Cobalt-based catalysts on 13X zeolite for efficient ammonia cracking to hydrogen

The development of cost-effective, non-precious metal catalysts for relatively low-temperature ammonia cracking is important for sustainable CO₂-free hydrogen production. In this study, cobalt-based catalysts supported on 13X zeolite were synthesized and evaluated for NH₃ decomposition. Additionally, 15 wt% Co oxide catalysts supported on γ-Al₂O₃ and In₂O₃ were synthesised to assess the effect of support properties. Catalyst performance was evaluated using fixed-bed reactor in temperature range of 350–650 °C. Among all catalysts, 15% Co/13X exhibited the highest activity at 450 and 500 °C, achieving > 95% NH₃ conversion at 500 °C with excellent time-on-stream stability over 13 h. Comprehensive characterization techniques, including H₂-TPR, NH₃-TPD, H₂-TPD, CO₂-TPD, and XPS, were employed to correlate structure activity relationships. The superior performance of 15% Co/13X is attributed to its enhanced reducibility, facilitating the formation of metallic Co⁰ active sites, and a favorable balance of surface acidity and basicity for NH₃ adsorption and activation. Although 5% and10% Co/13X showed slightly higher acidity, lower Co⁰ content resulted in lower activity due to limited cobalt availability. Compared to 15%Co/13X, 15% Co supported by Al₂O₃ and In₂O₃ demonstrated inferior activity due to weaker reduction properties and low NH₃ adsorption capacity. XPS analysis after reaction confirmed the formation and stability of Co⁰ species in Co/13X during ammonia decomposition. These findings highlight the importance of optimizing both metal loading and support characteristics to develop efficient, stable, and cost-effective non-noble metal catalysts for hydrogen production from ammonia.