Preparation and characterization of H3PW12O40 supported on niobia

Caliman, Ednéia; Dias, José A.; Dias, Sílvia C.L.; Garcia, Fillipe A.C.; Macedo, Julio L. de; Almeida, Liana S.

doi:10.1016/j.micromeso.2010.02.004

Cited by 50 publications

(32 citation statements)

References 38 publications

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“…This is sustained by similar results obtained for H 3 PW supported on alumina and niobia. 10,12 Formation of lacunary species ([PW 11 O 39 ] 7− ) is disregarded because no characteristic signal at −10.4 ppm is present. 31 Thus, this corroborates to an interaction between the Keggin structure and the support, which gave rise to the shift in the main hydrate H 3 PW Keggin signal and an additional signal.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, anhydrous H 3 PW exhibited a single signal around −10 to −11 ppm. 8,12 It is worth to note the differences on the characteristic signals of the anhydrous, hydrated and supported H 3 PW/silica-alumina. Pure hydrated H 3 PW shows a single signal (ca.…”

Section: Resultsmentioning

confidence: 99%

“…The nature of the support and the conditions used in the catalyst synthesis are important parameters for improving the stability of H 3 PW supported materials. [9][10][11][12]42 The commercial silica-alumina showed 489 m 2 g -1 (S BET ) and 0.69 cm 3 g -1 of pore volume (P v . Table 1 shows the normalized (S N ) and decreased (S D ) calculated specific surface values for all the samples, indicating that an approximated constant decrease of surface area was reached around 30% of impregnation.…”

Section: Resultsmentioning

confidence: 99%

“…The resulting slurry was kept under magnetic stirring for 1 h. Every 10 min, the stirring was stopped to remove an aliquot using a 1.0 mL Hamilton gas-tight syringe with a membrane filter in the tip (0.45 μm, 13 mm diameter). The H 3 PW concentration, corrected for the withdrawal volume, was measured by placing the sample in a 1 cm (0.5 mL) quartz cuvette and using a Beckman DU 650 UV-Vis spectrophotometer at a wavelength of 263 nm (maximum of the [PW 12 O 40 ] 3-absorption band). The value was obtained using the following analytical curve for H 3 …”

Section: Methodsmentioning

confidence: 99%

“…8 A key catalytic compound is 12-tungstophosphoric acid (H 3 PW 12 O 40 , H 3 PW), which has been heterogenized by anchoring it to a variety of supports (e.g., silica, alumina, zirconia, niobia). [9][10][11][12] From POMs, H 3 PW is the strongest heteropolyacid (HPA), and its solid acidity can be finely controlled by heterogenization. 13 A challenge in the technological application of supported HPA is to avoid leaching in polar solvents due to their high solubility when it is used in batch reactions.…”

Section: Introductionmentioning

confidence: 99%

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Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina

Mattos¹,

Carvalho²,

Freitas³

et al. 2016

Journal of the Brazilian Chemical Society

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This work deals with preparation and characterization of H 3 PW 12 O 40 (H 3 PW) supported on silica-alumina. Impregnation of H 3 PW (15, 20, 30 and 40 wt.%) on commercial silica-alumina support in acidic aqueous solution is effective for preparing this catalyst keeping its Keggin structure, according to different methods of characterization. The catalysts were tested in a model reaction of acetic acid with ethanol and 30 wt.% H 3 PW/SiO 2 -Al 2 O 3 had the highest activity under the conditions: catalyst calcination at 300 °C, temperature of 100 °C, acetic acid:ethanol molar ratio of 2:1 and catalyst:acetic acid mass ratio of 10 wt.%. The reaction yield was 79 and 100% selectivity for ethyl acetate over three reutilizations, for reaction time of 2 h. The calculated total acid site distribution was 0.299 mmol g -1 (97% of the theoretical probed by pyridine), and most of these (0.236 mmol g -1 ) were Brønsted weak-medium strength (pyridine desorption between 300 and 500 °C).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina

Mattos¹,

Carvalho²,

Freitas³

et al. 2016

Journal of the Brazilian Chemical Society

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Samarium‐exchanged Heteropoly Tungstate: An Efficient Solid Acid Catalyst for the Synthesis of Glycerol Carbonate from Glycerol and Benzylation of Anisole

et al. 2012

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Samarium‐exchanged heteropoly tungstate (SmxTPA) is an efficient catalyst for the synthesis of glycerol carbonate from glycerol and urea. The catalysts with varying Sm content were prepared and characterized by FT‐IR spectroscopy, XRD, laser Raman spectroscopy, temperature‐programmed desorption of ammonia, and X‐ray photo electron spectroscopy. The activity of the catalysts is related to the Lewis and Brønsted acidity, which depends on the Sm content in the catalysts. Partially exchanged SmxTPA catalyst showed high activity, owing to a higher number of Lewis acidic sites. The catalyst exhibited consistent activity and selectivity during recycling. A plausible reaction mechanism is presented. The catalyst also exhibited high activity in the acid‐catalyzed benzylation of anisole.

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Effect of Acidity, Structure, and Stability of Supported 12-Tungstophosphoric Acid on Catalytic Reactions

Dias

Macedo

2013

Environmentally Benign Catalysts

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Preparation and characterization of H3PW12O40 supported on niobia

Cited by 50 publications

References 38 publications

Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina

Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina

Samarium‐exchanged Heteropoly Tungstate: An Efficient Solid Acid Catalyst for the Synthesis of Glycerol Carbonate from Glycerol and Benzylation of Anisole

Effect of Acidity, Structure, and Stability of Supported 12-Tungstophosphoric Acid on Catalytic Reactions

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