Effect of a Barium Promoter on the Stability and Activity of Carbon‐Supported Cobalt Catalysts for Ammonia Synthesis

Samples of barium‐promoted carbon‐supported cobalt catalysts for ammonia synthesis were prepared; the cobalt content was constant (27.4 wt %) and the amount of barium introduced differed within the range of 0–0.88 mmol gC+Co−1. Turbostratic carbon was used as the support. Several techniques, including X‐ray powder diffraction, TEM, Thermogravimetric analysis–mass spectrometry (methanation studies) and H2 temperature‐programmed desorption were used to examine the properties of the carbon support or catalytic materials. The reaction rate measurements were performed under the following conditions: T=400 °C, p=9.0 MPa, x =8.5 mol %, H2/N2=3:1. It was found that barium is an important component of the cobalt catalysts supported on activated carbon for ammonia synthesis. Barium inhibits the process of carbon support methanation, which also results in a decrease in the sintering of the active phase (cobalt). Moreover, even a small amount of barium significantly activates the cobalt surface in ammonia synthesis, suggesting that barium locates primarily on the surface of cobalt.