(128a) A Comparative Parameter Study of Ni-Cu/Sio­2 and Ni-Cu/Al2O3 Catalysts to Produce Cox- Free Hydrogen and Carbon Nanotubes Via Thermocatalytic Decomposition of Methane

Thermocatalytic decomposition (TCD) of methane is the most effective route for the production of CO_x-free hydrogen and carbon nanotubes, simultaneously. In this work, a parametric study of the effects of the process variables including metal loading, reaction temperature, preparation method and space velocity (W/Fa_o) was undertaken. The effect of copper added to Ni/SiO₂ and Ni/Al₂O₃ as a co-catalyst for the methane decomposition process has also been investigated. Copper as a nickel co-catalyst increases the methane decomposition and carbon yield over both of the catalysts. However, an increased operating temperature above 750 ^oC, raises the catalyst deactivation rate. At 750 °C, carbon was deposited as carbon nanofibers and resulted the highest methane conversion and carbon yield. Among the catalysts tested, the 60%Ni-10%Cu/Al₂O₃ catalyst showed the highest activity and stability due to the higher dispersion and stabilization of Ni particles due to the formation of nickel aluminate (NiAl₂O₄) spinel structure. The characterization of the fresh and spent catalysts has been carried out by using different techniques such as BET Surface area analysis, temperature programme reduction (TPR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, bulk deposition of highly uniform multi-walled carbon nanotubes with different diameters were dependent on the Ni crystalline size observed in the Ni-Cu/SiO­₂ and Ni-Cu/Al₂O₃ catalysts.