Formation of Ru–M/Sibunit Catalysts for Ammonia Synthesis

Шитова, Н. Б.; Dobrynkin, N. M.; Носков, А. С.; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.; Кочубей, Д. И.; Цырульников, П. Г.; Shlyapin, D. A.

doi:10.1023/b:kica.0000032178.09743.3f

Cited by 22 publications

(12 citation statements)

References 15 publications

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“…Cs + and K + reduction, at least under the present reduction conditions, seems possible if we consider chemisorbed H species (in equilibrium with molecular H2) as the reducing agent. Hence, as observed also in [34], the presence of Ru seems fundamental in order to catalyse the surface reduction of alkali metal ions, very likely through the dissociative adsorption of H2, so providing the atomic H needed for such a reduction. Some possible reaction pathways and the relative G calculations are proposed elsewhere [33,34].…”

Section: -O2 Chemisorptionmentioning

confidence: 75%

“…Hence, as observed also in [34], the presence of Ru seems fundamental in order to catalyse the surface reduction of alkali metal ions, very likely through the dissociative adsorption of H2, so providing the atomic H needed for such a reduction. Some possible reaction pathways and the relative G calculations are proposed elsewhere [33,34]. However, we have observed some overtaking of oxygen also in the case of the blank samples doped with Cs and K. This can be justified by the possible reduction of these ions even in the absence of Ru, if a proper amount of chemisorbed H species can form (e.g.…”

Section: -O2 Chemisorptionmentioning

confidence: 75%

“…Indeed, the TCD peak does not close within the experimental time lapse, at difference with what reported for a comparative sample prepared from Ru(NO)(NO3)3. Hence, we can hypothesise that the samples prepared from RuCl3 have to be activated more drastically, so to remove chlorides, well known poisons for this catalyst [1,17,32,34]. This "over-activation" could be avoided by a repeated washing of the sample after Ru reduction, leading to good catalyst performance even with a shorter activation [17].…”

Section: -Catalyst Activationmentioning

confidence: 99%

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Promoters state and catalyst activation during ammonia synthesis over Ru/C

Rossetti¹,

Mangiarini²,

Forni³

2007

Applied Catalysis A: General

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Carbon-supported, promoted Ru-based catalysts for ammonia synthesis proved to be interesting substitutes for the traditional Fe-based ones. A debate recently arose on the active state of promoters, mainly Cs and Ba, and on the effect of the latter on Ru active sites. In the present work a set of Ba-, Cs-and K-promoted samples has been characterised by various techniques. Higher H2 and O2 uptakes have been observed during reduction and chemisorption, respectively, on Cs-and K-promoted samples supported on graphitised carbon. No evidence of this has been observed with samples supported on active carbon. This is in line with the hypothesis of alkaline promoters partial reduction under the ammonia synthesis conditions, favoured by the formation of graphite intercalation compounds. Furthermore, some suggestions are here introduced on the beneficial role of Ba, especially in increasing the support resistance to methanation.Finally, the efficacy of catalyst activation was found to depend on the nature of Ru precursor. Indeed, a prolonged activation at relatively high temperature is usually needed with chloride precursors, to remove the counterion, a poison for the catalyst, whereas less dramatic conditions are required for different precursors, such as nitrosylnitrate.

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Section: -O2 Chemisorptionmentioning

confidence: 75%

Section: -O2 Chemisorptionmentioning

confidence: 75%

Section: -Catalyst Activationmentioning

confidence: 99%

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Promoters state and catalyst activation during ammonia synthesis over Ru/C

Rossetti¹,

Mangiarini²,

Forni³

2007

Applied Catalysis A: General

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“…Carbon-supported ruthenium catalysts modified with alkaline (Cs, Rb, K) and alkaline-earth metal compounds are among the most promising commercial catalysts now [3][4][5]. Previous study [6] demonstrated that the activity of Ru-Cs + /C (Sibunit) catalysts strongly depends on the sequence of introduction of ruthenium and promoter (cesium compounds). Indeed, active catalyst is produced when ruthenium is supported on the carbon material (Sibunit) before the introduction of cesium.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Rubidium and Cesium as Promoters in Carbon-supported Ruthenium Catalysts for Ammonia Synthesis

et al. 2007

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Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter-support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter-support and promoter-metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed.

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“…For example, we have found the interaction of the carbon support and oxygen in the catalyst (0.4%Ru + 5%CeO 2 /Sibunit) during oxidation of aniline at 493 K, while the self-oxidation process has been observed during oxidation of phenol at 453 K. Our recent EXAFS, XPS and TEM studies of the process of formation of active sites in Sibunit-supported promoted ruthenium catalysts [31] demonstrate that ruthenium is in the metal state in the freshly prepared samples reduced by hydrogen but, partly, in the form of RuO 2 (ca. 40 mol%) in the promoted catalysts after drying in air.…”

Section: Stability Of Supported Ru-ceo 2 Catalysts In Cwao Reactionsmentioning

confidence: 89%

Catalysts Ru–CeO2/Sibunit for catalytic wet air oxidation of aniline and phenol

et al. 2005

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Catalytic properties of carbon materials Sibunit (commercial samples) and ceria-promoted precious metals (Ru, Pt, Pd) supported on carbon were studied in the processes of catalytic wet air oxidation (CWAO) of aniline and phenol at elevated pressures and temperatures (T ¼ 433-473 K, P O2 ¼ 0.3-1.0 MPa). It was found that the activity increases when the catalyst is pretreated with hydrogen peroxide. An efficiency of Ru-CeO 2 /Sibunit catalyst with a low ruthenium content (~0.6% Ru) for deep cleaning of polluted waters is demonstrated.

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Formation of Ru–M/Sibunit Catalysts for Ammonia Synthesis

Cited by 22 publications

References 15 publications

Promoters state and catalyst activation during ammonia synthesis over Ru/C

Promoters state and catalyst activation during ammonia synthesis over Ru/C

Comparative Study of Rubidium and Cesium as Promoters in Carbon-supported Ruthenium Catalysts for Ammonia Synthesis

Catalysts Ru–CeO2/Sibunit for catalytic wet air oxidation of aniline and phenol

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