Oxygen heterogeneous removal

Furthermore, because these reactions result in the effective removal of NOx from ozone production, by removing N02, the model also predicts that O, concentrations will decrease. Figure 7.17, for example, shows the model results for the ratio of O, (R0i) with the heterogeneous removal of N03 and N2Os included to that without these aerosol reactions. In some locations, the 03 concentrations are predicted to be as much as 30% lower than they would have been in the absence of the heterogeneous reactions. Because 03 is also the major OH source on a global scale, via its photolysis to electronically excited oxygen atoms, O( D), which react in part with gas-phase water, this also decreases the predicted OH levels. 

In multiphase systems, biological reactions are always carried out in the presence of water. This is true even if the presence of water is almost negligible. The biocatalyst maybe present as a solid phase, for example as immobilised enzymes or cells, or as an individual cell the substrate may also constitute a solid phase. When necessary, gas is sparged into reactors to supply oxygen or a gaseous substrate and to remove carbon dioxide. Thus, heterogeneous systems with four phases involved are very typical cases. 

Phthalocyanine complexes are some of the few heterogeneous organic catalysts that have found their way into practical application. They are used to remove mercaptans from oil by selective oxidation into disulfides 98> and they also used in fuel cell cathodes, where they catalyze the reduction of oxygen 94 ... 

The reduction of alkyl halides to organometallic compounds in aprotic solvents involves a heterogeneous reaction on the metal surface. This metal surface must be pure metal if it is to react efficiently in the desired way. If the surface of the metal has reacted with oxygen (Li, Mg, Zn) or even with nitrogen (Li), one must first remove the metal oxide or lithium nitride layer. This can be accomplished in the following ways ... 

All of these features considerably improve the sorption capacity of carbons, and their capacity to remove contaminants and pollutants interacting with the surface of carbons in a dispersive way [177], In addition, active carbon contains heteroatoms such as oxygen, and, to a smaller degree, nitrogen and sulfur. These atoms are bound to the activated carbon surface in the form of functional groups, which are acidic or basic, giving the activated carbon surface an acidic or basic character, respectively [173,178], It is as well necessary to state that the chemical heterogeneity of the carbon surface is mostly the result of the presence of heteroatoms [175],... 

---