EFFECT OF POTASSIUM AND BARIUM ON THE STABILITY OF A CARBON-SUPPORTEDRUTHENIUM CATALYST FOR THE SYNTHESIS OF AMMONIA

The effect of potassium and barium on the activity and thermal stabili ty of a carbon-based ruthenium catalyst for the synthesis of ammonia h as been studied. Kinetic measurements in NH3 synthesis were carried ou t 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 supplem ented 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 i n NH3 synthesis and more resistant to overheating than the catalyst pr omoted with potassium. The activity of Ba-Ru/C is much higher than tha t of a commercial fused-iron catalyst. This is important for industria l practice. (C) 1998 Elsevier Science B.V. All rights reserved.