Crystallite Size Determination of Highly Dispersed Unsupported MoS2Catalysts

Calais, Christophe; Matsubayashi, Nobuyuki; Geantet, Christophe; Yoshimura, Y.; Shimada, Hiromichi; Nishijima, Akio; Lacroix, Michel; Breysse, M.

doi:10.1006/jcat.1998.1934

Cited by 108 publications

(62 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Um composto chave nessa busca envolve o dissulfeto de molibdênio dopado com níquel ou cobalto e ancorado na superfície de suportes inertes [14][15][16][17] ou ainda altamente disperso no meio reacional 18,[28][29][30] . O processo envolve a remoção de poluentes de combustíveis, na presença de hidrogênio.…”

Section: Uso Em Catáliseunclassified

“…No caso da síntese de catalisadores dispersados no meio reacional [28][29][30] , utiliza-se a decomposição do tetratiomolibdato de amônio na presença de ácido sulfídrico e atmosfera redutora de hidrogênio [28][29][30] (eq. 2,7), sulfetação de heptamolibdato de amônio com ácido sulfídrico 29 ou reação do tiocianato de potássio com óxido de molibdênio 30 (eq.…”

Section: Figura 2 Possibilidades Do Posicionamento Dos áTomos De Níqunclassified

“…2,7), sulfetação de heptamolibdato de amônio com ácido sulfídrico 29 ou reação do tiocianato de potássio com óxido de molibdênio 30 (eq. 8).…”

Section: Figura 2 Possibilidades Do Posicionamento Dos áTomos De Níqunclassified

See 2 more Smart Citations

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Wypych

2002

Quím. Nova

View full text Add to dashboard Cite

Recebido em 6/10/00; aceito em 4/4/01 MOLYBDENUM DISULFIDE, A MULTIFUNCTIONAL AND REMARKABLE MATERIAL. The aim of this work is to review the chemical and physical properties of layered molybdenum disulfide. The three polymorphic/polytypic modifications of the compound were found, the polytypes 2H (molybdenite) and 3R are semiconductors while the polymorph 1T is an electronic conductor. 2H-MoS 2 has several important industrial applications as hydrotreatment catalysts, energy storage devices, solar cells, solid lubricants, among others. When intercalated, the 2H phase changes to a distorted 1T phase, producing unstable intercalation compounds that can be exfoliated in solution, producing single layers and consequently nanocomposites. The direct synthesis of the 1T phase produces stable intercalation compounds. Recently molybdenum disulfide was prepared as nanotubes and fulerenelike structures that bring new insights in the investigation of this important material.Keywords: molybdenum disulfide; intercalation; layered materials. INTRODUÇÃOO dissulfeto de molibdênio pertence a uma classe de materiais conhecidos como compostos lamelares e ocorre em três modificações polimórficas/politípicas 1,2 . A fase mais comum (2H) ocorre na natureza na forma de molibdenita. Nas modificações 2H e 3R, áto-mos de molibdênio estão ligados covalentemente à átomos de enxofre numa geometria trigonal prismática regular (Figura 1). Os prismas trigonais estão ligados entre si pelas arestas, produzindo unidades bidimensionais conhecidas como lamelas. Essas lamelas que, estão conectadas por forças fracas do tipo Van der Waals, podem se ordenar de maneira diferente originando os dois politipos. Na fase 1T a forma ondulada se deve à distorção da esfera de coordenação octaédrica do centro metálico 2 . A forma do politipo 1T não distorcida está representada na Figura 1. Figura 1. Representação esquemática das estrutura das fases 2H, 3R e 1T (não distorcida), do dissulfeto de molibdênio.As propriedades dos politipos são diferentes. A fase 1T é condutora 2 enquanto que as fases 2H e 3R são diamagnéticas e semicondutoras 3. Além das três formas conhecidas de hábito cristalino, o dissulfeto de molibdênio se apresenta na forma amorfa 4,5 , como nanotubos 6,7 e esferas de dimensões nanoscópicas 7,8 semelhantes as estruturas dos fulerenos.As aplicações do dissulfeto de molibdênio vão desde baterias no estado sólido que utilizam meio não aquoso e íons lítio intercaláveis [9][10][11] , células solares 12 , como lubrificantes sólidos 13 , catalisadores [14][15][16][17][18] , onde desempenha um papel de importância fundamental, além de outras.Um dos processos de síntese do dissulfeto de molibdênio nas fases polimórficas 2H e 3R é a reação térmica direta entre o molibdênio metálico e enxofre elementar em ampolas de quartzo. Quando cristais grandes forem necessários utiliza-se o método de transporte de vapor químico com um halogeneto como o iodo como agente transportante 19 (Eq.1).Mo + 2 S ® MoS 2 + 2 I 2 « MoI 4 + S 2Nesse procedimento, quantidades estequ...

