Sulfur uptake and exchange, HDS activity and structure of sulfided, Al2O3 supported MoOx, PdMoOx and PtMoOx catalysts

Paál, Z.; Koltai, Tamás; Matusek, K.; Manoli, Jean‐Marie; Potvin, Claude; Wild, Ute; Tétényi, P.

doi:10.1039/b009047f

Cited by 22 publications

(16 citation statements)

References 27 publications

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“…Consequently, the molybdenum-oxide layer is to be regarded as being near to the monomolecular one on the alumina surface in the two metal-promoted samples, similarly to the observations made before [6,7,10] with non-promoted molybdena-alumina samples. It is of interest to note that the surface coverage of the NiMoO x sample is to some extent higher than that for the non-promoted one (82% [10]. In contrast to this, the addition of Co does not influence the surface coverage of the support by molybdena.…”

Section: Resultsmentioning

confidence: 58%

“…In contrast to this, the addition of Co does not influence the surface coverage of the support by molybdena. It is worth noticing that the amounts of irreversible sulfur uptake [10], and the conversion rate of thiophene hydrodesulfurization are higher on the NiMo sample as compared to those on CoMo [18]. The data available, however, are not sufficient for making any definite conclusion, but the differences observed between the two catalysts deserve attention.…”

Section: Resultsmentioning

confidence: 84%

“…This practically equals to the area of oxygen ions bonded to Mo, as this approximation has been successfully proven [10]. Dividing 69,8x10 18 nm 2 with the area of one oxygen ion (see above) gives 1.275x10 21 for the number of oxygen ions, and 4.8x20 20 for that of Mo-ions in the surface layer of 1g NiMo-2, i.e.…”

Section: Resultsmentioning

confidence: 94%

“…The CO 2 chemisorption method has been applied for the determination of MoO x coverage on alumina in a flow system [10]. It was found that the MoO x layer reached 82±6% of the monomolecular layer, and was regarded as being near to monomolecular.…”

Section: Introductionmentioning

confidence: 99%

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On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

Matusek

Schay

Tétényi

2008

React Kinet Catal Lett

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The chemisorption of CO 2 has been studied on alumina-supported Co-and Nipromoted molybdenum-oxide (CoMo, NiMo) and, besides those, on monometallic Co and Ni. Chemisorbed amounts on the monometallic samples were equal to that on the alumina support. XPS measurements were performed with the NiMo and Ni samples. The amounts of surface Mo-and Al-ions were calculated. It could be established that molybdenum oxide forms a near to monomolecular layer on the Co-and Ni-promoted molybdena-alumina samples.

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Section: Resultsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

Matusek

Schay

Tétényi

2008

React Kinet Catal Lett

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“…In a number of cases, in order to obtain a composite oxide catalyst with an extended surface and high catalytic activity, Pt additives (up to 0.1 mass %) are used with reduction of MoO 3 by hydrogen [2][3][4][5]. We observed an increase in specific surface area and catalytic activity in oxidation of H 2 and CO [6] also when specimens of MoO 3 and WO 3 , promoted by small amounts of Cs + , were reduced.…”

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confidence: 97%

Effect of Pt, Pd, and Cs+ Additives on the Surface State and Catalytic Activity of WO3 in Oxidation of Hydrogen

