In Situ FTIR Studies of the Protonic Sites of H3PW12O40 and Its Acidic Cesium Salts MxH3−xPW12O40

Essayem, N.; Holmqvist, A.; Gayraud, P.Y; Védrine, J.C.; Taârit, Y. Ben

doi:10.1006/jcat.2000.3107

Cited by 135 publications

(80 citation statements)

References 24 publications

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“…IR spectroscopy was chosen as the method of analysis, because unlike calorimetry or TPD, it gives information on the nature of the sites and with the right probes is fairly sensitive to small energetic differences between sites. IR spectroscopy has been applied extensively for the structural characterization of heteropoly compounds at various temperatures and degrees of dehydration [62,63,64,65,66,67,68,69]. This method in addition delivers information on the structure of a sample after each treatment by investigating the lowfrequency range of the IR spectrum.…”

Section: Acid-base Properties Under Relevant Conditionsmentioning

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: Acid-base Properties Under Relevant Conditionsmentioning

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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“…Rather, the XRD profile observed for these supported catalysts were nearly identical with that observed for the as-prepared CeO 2 ( Figure 2a) 34,35 This is made possible by the fact that a linear correlation between the observed d 31 P and acidic strength may readily be inferred. [34][35][36][37][38] Moreover, the acid types and concentration may readily be determined by chemical shift assignment and spectral deconvolution of the observed 31 P spectrum. Accordingly, the 31 P NMR spectra of TMPO adsorbed on various catalysts are depicted in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Heteropoly Tungstate Supported on Metal Oxide Catalysts for Liquid Phase Oxidation of Benzyl Alcohol with Hydrogen Peroxide

Han¹,

Kuang²,

Chunhua³

et al. 2017

J. Braz. Chem. Soc.

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A series of metal oxide supported tungstophosphoric acid catalysts were prepared by impregnation. The physicochemical and acidic properties of these materials were characterized by a variety of different analytical and spectroscopic techniques, namely Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and nuclear magnetic resonance (NMR), and exploited as heterogeneous catalysts for selective oxidation of benzyl alcohol (BzOH)

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“…Figure 4( The band for δ(O-P-O) appeared at 594 cm -1 . 24,25 And the final band in these spectra observed at 522 cm -1 can be characteristized by the vibration symmetric for W-O-W. 15,24,25 Temperature-Programmed Desorption (TPD) Figure 5(a) and 5(b) shows the NH 3 -TPD profiles for both Cs HPAs. The NH 3 uptake is propotional to the number of acid sites present in the catalyst.…”

Section: Thermal Study By Using Tga and Dscmentioning

confidence: 94%

Selective synthesis of PEG-monoester using cesium heteropoly acid as heterogeneous catalyst

et al. 2017

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Esterification of oleic acid with polyethylene glycol 600 (PEG-600) to produce polyethylene glycol monooleate (PEG-monooleate) and polyethylene glycol dioleate (PEG-dioleate) as by-product has been studied in the presence of heterogeneous acid catalysts, i.e. cesium heteropoly acid (Cs HPA). The results are compared with those obtained from a classical homogeneous acid catalyst; p-toluene sulphonic acid (p-TSA). The reaction was conducted under nitrogen flow with vigorous stirring at 130 °C and 150 °C. The catalyst loading kept at 4% and the reaction was monitored at 1, 3, 7 and 24 hours. Reaction samples were analyzed using high performance liquid chromatography (HPLC) equipped with evaporative light scattering detector (ELSD). The results obtained showed that Cs HPAs exhibit 100% selectivity of PEG-monooleate from the first hour until 24 hours. However, this does not happen with homogeneous p-TSA, where formation of by-product; PEG-dioleate is observed in the initial stage. It is also showed that the mole ratio is the most important parameter not only to produce high yield of monoester but also to maintain it along the reaction. Chemical and physical properties of catalysts were characterized using Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Tranmittance Infra-Red (FTIR), ammonia temperature programmed desorption (NH 3 -TPD) and X-ray Diffraction (XRD).

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In Situ FTIR Studies of the Protonic Sites of H3PW12O40 and Its Acidic Cesium Salts MxH3−xPW12O40

Cited by 135 publications

References 24 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

Heteropoly Tungstate Supported on Metal Oxide Catalysts for Liquid Phase Oxidation of Benzyl Alcohol with Hydrogen Peroxide

Selective synthesis of PEG-monoester using cesium heteropoly acid as heterogeneous catalyst

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