show abstract

Section: Uso Em Catáliseunclassified

Section: Figura 2 Possibilidades Do Posicionamento Dos áTomos De Níqunclassified

See 1 more Smart Citation

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Wypych

2002

Quím. Nova

View full text Add to dashboard Cite

show abstract

“…Up to now, numerous experimental techniques have been employed to better characterize the catalytically "CoMoS" or "NiMoS" active phases [2,3]. Experimental techniques involved in the characterization of these complex phases consist of transition electron microscopy (TEM) [4,5], X-ray photoelectron spectroscopy (XPS) [6][7][8][9], Mössbauer spectroscopy [10][11][12], laser Raman spectroscopy [5,13], extended X-ray absorption fine structure (EXAFS) [14][15][16][17][18], and IR spectroscopy [19,20]. These techniques furnished many detailed features of the so-called Co(Ni)MoS active phase made of MoS 2 layers with a stacking close to 1 [21] and nanometer sizes (less than 30 Å), "decorated" by Co or Ni at the edges.…”

Section: Introductionmentioning

confidence: 99%

A DFT Study of CoMoS and NiMoS Catalysts: from Nano-Crystallite Morphology to Selective Hydrodesulfurization

Krebs

Daudin²,

Raybaud³

2009

Oil & Gas Science and Technology - Rev. IFP

View full text Add to dashboard Cite

Résumé -Étude DFT des catalyseurs CoMoS et NiMoS : de la morphologie des nano-cristallites à l'hydrodésulfuration sélective -Cet article présente des résultats récents obtenus dans des études utilisant la théorie de la fonctionnelle de la densité (DFT) pour la caractérisation à l'échelle atomique des phases actives Co(Ni)MoS utilisées en catalyse d'hydrodésulfuration (HDS) sélective. L'effet des conditions du milieu réactionnel sulfo-réducteur sur la stabilité et la nature des sites actifs localisés au bord des nano-cristallites Co(Ni)MoS est mis en évidence. En combinant les calculs DFT et un modèle thermodynamique, il apparaît que la teneur en promoteur sur les bords des cristallites en conjonction avec la morphologie des cristallites dépend des conditions sulfo-réductrices. Nous montrons ensuite comment la nature des sites actifs Co(Ni)Mo influence l'HDS sélective de molécules soufrées légères (alkylthiophènes) vis-à-vis de l'hydrogénation (HydO) des oléfines légères (alkyl-butènes). La combinaison des calculs DFT d'adsorption de deux molécules modèles (2-méthyl-thiophène et 2,3-diméthyl-but-1-ène) avec la modélisation cinétique de la sélectivité HDS/HydO permet de proposer une explication de l'origine de cette sélectivité basée sur la compétition d'adsorption des réactifs. Abstract -A DFT Study of CoMoS and NiMoS Catalysts from Nano-Crystallite Morphology to Selective Hydrodesulfurization -This paper reports an overview of recent DFT studies on the atomic scale characterization of Co(Ni)MoS active phases used in selective hydrodesulfurization (HDS) catalysis. A peculiar attention is paid to the effect of the sulfo-reductive reaction conditions on the

show abstract

“…When used with discrete nanoparticles for size determination, this method typically produces results that are smaller than found by Scherrer analysis of x-ray diffraction (XRD) data, 47,55,56 an effect attributed to XRD being more sensitive to the size distribution of larger particles compared to EXAFS which is more sensitive to smaller particle sizes in a polydisperse sample. 50 Transmission electron microscopy (TEM) has also been shown to produce estimates of particle size larger than EXAFS for discrete particles.…”

Section: Fig 10 (Upper) Average Radiusmentioning

confidence: 97%

Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu

Olive

Wang

Booth

et al. 2016

Journal of Applied Physics

View full text Add to dashboard Cite

The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curve have been determined using an amplitude-ratio method, standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to previous electrical resistivity-and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Together, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.

show abstract

Crystallite Size Determination of Highly Dispersed Unsupported MoS2Catalysts

Cited by 108 publications

References 39 publications

Dissulfeto de molibdênio, um material multifuncional e surpreendente

Dissulfeto de molibdênio, um material multifuncional e surpreendente

A DFT Study of CoMoS and NiMoS Catalysts: from Nano-Crystallite Morphology to Selective Hydrodesulfurization

Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu

Contact Info

Product

Resources

About