Hydrogenation, general destructive

From an elemental perspective, most of the mass of POM and DOM is carbon. Thus, DOC and POC concentrations are generally representative of the entire DOM and POM pools. Because DOC and POC concentrations are more easily measured than those of the other elements (nitrogen, phosphorus, oxygen, and hydrogen), far more data has been collected on their concentrations and reactivity as compared to that of DON, PON, DOP, or POP. DOM and POM concentrations are not measured for technical reasons and because the total mass of organic matter provides little insight into the biogeochemical processes responsible for its formation and destruction. 

Many compounds sensitize biomolecules to damage by UVA (320-380 nm) and visible light. Two general mechanisms of sensitization are encountered. The Type I mechanism involves electron or hydrogen transfer from the target molecule to the photosensitizer in its triplet state. If 02 is present, this can be reduced to 02 by the reduced sensitizer. In the Type II mechanism, the excited sensitizer is quenched by 02, which is excited to the singlet state (typically A"g) and attacks the target molecule. Photosensitization is exploited in photodynamic therapy (PDT) for the destruction of cancerous or other unwanted cells. 

In the late 1980s, however, the discovery of a noble metal catalyst that could tolerate and destroy halogenated hydrocarbons such as methyl bromide in a fixed-bed system was reported (52,53). The products of the reaction were water, carbon dioxide, hydrogen bromide, and bromine. Generally, a scmbber would be needed to prevent downstream equipment corrosion. However, if the focus of the control is the VOCs and the CO rather than the methyl bromide, a modified catalyst formulation can be used that is able to tolerate the methyl bromide, but not destroy it. In this case the methyl bromide passes through the bed unaffected, and designing the system to avoid downstream effects is not necessary. Destruction efficiencies of hydrocarbons and CO of better than 95% have been reported, and methyl bromide destructions between 0 and 85% (52). 

Although the definition of the two processes is purely arbitrary it is generally assumed that destructive hydrogenation (which is characterized by the cleavage of carbon-to-carbon linkage and is accompanied by hydrogen saturation of... 

The I.R. spectra of the recovered catalysts indicated that the [M(PC)] were not altered. An exception to this was observed with the Sn(II) and Sn(IV) catalysts where the [M(PC)] could not be recovered. In fact the [Sn(PC)] appeared to be irreversibly converted to a colorless material, presumably via hydrogenation of the PC aromatic ring system. It is interesting to note that for [Sn(PC)] the activity of the homogeneous catalyst is some five-fold higher than for the supported catalyst. In general, for the other [M(PC)] the increase is two-fold or less as expected. The enhancement of the activity for the homogeneous [Sn(PC)] may be related to the irreversible destruction under reaction conditions. 

A number of terms are used for the thermal decomposition of wood and generally refer to similar processing methods carbonization, pyrolysis, gasification, wood distillation, destructive distillation, and dry distillation. All result in the thermal breakdown of the wood polymers to smaller molecules in quantities dependent on reaction conditions. The hydrogen content of the gas increases with increasing temperature of pyrolysis. The wood gas has a fuel value of 300 BTU/ft3. 

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