The influence of pre-treatment gas mixture upon the ammonia synthesis activity of Co–Re catalysts

McAulay, Karen A.; Hargreaves, J. S. J.; McFarlane, Andrew R.; Price, Daniel J.; Spencer, Nicholas A.; Bion, Nicolas; Can, Fabien; Richard, Mélissandre; Greer, Heather F.; Zhou, Wuzong

doi:10.1016/j.catcom.2015.04.016

Cited by 23 publications

(18 citation statements)

References 14 publications

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“…The mass spectrometer (MS) signal is shown in Fig. 9, confirming the 20 min lag-time before ammonia production starts for the sample pre-treated in H 2 /Ar, as has already been reported [9]. For CoRe 1.6 pre-treated in H 2 /N 2 (reaction gas) ammonia production starts immediately.…”

Section: Resultssupporting

confidence: 83%

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

et al. 2018

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A cobalt rhenium catalyst active for ammonia synthesis at 400 °C and ambient pressure was studied using in situ XAS to elucidate the reducibility and local environment of the two metals during reaction conditions. The ammonia reactivity is greatly affected by the gas mixture used in the pre-treatment step. Following H 2 /Ar pre-treatment, a subsequent 20 min induction period is also observed before ammonia production occurs whereas ammonia production commences immediately following comparable H 2 /N 2 pre-treatment. In situ XAS at the Co K-edge and Re L III -edge show that cobalt initiates reduction, undergoing reduction between 225 and 300 °C, whereas reduction of rhenium starts at 300 °C. The reduction of rhenium is near complete below 400 °C, as also confirmed by H 2 -TPR measurements. A synergistic co-metal effect is observed for the cobalt rhenium system, as complete reduction of both cobalt and rhenium independently requires higher temperatures. The phases present in the cobalt rhenium catalyst during ammonia production following both pre-treatments are largely bimetallic Co-Re phases, and also monometallic Co and Re phases. The presence of nitrogen during the reduction step strongly promotes mixing of the two metals, and the bimetallic Co-Re phase is believed to be a pre-requisite for activity.

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Section: Resultssupporting

confidence: 83%

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

et al. 2018

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“…Therefore, a continuous effort to improve the Haber-Bosch process and develop new catalysts is being devoted. At the beginning of the twenty-first century, several new catalysts mostly based on cobalt compounds were presented (Hargreaves 2014;Jacobsen 2000;Kojima and Aika 2001a;McAulay et al 2015;Moszyński et al 2010Moszyński et al , 2015Moszyński et al , 2018Tarka et al 2015Tarka et al , 2017Zybert et al 2016). Among this materials, cobalt molybdenum nitrides are considered as a possible replacement for the commercial multi-promoted iron catalyst.…”

Section: Introductionmentioning

confidence: 99%

Thermal stability of catalyst for ammonia synthesis based on cobalt molybdenum nitrides

et al. 2018

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The formation and stability of an ammonia synthesis catalyst, based on cobalt molybdenum nitrides, were studied. The activation process of the catalyst was examined by in situ X-ray diffractometry. The thermal stability of obtained active phase of the catalyst was tested at 700 °C under ammonia atmosphere, N 2 /H 2 mixture and under pure hydrogen. The presence of Co 2 Mo 3 N and Co 3 Mo 3 N phases in the catalyst was confirmed. The phase composition was stable in a long-term test performed under nitrogen/hydrogen atmosphere. Co 3 Mo 3 N phase decomposed into Co 6 Mo 6 N after exposure to pure hydrogen.

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“…5 Finally, it is worth pointing out that both Co and Re nanoparticles have applications beyond FTcatalysis (e.g. NH3-synthesis [46][47], and that the reported findings will be of relevance for a wide audience.…”

Section: Discussionmentioning

confidence: 99%

Nucleation, Alloying, and Stability of Co–Re Bimetallic Nanoparticles on Al₂O₃/NiAl(110)

et al. 2018

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This paper reports on preparation and characterization of nanostructured Re and Co-Re/Al2O3/NiAl(110) surfaces designed as model catalysts for operando studies of Fischer-Tropsch synthesis. Scanning tunneling microscopy on pure Re particles identified strong Re-Al2O3 support 2 interaction, resulting in uniform nucleation and growth on random point defects. X-ray photoelectron spectroscopy confirmed the strong interaction through a shift in the binding energy, in addition to size-dependent final state effects. CoRe particles were prepared by sequential deposition of the two metals, resulting in core-shell structures in which the shell was (strongly) enriched with the metal deposited second. Annealing of bimetallic particles allowed for elemental redistribution, as was concluded from the XPS data and supported by modeling. The annealing also resulted in sintering of bimetallic clusters. Interestingly, the thermal stability of the CoRe surfaces prepared by sequential deposition of Co, followed by Re, was better than that of both pure Co and pure Re.

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The influence of pre-treatment gas mixture upon the ammonia synthesis activity of Co–Re catalysts

Cited by 23 publications

References 14 publications

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

Thermal stability of catalyst for ammonia synthesis based on cobalt molybdenum nitrides

Nucleation, Alloying, and Stability of Co–Re Bimetallic Nanoparticles on Al₂O₃/NiAl(110)

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The influence of pre-treatment gas mixture upon the ammonia synthesis activity of Co–Re catalysts

Cited by 23 publications

References 14 publications

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

An In Situ XAS Study of the Cobalt Rhenium Catalyst for Ammonia Synthesis

Thermal stability of catalyst for ammonia synthesis based on cobalt molybdenum nitrides

Nucleation, Alloying, and Stability of Co–Re Bimetallic Nanoparticles on Al2O3/NiAl(110)

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Nucleation, Alloying, and Stability of Co–Re Bimetallic Nanoparticles on Al₂O₃/NiAl(110)