In this study, microscale nickel (Ni, 0.33 wt%) and iron (Fe, 0.26 wt%) catalysts coated on cordierite particles were used in the partial oxidation of methane to form syngas by a microwave-assisted process. Microwave treatment can be applied by coupling with materials having higher dielectric loss values. This is because Ni has more electron holes and a higher activity than Fe, and Ni-based catalysts produce heat much faster than Fe-based catalysts upon microwave treatment (208.8 vs 26 ℃/min). Under the same experimental conditions of a volumetric ratio of CH 4 /air of 1:1, a microwave output power of 450 W, and the reaction time set to 360 min, higher H 2 and CO yields were obtained with the Ni catalyst than with the Fe catalyst (54.7 vs 46.0% for H 2 and 19.7 vs 14.4% for CO). The coke content was determined to be 0.4 wt% for the Ni catalyst and 0.51 wt% for the Fe catalyst. The shape of the coke was different for the two catalysts; finely shaped coke was observed for the Ni catalyst, whereas thicker multilayered coke appeared on the Fe catalyst.

A platinum/palladium/rhodium (Pt/Pd/Rh) spent catalyst (Pt/Pd/Rh ratio of about 0.16/0.001/0.01 wt%) supported on MgO-Al 2 O 3 -SiO 2 as the main carrier was studied in the methane partial oxidation process. By utilizing the characteristics of microwave selectivity to couple with the material with high dielectric losses, micron iron powder was chosen during the microwave treatment since it has a higher dielectric constant than the Pt/Pd/Rh components. It was placed at the bottom of the reactor, where it could absorb microwave energy and convert it into heat energy, thereby enabling the partial oxidation reaction to occur. Under the same experimental conditions, namely, CH 4 /air volume ratio of 1:2, microwave power of 450 W, and reaction time of 330 min, the results showed that the yields of syngas were higher when the micron iron was used with the Pt/Pd/Rh spent catalyst than when the catalyst was used alone. The yields were 67.3 and 11.6%, compared with 41.5 and 11.5%, for H 2 and CO, respectively, when using the micron iron combined catalyst rather than micron iron alone. It was also found that the coke deposed on the surface of the Pt/Pd/Rh catalyst had a filamentous shape.