Improved (Photo)catalytic Propene Hydration in a Gas/Solid System by Using Heteropolyacid/Oxide Composites: Electron Paramagnetic Resonance, Acidity, and Role of Water

Abstract

Binary materials composed of the oxides SiO 2 , TiO 2 and N-doped TiO 2 and the Keggin heteropolyacid (PW 12 ) 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 PW 12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous pres-Eur.

Local Structure of Supported Keggin and Wells–Dawson Heteropolyacids and Its Influence on the Catalytic Activity

“…Gaigneaux et al have observed that the use of TiO2 as support, in comparison to the use of boron nitride with a more hydrophobic surface, could induce a better dispersion by virtue of its hydroxylated surface, but at the same time TiO2 could give rise to a decrease of the acidic strength of the HPA [19]. As far as the catalytic photo-assisted activity of the supported HPAs is concerned, it has been demonstrated that the use of semiconductor oxides as supports plays a beneficial role in the cluster photocatalytic activity due to the ability of the activated HPA * species to be reduced by the photogenerated electrons of the conduction band of the UVactivated semiconductor [5,20]. In order to study the local structural effects generated by the supports on the HPAs clusters, X-ray absorption spectroscopy (XAS) can be very useful.…”

“…19 As far as the catalytic photoassisted activity of the supported HPAs is concerned, it has been demonstrated that the use of semiconductor oxides as supports plays a beneficial role in the cluster photocatalytic activity due to the ability of the activated HPA* species to be reduced by the photogenerated electrons of the conduction band of the UV-activated semiconductor. 5,20 To study the local structural effects generated by the supports on the HPAs clusters, X-ray absorption spectroscopy (XAS) can be very useful. XAS is one of the most employed techniques in the heterogeneous catalysis and can be stated as an informative spectroscopy to study W species on several supports.…”

Heteropolyacids supported on boron nitride and carbon nitride for catalytic and catalytic photo-assisted alcohol dehydration

“…The use of a photocatalyst as a support for HPAs further improved the activity of the composite, particularly under irradiation [23,24]. In the last case the increase of activity was correlated, thanks to the electron paramagnetic resonance (EPR) study, to the capability of the semiconductor to transfer photo-generated electrons to the activated HPA* species that consequently hinders the electron-hole pair recombination [25].…”