Methane release, surface hydroxyl

Hydroxyl Population. All of these facts indicate a connection between the hydroxyl population on the silica surface and the catalyst s activity and relative termination rate. Figure 3 plots this decrease in the hydroxyl population. Silica, containing no chromium, was calcined at various temperatures and then reacted with CH3MgI solution. The amount of methane released was taken as an indication of the surface hydroxyl content. As the activation temperature was increased, the hydroxyl population decreased from over 4 OH/nm at 200 C to less than 1 OH/nm at 900 C. However, it never actually reached zero even at the highest temperatures studied, but was always significant compared to the coverage by chromium. 

Late metals can also be bound to silica. For example, fMeRhL2(CO)] (L = PMes) reacts with silica surface hydroxyl groups to give a surface-bound Rh(I) species, 932, with release of methane. ... 

In summary, if organic compounds can see solar radiation either in surface water or in the atmosphere, there are many mechanisms that can result in their transformation. The hydroxyl radical is extremely versatile and any compound with a C—H bond may react by this process. In a sense, these processes are a mixed blessing in that on the one hand compounds emitted in significant amounts react to produce a major impact on air quality. By contrast, these processes are probably the most efficient in the degradation of compounds released into the environment. Those compounds that react slowly or not at all, such as the freons and methane, can contribute to global impacts. The significance of these transformation processes is obvious. 

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