Atmospheric‐pressure nonthermal plasma synthesis of ammonia over ruthenium catalysts

Abstract

Atmospheric‐pressure nonthermal plasma was used to synthesize ammonia from nitrogen and hydrogen over ruthenium catalysts. Formation of NH 3 in a N 2 ‐H 2 mixture altered the plasma characteristics due to the low ionization potential of NH 3 (10.15 eV). The optimum gas ratio was found at N 2 :H 2 = 4:1 by volume (i.e., N 2 ‐rich conditions). When plasma was operated at a temperature below 250 ° C, the NH 3 concentration increased linearly with increasing specific input energy (SIE). For the Ru(2)‐Mg(5)/γ‐Al 2 O 3 catalyst at 250 ° C, pulse energization was four times more efficient than the AC energization case. The presence of RuO 2 was found to be beneficial for the NH 3 synthesis via plasma‐catalysis. The addition of a small amount of O 2 was found to be effective for the in situ regeneration of the deactivated catalyst. The effect of metal promoters was in the order of Mg > K > Cs > no promoter.