Alternative Noniron Catalysts

Tennison, S.R.

doi:10.1007/978-1-4757-9592-9_9

Cited by 60 publications

(41 citation statements)

References 131 publications

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“…It should be underlined that Cs (or K) as promoters are active in ammonia synthesis also when used with AC, though their reduction in this case is unlikely (vide supra). Indeed, it has been shown by XPS analysis [1,25] that, even if present in their oxidised form, these promoters, as well as BaO, show some electron-donor effect, leading to a shift of Ru binding energy. However, without proper support environment, the effect of K and Cs is very weak with respect to BaO.…”

Section: -O2 Chemisorptionmentioning

confidence: 99%

“…As for promoters effect, since the earlier work of Aika and co-workers [1,24] it is widely accepted that unpromoted Ru-based samples are almost completely inactive during ammonia synthesis, mainly when active or graphitised carbon is used as support, due to its electron-withdrawing effect [25]. Among the possible promoters, electron-donors are preferred, in order to facilitate electron transfer to Ru and so to enhance the rate of the rate-determining step of the reaction, i.e.…”

Section: -Introductionmentioning

confidence: 99%

“…Ru-based catalysts raised interest in the last years as possible substitutes for the traditional Fe-based ones for the synthesis of ammonia [1][2][3][4][5][6][7]. Many possible formulations have been proposed, widely differing as for support (mainly active or graphitised carbon [2,[4][5][6]8] and MgO [9][10][11]), Ru precursor (chloride [5,12,13], potassium ruthenate [2], carbonyls [14][15][16], nitrosylnitrate [17,18]) and promoters (alkali-, alkali-earth-and lanthanide-oxides).…”

Section: -Introductionmentioning

confidence: 99%

“…Indeed, alkaline metals play an electron-donor role even in their oxidised form [1] as evidenced by XPS experiments [25]. However, some recent new findings seem to point to the possible partial reduction of Cs and K to metal state during catalyst activation [13,28,29].…”

Section: -Introductionmentioning

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: 99%

Section: -Introductionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Rossetti¹,

Mangiarini²,

Forni³

2007

Applied Catalysis A: General

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“…organic synthesis [19], partial oxidation of hydrocarbons [20], Fischer-Tropsch synthesis [21] and ammonia synthesis [22]. Recently, ruthenium catalysts have been applied in the reaction of wet air oxidation of various pollutants [23][24][25] and complete oxidation of volatile organic compounds [26].…”

Section: Introductionmentioning

confidence: 99%

Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

Cheng

et al. 2009

Applied Catalysis B: Environmental

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Synthese vielkerniger gemischtmetallischer Cluster durch Verknüpfung anionischer Ruthenium-Carbido-Cluster über Palladiumeinheiten

2000

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Vielkern-Clusterkomplexe und speziell heterometallische Cluster haben auf Grund ihrer vielseitigen Eigenschaften groûe Aufmerksamkeit erregt. [1, 2] Erwähnt sei hier beispielsweise ihre Verwendung als Vorstufe für metallische Dispersionen mit diskreter Metallatomverteilung, die als heterogene Katalysatoren ein Rolle spielen könnten. [3] Die Verknüpfung zweier kleinerer Clustereinheiten über verschiedene, verbrückende Metallatome sollte eine Möglichkeit bieten, schnell und elegant zu gröûeren Vielkern-Clustern zu gelangen. Eine Vielzahl dieser Verknüpfungen durch Umsetzung anionischer Übergangsmetallcluster mit den Kationen oder Halogeniden von Cu, [4] Ag, [5,6] Au [4e, 7] und Hg [7d, 8] ist beschrieben worden. Diese werden hierbei sandwichartig zwischen den beiden Clusterhälften eingebaut. Dagegen verläuft die Umsetzung von Clusteranionen mit Kationen oder Halogeniden der Übergangsmetalle aus der VIII. Gruppe unter Bildung riesiger Cluster, bestehend aus zwei unterschiedlichen Übergangsmetallen. Beispiele hierfür sind [Ni 38 Pt 6 (CO) 48 (H) 6Àn ] nÀ , [9] [Pd 33 Ni 9 (CO) 41 (PPh 3 ) 6 ] 4À , [10] [Ni 36 Pt 4 (CO) 45 ] 6À[11] und [Fe 6 Pd 6 (CO) 24 H] 3À . [12] In all diesen Beispielen wird Fragmentierung und anschlieûende Reorganisation der ursprünglich eingesetzten Clusterkomponente als Hauptreaktion beobachtet. Wir berichten hier über die Kupplung von Ruthenium-Carbido-Carbonyl-Clustern durch Palladiumreagentien zur Erzeugung vielkerniger Ru/Pd-Komplexe eines ¹Sandwich-Clusterª-Strukturtyps. Im Unterschied zur unvorhersehbaren Clusterbildung durch Fragmentierung und spontane Reaggregation der Edukte erhält man nach dieser Methode Strukuren ähnlich jenen, die durch den Einsatz von Metallen der Gruppen Ib und IIb als Kupplungskomponenten erhalten werden. Die Verwendung eines Übergangsmetalls der VIII. Gruppe als verbrückendes Reagens sollte die Möglichkeiten dieser Methode zur gezielten Synthese groûer, heterometallischer Cluster erweitern, vor allem unter dem Gesichtspunkt der Anwendung auf die rationale Synthese maûgeschneiderter Legierungskatalysatoren. Besonders wichtig erscheint uns dies insofern, als sowohl Ruthenium wie auch Palladium als Heterogenkatalysatoren in vielen industriellen Prozessen Anwendung finden. [13] Die Umsetzung des fünfkernigen Ruthenium-Carbido-Anions [Ru 5 C(CO) 14 ] 2À (Gegenion PPN N(PPh 3 ) 2 ) mit zwei ¾quivalenten [{Pd(C 3 H 5 )Cl} 2 ] in THF bei Raumtemperatur lieferte nach 12 h in 52 % Ausbeute dunkelrote Kristalle des ungeladenen Clusters [Pd 8 Ru 10 C 2 (CO) 27 (C 3 H 5 ) 4 ] 1. Die Röntgenstrukturanalyse (Abbildung 1) ergab, dass dieses Abbildung 1. Struktur von 1 im Kristall. Aus Gründen der Übersichtlichkeit wurden 26 CO-Liganden weggelassen. Vier Pd-Ru-Bindungen (Pd7-Ru14, Pd7-Ru24, Pd8-Ru15, Pd8-Ru25) und eine Pd-Pd-Bindung (Pd2-Pd5) haben verbrückende CO-Liganden, vier Pd-Ru-Bindungen (Pd1-Ru13, Pd3-Ru12, Pd4-Ru23, Pd6-Ru22) haben halbverbrückende CO-Liganden. Alle anderen CO-Liganden sind terminal an Rutheniumatome gebunden. Ausgewählte Bindungslängen [] und -wi...

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Alternative Noniron Catalysts

Cited by 60 publications

References 131 publications

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

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

Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

Synthese vielkerniger gemischtmetallischer Cluster durch Verknüpfung anionischer Ruthenium-Carbido-Cluster über Palladiumeinheiten

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