Fischer–Tropsch synthesis: study of the promotion of Re on the reduction property of Co/Al2O3 catalysts by in situ EXAFS/XANES of Co K and Re LIII edges and XPS

Jacobs, Gary; Chaney, John A.; Patterson, Patricia M.; Das, Tapan K.; Davis, Burtron H.

doi:10.1016/j.apcata.2003.12.049

Cited by 199 publications

(119 citation statements)

References 34 publications

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“…Re reduces to a metallic state at higher temperatures than Ru and therefore, can facilitate the second cobalt reduction step, from CoO to Co 0 . 96 Hilmen et al performed TPR experiments on Co/Al 2 O 3 and Co-Re/Al 2 O 3 catalysts, and on physical mixtures of Co/Al 2 O 3 and Re/Al 2 O 3 , and they suggested that no direct contact between Re and Co is necessary to achieve the promotion by Re. 86 Hence, Re might be in many cases located on the support material rather than decorating the surface of Co.…”

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

“…Re promotion has also been widely investigated in Cobased F-T catalysis. [85][86][87][88][89][90][91][92][93][94][95][96][97][98]153,168,171,174,177,253 Re is regarded as a structural promoter and it has been frequently reported to increase the Co reducibility via a hydrogen spillover effect, leading to catalysts with enhanced Co dispersions. Re reduces to a metallic state at higher temperatures than Ru and therefore, can facilitate the second cobalt reduction step, from CoO to Co 0 .…”

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

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Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Morales¹,

Weckhuysen²

2006

ChemInform

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Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Morales¹,

Weckhuysen²

2006

ChemInform

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“…In situ X-ray absorption spectroscopy (XAS) has been reported in the literature as an efficient tool for studying the rhenium cobalt catalyst used in the Fischer-Tropsch Process [10][11][12][13][14][15]. Since XAS is an element specific probe, information related to the local environment of each constituent, Co or Re, can be obtained in an independent manner [16].…”

mentioning

confidence: 99%

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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“…78,79 Re appears not to promote cobalt reduction until the Re itself has been reduced. 80 In all three cases the role of Pt or Re in initially reducing the cobalt is implicated in the mechanism of promotion. The challenge here, however, is in trying to look at EXAFS data averaging over a sample where only trace amounts of platinum are present and a range of particle sizes and levels of Co-Pt mixing could be present in different regions of the sample.…”

Section: Precious Metal Promotion Effects Studied Using Nanomaterialsmentioning

confidence: 98%