Atmospheric‐pressure nonthermal plasma was used to synthesize ammonia from nitrogen and hydrogen over ruthenium catalysts. Formation of NH3 in a N2‐H2 mixture altered the plasma characteristics due to the low ionization potential of NH3 (10.15 eV). The optimum gas ratio was found at N2:H2 = 4:1 by volume (i.e., N2‐rich conditions). When plasma was operated at a temperature below 250 °C, the NH3 concentration increased linearly with increasing specific input energy (SIE). For the Ru(2)‐Mg(5)/γ‐Al2O3 catalyst at 250 °C, pulse energization was four times more efficient than the AC energization case. The presence of RuO2 was found to be beneficial for the NH3 synthesis via plasma‐catalysis. The addition of a small amount of O2 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.
The effects of humidity on gas temperature in the afterglow of a pulsed positive corona discharge are studied. The gas temperature is measured using the laser-induced fluorescence (LIF) of NO molecules. The discharge occurs in a 13 mm point-to-plane gap under atmospheric pressure. When the water vapor concentration in air is increased from 0.5% to 2.4%, the temperature increases from 550 to 850 K near the anode tip, and from 350 to 650 K at a position 2.5 mm from the anode tip. The gas heating in the humid environment is due to the fast vibration-to-vibration processes of the O 2 -H 2 O and N 2 -H 2 O systems and the extremely rapid vibration-to-translation process of the H 2 O-H 2 O system. These processes accelerate the transfer of energy from O 2 (v) and N 2 (v) to translational energy. Measurements of the LIF of O 2 (v = 6) show that the decay rate of O 2 (v) density is increased by humidification.
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