Tracing the conversion of aurichalcite to a copper catalyst by combined X-ray absorption and diffraction

Couves, J. W.; Thomas, John Meurig; Waller, David; Jones, Richard H.; Dent, Andrew J.; Derbyshire, G.E.; Greaves, G.N.

doi:10.1038/354465a0

Cited by 211 publications

(128 citation statements)

References 8 publications

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“…The authors conclude that reconstruction of Cu particles in the presence of H 2 O provide a more reasonable explanation than competitive adsorption for the observed inhibition of methanol synthesis reaction rates by H 2 O [27]. In reference [23], a simultaneous sharpening of XRD lines for Cu metal, and a decrease in Cu EXAFS amplitude, was observed as the reduction temperature was increased from 543 to 773 K. Since XRD is most sensitive to the largest particles, but EXAFS also detects the smallest, it appears that Couves et al [23] detected the evolution of a bimodal distribution of crystallite sizes, with the largest Cu particles getting larger and the smallest getting smaller. XAS alone cannot detect a bimodal particle size distribution, but disagreement between XAS and XRD on average crystallite size provides circumstantial evidence for bimodal distributions.…”

Section: Introductionmentioning

confidence: 99%

“…Several recent reports demonstrate how XAS studies at reaction conditions are essential to determine the oxidation state and structure of Cu species during methanol synthesis [21][22][23]. Cu crystallites in Cu-Zn binary catalysts were completely reduced to Cu(0) after treatment with H 2 at 493 K, but remained as Cu(II) in Cu-Zn-Al ternary catalysts after H 2 treatment at 493 K [21].…”

Section: Introductionmentioning

confidence: 99%

“…Couves et al [23] prepared a material resembling a methanol synthesis catalyst by treating the mineral aurichalchite (Cu 5-x Zn x (OH) 6 (CO 3 ) 2 ) in air at 723 K and then reducing in H 2 at 543 K and then 773 K. XAS spectra and XRD patterns were measured simultaneously. Cu(0) crystallites of about 10 nm diameter were detected after reduction at 543 K. As the reduction temperature was increased to 773 K, the Cu(0) XRD lines narrowed, and the amplitude of the EXAFS signal declined.…”

Section: Introductionmentioning

confidence: 99%

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New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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X-ray absorption spectroscopic studies from several different groups provide a consistent structural picture of methanol synthesis catalysts. Copper metal is the principal Cu species detected in all in-situ XAS studies. A small amount of Cu(II) persisted in many samples reduced below 600 K, but it appears to be catalytically irrelevant. Cu(I) was not detected in any of the in-situ XAS studies. The Zn structure did not change in response to chemical treatments in any of the ZnO-containing methanol synthesis catalysts.We conclude that the slow approach to steady-state rate of methanol synthesis from CO/H 2 mixtures cannot result from changes in the Cu metal component of Cu/SiO 2 catalysts. By eliminating this possibility, we provide indirect evidence for the proposal that initial induction periods reflect slow changes in the surface of the SiO 2 or ZnO component in the catalysts. A bifunctional mechanism involving the formation of formate from CO on support hydroxyl groups would increase methanol synthesis rates as OH groups are formed by hydrolysis of Si-O bonds using the H 2 O formed in slow methanation side reactions. The bifunctional mechanism is not required for the synthesis of methanol from CO 2 -containing mixtures, because formate can form on Cu directly from CO 2 and H 2 .

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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“…The necessity to exploit in situ methods has been emphasized repeatedly by others 21 and the arrival of synchrotron radiation sources has accelerated the rewarding application to catalytic science of this tunable, powerful source of electromagnetic radiation. Since the early 1990s, it has become routinely possible to record in parallel both the short-range chemical nature and structure of an active site and the long-range crystallographic order of its surrounding matrix 22 . Free-electron lasers, and their temporal resolutions, permit in situ studies of biocatalysts, as demonstrated in the work of Chapman, Spence and co-workers at Stanford University 23 .…”

