Catalytic Methane Decomposition over Bimetallic Transition Metals Supported on Composite Aerogel

Bimetallic transition metals over single Al2O3 support and TiO2·Al2O3 composite support aerogel catalysts (9Ni-1Co/Al2O3 and 9Ni-1Co/Al2O3·TiO2) were synthesized by the sol–gel technique and tested in the methane decomposition reaction for production of COx-free hydrogen and base-growth carbon nanotubes (CNTs). Compared to monometallic catalysts and other bimetallic catalysts with different Ni/Co molar ratios such as 5Ni-5Co/Al2O3, 3Ni-7Co/Al2O3, and 1Ni-9Co/Al2O3, mesoporous 9Ni-1Co/Al2O3 aerogel catalysts have higher catalytic activity and stability. Furthermore, aerogel catalysts (9Ni-1Co/Al2O3·TiO2) consisting of bimetallic transition metals supported on TiO2·Al2O3 composite support displayed higher catalytic performance than 9Ni-1Co/Al2O3 aerogel catalyst. These results indicated that metal sintering phenomena on bimetallic transition metals was less severe than monometallic; meanwhile, the composite support improved metal dispersion, leading to higher utilization of metal species which enhanced the catalytic performance. The addition of TiO2 can increase the number of active sites for CNTs deposition and facilitate the transfer and removal of CNTs deposited on Ni and Co particles, which are beneficial for enhancing the utilization of Ni and Co nanoparticles and reducing the catalyst deactivation rate. Regeneration experiments on 9Ni-1Co/Al2O3 and 9Ni-1Co/Al2O3·TiO2 aerogel catalysts were carried out, and the results showed that these two aerogel catalysts still exhibited high catalytic performance after two regeneration cycles.