Untitled

Bazin, Dominique; Borkó, L.; Koppány, Zs.; Kovács, Imre; Stefler, G.; Sajó, L.I.; Schay, Z.; Guczi, L.

doi:10.1023/a:1021423802679

Cited by 37 publications

(23 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

“…Nonetheless, other authors have reported the existence of bimetallic interactions between Co and Re. For example, Bazin et al investigated the effect of Re on the structure of Re-Co/Al 2 O 3 catalysts by EXAFS 94 and the analysis of the Co K edge and Re L III edge provided direct evidence for Re-Co bond formation. Their results suggest that Re prevents the formation of cobalt surface phases, such as cobalt aluminate, resulting in an increase of the catalyst activity.…”

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

“…168 On the other hand, the selectivity of the Co sites is generally expected to be not directly affected by the presence of Re, 153 although some authors have reported improvements in the C 51 selectivity when using Re. 94,171 A possible explanation may be the influence of Re on the Co particle sizes distribution, which may also have an indirect effect on the selectivity due to the changes in the Co surface density. Some differences found in literature may also arise from comparisons of the catalysts at different conversions, which lead to significant variations in selectivities.…”

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

See 2 more Smart Citations

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Morales¹,

Weckhuysen²

2006

ChemInform

View full text Add to dashboard Cite

show abstract

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

Section: Overview Of the Promoter Elements Used Inmentioning

confidence: 99%

See 1 more Smart Citation

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Morales¹,

Weckhuysen²

2006

ChemInform

View full text Add to dashboard Cite

show abstract

“…Using a standard 10 h H 2 reduction treatment of 350°C, Jacobs et al [11] showed by hydrogen chemisorption/pulse reoxidation measurements that in all cases (Pt, Ru, and Re), gains in active site densities (i.e., number of cobalt atoms exposed at the surface) were directly due to the higher extents of reduction gained by promoter addition. The three promoters, Pt, Ru and Re, have all been observed to exhibit direct contact with Co at the atomic level by EXAFS spectroscopy [12,[17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Fischer–Tropsch Synthesis: Preconditioning Effects Upon Co-Containing Promoted and Unpromoted Catalysts

et al. 2012

View full text Add to dashboard Cite

In the preparation and evaluation of FischerTropsch (FT) catalysts, active catalysts formed by both incipient wetness impregnation (IWI) and atomic layer deposition (ALD) of major components were demonstrated. ALD-deposited Co on a silica support was more effective than a similar catalyst deposited upon a support of ALD-deposited Al 2 O 3 on silica. The addition of Co reduction promoters including Pt, Ir and Ru using either ALD or IWI has been shown to strongly affect the catalyst pre-conditioning step. CO conversion results were consistent with previously reported Temperature Programmed Reduction X-ray Absorption Near-edge Structure/Extended X-ray Absorption Fine Structure Spectroscopy (TPR-XANES/EXAFS) experiments observing the nature of chemical transformations occurring during the activation of cobalt-based FT catalysts in hydrogen. Specifically, there exists a 2-step reduction process involving Co 3 O 4 to CoO and CoO to Co 0 transformations. The extent of catalyst preconditioning was strongly affected by the reduction temperature (with 400°C preferred) and the loading of the promoter. This was demonstrated using a continuous-flow catalytic-bed unit with a 2:1 molar blend of H 2 :CO, at temperatures ranging from about 260 to 300°C, pressures averaging 1.3 MPa (190 psia), and gas space velocities about 24 NL/h-g.

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Untitled

Cited by 37 publications

References 21 publications

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

Fischer–Tropsch Synthesis: Preconditioning Effects Upon Co-Containing Promoted and Unpromoted Catalysts

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

Contact Info

Product

Resources

About