Crystallization Behavior of Tungstate on Zirconia and Its Relationship to Acidic Properties

Boyse, Raymond A.; Ko, Edmond I.

doi:10.1006/jcat.1997.1761

Cited by 123 publications

(104 citation statements)

References 25 publications

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“…The amount of strong L acid sites over PWZr-110b was fewer, only 3.7 mol/g. As suggested by Boyse and Ko [18], a distinct decrease in the B and L acid sites over PWZr-110 may be related to the formation of considerable WO 3 microcrystallites. …”

Section: Surface Aciditymentioning

confidence: 57%

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WO3 microcrystallites: One of the crucial factors controlling the isomerization activity of Pt/WO3–ZrO2

et al. 2011

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Section: Surface Aciditymentioning

confidence: 57%

“…2. The Raman bands at 706-712 cm −1 and 810 cm −1 are generally assigned to the characteristic bands of WO 3 microcrystallites [3,4,18]. The band centering at 970-990 cm −1 is assigned to the stretching mode of W O in highly distorted octahedral coordinated amorphous tungsten oxide species [4,19].…”

Section: Crystalline Structurementioning

confidence: 99%

WO3 microcrystallites: One of the crucial factors controlling the isomerization activity of Pt/WO3–ZrO2

et al. 2011

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“…In order to study the effect of tungsten, gold was deposited also on zirconia by cation adsorption of [Au(en) 2 ] 3+ complex using the same conditions applied to the W-containing samples. Since the incorporation of WO x species stabilizes the tetragonal phase of zirconia [14,[16][17][18][19][20][21][22], WO x -free tetragonal zirconia was used for the preparation of ZrO 2 -supported gold sample. The goal was to eliminate the effect of crystal phase on the interaction of gold precursor with the support because there are differences in the acid-base properties [23], and types and concentration of the surface hydroxyl groups [24] of zirconia polymorphs.…”

Section: Sample Preparationmentioning

confidence: 99%

“…It is well known that tungstated zirconia contains acidic protons and their amount increases with the surface density of the WO x species [13,[16][17][18][19][20]30]. It is reasonable to propose that as higher the concentration of acidic hydroxyls on the support surface as larger the amount of deprotonated M O − surface sites (M = W and Zr) thus leading to greater number of anchoring sites for the [Au(en) 2 ] 3+ complex resulting in higher surface concentration of gold.…”

Section: Structural Characterizationmentioning

confidence: 99%

Spectroscopic characterization of gold supported on tungstated zirconia

Kantcheva¹,

Milanova²,

Avramova³

et al. 2012

Catalysis Today

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Keywords:Gold supported on tungstated zirconia XRD DR-UV-vis spectroscopy XPS In situ FT-IR spectroscopy of adsorbed CO and CO + O2 a b s t r a c t Gold catalysts supported on tungstated zirconia (containing 5-20 wt% WO 3 ) are prepared by cationic adsorption from aqueous solution of [Au(en) 2 ]Cl 3 complex. The materials are characterized by XRD, DR-UV-vis spectroscopy and XPS. The nature of the deposited gold species is studied by FT-IR spectroscopy of adsorbed CO. It is concluded that the gold particles occupy preferentially the WO x -free zirconia surface and the dispersion of gold depends on the amount of coodinatively unsaturated (cus) Zr 4+ ions. Modification of zirconia by tungsten increases the gold uptake but at the same time causes decrease in the concentration of (cus) Zr 4+ ions thus lowering the dispersion of gold clusters. According to the results of in situ FT-IR spectroscopy, the Au/WO x ZrO 2 catalysts display higher activity in the CO oxidation in the low-temperature range (up to 150• C) than the WO x -free Au/ZrO 2 sample. The low-temperature activity of the W-containing catalysts could be associated with decreased basicity of the support oxide ions resulting in reduced accumulation of stable carbonate species.

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“…In particular, the sol-gel method stabilizes the surface area and the pore volume of the catalysts with respect to the traditional synthetic procedures. Despite these remarkable advantages, only few investigations concerning the sol-gel preparation of ZW systems are present in literature [15,19,20].…”

Section: Introductionmentioning

confidence: 99%

Aerogel and xerogel WO3/ZrO2 samples for fine chemicals production

Signoretto

Ghedini

Menegazzo

et al. 2013

Microporous and Mesoporous Materials

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a b s t r a c t WO 3 /ZrO 2 systems were prepared by sol-gel technique using different procedures for the solvent extraction: evaporation in vacuum at room temperature (xerogel) and extraction in supercritical conditions (aerogel). Two reactions of industrial interest were investigated under mild conditions: (i) acylation of veratrole with acetic anhydride; (ii) acylation of anisole with benzoic anhydride. Several techniques were employed in order to study the influence of the synthetic parameters on texture and catalytic activity: N 2 physisorption, Fourier transformed-infrared spectroscopy, X-ray photoelectron spectroscopy, temperature programmed reduction and temperature programmed oxidation analyses. The solvent extraction strongly influences metal reducibility, surface area, pores organisation, W/Zr surface density and metallic interactions. The aerogel sample shows the best catalytic results for both conversion and yield. The supercritical extraction plays a central role especially in the recycling: by proper air activation, the aerogel sample attains the complete restoration of the catalytic activity even after three runs.

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Crystallization Behavior of Tungstate on Zirconia and Its Relationship to Acidic Properties

Cited by 123 publications

References 25 publications

WO3 microcrystallites: One of the crucial factors controlling the isomerization activity of Pt/WO3–ZrO2

WO3 microcrystallites: One of the crucial factors controlling the isomerization activity of Pt/WO3–ZrO2

Spectroscopic characterization of gold supported on tungstated zirconia

Aerogel and xerogel WO3/ZrO2 samples for fine chemicals production

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