The Synthesis of Ammonia in the Low Voltage Arc

Brewer, A. Keith; Miller, R. R.

doi:10.1021/ja01359a018

Cited by 18 publications

(13 citation statements)

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“…Bai et al also reported similar N 2 :H 2 ratios of 4:1–9:1 using a DBD reactor with one of the dielectric barriers coated with MgO catalyst . Early studies at low pressure (0.3 Torr) arc discharge also indicated that the maximum rate of NH 3 synthesis was obtained with a N 2 :H 2 ratio of about 5:1; that is, the dissociation of N 2 is the rate‐limiting step in NH 3 synthesis using plasma. Unless otherwise noted, a N 2 :H 2 ratio of 4:1 was used throughout this study.…”

Section: Resultsmentioning

confidence: 90%

“…Plasma chemistry using electrical discharge has attracted considerable attention due to its intrinsic characteristics, including ultra‐fast reaction times (∼10 −4 s), mild reaction conditions (ambient pressure and temperature), rapid start‐up and shutoff, and adaptability to a hybrid system in combination with other technologies. Electrical discharge plasma has also been studied in the direct synthesis of NH 3 from N 2 and H 2 at ambient temperature and pressures of several Torr . However, plasma synthesis of NH 3 has given low energy yields.…”

Section: Introductionmentioning

confidence: 99%

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Atmospheric‐pressure nonthermal plasma synthesis of ammonia over ruthenium catalysts

Kim

Teramoto

Ogata

et al. 2016

Plasma Processes & Polymers

126

224

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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.

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Section: Resultsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Atmospheric‐pressure nonthermal plasma synthesis of ammonia over ruthenium catalysts

Kim

Teramoto

Ogata

et al. 2016

Plasma Processes & Polymers

126

224

View full text Add to dashboard Cite

show abstract

“…Since Brewer and Westhaver first proposed a probable mechanism in a catalyst-free DC glow discharge in 1929, [24][25] other research groups have proposed probable reaction pathways in various types of plasmas such as DBD, [4,26,39] gliding arc [40] and RF. [21,30] Evidently, there have been significant variations about which physical parameter is claimed to "control" the formation of ammonia, but all proposed mechanisms -regardless the type of plasma or reactor configuration -have in common that the formation of NH x species is believed to occur on surfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 close to the plasma phase.…”

Section: Proposed Reaction Pathwaymentioning

confidence: 99%

Enhancement of the Yield of Ammonia by Hydrogen‐Sink Effect during Plasma Catalysis

et al. 2019

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Plasma‐catalytic ammonia synthesis has been known since the early 1900s, but only until now efforts to optimize catalysts for this purpose are emerging. Here, we investigate various transition metals, low‐melting‐point metals, and gallium‐rich alloy catalysts for their activity towards ammonia production under a plasma environment. The best three pure metal catalysts were Ni, Sn and Au, which are not traditional catalysts for the current industrial ammonia synthesis. The ammonia yields for these catalysts were 34 %, 29 %, and 19 %, respectively. Synergistic effects were detected when employing alloys, as some alloys presented ∼25–50 % higher yields than their constituent metals. The employed metals were classified into two categories. Category I metals (Cu, Ag, Au and Fe), which are nitrophobic (excluding Fe, the Haber‐Bosch catalyst) and poor hydrogen sinks. For these metals, the measured concentration of Hα in the gas phase tended to correlate inversely with ammonia yield and directly with the H binding strength on the catalyst surface. Category II metals (Ga, In, Sn and Ni), which are good hydrogen sinks, tend to have a lower concentration of Hα in the gas phase than that of category I metals, which is consistent with their expected sink behavior. For these metals, the concentration of Hα correlates with ammonia yield. Plasma characterization experiments and DFT calculations suggest that the higher performance of Ni and Sn is related to the benefit of dissolving hydrogen to slow down H recombination, which is a feature that could be potentially optimized in future studies by rationally altering the catalyst composition.

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“…277 However, research conducted on ammonia synthesis in this type of reactor is limited. 197,201,202,303,304 Brewer et al 197 first published on the application of low voltage arcs for ammonia synthesis in 1931. A detailed study on ammonia synthesis in an arc plasma was conducted by van Helden et al 201,202 Implementing catalysts in arc reactors, for inplasma catalysis, is not feasible, due to the excessive temperatures.…”

Section: Performance In Various Types Of Plasma Reactorsmentioning

confidence: 99%