Catalysis by Heteropoly Compounds. III. The Structure and Properties of 12-Heteropolyacids of Molybdenum and Tungsten (H3PMo12−<i>x</i>W<i>x</i>O40) and Their Salts Pertinent to Heterogeneous Catalysis

Misono, Makoto; Mizuno, Noritaka; Katamura, Koichi; Kasai, Atsushi; Konishi, Yasuo; Sakata, Kanji; Okuhara, Toshio; Yoneda, Yukio

doi:10.1246/bcsj.55.400

Cited by 242 publications

(71 citation statements)

References 6 publications

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“…As this water may be absent under reaction conditions it is adequate to probe the acid-base properties of activated samples with a suitable method. The acidity of solid heteropoly compounds [38] has been investigated through interaction with bases combined with different methods of analysis: (i) Hammett indicators + visual inspection [39], (ii) ammonia + temperature programmed desorption (TPD) [40,41], IR spectroscopy [42], calorimetry [43,44], and (iii) pyridine + TPD, IR spectroscopy [45,46]. The use of Hammett indicators is difficult because many heteropoly compounds are strongly colored.…”

Section: Introductionmentioning

confidence: 99%

The structure of molybdenum-heteropoly acids under conditions of gas-phase selective oxidation catalysis: a multi-method in situ study

Jentoft

Klokishner

Kröhnert

et al. 2003

Applied Catalysis A: General

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The present study focuses on the evidence about the existence of Keggin ions under various reactive conditions. The stability of the hydrated parent heteropoly acid (HPA) phases is probed in water, by thermal methods in the gas phase, by in situ X-ray diffraction and in situ EXAFS. An extensive analysis of the in situ optical spectra as UV-Vis-NIR in diffuse reflectance yields detailed information about the activated species that are clearly different from Keggin ions but are also clearly no fragments of binary oxides in crystalline or amorphous form. Infrared spectroscopy with CO as probe molecule is used to investigate active sites for their acidity. Besides -OH groups evidence for electron-rich Lewis acid sites was found in activated HPA. All information fit into a picture of a metastable defective polyoxometallate anion that is oligomerised to prevent crystallisation of binary oxides as the true nature of the "active HPA" catalyst. The as-synthesized HPA crystal is thus a pre catalyst and the precursor oxide mixture is the final deactivated state of the catalyst.

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Section: Introductionmentioning

confidence: 99%

The structure of molybdenum-heteropoly acids under conditions of gas-phase selective oxidation catalysis: a multi-method in situ study

Jentoft

Klokishner

Kröhnert

et al. 2003

Applied Catalysis A: General

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“…For the samples with various Teflon loading, three typical characteristic peaks still appear, but they are very diffuse pattern and shift to lower 2h angles, indicating an increase in d-space. This could be attributed to two factors: (i) the change of crystallization water number of HSiW in the step of impregnation [26] and (ii) the strong interaction between HSiW and silica [27] in Fig. 2b.…”

Section: Characterization Of Catalystsmentioning

confidence: 98%

Esterification of Acetic Acid with N-Butanol Over the Catalysts of Surface Hydrophobicity and Lipophobicity

et al. 2008

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A series of silica-supported silicotungstic acid catalysts (H 4 SiW 12 O 40 , abbreviated as HSiW), modified with various loadings of Teflon (HSiW/SiO 2 -Teflon), were prepared by impregnation method. The surface properties of the catalysts were studied by means of XRD, BET, NH 3 -TPD and the Drop Shape Analyzer (DSA) measurements. Both the surface hydrophobicity and the surface lipophobicity of HSiW/SiO 2 -Teflon catalysts are enhanced by means of the addition of Teflon. HSiW/SiO 2 -Teflon exhibit better activity than that of HSiW/SiO 2 in the esterification of acetic acid with n-butanol. Surface hydrophobicity and lipophobicity of the catalysts lead to more effective to remove product molecules and decrease the interaction between H 2 O molecules and the catalyst surface, especially at low reaction temperature and appropriate WHSV.

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“…Yield for propylene was calculated by multiplying conversion of 2-propanol and selectivity for propylene. [9,26]. The higher desorption peak temperature corresponds to the higher acid strength of HPA catalyst.…”

Section: Vapor-phase 2-propanol Conversion Reactionmentioning

confidence: 99%

Acid Strength of H3PW x Mo12−x O40 and H6P2W x Mo18−x O62 Heteropolyacid Catalysts as a Probe of Acid Catalysis for 2-Propanol Conversion Reaction

Park

Lee

et al. 2008

Catal Lett

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Acid strength of H 3 PW x Mo 12-x O 40 (x = 0, 3, 6, 9, and 12) Keggin heteropolyacid (HPA) and H 6 P 2 W x Mo 18-x O 62 (x = 0, 3, 9, 15, and 18) Wells-Dawson HPA catalysts was determined by NH 3 -TPD measurements. Desorption peak temperature (acid strength) of H 3 PW x Mo 12-x O 40 and H 6 P 2 W x Mo 18-x O 62 catalysts showed the same trend with respect to tungsten substitution, and increased with increasing tungsten substitution in both families of HPA catalysts. In order to correlate the acid strength with the acid catalysis of HPAs, vapor-phase 2-propanol conversion reaction was carried out as a model reaction. Yield for propylene (a product formed by acid catalysis of HPA) increased with increasing tungsten substitution and with increasing desorption peak temperature (acid strength) across both HPA families, regardless of the identity of HPA catalyst (without HPA structural sensitivity). The acid strength of H 3 PW x Mo 12-x O 40 and H 6 P 2 W x Mo 18-x O 62 catalysts could be utilized as a probe of acid catalysis for 2-propanol conversion reaction.

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Catalysis by Heteropoly Compounds. III. The Structure and Properties of 12-Heteropolyacids of Molybdenum and Tungsten (H3PMo12−xWxO40) and Their Salts Pertinent to Heterogeneous Catalysis

Cited by 242 publications

References 6 publications

The structure of molybdenum-heteropoly acids under conditions of gas-phase selective oxidation catalysis: a multi-method in situ study

The structure of molybdenum-heteropoly acids under conditions of gas-phase selective oxidation catalysis: a multi-method in situ study

Esterification of Acetic Acid with N-Butanol Over the Catalysts of Surface Hydrophobicity and Lipophobicity

Acid Strength of H3PW x Mo12−x O40 and H6P2W x Mo18−x O62 Heteropolyacid Catalysts as a Probe of Acid Catalysis for 2-Propanol Conversion Reaction

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