Oxygen degradation

Oxygenate-degrading microorganisms are typically slow growing and may not be present natively at all sites pilot or treatability studies may be needed to confirm the applicability of bioremediation at a specific site. 

In dilute, alkaline solution, air (or, preferably, oxygen) degrades a sugar... 

The color of the polymer can also be affected by inappropriate reaction conditions in the polymerization process, such as temperature, residence time, deposits of degraded polymer or the presence of oxygen. Degradation of polyesters and the generation of chromophores are thermally effected [29b, 29c, 39], The mechanism of thermal decomposition is based on the pyrolysis of esters and the formation of unsaturated compounds, which can then polymerize into colored products. It can be assumed that the discoloration takes place via polymerization of the vinyl ester end groups or by further reaction of AA to polyene aldehydes. 

Primary organics are emitted to the atmosphere by industrial sources (oil refineries, chemical plants, producers and users of solvents and plasticizers), vehicles (as a result of incomplete fuel combustion, oxygenated degradation products of lubricating oil, polymers from tires), and agricultural activities (use of pesticides). An exhaustive literature survey is beyond the scope of this section, but can be found in Air Quaiity Criteria for Particulate Matter many useful references are also available. 

M. Schaer, F. Niiesch, D. Berner, W. Leo, L. Zuppirol, Water vapor and oxygen degradation mechanisms in organic light emitting diodes, Adv. Fund. Mater. 11 (2001) 116-121. 

Even with added oxygen, degradation of acetic acid clearly depends on the electrical charge and the controlling mechanism is electrochemical rather than chemical oxidation. Acetic acid is a component that is known to oxidize minimally under wet oxidation conditions (see 0 A line). 

The excess air s introduction of oxygen degrades the principal chemical absorbents (alkanolamines) and increases solvent consumption. This degradation is also exacerbated by the presence of sulphur in the flue gas, e.g. from fuel oil. This is illustrated in Figure 6.2 and Table 6.4 which illustrates process flows and utilities consumption for the reduction of carbon dioxide in a flue gas to below 2% using a standard sorbent (MEA) and a solvent under development (SH amine) ... 

As with other organic polymers, HIPS is susceptible to degradation when heated in the presence of oxygen. Degradation is a broad term that takes on different meanings to the end user. While it is not easily seen at the molecular level, degradation is recognizable when a finished part is put into its intended use. Typical macroscopic evidence is seen in... 

Villar D, Vara-Vega A, Landazuri MO, Del Peso L. Identification of a region on HIF prolyl 4-hydroxylases that determines their specificity for the oxygen degradation domains. Biochem. J. 2007 408 231-240. 

The polymerization of pyrrole over Cu(II)-exchanged ZSM-5 zeolites was studied with resonance Raman spectroscopy. The authors found that a critical concentration of cupric ions must be exceeded to observe polymerization. Hosts with low Si/Al ratios gave partially oxidized pol5rpyrrole (having quinoidal and aromatic structures) and pyrrole monomer. The quinoidal structure was associated with the charge carriers. Residual oxygen degraded the polymer. 

C Bonini, M D Auria, L D Alessio, G Mauriello, D Tofani, DViggiano, and F Zimbardi. Singlet Oxygen Degradation of Lignin. J Photochem Photobiol A Chem 113 119-124,... 

Most organic materials contain sites where radicals can form more or less easily, depending upon structure. Only perfluorinated molecules are totally free of such sites since radical formation usually involves abstraction of hydrogen radicals. Both the polymer and abstracted hydrogen radicals become stabilized by the intervention of oxygen. Degradation in the form of crosslinking, chain scission or both follows. The... 

Formate, oxalate, acetate Acid in feed gas Oxygen degradation Thermal degradation... 

FIGURE 10.6 Oxygen degrades thin phase capillary column [reprinted with permission... 

The presence of double bonds in butyl rubber does not result in strong resistance to light and oxygen. Degradation rate is partly dependent on the content of unsaturated butyl, so that Improved weathering and ozone resistances can be achieved by optimizing the formulation. Resistance is influenced by the type and concentration of the crosslinker as well as by the fillers added [83]. 

Thermal degradation is defined as degradation at elevated temperatures in the absence of oxygen. Degradation rates and specific reaction mechanisms of thermal degradation depend on the structure of the plastics and the temperature. Thermal-... 

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