Metal oxide-support interactions in silica-supported iron oxide catalysts probed by nitric oxide adsorption

Yuen, S. H.; Kubsh, Joseph E.; Dumesic, James A.; Topsoee, N.‐Y.; Topsoee, H.; Chen, Y.

doi:10.1021/j100212a042

Cited by 97 publications

(52 citation statements)

References 12 publications

(13 reference statements)

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“…[46,47,54] The lower the coordination, the higher the number of coordinative positions occupied by adsorbed NO. Surface Fe 2 + sites yielding tri-, di-and mononitrosyls will hereafter be referred to as Fe Figure 8A).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…[44] The nature and abundance of the surface active sites have been evaluated by means of the adsorption of nitric oxide as a probe molecule, commonly employed on iron centres of various materials. [45][46][47] The fibre surface was previously deprived of the adsorbed molecules by outgassing under vacuum. The coordinative unsaturations created in such a way were filled by NO molecules, the vibrational features of which depend on the characteristics of the related surface centre.…”

Section: Modification Induced In Surface Propertiesmentioning

confidence: 99%

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A Biomimetic Approach to the Chemical Inactivation of Chrysotile Fibres by Lichen Metabolites

Turci

Favero‐Longo

Tomatis

et al. 2007

Chemistry A European J

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Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic, pulvinic and oxalic acid (0.005, 0.5 and 50 mM) were put in contact with chrysotile fibres, either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal, measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si, while chrysotile-balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mM oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mM oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile-balangeroite (B) only occurs with 50 mM oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation, some new phases (Fe(2)O(3), CaMg(CO(3))(2), Ca(C(2)O(4)) x H(2)O and Mg(C(2)O(4))2 x H(2)O), similar to those observed in the field, were detected by XRD and micro-Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity, a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mM oxalic acid, while all lichen metabolites reduce the activity of chrysotile-balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions, evidenced by NO adsorption, accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks, colonised by lichens, could be exposed to a natural bioattenuation and considered as a transient environmental hazard.

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Section: Wwwchemeurjorgmentioning

confidence: 99%

Section: Modification Induced In Surface Propertiesmentioning

confidence: 99%

A Biomimetic Approach to the Chemical Inactivation of Chrysotile Fibres by Lichen Metabolites

Turci

Favero‐Longo

Tomatis

et al. 2007

Chemistry A European J

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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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“…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%

“…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%

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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Metal oxide-support interactions in silica-supported iron oxide catalysts probed by nitric oxide adsorption

Cited by 97 publications

References 12 publications

A Biomimetic Approach to the Chemical Inactivation of Chrysotile Fibres by Lichen Metabolites

A Biomimetic Approach to the Chemical Inactivation of Chrysotile Fibres by Lichen Metabolites

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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