Plasma catalytic reaction in ammonia synthesis in the microwave discharge

Abstract
Practically, ammonia is made in the Haber process, in which the synthesis is carried out on promoted iron catalyst at higher pressures and temperatures. In the plasma process, NH radicals were formed in the nitrogen-hydrogen plasma and the NH radicals would be quenched by hydrogen molecules to form ammonia. When the catalyst was placed in the plasma, synergistic effects of plasmas and catalysts on the ammonia synthesis were observed. The species in the ECR plasma do not collid in the plasma and the ammonia formation reaction would proceed only on the surface of the catalyst. Thus the reaction ocurred in the ECR plasma apparatus was investigated from both the identifications of species in the plasma and adsorbed species on the surface of steel substrate placed in the plasma to clarify the reaction scheme of the ammonia synthesis. A dissociative adsorption of excited nitrogen molecules and molecular ions or a direct adsorption of NH radicals on the surface of the catalyst would promote the formation reaction of ammonia.