Effect of textural properties of alumina support on the catalytic performance of Ni/Al2O3 catalysts for hydrogen production via methane decomposition

• The Ni/Al2O3 catalysts with various Al2O3 structures have been investigated for CDM.
• The Ni/Al2O3(NP) catalyst exhibits the highest catalytic activity.
• The formation of NiAl2O4 inhibits the catalytic activity of Ni/Al2O3(HS) catalyst.

Catalytic performance of 60 wt.% Ni supported on different morphological structure of alumina was studied for COx-free hydrogen production by methane decomposition. The Al2O3 supports were prepared by reverse microemulsion and precipitation techniques to obtain alumina hollow sphere (HS) and alumina nanoparticles (NP) structures, respectively. These materials were compared with the commercial alumina (bulk) to investigate the effect of the support structure on the catalytic activity and stability of Ni particles. The fresh and used catalysts were characterized by XRD, BET, TGA, H2-TPR, TEM and Raman spectroscopy. The results revealed that the texture properties of Al2O3 support play a crucial role on the catalyst performance. The Ni/Al2O3 nanoparticles (NP) catalyst exhibited the highest catalytic decomposition activity due to its better metal site distribution. The TPR results showed that almost all NiO particles in this catalyst were located extensively on the external surface of Al2O3 nanoparticles. On the other hand, the Ni/Al2O3 hollow sphere (HS) catalyst showed a lower activity due to the formation of large quantities of NiAl2O4 species. TEM and Raman spectroscopy data proved that longer and smaller size of multi-walled carbon nanotubes (MWCNT) with a relatively uniform diameters were obtained on the Ni/Al2O3 nanoparticles, compared to the other catalysts.