act as natural oxygen carrier. Hemocyanin is discussed in previous question. 

The reaction is exothermic (see Exercise 12.1), but, since it is very slow, a catalyst is necessary. Nitric oxide, once again, can serve as an oxygen carrier, as in the lead chamber process (Section 10.2) and in reaction 10.8, where (CH3)2S generated in the kraft process is converted to DMSO. Even so, at the elevated temperatures required, reaction 12.1 needs to be forced to completion by absorption of the steam in concentrated sulfuric acid or some other desiccant. In variants of the Deacon process, copper chloride acts as the catalyst or as an intermediate for chlorine regeneration. 

Several perfluoroalkyl and cycloalkyl bromides were tested for potential as oxygen carriers, blood substitutes, radiopaque agents, for other medical applications or as intermediates. Their LD50 toxicity data are listed in Table 14 (for additional information, see also ref 2). 

The adamantane work was undertaken as a contribution to the artificial fluorocarbon blood substitute area. The use of fluorocarbons as artificial blood and as oxygen carriers in other applications is an area that is being developed by Leland Gark, Jr., of Cincinnati Children s Hospital and Paul Geyer of Peter Bent Brigham Hospital in Boston. The reader who is unfamiliar with this area of research will find reviews on the subject to be extremely interesting (68). The... 

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