Effects of CeO2 addition on Ni/Al2O3 catalysts for the reaction of ammonia decomposition to hydrogen

Abstract

Effects of CeO2 addition on the catalytic performance of Ni/Al2O3 catalysts for ammonia decomposition to hydrogen were investigated by activity studies and some physico-chemical methods like N2-adsorption/-desorption, H2-chemisorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed surface reduction (NH3-TPSR). The results showed that the addition of CeO2 greatly improved the catalytic activity and stability of Ni/Al2O3 catalysts for ammonia decomposition to COx-free hydrogen. 98.3% NH3 conversion and 32.9mmol/(mingcat) H2 formation rate were achieved over CeO2 promoted Ni/Al2O3 catalyst at 823K and 30000ml/(hgcat) NH3 space velocity. The characterization results indicate that the addition of CeO2 enlarged the catalyst pores, moderated the interaction between Ni and alumnia, suppressed Ni0 crystallites from sintering, and improved the recombinative desorption of N adatoms from the Ni0 surface.