Catalytic Performance of Hydroxyapatite-Based Supports: Tailored vs. Commercial Formulations for Dry Reforming of Methane

Catalyst deactivation, mainly due to coke deposition, presents a significant challenge in the process of dry reforming of methane (DRM). This study focused on coke-resistant catalysts for DRM, particularly nickel-based catalysts supported on hydroxyapatite (HAP). A novel HAP formulation (HAPS) with a Ca/P ratio of 1.54, below the stochiometric ratio studied in previous studies, was compared with commercial HAP (HAPC), and both were impregnated with 10 wt% nickel. The synthesis of HAPS involved low temperature (60 °C), moderate stirring, and a pH of 11, using a custom setup. Dry-reforming reactions were conducted under severe conditions (T = 800 °C) to assess the resistivity of both supports over 120 h. Our findings indicated sustained high conversion rates, reaching 93% for CH4 and 98% for CO2 with HAPS, despite an increase in gas hourly space velocity. Characterisation, including X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy, revealed coke formation using HAPC, leading to initial deactivation, in contrast with the custom support. This discrepancy may be attributed to the distinct physical and chemical properties of the catalysts, their reaction mechanisms, and the deactivation precursors. Overall, the performance of nickel-based catalysts significantly hinges on support–catalyst interactions, in addition to thermal stability.