ABSTRACT
Simple dehydrogenative coupling of methane is thermodynamically unfavorable [Eq. (9.4)], whereas all reactions involving oxygen such as, say, partial oxydation of methane to formaldehyde [Eq. (9.5)] or methanol [Eq. (9.6)] are thermodynamically favored. However, a much larger decrease of Gibbs free energy accompanies the total oxidation of methane to CO, C02, and H20 [Eqs. (9.7) and (9.9)] and therefore one can expect that they will preferentially take place. The ~Q change of the oxidative coupling of methane [Eq. (9.8)] is comparable to that of its total oxidation; the main problem in upgrading methane is therefore the question of how to achieve high conversion without significant loss of methane in complete combustion. Because methanol and formaldehyde are more easily oxidized than methane, their subsequent oxidation as well as the parallel reaction of direct oxidation of methane must be suppressed.
