Search results for " heteropolyacids"
showing 5 items of 5 documents
Study of the photocatalytic activity of Keggin and Wells Dawson heteropolyacids: role of the acidity and of the pseudo-liquid phase regime
2017
Study of the photocatalytic activity of Keggin and Wells Dawson heteropolyacids: role of the acidity and of the pseudo-liquid phase regime
Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites.
2015
Photocatalytic conversion of glucose was carried out in aqueous suspensions in the presence of dfifferent commercial and home prepared TiO2 samples functionalized with a commercial heteropolyacid. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst.
Local Structure of Supported Keggin and Wells-Dawson Heteropolyacids and Its Influence on the Catalytic Activity
2019
[EN] Keggin [PW12O40]3– and Wells–Dawson [P2W18O62]6– heteropolyanions are nanosized transition-metal-oxygen clusters belonging to the heteropolyacids (HPAs) family. They are widely used as catalysts due to their high Brønsted acidity, and their dispersion on solid supports favors the accessibility to their acid sites generally increasing the catalytic activity. A series of binary materials composed of Keggin or Wells–Dawson HPAs and SiO2, TiO2, and ZrO2 have been prepared by impregnation or solvothermal methods. Remarkable differences have been found in the catalytic activities among the unsupported and supported HPAs. These differences have been correlated in the past to the structural ch…
Improved (photo)catalytic propene hydration in a gas/solid system by using heteropolyacid/oxide composites: Electron paramagnetic resonance, acidity,…
2017
Binary materials composed of the oxides SiO2, TiO2 and N-doped TiO2 and the Keggin heteropolyacid (PW12) were prepared and physicochemically characterized. They were used as catalysts and photocatalysts for the hydration of propene to 2-propanol. The characterization of the samples, particularly the electron paramagnetic resonance (EPR) spectroscopy results and the acidity properties, were useful to explain the key role played by the PW12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous pres-ence of heat and UV light improved the activity of PW12 in the thermal process, and the binary materials showed better (photo)catalytic activities than t…
Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites.
2015
Commercial and home prepared TiO2 samples were functionalized with a commercial Keggin heteropolyacid (HPA) H 3PW12O 40 (PW12) or with a hydrothermally home prepared K 7PW11O 39 salt (PW11). All the materials were characterized by specific surface area measurements (BET), XRD analyses, Raman, DRS along with SEM observations and they have been used for glucose photocatalytic conversion in an aqueous suspension. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst. Gluconic acid, arabinose, erythrose and formic acid were observed as oxidation products when bare TiO2 or HPA/TiO2 composite materials were used. Glucose isomer…