Fabrication and evaluation of the Mn-promoted Ni/FeAl2O4 catalysts in the thermocatalytic decomposition of methane: Impact of various promoters

This research is focused on the designing and developing catalytic systems over various metal oxides (CuO, Cr2O3, Co3O4, ZnO, and MnO2) promoted NiO/FeAl2O4 catalysts in the thermocatalytic decomposition of CH4. The catalysts were synthesized based on the wet impregnation method, and the nominal NiO content was fixed at 50 wt% along with each transition metal at 10 wt%. The controlled preparation method caused the sample doped with MnO2 to show the highest specific surface area (46.8 m2/g) and the lowest particle size (10.6 nm) among the promoted samples. The activity test revealed that the MnO2(10)-NiO(50)/FeAl2O4 catalyst was the most active and stable catalyst in the CH4 decomposition reaction. At 700 degrees C, the CH4 conversion and H2 yield were 62.3 and 66 % over this catalyst. Also, the decline in its initial activity was only 3 % during the 300 min reaction time at 575 degrees C. Also, the results indicated that the catalytic efficiency and rate of carbon production increased by raising the MnO2 content from 5 to 10 wt%. However, the high amount of the deposited carbon and decline in metal dispersion led to the catalytic activity being reduced when the MnO2 loading was increased from 10 to 15 wt%. The impact of calcination temperature (600, 700, and 800 degrees C) was also investigated on the characterization features and conversion rate of the selected catalyst, and the results revealed that the catalyst calcined at 600 degrees C displayed the highest efficiency under studied conditions. Furthermore, the results indicated that the catalytic activity and stability decreased by increasing the GHSV value from 40000 to 60000 ml.h-1.g-1cat and CH4:N2 molar ratio from 10:90 to 30:70. Also, the CH4 conversion decreased from 47 to 28 % when the reduction temperature increased from 700 to 800 degrees C, respectively.