Effect of Water Vapor on the Reduction of Ru-Promoted Co/Al2O3

Zhang, Yulong; Wei, Dongguang; Hammache, Sonia; Goodwin, James G.

doi:10.1006/jcat.1999.2666

Cited by 117 publications

(61 citation statements)

References 44 publications

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“…Although the applied gas hourly space velocities are high and consequently the pH2:pH2O ratio is not expected to change dramatically, it is evident that even minor changes have an effect in the reduction process. The results are in agreement with previous TPR studies on Ru/Co/γ-Al2O3 catalysts demonstrating that even with an inlet pH2:pH2O ratio of 8 an approximate delay of 5 o C and 65 o C in the temperatures of the maximum H2 consumption rates was observed 8 . The loss of active metal due to strong interaction with the γ-Al2O3 support has been a topic of scientific interest for many years.…”

Section: = 66515 (å) + 274·10 -4 T (å /K)supporting

confidence: 92%

“…Rutherford backscattering spectrometry (RBS) and X-ray Absorption Near Edge Structure (XANES) studies also Furthermore detailed TPR and XANES studies pointed on the formation of such a compound during catalyst reduction 7,8,19 . Although (XANES) has been regularly applied for the detection of Co-support mixed compounds 14,20,21 , due to its sensitivity towards oxidation state and local geometry, direct observation on the exact timing of this interaction has not been reported.…”

Section: Co3o4 + H2 → 3coo + H2omentioning

confidence: 99%

“…The loss of active metal due to strong interaction with the γ-Al2O3 support has been a topic of scientific interest for many years. It has been proposed that the formation of mixed cobaltsupport oxide phases takes place during calcination [16][17][18] , reduction 7,8,33 and at reaction condition 14,34,35 . Although the high temperature chemistry of this solid-state reaction resulting in the crystalline spinel CoAl2O4 rich in Co 2+ Td is reasonably known, the formation of the non-stoichiometric surface compound that lacks long range order is difficult to be detected.…”

Section: = 66515 (å) + 274·10 -4 T (å /K)mentioning

confidence: 99%

“…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][8][9] or by advanced in situ techniques including X-ray powder diffraction (XRPD) 10 , X-ray absorption spectroscopy (XAS) [11][12][13][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.…”

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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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Section: = 66515 (å) + 274·10 -4 T (å /K)supporting

confidence: 92%

Section: Co3o4 + H2 → 3coo + H2omentioning

confidence: 99%

Section: = 66515 (å) + 274·10 -4 T (å /K)mentioning

confidence: 99%

mentioning

confidence: 99%

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

et al. 2016

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“…3. The two peaks centred at 633 and 833 K on Co/AlPO-11 (1.6 wt.% Co) were due to the reduction of Co 3 O 4 and CoO (or Co species interacting strongly with support), respectively [19][20][21]. For CoAPO-5, CoAPO-11 and CoAPSO-34, no peak was detected at lower temperature and H 2 consumption only occurred after 973 K, which could be caused by the reduction of non-framework cobalt and aluminium species, formed after the collapse of molecular sieves structures [22].…”

Section: Temperature-programmed Reductionmentioning

confidence: 99%

Characterization of metal-containing molecular sieves and their catalytic properties in the selective oxidation of cyclohexane

Tian

Liu

et al. 2004

Catalysis Today

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Tailor‐Made Inorganic Nanopeapods: Structural Design of Linear Noble Metal Nanoparticle Chains

et al. 2008

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Linear noble-metal nanoparticle (NP) chains have been demonstrated both theoretically and experimentally to be promising candidates for applications in one-dimensional nano-optical devices (e.g. plasmonic waveguides, plasmonic printing). [1][2][3][4] The ability of metal NP chains to transport electromagnetic energy below the diffraction limit has major advantages for scaling down the size of optical devices and components to the nanometer scale. Precise control of particle size, shape and separation in metal NP chains is an important issue for constructing nano-optical devices. Conventional electron-beam lithographic techniques and scanning-probe manipulation have enabled excellent control over the size and position of metal NPs but are time-consuming and costly. [2,5] Self-assembly routes enable metal NPs to be incorporated into preformed grooves but can control neither the separation between NPs nor their densities.[6] Other approaches to the fabrication of metal NP chains, including wet-chemistry etching [7] and exploitation of the Rayleigh instability of metal nanowires (NWs), [8] suffer from low throughput and limited controllability. Herein, we show a facile and controllable route to the fabrication of linear noble-metal NP chains, in which the size and the separation of optically interesting NPs can be controlled easily. As an example, Pt@CoAl 2 O 4 inorganic peapod nanostructures, which consist of well-defined Pt NPs encapsulated in continuous CoAl 2 O 4 nanoshells, were realized by electrodeposition of cobalt/platinum multilayered (ML) NWs into nanoporous anodic aluminum oxide (AAO) membranes and subsequent solid-state reaction at high temperature.Fabrication of Pt@CoAl 2 O 4 inorganic nanopeapods is schematically illustrated in Figure 1 a. First, Co/Pt ML NWs were electrodeposited into the nanoporous AAO template by pulsed potential electrodeposition. As-prepared Co/Pt ML NWs with alternately distributed Co and Pt segments served as the precursors and the backbones for subsequent generation of Pt@CoAl 2 O 4 inorganic nanopeapods (see Figure S1 in the Supporting Information). The size (diameter, D Pt ) and separation (center-to-center distance, D c-c ) of Pt "peas" in peapod nanostructures were also defined in this step by the lengths of Pt (L Pt ) and Co segments (L Co ), respectively. After electrodeposition, the Co/Pt ML NWs/AAO composite membrane was annealed at 700 8C in an ambient atmosphere for 1-5 h. During heat treatment, Co segments reacted with alumina to form continuous CoAl 2 O 4 nanoshells, that is, the "pods", while most Pt segments agglomerated into a spherical shape to minimize their surface energy, forming the peas. Thus, the peapod nanostructures were obtained. As-prepared Pt@CoAl 2 O 4 inorganic nanopeapods can either be kept in the porous AAO template or be easily released from the template by selectively removing the surrounding alumina (see Figure S2a in the Supporting Information).Recently, exploitation of the Rayleigh instability of metal NWs has been considered as an effective...

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Effect of Water Vapor on the Reduction of Ru-Promoted Co/Al2O3

Cited by 117 publications

References 44 publications

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

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

Characterization of metal-containing molecular sieves and their catalytic properties in the selective oxidation of cyclohexane

Tailor‐Made Inorganic Nanopeapods: Structural Design of Linear Noble Metal Nanoparticle Chains

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Effect of Water Vapor on the Reduction of Ru-Promoted Co/Al2O3

Cited by 117 publications

References 44 publications

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

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

Characterization of metal-containing molecular sieves and their catalytic properties in the selective oxidation of cyclohexane

Tailor‐Made Inorganic Nanopeapods: Structural Design of Linear Noble Metal Nanoparticle Chains

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

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