Promoting effect of La additive on the Ni/Al2O3 catalyst in the catalytic decomposition of ammonia

The calcination conditions of Al₂O₃ support and active Ni component in the Ni/Al₂O₃ catalyst for the ammonia decomposition were optimized. On the basis of that, the promoting effect of La addition on the Ni/Al₂O₃ catalyst in the catalytic decomposition of ammonia was investigated. The results indicate that at 550 ° and a WHSV of 36000 mL/(g·h), the ammonia conversion over 10%Ni/5La-Al₂O₃ with a La loading of 5% reaches 83.2%. The ammonia conversion achieves 92.2% at 524 ° when the content of La is further increased to 15% and the catalytic activity of 10%Ni/15La-Al₂O₃ displays no obvious decline within 100 h. Combining with the XRD, XPS, TEM and H₂-TPR results, the superior performance of La-promoted Ni/Al₂O₃ catalyst in the ammonia decomposition is ascribed to that the addition of La can improve the reductive properties of Ni, enrich the surface oxygen defect and nickel content, increase the adsorption sites of NH₃ molecules and stabilize the Al-based support structure. These results should be conducive to the understanding of the co-catalytic effect of rare earth element La and the development of efficient Ni-based ammonia decomposition catalysts.