Catalysis on Pd/WO3 and Pd/WO2: Effect of the Modifications of the Surface States Due to Redox Treatments on the Skeletal Rearrangement of Hydrocarbons

Bigey, C.; Hilaire, L.; Maire, G.

doi:10.1006/jcat.1999.2466

Cited by 81 publications

(39 citation statements)

References 54 publications

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“…helium, propene, and hydrogen) to WO 2 or tungsten metal is detected during the decomposition of APT under hydrogen only. [17,[26][27][28] Apparently, propene is not capable of further reducing WO 3 in the temperature range employed. This difference between the reducing powers of hydrogen and propene has already been observed for the reduction of MoO 3 under propene and hydrogen.…”

Section: Discussion Thermal Decomposition Of Ammonium Paratungstatementioning

confidence: 92%

In Situ XAS and XRD Studies on the Structural Evolution of Ammonium Paratungstate During Thermal Decomposition

et al. 2005

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Keywords:In situ studies / X-ray absorption spectroscopy / X-ray diffraction / Tungsten / Oxidation / Decomposition / Structure-activity relationships / Heterogeneous catalysisThe bulk structural evolution during the decomposition of ammonium paratungstate (APT) under various oxidizing and reducing gases was elucidated by the complementary techniques, in situ XAS, in situ XRD, and TG/DSC, combined with mass spectrometry. In the temperature range from 300 to 650 K, the decomposition of APT proceeds nearly independently of the gas employed. At higher temperatures, an oxidizing gas results in the formation of crystalline triclinic WO 3 as the majority phase at 773 K, while mildly reducing gases (propene, propene and oxygen, and helium) result in the formation of partially reduced and highly disordered tungsten bronzes. No further reduction is observed under propene or helium, and this indicates a strongly hindered oxygen mobility in the tungsten oxide lattice in the temperature range employed. The decomposition of APT under hydrogen results in the formation of WO 2 and, eventually, tungsten me-

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Section: Discussion Thermal Decomposition Of Ammonium Paratungstatementioning

confidence: 92%

In Situ XAS and XRD Studies on the Structural Evolution of Ammonium Paratungstate During Thermal Decomposition

et al. 2005

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“…The lowest intensity peak centered at 532.73 eV (O III ) can be attributed to the chemisorbed oxygen impurities as -CO 3 , adsorbed H 2 O or adsorbed O 2À . 21,[36][37][38][39][40][41][42] Figure 4 shows the FTIR spectra of both the unfunctionalized and functionalized WO 3 thin films: curve (1) is Si/WO 3 ; curve (2) is Si/WO 3 @Solvent- APTES; curve (3) is Si/WO 3 @solvent-APTES-SA; curve (4) is Si/WO 3 @O 2 plasma-APTES-SA; and curve (5) is Si/WO 3 @O 2 plasma-APTES-SA. The detailed FTIR spectra in the wavenumber range of 2000-400 cm À1 are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The peak located at higher binding energies ($41.4 eV) are assigned to W5p 3/2 of the W 6+ ions. 21,[36][37][38][39][40][41][42] Figure 3b shows the XPS of the O 1s core level spectra of the WO 3 thin films. The O 1s core level spectra are clearly asymmetric.…”

Section: Resultsmentioning

confidence: 99%

Surface Functionalization of WO3 Thin Films with (3-Aminopropyl)triethoxysilane and Succinic Anhydride

Tran

et al. 2017

Journal of Elec Materi

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We report effects of oxygen plasma treatment on the surface functionalization of WO 3 thin films with (3-aminopropyl)triethoxysilane (APTES) and succinic anhydride (SA). X-ray diffraction and x-ray photoelectron spectroscopy results indicate the existence of the WO 3 phase. Fourier transform infrared spectroscopy measurement shows clear bands at 1040 cm À1 (Si-O-Si), 1556 cm À1 (N-H), 1655 cm À1 (C=O), 2937 cm À1 (C-H) and 3298 cm À1 (N-H), confirming the surface functionalization efficiency enhanced by prior treatment of oxygen plasma. It thus follows that the prior oxygen plasma treatment activates hydroxylation with more -OH groups on the WO 3 surface, which can pave a highly efficient way to the surface functionalization by APTES and SA.

