Deposition of tungsten-oxo-species on zirconia

Yori, Juan Carlos; Parera, J.M.

doi:10.1007/bf02475348

Cited by 6 publications

(3 citation statements)

References 10 publications

(10 reference statements)

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“…For the IM method, the support was soaked by an ammonium metatungstate solution whose pH was adjusted to 6 by an ammonia solution. This pH was chosen according to Yori’s finding: , such a pH value is lower than the isoelectric point (IEP) of Zr(OH) 4 and can make large-sized metatungstate species (W 12 O 39 ) 6– evolve into small-sized (HW 6 O 21 ) 5– . The slurry was kept at room temperature for 12 h, dried at 110 °C for 4 h, and calcined at 450–750 °C for 4 h. The corresponding catalyst was designated as x -W/Zr-IM- y , where x and y refer to the tungsten content and the calcination temperature, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…27 At pH values above 9, although tungsten-containing anions are dominantly present in smaller-sized WO 4 2− species, the surface of the hydrous zirconia is negatively charged and an electrostatic repulsion will exist between the surface and the tungstate, so the adsorption of tungstate on zirconia may be greatly inhibited and the antisintering effect of tungsten is weakened. 17 However, at pH values near and lower than 6, (HW 6 O 21 ) 5− species <1 nm in size are formed and the zirconia surface is positively charged; 26 both effects are convenient to the adsorption of tungstate on zirconia and thus promote the antisintering effect of tungsten on zirconia. Therefore, to retain more tetragonal zirconia at the same tungsten content, HD may require milder hydrothermal conditions than HCP.…”

Section: Energy and Fuelsmentioning

confidence: 99%

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Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Wang

et al. 2012

Energy Fuels

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Tungsten oxide was supported on zirconia via hydrothermal and conventional impregnation methods and used as a catalyst to reduce the viscosity of heavy crude oil without the addition of water. Their properties and viscosity reduction activity were compared. X-ray diffraction and the Rietveld method were used to characterize the crystal structure and determine the phase composition. The properties of catalysts were also measured by N2 adsorption–desorption, differential scanning calorimetry, a Hammett indicator, and ammonia temperature-programmed desorption. Compared with the impregnation method, the hydrothermal method facilitates the formation of strong tungsten–zirconia interaction and promotes the diffusion of tungstate on zirconia, hence leading to better-dispersed tungsten oxide, as well as more tetragonal zirconia and acid sites. Under the reaction conditions of 220 °C, 6 h, and 2 MPa, the catalysts prepared via the hydrothermal method exhibit higher viscosity reduction activity than those prepared by impregnation. It is found the catalytic activity mainly depends on the acidity of the catalyst. The catalyst containing 20 wt % tungsten prepared by the hydrothermal method can attain a viscosity reduction ratio of 82.2% and reduce the viscosity of oil from 5.74 Pa s (50 °C) to 1.02 Pa s. Different from the widely used aquathermolysis technique, the presence of water is not required and the viscosity of the treated oil will not regress, even over long periods of time.

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Section: Methodsmentioning

confidence: 99%

Section: Energy and Fuelsmentioning

confidence: 99%

Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Wang

et al. 2012

Energy Fuels

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“…WO x −ZrO 2 (WZ) was obtained by impregnation of ZH with a solution of ammonium metatungstate, which had been previously stabilized at pH = 6 for a week. This procedure is known to enrich the solution in medium size tungstate anions . The volume and concentration of the solution were adjusted in order to get a 15% W in the final catalyst.…”

Section: Methodsmentioning

confidence: 99%

Optimization of Pt/WO_x−ZrO₂Catalysts for the Production of Reformulated Fuels by Isomerization−Cracking of Medium Length C₈−C₁₂Paraffins

et al. 2008

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The effect of the temperature of calcination of the support on the structural properties of ZrO2 and on the activity of the acid and metal functions of a Pt/WO x −ZrO2 catalyst used in the isomerization−cracking of medium length paraffinic C8−C12 cuts was studied. n-Octane was used as model molecule. The calcination temperature was varied in order to change the metal/acid balance and to increase the yield of the reaction to isoparaffins of high octane number. Four supports were prepared by impregnating Zr(OH)4 with ammonium metatungstate (15% W) and then they were calcined at 500, 600, 700, and 800 °C. These supports were then impregnated with H2Cl6Pt (1% Pt) and calcined in air at 500 °C. They were characterized by means of chemical analysis, XRD, N2 adsorption, pyridine TPD, hydrogen chemisorption, temperature-programmed reduction, and infrared spectroscopy of adsorbed CO. The catalytic activity of the catalysts was evaluated with the test reactions of n-octane (300 °C, 1 atm, WHSV = 1, H2/n-C8 = 6), n-butane (350 °C, WHSV = 1, H2/n-C4 = 6), and cyclohexane (300 °C, 1 atm, WHSV = 12.6, H2/CH = 1.4). The results reveal a strong influence of the calcination temperature on the final metal/acid balance of the catalysts. At 5 min time on stream, all catalysts produce a RON gain of 55 points. In general, the higher the calcination temperature the higher the promoting action of W for generating strong acid sites and the higher the concentration of Ptδ+ of the metal function. The highest liquid yield and isoparaffin yield were obtained with the sample calcined at 700 °C. The sample calcined at 800 °C had the highest cracking activity and the maximum yield of isobutane and propane.

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Epoxidation of cyclohexene and indene with hydrogen peroxide in the presence of WO5 onto hydroxyapatite as catalyst

Crosman¹,

Gelbard²,

Poncelet³

et al. 2004

Applied Catalysis A: General

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Deposition of tungsten-oxo-species on zirconia

Abstract: The deposition of tungsten oxo-species on zirconia is selective. The adsorption of less polymeric species (WO42" and (HW6021) s') produced by decomposition of the W120396" is predominant during the impregnation step.

Cited by 6 publications

References 10 publications

Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Optimization of Pt/WO_x−ZrO₂Catalysts for the Production of Reformulated Fuels by Isomerization−Cracking of Medium Length C₈−C₁₂Paraffins

Epoxidation of cyclohexene and indene with hydrogen peroxide in the presence of WO5 onto hydroxyapatite as catalyst

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Deposition of tungsten-oxo-species on zirconia

Abstract: The deposition of tungsten oxo-species on zirconia is selective. The adsorption of less polymeric species (WO42" and (HW6021) s') produced by decomposition of the W120396" is predominant during the impregnation step.

Cited by 6 publications

References 10 publications

Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Supporting Tungsten Oxide on Zirconia by Hydrothermal and Impregnation Methods and Its Use as a Catalyst To Reduce the Viscosity of Heavy Crude Oil

Optimization of Pt/WOx−ZrO2Catalysts for the Production of Reformulated Fuels by Isomerization−Cracking of Medium Length C8−C12Paraffins

Epoxidation of cyclohexene and indene with hydrogen peroxide in the presence of WO5 onto hydroxyapatite as catalyst

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Optimization of Pt/WO_x−ZrO₂Catalysts for the Production of Reformulated Fuels by Isomerization−Cracking of Medium Length C₈−C₁₂Paraffins