Experimental study and statistical analysis of hydrogen yield in methane steam reforming over a hydroxyapatite-supported nickel catalyst

Abstract

This study aimed to investigate the use of hydroxyapatite (HAp) as a catalyst support for the methane steam reforming (MSR) process. Catalysts were prepared via incipient wetness impregnation using nickel as the active metal and characterized by N₂ physisorption analysis, X-ray diffraction, H₂ temperature-programmed reduction, and transmission electron microscopy. The effects of four key parameters in hydrogen production—nickel loading (Ni wt%), inlet steam-to-methane (H₂O/CH₄) ratio, space velocity (SV), and temperature (T)—were evaluated via a statistical analysis. Thermodynamic calculations were also used to compare the catalyst activity results with the equilibrium conditions. The findings confirmed the effectiveness and stability of HAp as a support, exhibiting high thermal stability, coke resistance, and a mesoporous structure with an average specific surface area of 65 m²·g⁻¹. The calcined Ni/HAp catalyst mainly comprised crystalline NiO and displayed a higher surface area of 54 m²·g⁻¹ and superior dispersion at loadings of 5 and 10 wt% Ni compared to 15 wt% Ni. The temperature, SV, and inlet reactant ratio significantly influenced the process. A long-term stability test carried out under optimal conditions over 98 h demonstrated the consistent activity and stability of the 10 wt%Ni/HAp catalyst, maintaining a high methane conversion of 99 % and yielding 90 % hydrogen, 80 % carbon monoxide, and 20 % carbon dioxide, with no observed carbon deposition on the catalyst surface.