Oxidation of Lower Alkanes Over Oxide Catalysts

Oxidation of Lower Alkanes Over Oxide Catalysts 

Nitrous oxide first attracted considerable attention in the 1980s in relation to the search for ways for the oxidative conversion of methane into valuable chemical products. Although practical application of N20 for solving this problem was economically not feasible, such studies may be useful for better understanding the activation mechanism of methane, thus improving the possibility of getting better results with 02. 

Numerous works on the oxidation of methane to methanol and/or formaldehyde as well as on the oxidative dimerization of methane were reviewed by many authors [22-27]. First, high selectivity of methane oxidation by N20 was reported by Lunsford et al. [28-30], Over a supported Mo oxide [30], the total selectivity to methanol and formaldehyde at low methane conversions attained 100%, although this rapidly dropped as the conversion increased (Table 7.4). High selectivity for this reaction was obtained also with supported vanadium oxide [31]. 

When N20 is replaced by 02, the selectivity sharply decreases. This is the conclusion of all researchers in the field [31-34]. As for the reactivity of these oxidants, opinions differ. Thus, Zhen et al. [31] and Barbaux et al. [34] observed a higher methane conversion in the presence of 02, while Chen and Wilcox [33], conversely, saw greater conversion in the presence of N20. 

Lunsford and coauthors suggested the following reaction mechanism [30], which 

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