Methane to methanol and its derivatives

Various both heterogeneous and homogeneous catalytic systems have been developed for methane oxidation to methanol in gas or liquid phases. Achievements in this field before 2008 are discussed in several previous reviews [10,34,60]. Inspired by the high performance of MMO, Fe- and Cu-containing zeolites were prepared to mimic catalytically active metal-oxide sites and applied for gas-phase oxidation of methane to methanol using N2O [61,62] or O2 [63,64] as oxidizing agents. However, the achieved methanol yields are rather low. 

Remarkable performance in terms of methanol selectivity at industrially relevant methane conversions was reported by the group of G. Yuan [65,66]. In Ref. [65], methanol yields up to 28% were reported upon methane oxidation in 

Not only Fe species in ZSM-5 but also supported Au-Pd nanoparticles have been found to catalyze the methane oxidation to methanol with hydrogen peroxide [75]. However, they perform less active and selective than the iron species. Moreover, these catalytic systems also differ in their reaction mechanism. In contrast to the oxidation of methane over Fe-ZSM-5, methyl radicals are involved in methanol formation over supported Au-Pd nanoparticles. 

Using NO as an oxidizing agent, methanol selectivity of aroimd 90% at a methane conversion of 7% was achieved over VO /MCM-41 [81]. Oxygen of supported isolated VO species was suggested to be responsible for methanol formation from methane under irradiation ( 270 nm). The reduced VO center is reoxidized by NO. However, the use of NO as an oxidizing agent is too expensive for commercial methane oxidation. Unfortunately, VO c/MCM-41 was not selective for methanol formation in presence of O2. 

Although our knowledge on the partial oxidation of methane to methanol was improved, there remains a need for better catalytic materials with a reduced activity for consecutive overoxidation of primarily formed methanol to carbon oxides. Alternatively, approaches aimed on methane conversion to kinetically more stable methanol derivatives may be of interest for further research. 

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