Promoting effects of iridium on nickel based catalyst in ammonia decomposition

Nickel-iridium bimetallic catalysts with different iridium contents were prepared by the wet impregnation method. Their catalytic performances in ammonia decomposition were investigated. The results illustrated that the activity of nickel catalyst in ammonia decomposition at low temperature (300°C to 450°C) was significantly enhanced by adding iridium to the catalyst. A maximum ammonia conversion was observed with the iridium content being 0.7 wt%. At 400°C, the ammonia conversion over 10%Ni-0.7%Ir/γ-Al2O3 catalyst was 43.55%, which was 40.0% higher than that on the corresponding catalyst without iridium. X-ray diffraction (XRD) suggested that the addition of iridium provided a better dispersion of active nickel species. Temperature programmed reduction (H2-TPR) profiles demonstrated that there was a synergetic effect between iridium and nickel, and adding iridium to the catalyst may reduce the interaction between the active species and support. Temperature programmed desorption (H2-TPD) indicated that 10%Ni-0.7%Ir/γ-Al2O3 catalyst had more active sites than the corresponding 10%Ni/γ-Al2O3.