Study of the decomposition pathway of 12-molybdophosphoric acid in aqueous solutions by micro Raman spectroscopy

Bajuk‐Bogdanović, Danica; Uskoković‐Marković, Snežana; Hercigonja, Radmila; Popa, Alexandru; Holclajtner-Antunović, Ivanka

doi:10.1016/j.saa.2015.08.029

Cited by 21 publications

(17 citation statements)

References 31 publications

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“…For Cat-B and Cat-B-V, there are three intense peaks that can be attributed to the Keggin anion. The peak at 900 cm −1 can be assigned to the Mo-O-Mo vibration, and the peaks at 989 and 1000 cm −1 can be attributed to the Mo-O vibration in the Keggin anion [26,27]. The results further confirm that the materials have different structures.…”

Section: Resultssupporting

confidence: 52%

“…2, the Raman spectra in the range 700-1100 cm −1 under ambient conditions provide evidence for the different structures. For Cat-A and Cat-A-V, the peaks at 817 and 993 cm −1 can be attributed to the Mo-O-Mo symmetric stretch and the Mo=O vibration, respectively [23][24][25][26]. For Cat-B and Cat-B-V, there are three intense peaks that can be attributed to the Keggin anion.…”

Section: Resultsmentioning

confidence: 99%

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The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

Zhang

Liu

et al. 2018

Catal Lett

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Heteropolyacids and their salts have been effectively used in selective catalytic reduction because of the Keggin structure and extraordinarily strong acidity. Catalysts with and without the Keggin structure were synthesized to further investigate the effects of heteropolyoxometallate on low temperature NH 3 -SCR. XRD, BET, Raman, H 2 -TPR, NH 3 -TPD, FT-IR, and SO 2 -TPD techniques were used to characterize the physicochemical characteristics of the catalysts. Results indicate that catalysts with the Keggin structure had more surface Brönsted and Lewis acid sites, and these catalysts had significantly improved performances in the SCR reaction and in SO 2 poisoning resistance. Graphical AbstractKeywords SCR catalyst · Ammonium heteropolyacid salt · Keggin structure Rui Wu and Ningqiang Zhang have contributed equally.

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

Zhang

Liu

et al. 2018

Catal Lett

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“…188 The UV-vis, IR and between 0 and 12 manifest that already at pH 1.5 the intact Keggin anion decomposes into lacunary forms, and at pH 7, monomeric molybdate and phosphate dominate in the solution. [189][190][191][192] {PMo 12 } co-exists with its monolacunary form {PMo 11 } between pH 1.5 and 5 (Fig. 15) 193,194 The yield of both aand b-forms (at pH 4.0 and 1.2, respectively) is independent of molybdate concentrations between 0.015 and 0.100 M. Later, using ESI-MS the formation of molybdosilicates was detected between pH 1 and 2.…”

Section: During Aging In Solution [Mo VI O 4 ] 2à -Hp V Omentioning

confidence: 97%

Polyoxometalates in solution: speciation under spotlight

2020

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“…The degradation of Keggin POM {PMo12} in water with increasing pH have been reported in the literature, and the 31 P NMR spectra obtained in this study (see Figure 5) are comparable to those published. [42][43][44][45] The four main identified POM species resulting from the {PMo12} decomposition in the pH range 0-7 are PMo11O39 2). In the presence of two eq.…”

Section: Titration Of Cds With Pomsmentioning

confidence: 99%

Improvement of the Hydrolytic Stability of the Keggin Molybdo- and Tungsto-Phosphate Anions by Cyclodextrins

et al. 2022

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Keggin-type molybdo-and tungsto-phosphate polyoxoanions are among the most popular polyoxometalates (POMs), but suffer from their limited stability at low pH in aqueous solution. Their superchaotropic properties generate strong supramolecular complexes with cyclodextrins (CDs) which significantly affect the hydrolytic stability of POM. This chaotropically-driven stabilization effect was systematically monitored by 31 P NMR spectroscopy covering a wide range of pH (from 0 to 8) and varying the nature of the CD (a-, b-, and g-form).A shift of ca. two pH units of the stability domains of these POMs were found in the presence of two eq. g-CD compared to pure water, leading to keep intact the PW12O40 3anion without any decomposition up to pH 3.5 (versus 1.5 in pure water) and pH 2.5 for PMo12O40 3which begins to decompose even at pH 0 in pure water. The effect of the smaller CDs (a-and b-form) is much less pronounced (only 0.5 pH units shift of stability domain) confirming the importance of host-guest size matching to form a sandwich-type inclusion complex, and thus protect the POM structure against basic hydrolysis. Such complexation was further supported by 183 W and 1 H NMR spectroscopy. Finally, using quantitative 31 P NMR analyzes, the new speciation and formation constants of phosphomolybdates and phosphotungstates in the presence of cyclodextrins are determined and compared to those previously reported in pure water or in 50:50 water/1,4-dioxane mixture.

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Study of the decomposition pathway of 12-molybdophosphoric acid in aqueous solutions by micro Raman spectroscopy

Cited by 21 publications

References 31 publications

The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

Polyoxometalates in solution: speciation under spotlight

Improvement of the Hydrolytic Stability of the Keggin Molybdo- and Tungsto-Phosphate Anions by Cyclodextrins

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