Co₃O₄ Nanowire Arrays Grown on Carbon Nanotube-Based Films for Fischer-Tropsch Synthesis

Agglomeration is generally considered as one of the main reasons for catalytic deactivation, and the use of metallic-structured supported catalysts is considered as a potential way to solve the problem. In this study, Co3O4 nanowire array catalysts with different morphologies were innovatively synthesized on a carbon nanotube film (CF) substrate by a hydrothermal self-assembly method, and the processes are rather simple and fast. Also, the Fischer-Tropsch synthesis (FTS) performance of Co/CF-H (grain-like array) and Co/CF(A)-H (smooth rod-like array) catalysts was investigated in a fixed bed reactor. The robust metal-support interface between the carbon nanotube and cobalt species allows stabilization of Co3O4 against sintering. Extremely high cobalt loadings (>70%) were achieved on both catalysts with a nanoarray structure (Co/CF-H and Co/CF(A)-H). The catalytic results showed that the nanowire array catalysts exhibited 2.4-6 times higher cobalt time yield and good stability in comparison with those of the impregnated counterpart. The appropriate size and porous structure of Co3O4 nanowires in Co/CFH resulted in a more accessible surface and much higher FTS activity than Co/CF(A)-H. Moreover, the ordered structure of the Co3O4 nanoarray in both monolith catalysts maintained their original morphologies after catalytic tests. Also, the thermal stabilities of these two catalysts in a H-2-containing atmosphere were studied, and the structure of grain-like arrays on Co/CF-H was disassembled, while rod-like arrays on Co/CF(A)-H were still well retained up to 800 degrees C, with small cobalt particles migrating on the rod surface, indicating its excellent thermal stability.