et al. 2005

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We have shown that additions of Pt(Pd) and Cs + to WO 3 significantly increase its specific surface area and catalytic activity in H 2 oxidation. After reduction, the promoted specimens contain the phases WO 3 , WO 2.9 , H x WO 3 ; and in the case of Cs + additions, Cs x WO 3 . According to X-ray photoelectron spectroscopy (XPS), the Pt and Pd have an oxidation state close to 0, while tungsten has a +5 oxidation state. The W:O ratio indicates the content of oxygen vacancies in the surface layer. The data are explained taking into account hydrogen spillover from Pt(Pd) to the support.Key words: oxidation of H 2 , tungsten oxides, hydrogen spillover, X-ray photon electron spectroscopy (XPS), X-ray phase analysis.We know that some transition metal oxides, such as MoO 3 , when partially reduced significantly increase their specific surface area and catalytic activity in incomplete oxidation reactions [1] and isomerization of hydrocarbons [2, 3], which is explained by formation of unstable hydrogen-containing oxide bronzes on their surface and also compounds containing the metal in different valence states [1][2][3]. In a number of cases, in order to obtain a composite oxide catalyst with an extended surface and high catalytic activity, Pt additives (up to 0.1 mass %) are used with reduction of MoO 3 by hydrogen [2][3][4][5]. We observed an increase in specific surface area and catalytic activity in oxidation of H 2 and CO [6] also when specimens of MoO 3 and WO 3 , promoted by small amounts of Cs + , were reduced. This paper is devoted to a study of the combined effect of modifiers, specifically platinum (or palladium) and Cs + , on the catalytic activity of WO 3 when they are introduced at the same time, which is certainly of interest for development of new catalytic systems.We used the impregnation method to prepare catalysts based on tungsten trioxide promoted by small amounts of Pt(Pd) and Cs + . Tungsten trioxide (Reakhim, special-purity, 99.9999 mass %) was impregnated with aqueous solutions of H 2 PtCl 6 or PdCl 2 , calculated on the basis of 0.1 mass % and 0.5 mass % metal in the specimen, and then were dried at 393 K and reduced by hydrogen for 1 h at 673 K. When Pt(Pd) and Cs + were introduced in combination, the components were sequentially applied: specimens containing Pt(Pd) were impregnated with a CsIO 3 solution, calculated on the basis of 0.05 mass % Cs + in the oxide, and were reduced by hydrogen at a temperature of 673 K for 1 h. According to data obtained by temperature programmed desorption with mass spectrometric analysis of the desorbed species (Selmi MX7304 mass spectrometer), the specimens of the catalysts obtained after reduction by hydrogen did not contain even trace amounts of iodine. In order to compare the synthesized catalysts with standard catalysts, we prepared Pt(Pd)/γ-Al 2 O 3 specimens with a low specific surface area (S sp = 3.6 m 2 /g) and a metal content of 0.1 mass % and 0.5 mass %. Hydrogen reduction of these catalysts was carried out under the same conditions as for the speci...

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ChemInform Abstract: Sulfur Uptake and Exchange, HDS Activity and Structure of Sulfided, Al₂O₃ Supported MoO_x, PdMoO_x and PtMoO_x Catalysts.

Paál¹,

Koltai²,

Matusek³

et al. 2001

ChemInform

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Sulfur uptake and exchange, HDS activity and structure of sulfided, Al2O3 supported MoOx, PdMoOx and PtMoOx catalysts

Cited by 22 publications

References 27 publications

On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

Effect of Pt, Pd, and Cs+ Additives on the Surface State and Catalytic Activity of WO3 in Oxidation of Hydrogen

ChemInform Abstract: Sulfur Uptake and Exchange, HDS Activity and Structure of Sulfided, Al₂O₃ Supported MoO_x, PdMoO_x and PtMoO_x Catalysts.

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Sulfur uptake and exchange, HDS activity and structure of sulfided, Al2O3 supported MoOx, PdMoOx and PtMoOx catalysts

Cited by 22 publications

References 27 publications

On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

On the surface coverage of alumina by molybdenum-oxide in nickel - and cobalt-promoted MoOx/Al2O3 catalysts

Effect of Pt, Pd, and Cs+ Additives on the Surface State and Catalytic Activity of WO3 in Oxidation of Hydrogen

ChemInform Abstract: Sulfur Uptake and Exchange, HDS Activity and Structure of Sulfided, Al2O3 Supported MoOx, PdMoOx and PtMoOx Catalysts.

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ChemInform Abstract: Sulfur Uptake and Exchange, HDS Activity and Structure of Sulfided, Al₂O₃ Supported MoO_x, PdMoO_x and PtMoO_x Catalysts.