Production of Oxygen

Nearly all commercial oxygen is obtained from air. The normal boiling point of O2 is —183 °C, whereas that of N2, the other principal component of air, is —196 °C. Thus, when air is liquefied and then allowed to warm, the N2 boils off, leaving liquid O2 contaminated mainty by small amounts of N2 and Ar. 

In the laboratory, O2 can be obtained by heating either aqueous hy drogen peroxide or solid potassium chlorate (KCIO3)  

Manganese dioxide (Mn02) catalyzes both reactions. 

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Spiral-wound modules are much more commonly used in low pressure or vacuum gas separation appHcations, such as the production of oxygen-enriched air, or the separation of organic vapors from air. In these appHcations, the feed gas is at close to ambient pressure, and a vacuum is drawn on the permeate side of the membrane. Parasitic pressure drops on the permeate side of the membrane and the difficulty in making high performance hollow-fine fiber membranes from the mbbery polymers used to make these membranes both work against hollow-fine fiber modules for this appHcation. 

Worldwide annual production of oxygen may be estimated to be about 70 x 10 . The five largest producing areas during the 1980s were... 

Figure 1-6B. This low pressure cycle is used for production of oxygen in steady state conditions. By permission, Air Products and Chemicals Inc.

Dehydrogenation of butanes is a second source of butenes. However, this source is becoming more important because isobutylene (a butene isomer) is currently highly demanded for the production of oxygenates as gasoline additives. 

We cover each of these types of examples in separate chapters of this book, but there is a clear connection as well. In all of these examples, the main factor that maintains thermodynamic disequilibrium is the living biosphere. Without the biosphere, some abiotic photochemical reactions would proceed, as would reactions associated with volcanism. But without the continuous production of oxygen in photosynthesis, various oxidation processes (e.g., with reduced organic matter at the Earth s surface, reduced sulfur or iron compounds in rocks and sediments) would consume free O2 and move the atmosphere towards thermodynamic equilibrium. The present-day chemical functioning of the planet is thus intimately tied to the biosphere. 

Note that this estimate of the annual O2 loss to weathering processes is approximately equal to the estimated annual production of oxygen estimated above. Hence, the weathering of rocks and burial of organic carbon in sediments during their formation are important processes for the oxygen content of the atmosphere. 

Emmendorffer, A., Roesler, J., Eisner, J., Raeder, E., Lohmann-Mathes, M.L. and Meier, B. (1993). Production of oxygen radicals by fibroblasts and neutrophils from a patient with x-linked chronic granulomatous disease. Eur. J. Haematol. 51, 223—227. 

Ethanolamine ammonia lyase has a molecular weight of 520,000 and consists of 8 or 10 subunits. Two 5 -deoxyadenosylcobalamin molecular bind per enzyme molecule, and recent kinetic studies by Babior show that these two molecules carry out catalysis independently. Evidence is available that this enzyme functions by a radical mechanism since both spin labeling and Co(II) esr experiments indicate that Co(II) is an intermediate during H-transfer. Also, 5 -deoxyadenosine has been detected as a product of oxygenation of the enzyme-substrate complex (99—101). 

M (altered lung macrophage function including decreased phagocytosis, increased production of oxygen radicals, and increased LDH and lysozyme activities)... 

The production of oxygen-containing organic molecules is not as well understood. Although methanol appears to be produced at least partially by the radiative... 

The unusual peroxycarbonyl ligand in these complexes was first charac-terized in Os(C(O)O0)Cl(NO)(PPh3)2, the product of oxygenation of 95 (39). The peroxycarbonyl ligand is cleaved from 96 by reaction with HC1, and the octahedral, d6 carbyne complex 98 can be isolated. Similar treatment of 97 affords cationic complex 99 (131). ... 

Protection from unwanted side products of oxygen reactions uses the cytoplasmic Cu/Zn superoxide dismutase and vesicular haem catalases as in all eukaryotes as... 

However, the process is very complex and involves several intermediates such as chlorophyll (of which there is more than one type). Chlorophylls are porphyrins that contain magnesium. The growth of plants is responsible for the production of oxygen in the atmosphere as well as food and natural fibers. 

Holland et al. [125] have shown that the potent vascular smooth muscle cell mitogen and phospholipase A2 activator thrombin stimulated superoxide production in human endothelial cells, which was inhibited by the NADPH oxidase inhibitors. Similarly, thrombin enhanced the production of oxygen species and the expression of )Alphos and Rac2 subunits of NADPH oxidase in VSMCs [126,127]. Greene et al. [128] demonstrated that the activator of NO synthase neuropeptide bradykinin is also able to stimulate NADPH oxidase in VSMCs. Similar to XO, NADPH oxidase enhanced superoxide production in pulmonary artery smooth muscle cells upon exposure to hypoxia [129]. 

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