Ozone, atmosphere methane oxidation cycle

The methane oxidation to methanal is thus realized in the catalytic cycle in which atmospheric 02 is the oxidant and the OH radicals are the catalyst, and which is coupled to photoassisted dissociation of nitrogen dioxide (Figure 9.7). The latter process yields two ozone molecules per photocatalytic cycle. 

The photochemistry of the ethane and higher hydrocarbon oxidation in the atmosphere follows similar reaction paths as for methane, although reactions occur faster because of the higher reactivity of these molecules [33, 36]. In the case of ethane, there can be a net production of five ozone molecules per ethane molecule consumed, if sufficient NO is present in the atmosphere. The cycle of reactions, cycle C4, that produces ozone from ethane is shown in Box 5.3. The compound peroxyacetyl nitrate, CH3(C=0)02N02, which appears in C4 is a strong phytotoxicant and air pollutant, better known by the acronym PAN [37]. The compound, CH2O, is formaldehyde and CH3CHO is acetaldehyde. 

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