(544fh) Methane Decomposition for the Production of COx-Free Hydrogen and All Base Growth Carbon Nanotubes over Transition Metal Aerogel Catalysts

Bingying Gao^a, I-Wen Wang^a, Lili Ren^b, Hanjing Tian^a, Jianli Hu^b,*

1. Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506
2. ^b. School of Chemistry and Chemical Engineering, Southeast University, Jiangning District, Nanjing, Jiangsu Province 211189, China

Chemical Functional nanocomposite aerogel (Ni/Al₂O₃ and Co/Al₂O₃) catalysts have been developed for the methane decomposition to simultaneously produce COx-free H₂ and carbon nanotubes (CNTs). The objectives of this study were to characterize the properties of supported metal aerogel catalysts and structural morphologies of CNTs to elucidate the “base growth” mechanism of CNTs over these unique catalytic systems. In this study, Ni/Al₂O₃ and Co/Al₂O₃ aerogels were synthesized with various metal loadings, and then tested in methane reduction-decomposition cycles. Experimental results showed that both Ni/Al₂O₃ and Co/Al₂O₃ aerogel catalysts exhibited higher activity and stability than mono- or bimetallic Ni, Fe, and Co catalysts synthesized by conventional incipient wetness technique. The properties of fresh and spent aerogel catalysts were characterized by XRD, TGA, Raman, XPS, BET, SEM, and TEM. TGA analysis confirmed the absence of amorphous carbon formation during CH₄ decomposition over Ni/Al₂O₃ and Co/Al₂O₃ aerogel catalysts. Preliminary experimental results indicated that the CNTs formed over Ni/Al₂O₃ and Co/Al₂O₃ aerogel catalysts are all base-growth by nature. The selective synthesis of base-growth CNTs is due to the metal-support interaction and unique porosity presented in aerogel structure. Base-growth CNTs possess advantages than conventional tip-growth. This is largely because of the ease of separation and regeneration for industrial processing. Re-oxidation of the spent carriers will be conducted by introducing air into the reactor. Structural morphology and growth mechanism of CNT’s were correlated with surface and lattice structure of prepared aerogels. Regeneration of the spent Ni/Al₂O₃ aerogel catalyst was conducted by passing carrier gas to the reactor. The regeneration protocol developed can resume initial activity. In this study, a 60 wt% Ni/Al₂O₃ aerogel catalyst was tested and regenerated repeatedly.