Atmospheric-pressure nonthermal plasma synthesis of ammonia over ruthenium catalysts

Atmospheric-pressure nonthermal plasma was used to synthesize ammonia from nitrogen and hydrogen over ruthenium catalysts. Formation of NH3 in a N-2-H-2 mixture altered the plasma characteristics due to the low ionization potential of NH3 (10.15eV). 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 degrees C, the NH3 concentration increased linearly with increasing specific input energy (SIE). For the Ru(2)-Mg(5)/-Al2O3 catalyst at 250 degrees 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 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.