The Direct Partial Oxidation of Methane to Dimethyl Ether over Pt/Y₂O₃Catalysts Using an NO/O₂Shuttle

Abstract

Using a mixture of NO + O2 as the oxidant enabled the direct selective oxidation of methane to dimethyl ether (DME) over Pt/Y2O3. The reaction was carried out in a fixed bed reactor at 0.1 MPa over a temperature range of 275–375 °C. During the activity tests, the only carbon‐containing products were DME and CO2. The DME productivity (μmol gcat−1 h−1) was comparable to oxygenate productivities reported in the literature for strong oxidants (N2O, H2O2, O3). The NO + O2 mixture formed NO2, which acted as the oxygen atom carrier for the ultimate oxidant O2. During the methane partial oxidation reaction, NO and NO2 were not reduced to N2. In situ FTIR showed the formation of surface nitrate species, which are considered to be key intermediate species for the selective oxidation.

A Review on Deactivation and Regeneration of Catalysts for Dimethyl Ether Synthesis

“…During the tests carried out under these conditions and the mixture of CH 4 :NO:O 2 inert gas with a ratio of 20:1:1:78 and the catalyst in the amount of 0.3 g, it was possible to obtain DME in the amount of 110 µmol/(g•h). The low conversion of methane, at the level of 5%, resulted from the need to use an excess of it in order to prevent the formation of an explosive atmosphere in combination with oxygen [27,28] diagram below (Figure 3) shows the likely steps in the oxidation of methane to DME on the catalyst's surface.…”

“…Probable steps in the oxidation of methane to DME on the catalyst's surface. (a) Form of OCH 3-by the reaction of CH 3+ and NO2; (b) Formation of DME from the reaction of OCH CH 3+.Reproduced with copyright permission from[27]…”

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

“…The results showed that NO was reduced to N 2 ; however, surface nitrate species were formed, considered key intermediate species for selective oxidation. [215] At the same time, Kye et al used CO as a promotor to improve the catalytic activity of Pt/CeO 2 over CH 4 activation and its conversion into methanol with a selectivity of over 95% at 300 °C. The performance of Pt/CeO 2 was attributed to active lattice oxygen produced at the Pt/CeO 2 interface, which enables selective reaction routes for converting CH 4 to methanol.…”

“…The results showed that NO was reduced to N 2 ; however, surface nitrate species were formed, considered key intermediate species for selective oxidation. [ 215 ] At the same time, Kye et al. used CO as a promotor to improve the catalytic activity of Pt/CeO 2 over CH 4 activation and its conversion into methanol with a selectivity of over 95% at 300 °C.…”

Esterification Product Protection Strategies for Direct and Selective Methane Conversion

“…This scheme is commonly proposed for the recycling of SO 3 in methyl bisulfate systems as mentioned previously, and more recently a catalytic system for the conversion of methane to DME with NO 2 produced in the couple gas phase reaction of NO and O 2 . [24] In both cases, it is crucial that the recycling scheme does not pose complicated gas separation with burdensome energy duties or substantial purges of the valuable feedstocks. Overall, these approaches that indirectly use O 2 as the final oxidant are conceptually interesting, yet their practicality relies on the ultimate ability to address these process-oriented issues.…”