A high performance barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide for ammonia synthesis.

Ammonia synthesis was performed over a barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide. The rate of NH formation over this catalyst was about 3.5 times higher than that over the unpromoted catalyst at 9 MPa and 400 °C. Furthermore, no sign of thermal deactivation was observed during long-term overheating at 600 °C for 360 h. The results of physicochemical studies, including XRPD, DRIFTS, H-TPD, CO-TPD, N + H TPSR and kinetic analysis, revealed that the addition of Ba promoter increased the surface basicity of the catalyst and modified the adsorption properties of the Co surface towards H and NH. The decreased adsorption strength of the corresponding sites towards hydrogen and ammonia resulted in greater availability of active sites in the Ba-promoted cobalt catalyst. These characteristics are considered to have a profound effect on the performance of this catalyst in NH synthesis.