Plasma chemical synthesis. II. Effect of wall surface on the synthesis of ammonia

Touvelle, M. S.; Licea, J.L. Munoz; Venugopalan, M.

doi:10.1007/bf01016001

Cited by 31 publications

(44 citation statements)

References 9 publications

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“…This seems to be in contrast to experiments of various research groups in the world, in which it was shown that the ammonia production is dependent on the type of wall material, e.g., iron, stainless-steel, copper, nickel, silver, aluminum, Pyrex, zinc, or platinum. [9][10][11][12][13] However, a major difference with our experiments is that in those experiments the wall is used to form adsorbed nitrogen atoms by the dissociative adsorption We observed that the ammonia molar fraction is independent of the two wall materials studied, which indicates that the N and H flux to the surface is most likely not changed by an a-SiN x deposited wall. The high N and H flux to the surface leads to a surface covered with N and H radicals and other molecular radicals.…”

Section: Influence Of Surface Materials On Ammonia Productionmentioning

confidence: 77%

“…It was shown by various research groups that ammonia production using plasmas is dependent on the type of wall material ͑up to a factor of 3͒. [10][11][12][13] The wall is namely still used as a catalyst to form adsorbed nitrogen atoms by the dissociative adsorption of excited N 2 molecules or molecular nitrogen ions. In 1989, Uyama and Matsumoto reported that zeolite added to the downstream plasma in high-frequency discharges facilitated the ammonia production.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Influence Of Surface Materials On Ammonia Productionmentioning

confidence: 77%

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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“…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%

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

106

146

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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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“…The reaction yield is low (15%) but residual gases can be recycled, increasing thus the efficiency up to 98%. Similar methods have been experimented using an iron catalytic electrode, placed within an N 2 -H 2 discharge or in the discharge afterglow to produce NH 3 [23][24][25] or hydrazine [26] or for nitriding treatments of iron [27]. Different discharges have been tested like dc and ac discharge current, rf, and microwave discharge.…”

Section: N X H Y Radicals and Molecules Produced In Ar-n 2 -H 2 Expanmentioning

confidence: 99%

A Thermochemical Process Using Expanding Plasma for Nitriding Thin Molybdenum Films at Low Temperature

Jauberteau¹,

Jauberteau²,

Touimi³

et al. 2012

ENG

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The mechanical and chemical properties of transition metal nitrides are very attractive for numerous industrial applications. Thin nitride films are expected to be good diffusion barrier in microelectronic devices. Nitrogen diffuses into the whole thickness of the molybdenum film heated at low temperature and exposed to expanding plasma of (Ar-N 2 -H 2 ) compared with pure N 2 plasma. NH x species in the plasma are produced by different homogeneous or heterogeneous reactive mechanisms that results in an expansion of the plasma compared with pure N 2 plasma. NH x species and probably H atoms improve the transfer of nitrogen into the metal by preventing the formation of MoO 2 oxides which act as a barrier of diffusion for nitrogen.

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Plasma chemical synthesis. II. Effect of wall surface on the synthesis of ammonia

Cited by 31 publications

References 9 publications

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

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

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

A Thermochemical Process Using Expanding Plasma for Nitriding Thin Molybdenum Films at Low Temperature

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