Hydroxyapatite Derived from Salmon Bone As Green Ecoefficient Support for Ceria-Doped Nickel Catalyst for CO₂...

Hydroxyapatite (HA) derived from salmon bone byproducts is used as a green support for the nanostructured nickel catalysts applied in the methanation of carbon dioxide (CO₂). Undoped nickel catalysts and various ceria-doped nickel supported on hydroxyapatite (HA) were prepared by coimpregnation. Characteristics of the as-prepared catalysts were investigated by the various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), hydrogen temperature-programmed reduction (H₂-TPR), carbon dioxide temperature-programmed desorption (CO₂-TPD), and energy-dispersive X-ray spectroscopy (EDX). The catalyst activity was assessed throughout CO₂ methanation in the low-temperature range of 225-350 °C with the molar ratio of H₂/CO₂ = 4/1. The function of HA and ceria provided a high dispersity of nickel particles over the catalyst surface with the size range of 24.5-25.8 nm, leading to improvement in the reduction and CO₂ adsorption capacity of the catalysts as well as enhancing the catalytic efficiency in CO₂ methanation. The 10Ni/HA catalyst reduced at suitable conditions of 400 °C for 2 h showed the highest catalytic performance among the tested catalysts. CO₂ conversion and CH₄ selectivity reached 76.6 and 100% at a reaction temperature of 350 °C, respectively. The results show that the Ni/HA sample doped with 6.0 wt % ceria was the best, with the CO₂ conversion and the CH₄ selectivity reaching 92.5% and 100%, respectively, at a reaction temperature of 325 °C.