Investigating the operation parameters for ammonia synthesis in dielectric barrier discharge reactors

Abstract

Abstract Plasma-assisted nitrogen fixation has been considered a potential green alternative for conventional Haber–Bosch process and has recently received a lot of attention. Ammonia synthesis in nonthermal plasma reactors at atmospheric pressure has been investigated in this research with a 5% Ru/ α -Al 2 O 3 catalyst. The operating parameters including feed molar ratio, flow rate, applied voltage, discharge power and argon dilution were investigated to provide information for optimization of NH 3 concentration and energy consumption. Difference between the blank reactor and the catalyst-packed reactor were presented with a discussion on their own optimal parameters. The optimal feed gas ratio (N 2 :H 2 ) for blank reactor and the catalyst-packed reactor are 1:3 and 2:1 correspondingly. Higher flow rate resulted in a lower NH 3 concentration and energy consumption in both blank reactor and the catalyst-packed reactor. Ammonia concentration of 1.49% was achieved in a catalytic DBD reactor with 120 ml min −1 , 2:1 N 2 /H 2 feed gas ratio and 38.4 W discharge power, corresponding to the energy consumption of 32.39 MJ mol −1 . The discharge power and the reactor temperature is important to the synthesis of ammonia in catalytic DBD reactor and the effect of heat build-up in the reactor on NH 3 concentration was observed. Argon addition improved the conversion of nitrogen and hydrogen at a cost of energy consumption and production rate in both blank and catalyst-packed reactor, but it is more beneficial for increasing the conversion of reactants in the case of catalytic DBD reactor.