Microwave assisted heterogeneous catalysis: effects of varying oxygen concentrations on the oxidative coupling of methane

Abstract

The oxidative coupling of methane was investigated over alumina supported La 2 O 3 /CeO 2 catalysts under microwave dielectric heating conditions at different oxygen concentrations. It was observed that, at a given temperature using microwave heating, selectivities for both ethane and ethylene were notably higher when oxygen was absent than that in oxygen/methane mixtures. The differences were attributed to the localised heating of microwave radiation resulting in temperature inhomogeneity in the catalyst bed. A simplified model was used to estimate the temperature inhomogeneity; the temperature at the centre of the catalyst bed was 85°C greater than that at the periphery when the catalyst was heated by microwaves in a gas mixture with an oxygen concentration of 12.5% (v/v), and the temperature difference was estimated to be 168°C in the absence of oxygen.

Oxidative coupling of methane under microwave: core–shell catalysts for selective C2 production and homogeneous temperature control

“…Furthermore, the differences found in the selectivity and yield towards C 2 were more noticeable in the absence of oxygen. 37 The aforementioned results clearly highlight that the use of microwave radiation as the heating source for the OCM process can enhance the yield towards C 2 hydrocarbons. To explain the positive impacts derived from microwave heating, the presence of hotspots in the catalytic bed has been suggested.…”

“…Furthermore, the differences found in the selectivity and yield towards C 2 were more noticeable in the absence of oxygen. 37…”

Gaseous Reactants in Microwave‐Assisted Synthesis

“…These results led to the conclusion that continuation of the oxidation of ethane to CO x is inhibited. Oxidative coupling of methane was investigated by Ni et al over alumina supported La 2 O 3 /CeO 2 catalysts under microwave dielectric heating conditions at different oxygen concentrations [91]. It was observed that, at a given temperature using microwave heating, selectivity for both ethane and ethylene was notably higher when oxygen was absent than that in oxygen-methane mixtures.…”

Effect of surface treatment technique on properties and performance of Na2WO4‐TiO2‐MnOx/SiO2 for oxidative coupling of methane

“…In addition, it is capable of being upscaled to the commercial level. Therefore, several works have reported the use of microwave radiation as a surface treatment process for producing ordered porous materials 27‐33 . Bond et al 34 .…”

“…Therefore, several works have reported the use of microwave radiation as a surface treatment process for producing ordered porous materials. [27][28][29][30][31][32][33] Bond et al 34 investigated the effect of microwave heating on the properties and activity of alumina-supported Ni catalysts in OCM reaction and compared these catalysts with those obtained by conventional heating. The results showed that the distribution of Ni on the support was much more uniform in the microwaved catalysts.…”