Catalytic activity of Co/γ-Al2O3 catalysts for decomposition of ammonia to produce hydrogen

Abstract

This paper aims to study the performance of Co/meso-Al2O3 catalysts for ammonia decomposition to produce hydrogen. High-performance Co/meso-Al2O3 catalysts were prepared using a sequential metal loading approach. The synthesized catalysts were analyzed by several techniques including X-ray diffraction (XRD), N2 physisorption analysis, temperature-programmed reduction (H2-TPR), temperature-programmed desorption (NH3-TPD) and transmission electron microscope (TEM). The effect of metal loading, decomposition temperature and weight hourly space velocity (WHSV) on the catalyst activity were studied. Temperature-programmed desorption (NH3-TPD) analysis showed the coexistence of weak acidic sites and strong acidic sites in the synthesized catalysts, indicative of weak metal–support interaction. The reaction activation energy of the catalysts followed the order of 26Co-CAT(A) < 9Co-CAT(A) < 16Co-CAT(A) < 5Co-CAT(A) < CAT(A). Particularly, 26 Co-CAT(A) exhibited significantly lower activation energy compared to the other catalyst, which was in line with its catalytic activity. This observation indicated that the cobalt loading in 26 Co-CAT(A) resulted in relatively weaker metal-support interactions, leading to lower desorption energy and thus allowing higher NH3 conversion at lower temperatures. These findings offer valuable insights for the development and optimization of advanced Co-based catalysts, facilitating the sustainable and efficient application of ammonia decomposition.