Heterogeneous Mn-Based Catalysts for the Aerobic Conversion of Methane-to-Methyl Trifluoroacetate

Methane conversion strategies that protect methanol via in situ esterification achieve higher yields compared to direct methane conversion without product protection; however, most of these high-yield systems operate under unfavorable conditions. To date, there is very limited work in developing heterogeneous catalysts for methane-to-methyl-ester conversion, and studies demonstrating the activity of manganese for methane conversion are limited. We have prepared a series of silica-, titania-, and zirconia-supported manganese catalysts and measured the activity of these catalysts for the aerobic conversion of methane to methyl trifluoroacetate in diluted trifluoroacetate acid. The silica-supported catalyst exhibits high overall activity, but significant amounts of homogeneously active manganese are observed. Titania- and zirconia-supported manganese catalysts catalyze the reaction heterogeneously with activities up to 613 μmol gcat–1 h–1 and show nondetectable leaching. Manganese oxide is poorly dispersed on titania and zirconia, whereas high dispersion is realized on silica. This work demonstrates a facilely synthesized supported manganese catalyst that converts methane heterogeneously in satisfactory yields under improved conditions in a diluted acid, compared to those of conventional methane-to-methyl-ester systems.