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

Abstract

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 °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 °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 °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 °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 °C, respectively.