A Time‐Resolved In Situ Quick‐XAS Investigation of Thermal Activation of Fischer–Tropsch Silica‐Supported Cobalt Catalysts

Hong, Jingping; Marceau, Éric; Khodakov, Andreï Y.; Griboval-Constant, Anne; Fontaine, Camille La; Briois, Valérie

doi:10.1002/chem.201103509

Cited by 26 publications

(32 citation statements)

References 28 publications

(46 reference statements)

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“…To further confirm the influence of the zeolite pore size on the Co distribution between the zeolite pores and external surface, the impregnated catalysts were analyzed by TEM (Figure ). In agreement with previous data, TEM images of the reference Co/SiO 2 demonstrate Co nanoparticles distributed irregularly with a diameter in the range of 10–50 nm. In the impregnated calcined Co/ZSM‐5, polycrystalline zeolite particles are covered by large agglomerates of Co nanoparticles (100–200 nm).…”

Section: Resultssupporting

confidence: 92%

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

et al. 2015

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This study focuses on the effects of the localization of Co species, zeolite structure, and acidity on the performance of Co bifunctional catalysts promoted with Pt for the direct synthesis of iso‐paraffins from syngas. ZSM‐5, MOR, and BEA were chosen as zeolites with different structures and pore diameters. The catalysts were prepared either by incipient wetness impregnation or by the mechanical mixing of the zeolite with a conventional silica‐supported Co catalyst. The increase in the pore size and open character of the zeolite structure from ZSM‐5 to BEA resulted in a higher fraction of Co located inside the pores of the catalysts prepared by impregnation. The catalytic performance was affected strongly by the zeolite acidity, pore structure, and Co distribution between the pores and the external surface. The selectivity to short‐chain iso‐paraffins is affected principally by the zeolite acidity, whereas the selectivity to long‐chain branched hydrocarbons mostly depends on steric effects.

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Section: Resultssupporting

confidence: 92%

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

et al. 2015

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“…On the same figure is recalled a quantitative analysis of cobalt nitrate conversion into Co 3 O 4 , extracted from XANES data at the Co K edge for CoRu/SiO 2 (white squares) and published formerly. 30 These results suggest a correlation between the elimination of Ru in the gas phase and the decomposition of cobalt nitrate into Co 3 O 4 , in the temperature range 130−190°C. According to thermodynamics, the transformation of RuO 2 or monometallic Ru into volatile RuO 4 in an oxidative atmosphere is not favored below 800°C.…”

Section: Research Articlementioning

confidence: 93%

“…In our previous reports on XAS at the Co K edge, we have shown that upon oxidative activation, hydrated cobalt(II) nitrate first dehydrates into anhydrous Co(NO 3 ) 2 , then decomposes into Co 3 O 4 nanoparticles, in line with XRD and with the literature. 30 …”

Section: ■ Experimental Sectionmentioning

confidence: 97%

Speciation of Ruthenium as a Reduction Promoter of Silica-Supported Co Catalysts: A Time-Resolved in Situ XAS Investigation

et al. 2015

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International audienceComplete reduction of the metal phase in cobalt-containing catalysts is often difficult to reach and can be promoted by a small amount of noble metals. Because these costly promoters are introduced in a very low quantity, their speciation and their chemical interaction with cobalt have seldom been studied in detail. We present here a time-resolved in situ X-ray absorption spectroscopy investigation of the speciation of ruthenium, used as a reduction promoter of cobalt, throughout the preparation of Co/SiO2 catalysts. In the cobalt(II) nitrate impregnation solution, ruthenium is detected as hydrated Ru(OH)4 short-chain oligomers that are deposited on silica upon drying. Co3O4 forms during calcination in air and catalyzes the elimination in the gas phase of 60% of Ru. The addition of a polyol, sorbitol, in the impregnation solution stabilizes the whole of Ru on the catalyst. Upon calcination, Ru(IV) ions are inserted inside Co3O4 nanoparticles. Reduction of the oxidic phase takes place in two distinct steps, at approximately the same temperatures regardless of the ruthenium content: first to Ru(III)-containing CoO nanoparticles (Ru ions modifying the intrinsic electronic properties of the oxidic nanoparticles); then to bimetallic Co nanoparticles containing Ru(0) atoms, via an autocatalytic process. Ru loadings as low as 0.2 wt % are sufficient to afford complete reduction of cobalt. Close association between Ru and Co from the beginning of the synthesis is thus necessary for a maximum promoting effec

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“…For instance, we have shown in our previous work that the deactivation of the Co/TiO 2 FTS catalyst under study takes approximately 10 days . This is one of the reasons that the problem of cobalt FTS catalyst deactivation has not yet been fully solved despite numerous studies using for example, combined XRD/EXAFS under reaction conditions …”

Section: Introductionmentioning

confidence: 99%

Combined Operando X‐ray Diffraction/Raman Spectroscopy of Catalytic Solids in the Laboratory: The Co/TiO₂ Fischer–Tropsch Synthesis Catalyst Showcase

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Weckhuysen

2016

ChemCatChem

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A novel laboratory setup for combined operando X‐ray diffraction and Raman spectroscopy of catalytic solids with online product analysis by gas chromatography is presented. The setup can be used with a laboratory‐based X‐ray source, which results in important advantages in terms of time‐on‐stream that can be measured, compared to synchrotron‐based experiments. The data quality was much improved by the use of a relatively high‐energy MoKα radiation instead of the more conventional CuKα radiation. We have applied the instrument to study the long‐term deactivation of Co/TiO2 Fischer–Tropsch synthesis (FTS) catalysts. No sign of Co sintering or bulk oxidation was found during the experiments. However, part of the metallic Co was converted into cobalt carbide (Co2C), at elevated pressure (10 bar). Furthermore, graphitic‐like coke species are clearly formed during FTS at atmospheric pressure, whereas at elevated pressure fluorescence hampered the interpretation of the measured Raman spectra.

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A Time‐Resolved In Situ Quick‐XAS Investigation of Thermal Activation of Fischer–Tropsch Silica‐Supported Cobalt Catalysts

Abstract: International audienc

Cited by 26 publications

References 28 publications

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

Speciation of Ruthenium as a Reduction Promoter of Silica-Supported Co Catalysts: A Time-Resolved in Situ XAS Investigation

Combined Operando X‐ray Diffraction/Raman Spectroscopy of Catalytic Solids in the Laboratory: The Co/TiO₂ Fischer–Tropsch Synthesis Catalyst Showcase

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A Time‐Resolved In Situ Quick‐XAS Investigation of Thermal Activation of Fischer–Tropsch Silica‐Supported Cobalt Catalysts

Abstract: International audienc

Cited by 26 publications

References 28 publications

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

The Role of Steric Effects and Acidity in the Direct Synthesis of iso‐Paraffins from Syngas on Cobalt Zeolite Catalysts

Speciation of Ruthenium as a Reduction Promoter of Silica-Supported Co Catalysts: A Time-Resolved in Situ XAS Investigation

Combined Operando X‐ray Diffraction/Raman Spectroscopy of Catalytic Solids in the Laboratory: The Co/TiO2 Fischer–Tropsch Synthesis Catalyst Showcase

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Combined Operando X‐ray Diffraction/Raman Spectroscopy of Catalytic Solids in the Laboratory: The Co/TiO₂ Fischer–Tropsch Synthesis Catalyst Showcase