Section: Catalyst Characterizationmentioning

confidence: 99%

The enduring relevance and academic fascination of catalysis

Thomas

2018

Nat Catal

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“…In situ XRPD measurements were performed at Stations BM01A and BM01B of the Swiss-Norwegian Beamlines (SNBL) 22 located at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. A capillary based in situ cell was used in a set-up configuration similar to that proposed previously 23,24 . The sample was heated by a vertical hot air blower.…”

Section: Co3o4 + H2 → 3coo + H2omentioning

confidence: 99%

Capturing metal-support interactions in situ during the reduction of a Re promoted Co/γ-Al₂O₃ catalyst

et al. 2016

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The reduction of a Re promoted Co/γ-Al2O3 catalyst was monitored in situ by synchrotron X-ray powder diffraction (XRPD) under H2 environment. Whole powder pattern analysis showed a non-linear expansion of the unit cell of γ-Al2O3 during the reduction process suggesting the diffusion of cobalt cations into the structure of the γ-Al2O3 support material. The cell expansion coincided with the formation of CoO phase. Evidence for the negative effect of the partial pressure of indigenous H2O on the reduction process was obtained by alternating XRPD probing of the inlet and outlet ends of the reactor.Catalyst activation is a critical step of the start-up procedure for most industrial catalytic processes. 1 Commonly a solid precursor is been subjected to specific conditions that allow transformation to the catalytically active component, ex situ or in situ. In many catalytic applications, the metallic surface of nanoparticles is the active component and therefore reduction of supported metal oxide precursors precedes. The reduction process is affected by various parameters such as the nature of the precursor, the size of the nanoparticles, the reactivity of the support, the reducing atmosphere. The execution of the activation step has an impact on catalyst structure and performance, avoiding risks of sintering or a lower final degree of reduction. 2 In the last decades, in situ investigations have boosted catalysis research and allowed the deconvolution of such complex phenomena. 3 Cobalt nanoparticles (NPs) supported on high surface area porous materials such as γ-Al2O3 are used in various processes. One of the most important industrial applications is the FischerTropsch synthesis (FTS). 4 FTS is the heart of Gas-to-Liquid (GTL) technologies and a tool for the utilization of synthesis gas derived from different feedstocks i.e. natural gas, coal and biomass. In cobalt based FTS carbon monoxide and hydrogen are converted into a mixture of linear long-chain hydrocarbons while significant amounts of steam are co-produced. The active metallic Co is commonly formed by reduction in H2 of the Co3O4 spinel precursor produced after drying and calcination of the impregnating source. The activation procedure is important for the optimization of catalysts selectivity 5 and stability 6 .The reduction of promoted and un-promoted γ-alumina supported Co3O4 NPs has been studied in detail either by conventional temperature programed reduction (TPR) 7-9 or by advanced in situ techniques including X-ray powder diffraction (XRPD) 10 , X-ray absorption spectroscopy (XAS) 11-14 and transmission electron microscopy (TEM) 15 . From the majority of the reports, it is evident that the reduction is a two-step process that reaches the polycrystalline metallic Co through a CoO intermediate. The use of dopants can either promote or impede this reduction process. Co3O4 + H2 → 3CoO + H2O(1)CoO + H2 → Co 0 + H2O (2) Although most of the reports agree on the steps of the reduction procedure the formation of mixed compounds of Co with the γ-Al2O3 support ...

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Tracing the conversion of aurichalcite to a copper catalyst by combined X-ray absorption and diffraction

Cited by 211 publications

References 8 publications

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

The enduring relevance and academic fascination of catalysis

Capturing metal-support interactions in situ during the reduction of a Re promoted Co/γ-Al₂O₃ catalyst

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Tracing the conversion of aurichalcite to a copper catalyst by combined X-ray absorption and diffraction

Cited by 211 publications

References 8 publications

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

The enduring relevance and academic fascination of catalysis

Capturing metal-support interactions in situ during the reduction of a Re promoted Co/γ-Al2O3 catalyst

Contact Info

Product

Resources

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Capturing metal-support interactions in situ during the reduction of a Re promoted Co/γ-Al₂O₃ catalyst