Mössbauer effect studies of chemisorption: Titration of surfaces of iron catalysts with polar molecules

Hobson, M.C.; Gager, H. M.

doi:10.1016/0021-9797(70)90194-3

Cited by 30 publications

(7 citation statements)

References 10 publications

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“…The dust was gravimetrically separated into three fractions as indicated; the iron metal appears in the light fraction because it is associated with a low-density glass phase. [ (7), the details of the adsorption of atoms on active surfaces (8), the chemical makeup of corrosion products at a metal surface (9), or the intermediates produced in a chemical transformation taking place in a solid (10). Under favorable conditions, intermediate products can be identified on the basis of a comparison of their hyperfine spectra with those of known compounds.…”

Section: The Mossbauer Effectmentioning

confidence: 99%

See 1 more Smart Citation

Mössbauer Spectroscopy: Recent Developments

Cohen¹

1972

Science

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In this review I have emphasized two basic points. First, Mössbauer spectroscopy has been widely used as a tool for basic research in solid-state physics, chemical structure, and magnetism. Second, the technique has been applied to many analytical and materials science problems where the nature of the sample prevents the use of more traditional approaches. Mössbauer spectroscopy research on frozen solutions, colloids, interface chemistry, and crystallographic transformations can be expected to increase rapidly in the next few years.

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Section: The Mossbauer Effectmentioning

confidence: 99%

“…20. The use of signs and cue marks with notations is common in the historical period (8)(9)(10)(11) and has been extensively documented for the Upper Paleolithic in (4) and (5). 21.…”

mentioning

confidence: 99%

Mössbauer Spectroscopy: Recent Developments

Cohen¹

1972

Science

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“…With the common oxidic supports silica and alumina it is difficult to prevent reaction of the iron(II), which is initially produced during reduction, with the support to iron(II) silicate or iron(II) aluminate. As both iron(II) silicate and iron(II) aluminate are very difficult to reduce [6][7][8][9][10][11], silica and alumina are not very suitable as support for iron-based Fischer-Tropsch catalysts. Zirconia does not form bulk iron(II) zirconate, although the interaction with iron oxide is sufficient [12][13][14][15][16] to anchor supported metallic iron particles through an intermediate very thin iron oxide layer.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of highly dispersed zirconia-supported iron-based catalysts for Fischer–Tropsch synthesis

Berg

Crajé

Kooyman

et al. 2002

Applied Catalysis A: General

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Zirconia-supported iron-based Fischer-Tropsch catalysts were prepared using incipient wetness impregnation. The choice of the precursor, in this case the chelating ammonium iron(III) citrate, and the applied calcination temperature determine the final distribution of the precursor on the zirconia support. Several techniques reveal that both an unpromoted and a potassium-promoted catalyst can be prepared, of which the iron(III) oxide exhibits a high dispersion and is, moreover, monodisperse.

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“…In addition, the Mössbauer measurements reveal the presence of high spin Fe 2+ species with quadrupole splittings at room temperature (2.7-1.7 mm/s) significantly higher than for bulk FeO (about 0.55 mm/s). These results point to the formation of ferrous species due to an intimate interaction with the support [9][10][11][13][14][15]18,[20][21][22][23][24]. One of the two iron(II) species is identified as a Fe 2+ which upon formation immediately migrates into the zirconia support to form a mixed oxide.…”

Section: Reduction and Reduction Model Of Fe/zromentioning

confidence: 99%

“…For iron catalysts supported on Al 2 O 3 and SiO 2 the formation of ferrous aluminates and silicates has been reported [18,[20][21][22][23][24]. Wielers et al [21] observed the formation of a silicate layer during reduction of trivalent iron indicating that, as soon as divalent iron is formed, iron migrates into the support.…”

Section: Introductionmentioning

confidence: 99%

Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

Berg

Crajé

Kraan

et al. 2003

Applied Catalysis A: General

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The reduction behaviour (the activation process) of two iron-based Fischer-Tropsch catalysts viz. an unpromoted and a potassium-promoted zirconia-supported iron catalyst is investigated. The initial dispersion of both catalysts is very high. To establish the nature of the iron species under hydrogen atmosphere, experiments were performed at ambient pressure. It is demonstrated for both catalysts that during reduction the carbon originating from the citrate complex used in the preparation procedure is not completely removed, whereby the largest amount of the carbon species is encountered on the potassium-promoted catalyst. During reduction at ambient pressure this residual carbon reacts with metallic iron and forms cementite (θ-Fe 3 C). The iron oxide of the potassium-promoted catalyst turns out to reduce more easily than the oxide of the unpromoted catalyst. Upon formation of divalent iron, this divalent species readily reacts with the support to give a stable mixed oxide. This mixed oxide is suggested to be a prerequisite in maintaining a high dispersion of the metallic iron particles. Based on the analyses presented here, a reduction model is proposed.

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Mössbauer effect studies of chemisorption: Titration of surfaces of iron catalysts with polar molecules

Cited by 30 publications

References 10 publications

Mössbauer Spectroscopy: Recent Developments

Mössbauer Spectroscopy: Recent Developments

Synthesis of highly dispersed zirconia-supported iron-based catalysts for Fischer–Tropsch synthesis

Reduction behaviour of Fe/ZrO2 and Fe/K/ZrO2 Fischer–Tropsch catalysts

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