In this paper, a Mn/NiCo2O4 catalyst was prepared for the complete oxidation of low-concentration methane. When the ratio of Mn: Co is 1:4, the catalyst has the best catalytic activity, and the best methane conversion temperature Feis 400 °C. In addition, the
catalytic activity remains stable during the long-term reaction, showing adequate thermal stability. The catalyst is grown on FeCrAl alloy by hydrothermal method to complete the catalytic oxidation of methane. In the catalysis process, the Mn/NiCo2O4-FeCrAl catalyst is
energized and the current is directly passed through the alloy substrate to generate Joule heat, reaching the optimal catalytic temperature for complete oxidation of methane.
Xiaodan Zhang,Fei Yu,Jie Zhang,Zhiyong Tang,Yuhan Sun
Wall-coating is an attractive approach for immobilizing catalyst into microchannels due to potential enhancement in heat and mass transfer and a small pressure drop. A novel hybrid method was thus developed for efficiently wall-coating special cobalt carbide catalyst into FeCrAlloy microchannels on the direct production of lower olefins from syngas. The effect of pretreatment was investigated to form a uniform Al2O3 layer on the surface of FeCrAlloy substrate. The small loss of coated catalyst layer in the mechanical adherence test by exposing the FeCrAlloy substrate to a fast nitrogen flow indicated its outstanding stability in the immobilization of cobalt carbide catalyst. The coating catalyst exhibited a stable and good activity after reaching the steady state. Additionally, calculations revealed that the wall-coated and fixed-bed microreactors had comparable mass transfer factor jD, but the former provided a five times larger heat transfer factor jH and 100 times lower pressure drop per unit length, confirming in detail the advantages of wall-coating. The proposed wall-coating strategy can be applied for immobilizing other catalyst within metallic microchannels, providing a practical technical solution for industrial implementation of microreactors.
Zirconolite wasteforms were designed for the co-immobilisation of CeO 2 (as a PuO 2 surrogate) and metallic iron, chromium, and aluminum , simulating contaminated FeCrAl alloy cladding. Zirconolite ceramics with the target composition Ca (1-3.87x) Ce 3.87x ZrTi (2-7.73x) Fe 5.73x Cr x Al x O 7 (x = 0–0.11), were synthesised via solid state reaction sintering at 1400 °C. Phase and microstructural evolution were investigated to ensure the oxidation of the metals, formation of zirconolite phase and densification of the final ceramics. It was found that both oxidation and solid-state reaction could be accomplished by processing at 900 °C and 1400 °C under ambient atmosphere, accompanied by the overall yield of zirconolite in the range 92.4–94.0 wt % between x = 0.01–0.07 f.u., with a dense microstructure observed. Polytype transitions from zirconolite-2M to -3T were evidenced, where the solubility limit was reached at substitution level of x = 0.11 and precipitation of CeO 2 was apparent. XPS analysis confirmed that an elevation in dopant concentration resulted in the partial reduction of Ce 4+ to Ce 3+ , whereas Fe, Cr and Al metals were oxidised to the trivalent state. This study demonstrated the feasibility for designing advanced ceramic wasteforms for the co-immobilisation of actinides and metallic cladding residues.
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