Effect of potassium and barium on the stability of a carbon-supported ruthenium catalyst for the synthesis of ammonia

The effect of potassium and barium on the activity and thermal stability of a carbon-based ruthenium catalyst for the synthesis of ammonia has been studied. Kinetic measurements in NH3 synthesis were carried out in a flow differential reactor operating at standard conditions (p=6 MPa, T=673 K, X-NH3 =8%, H-2 : N-2=3 : 1). Overheating of the samples was carried out at 793 K for 24 h. The examinations have been supplemented by XRD and chemisorption studies for the characterization of the ruthenium dispersion as well as by studying the catalysts methanation. It has been found that the barium-promoted catalyst is more active in NH3 synthesis and more resistant to overheating than the catalyst promoted with potassium. The activity of Ba-Ru/C is much higher than that of a commercial fused-iron catalyst. This is important for industrial practice. (C) 1998 Elsevier Science B.V. All rights reserved.