Synthesis of ammonia in high-frequency discharges

The synthesis of ammonia from nitrogen-hydrogen plasma prepared using radiofrequency discharge and microwave discharge was studied under the same experimental conditions except the driving frequency. Twice larger amounts of ammonia were adsorbed on zeolite used as adsorbent in the microwave discharge than in the radiofrequency discharge. Relative intensities of NH band head (A³–X^3–,0–0) as well as hydrogen atomic line (H) observed in the plasma prepared using microwave discharge were one order of magnitude larger than those in the plasma prepared using radiofrequency discharge. Since NH_x radicals and H atoms are considered ammonia precursors, the advantage of microwave discharge over radiofrequency discharge on ammonia synthesis is discussed from the results obtained above and from the plasma parameters,kT_e andn_e, obtained by the electric double probe technique.Partly presented at the 8th International Symposium on Plasma Chemistry, August 31 to September 4, 1987, Tokyo, Japan.