Effect of Supports on the Properties of Co-Mo nitride Catalysts for Ammonia Decomposition

摘要

Supported Co-Mo nitride catalysts have been synthesized by incipient-wetness impregnation method and temperature-programmed reaction in N_2-H_2 mixed gases. The effect of support types, namely carbon nanotubes(CNTs), active carbon(AC), 5A zeolite and Al_2O_3 on the properties of the prepared catalysts for ammonia decomposition has been investigated by XRD, H_2-TPR and SEM techniques. The results showed that CNTs was the optimum support for Co-Mo nitride catalyst. At 550 °C, NH3 conversions over CoMoN_x/AC, CoMoN_x/Al_2O_3 and CoMoN_x/5A Zeolite catalysts were only 14.7%, 65.4% and 68.7%, respectively, while NH3 conversion over CoMoNx/CNTs catalyst was up to 84.4%. XRD and H_2-TPR results indicated that the active species consist of CoMoO_4, MoO_3, γ-Mo_2N and Co_3Mo_3N crystallites, which can be reduced at elevated temperatures at H_2 atmosphere. The SEM characterization demonstrated that Co-Mo nitrides particles disperse uniformly on the CNTs.