Synthesis of ammonia in high-frequency discharges

Uyama, Haruo; Matsumoto, Osamu

doi:10.1007/bf01015824

Cited by 92 publications

(121 citation statements)

References 15 publications

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“…2 and 3, we must first allow for the production routes of NH 3 other than the surface reactions on the membrane-like catalyst. It has been previously substantiated that NH 3 formation in the plasma phase of N 2 -H 2 was progressed by reactions of NH radicals with hydrogen [4,6,7]. Kiyooka and Matsumoto [10] have also elucidated that large amounts of NH x radicals were produced on the surface of the stainless-steel wall of the ECR chamber as a catalyst.…”

Section: Ammonia Formation In the Plasma Reactor Without The Membranementioning

confidence: 94%

“…In the Haber process, dissociative adsorption of N 2 , which has been accepted to be the rate-determining step, is carried out on promoted iron catalysts at high temperatures and pressures [1,2]. It is well known that efficient activation of N 2 at ambient conditions can be achieved by low-temperature plasmas; therefore, a number of studies on plasma synthesis of ammonia have been undertaken [3][4][5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Catalytic Effects of Metal-loaded Membrane-like Alumina Tubes on Ammonia Synthesis in Atmospheric Pressure Plasma by Dielectric Barrier Discharge

Mizushima

Matsumoto

Ohkita

et al. 2006

Plasma Chem Plasma Process

103

145

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Plasma synthesis of ammonia was studied at atmospheric pressure using a dielectric-barrier-discharge-plasma reactor equipped with a metal-loaded membrane-like alumina tube as a catalyst between the electrodes. Introducing the pure alumina into N 2 -H 2 plasma resulted in an increase in the ammonia yield and the further improvement was achieved by loading the alumina with Ru, Pt, Ni, and Fe. These results clearly demonstrate the catalytic effects of the alumina and the metals in the plasma reaction. Temperature-programmed desorption and isotope exchange reaction of nitrogen revealed that plasma-excited N 2 molecules were subjected to dissociative adsorptions mainly on the alumina to form atomic N(a) (The suffix ''(a)'' denotes adsorbed species) species, which were converted into ammonia by H 2 plasma. A role of the metals is considered to be acceleration of ammonia formation by the reaction of the alumina-adsorbed N(a) atoms with plasma-activated hydrogen species.

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Section: Ammonia Formation In the Plasma Reactor Without The Membranementioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Catalytic Effects of Metal-loaded Membrane-like Alumina Tubes on Ammonia Synthesis in Atmospheric Pressure Plasma by Dielectric Barrier Discharge

Mizushima

Matsumoto

Ohkita

et al. 2006

Plasma Chem Plasma Process

103

145

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“…The ammonia production was ascribed to the surface reaction of NH x radicals adsorbed on the zeolite with hydrogen atoms. 14 The formation of ammonia in plasmas is still not completely understood but it is assumed that plasma-surface interactions play an important role. The formation of ammonia is generally ascribed to stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals.…”

Section: Introductionmentioning

confidence: 99%

“…Plasmas containing nitrogen and hydrogen are also extensively studied because of their widespread applications in research and industrial environments. The plasmas are used for the chemical synthesis of ammonia, 9,11,14 nitriding of materials, 17 the deposition of amorphous silicon nitride ͑a-SiN x :H͒ films for solar cell applications, 19 the plasma-assisted atomic layer deposition of TiN thin films, 20 and the etching of organic low k films. 21 Previously, we have shown that ammonia can be formed efficiently in plasmas generated from mixtures of nitrogen and hydrogen via plasma-activated catalysis.…”

Section: Introductionmentioning

confidence: 99%

Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

Helden¹,

Wagemans²,

Yagci³

et al. 2007

Journal of Applied Physics

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We investigated the efficiency and formation mechanism of ammonia generation in recombining plasmas generated from mixtures of N 2 and H 2 under various plasma conditions. In contrast to the Haber-Bosch process, in which the molecules are dissociated on a catalytic surface, under these plasma conditions the precursor molecules, N 2 and H 2 , are already dissociated in the gas phase. Surfaces are thus exposed to large fluxes of atomic N and H radicals. The ammonia production turns out to be strongly dependent on the fluxes of atomic N and H radicals to the surface. By optimizing the atomic N and H fluxes to the surface using an atomic nitrogen and hydrogen source ammonia can be formed efficiently, i.e., more than 10% of the total background pressure is measured to be ammonia. The results obtained show a strong similarity with results reported in literature, which were explained by the production of ammonia at the surface by stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals. Furthermore, our results indicate that the ammonia production is independent of wall material. The high fluxes of N and H radicals in our experiments result in a passivated surface, and the actual chemistry, leading to the formation of ammonia, takes place in an additional layer on top of this passivated surface.

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“…In high-frequency discharges it was reported in 1989 that zeolite added to the downstream plasma facilitated the ammonia production, which was ascribed to NH x radicals adsorbed on the zeolite. 2 We propose a different way of generating ammonia, i.e., via plasma-activated catalysis. In this process fluxes of hydrogen and nitrogen radicals are produced in a high density plasma source with high dissociation degree.…”

mentioning

confidence: 99%

Absolute density measurements of ammonia produced via plasma-activated catalysis

Vankan

Rutten

Mazouffre

et al. 2002

Applied Physics Letters

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The generation of ammonia from atomic hydrogen and nitrogen has been demonstrated by means of cavity enhanced absorption spectroscopy. The atomic species are produced in a thermal plasma source in which plasma is created from mixtures of hydrogen and nitrogen. It is shown that for large atomic flux conditions, 2% of the hydrogen and nitrogen can be converted to ammonia. The process in which the ammonia molecules are formed from atomic radicals at the fully covered surface is called plasma-activated catalysis.

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Synthesis of ammonia in high-frequency discharges

Cited by 92 publications

References 15 publications

Catalytic Effects of Metal-loaded Membrane-like Alumina Tubes on Ammonia Synthesis in Atmospheric Pressure Plasma by Dielectric Barrier Discharge

Catalytic Effects of Metal-loaded Membrane-like Alumina Tubes on Ammonia Synthesis in Atmospheric Pressure Plasma by Dielectric Barrier Discharge

Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

Absolute density measurements of ammonia produced via plasma-activated catalysis

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