Ruthenium ammonia decomposition

The dual-state behaviour of RU-AI2O3 catalysts may also arise from metal-support interaction. In the oxidized state, the catalyst was more selective for nitrogen formation in NO reduction than when in the reduced state. It was also active for the water-gas shift reaction whereas the reduced form was rather inactive and differences were also observed for ammonia decomposition and the CO-H2 reaction. The more active form does not appear to contain ruthenium oxide the reduced catalyst may have been de-activated by reaction with the support and its transformation to the more active form by oxidation may involve surface reconstruction and/or destruction of the metal-support interaction. 

Rarog-Pilecka W, Szmigeel D, Kowalczyk Z, Jodis S, Zielinski J (2003), Ammonia decomposition over the carbon-based ruthenium catalyst promoted with barium or cesium , J. Catal., 218, 465 69. 

In a more recent study, Li et al. [15] investigated the catalytic behavior of ruthenium catalysts supported on carbon materials with different porous and graphitic structures in the catalytic ammonia decomposition. They found that the catalytic activity followed the trend Ru/GC (graphitic carbon)> Ru/CNTs (carbon nantoubes) > Ru/CB-S (carbon black) > Ru/CB-C > Ru/CMK-3 (meso-porous carbon) = Ru/AC. It was concluded that the graphitic structure of the carbons was critical to the activity of the ruthenium catalysts, whereas the surface area and porosity were less important. 

S.R. Deshmukh, A.B. Mhadeshwar, D.G. Vlachos, Microreactor modeling for hydrogen production from ammonia decomposition on ruthenium, Ind. Eng. 

Suitable catalysts for ammonia decomposition are nickel, ruthenium and iridium... 

Ammonia decomposition was investigated by Choudhary et al. [283] over nickel, iridium and ruthenium catalysts supported by various carrier materials such as ZSM-5 and Y-zeolites, alumina and silica. Ruthenium on silica was most active, followed by iridium and nickel [283]. 

It is obvious that osmium and iron are the most effective elements under the conditions studied by Haber. On the other hand, ruthenium is the most active metal in ammonia decomposition. Since the two reactions are forward and backward steps of the same reaction, the most active metals should be the same, at least near equilibrium. The difference disclosed above is probably caused by some discrepancy in the reaction conditions. The ratio of H2/NH3 in the ammonia synthesis is much higher than that in the ammonia decomposition. Adsorbed N2 and H2 usually become inhibiting species, which depend on the ratio of H2/NH3 ratio. 

SSIMS has also been used to study the adsorption of propene on ruthenium [3.29], the decomposition of ammonia on silicon [3.30], and the decomposition of methane thiol on nickel [3.31]. 

Ruthenium Tri-iodide, RuU, was prepared by Claus4 by double decomposition of potassium iodide and ruthenium trichloride in aqueous solution.5 The salt separates out as a black amorphous precipitate which, on heating, evolves the whole of its iodine content. It absorbs ammonia, welding 2RuIs.7NH3, but does not appear to yield double salts with alkali iodides.5... 

A range of metals and metal oxides catalyze the reduction of NO. The most successful reducing agent is synthesis gas since the catalytic process is relatively fast 184), unlike the catalyzed decomposition of NO to N2 and O2. The observed nitrogen-containing products depend on the catalytic system used Pd- and Pt-based catalysts convert NO to NH3 184) whereas iridium and ruthenium systems minimize ammonia production and convert nitric oxide to dinitrogen. 

Rarog W, Kowalczyk Z, Sentek, J, Skadonowski D, Szmigiel D, Zielinski J (2001), Decomposition of ammonia over potassium promoted ruthenium catalyst supported on carbon , Appl. Catal. A Gen., 208, 213-216. 

Reduction of RU3(CO)12 with sodium in liquid ammonia gives a mixture of Na2Ru(C0)ij and NaHRu(CO)tt, which yields colorless, very unstable, volatile H2Ru(C0)i upon acidification with phosphoric acid (108). Decomposition of H2Ru(CO)i+ occurs rapidly at room temperature to give an inconpletely characterized polynuclear ruthenium carbonyl hydride, tentatively formulated as H2Ru3(CO)i2 ... 

The other uses as catalysts are for synthesis of ammonia, methylation of carbon monoxide or carbon dioxide, steam reforming of naphtha and LPG, decomposition of peroxide, and treatment of waste water, etc. Market prices of precious metals are shown in Table 16.2 [3]. Ruthenium has a low price compared to a precious metal. 

Based on the research results of monometallic catalysts, scientists also studied on bimetallic catalysts for N2 activation. They realized that the adsorption energy of N2 determines the catalysts properties. Under specific reaction conditions, it can estimate adsorption energy of N2 on catalyst. The catalytic efficiency of the elements for the synthesis and decomposition of ammonia was correlated with the chemisorption energy of nitrogen. An inverted parabolic function (volcano curve) was obtained by Ozaki et in which iron, ruthenium, and osmium mark the top of the volcano. 

An alkaline solution of this hydride is stable hydrolysis proceeds in the presence of ruthenium catalyst. It is a great virtue of this process (and also of the process of ammonia borane decomposition mentioned above) that the reaction stops instantly when the catalyst is lifted from the solution. Therefore, hydrogen generation can be controlled on demand that is, in harmony with fuel cell needs. 

The rate-limiting step in the decomposition reaction is a very sensitive function of the surface coverages of the various components and, in particular, of atomic nitrogen. Studies using both single-crystal and polycrystalline platinum and several other transition metals (tungsten, nickel, rhenium, and ruthenium ) have confirmed that the reaction follows the same pathway as the ammonia synthesis reaction on iron. All of the transition metals show broadly... 

Dissociative adsorption only occurs to any significant extent on ruthenium, although there is direct evidence that, as on most transition metals, it does not occur on the close-packed Ru(OOOl) face " or even on the open faces in the absence of promoters. The heat of adsorption of dissociated nitrogen is, however, high on the Ru(OOOl) surface (184 kJ moP with p es of 1.3 x 10 The coverage of N, derived from the decomposition of ammonia, is approximately 100% at 600 K falling slowly to 10% at 800 K in 2 x 10" torr ammonia. 

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