Graphical abstract

The dispersion of active metal species on the support material of a catalyst is crucial for efficient catalytic reactions. Surfactant-assisted melt infiltration (SAMI), in which catalytically active components are supported only by heating with a surfactant instead of a solvent, is a straightforward method for synthesizing highly dispersed catalysts. In this study, monometallic 10 wt% Ni catalyst and alkaline-earth-metal (Mg, Ca, Sr, and Ba)-doped Ni catalysts supported on the ultra-stable Y (USY) zeolite are prepared using SAMI for ammonia decomposition. The addition of Span^TM60 during the preparation of the Ni/USY catalyst improved its catalytic performance. Moreover, the Mg-promoted Ni/USY catalyst prepared via SAMI exhibited further enhancement in catalytic activity and stability, demonstrating the synergistic effect of the Span^TM60 surfactant and Mg promoter. Detailed characterization revealed that the improved performance of the surfactant-added Mg-promoted catalyst was due to the high dispersion of Ni and MgO particles and the enhanced acidic and basic properties, which affected the number of adsorption sites of NH₃ and the kinetic rate-determining step during NH₃ decomposition, respectively. The results showed that SAMI could be used to synthesize highly dispersed and active Ni catalysts on zeolites.