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“…Trioxides WO 3 or MoO 3 , promoted with small amounts of platinum group metals, are used as high-activity catalysts for processes of hydrogenation, isomerization, and oxidation of hydrocarbons [1][2][3], and also are sensitive elements for electrochromic devices [4] and semiconductor adsorption gas sensors [5][6][7].…”

mentioning

confidence: 99%

“…In the temperature range 313 K to 353 K, we have studied the kinetic behavior of the reaction on 0.1 mass % Pt(Pd)/WO 3 and Pt(Pd)/MoO 3 samples. We have established that the kinetics of H 2 oxidation on these catalysts correspond to an Eley -Rideal mechanism.Key words: oxidation of H 2 , partially reduced oxides WO 3 and MoO 3 , supported platinum and palladium, reaction kinetics.Trioxides WO 3 or MoO 3 , promoted with small amounts of platinum group metals, are used as high-activity catalysts for processes of hydrogenation, isomerization, and oxidation of hydrocarbons [1][2][3], and also are sensitive elements for electrochromic devices [4] and semiconductor adsorption gas sensors [5][6][7].The increase in catalytic activity and specific surface area of the indicated oxides upon addition of Pt or Pd is due to formation of two-phase systems during their reduction by hydrogen: trioxide/hydrogen-containing oxide bronze [7,8]. We showed earlier that adding Pt or Pd to WO 3 leads to a significant increase in the specific surface area and catalytic activity of the oxide in oxidation of H 2 , as a result of a change in the chemical composition of the catalyst [9].…”

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confidence: 99%

Catalytic Activity of WO3 and MoO3 with Pt and Pd Additives in Oxidation of Hydrogen

et al. 2005

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We have shown that WO 3 and MoO 3 with Pt or Pd additives exhibit high catalytic activity in the reaction of H 2 oxidation. In the temperature range 313 K to 353 K, we have studied the kinetic behavior of the reaction on 0.1 mass % Pt(Pd)/WO 3 and Pt(Pd)/MoO 3 samples. We have established that the kinetics of H 2 oxidation on these catalysts correspond to an Eley -Rideal mechanism.Key words: oxidation of H 2 , partially reduced oxides WO 3 and MoO 3 , supported platinum and palladium, reaction kinetics.Trioxides WO 3 or MoO 3 , promoted with small amounts of platinum group metals, are used as high-activity catalysts for processes of hydrogenation, isomerization, and oxidation of hydrocarbons [1][2][3], and also are sensitive elements for electrochromic devices [4] and semiconductor adsorption gas sensors [5][6][7].The increase in catalytic activity and specific surface area of the indicated oxides upon addition of Pt or Pd is due to formation of two-phase systems during their reduction by hydrogen: trioxide/hydrogen-containing oxide bronze [7,8]. We showed earlier that adding Pt or Pd to WO 3 leads to a significant increase in the specific surface area and catalytic activity of the oxide in oxidation of H 2 , as a result of a change in the chemical composition of the catalyst [9]. We used X-ray phase analysis to establish that in this case, the oxide bronze H x WO 3 and the oxide WO 2.9 are formed.The aim of this work was to determine the effect of the conditions for reduction of the trioxides WO 3 and MoO 3 by hydrogen in the presence of Pt or Pd on their catalytic activity in oxidation of H 2 , and also to study the kinetic behavior of this reaction.Catalysts based on WO 3 and MoO 3 were prepared by impregnation of the oxides with aqueous solutions of H 2 PtCl 6 and PdCl 2 calculated on the basis of 0.1 and 0.5 mass % of the metal within the composition of the sample; they were dried at 293 K and reduced by hydrogen (10% H 2 in Ar) at a temperature of 438 K (1 h) and 673 K (1 h and 5 h).The specific surface area of the catalysts (S sp ) was measured by low-temperature desorption of argon. The catalytic activity of the samples was studied in a flow-through apparatus under atmospheric pressure. The flow rate of the reaction mixture was 0.1 L/min; the weight of the catalyst was 0.5 g. The components of the reaction mixture were analyzed by chromatography. As the characteristic of the catalytic activity of the samples, we used the temperature at which a certain conversion of H 2 was achieved. The phase composition of the samples was determined by X-ray phase analysis (STOE STAPIDI diffractometer, MoK a radiation).According to X-ray phase analysis data, in the diffraction spectra of the catalysts based on MoO 3 containing 0.1 and 0.5 mass % Pt or Pd we observe intense peaks corresponding to the orthorhombic phases a 1 -and a 2 -MoO 3 (space group Pbmn, a = 3.961, b = 13.858, c = 3.695 Å and a = 3.963, b = 13.882, c = 3.707 Å respectively) and compounds obtained during reduction 0040-5760/05/4105-0329

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Catalysis on Pd/WO3 and Pd/WO2: Effect of the Modifications of the Surface States Due to Redox Treatments on the Skeletal Rearrangement of Hydrocarbons

Cited by 81 publications

References 54 publications

In Situ XAS and XRD Studies on the Structural Evolution of Ammonium Paratungstate During Thermal Decomposition

In Situ XAS and XRD Studies on the Structural Evolution of Ammonium Paratungstate During Thermal Decomposition

Surface Functionalization of WO3 Thin Films with (3-Aminopropyl)triethoxysilane and Succinic Anhydride

Catalytic Activity of WO3 and MoO3 with Pt and Pd Additives in Oxidation of Hydrogen

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