Defective titanium dioxide (TiO2) is of much significance due to its improved visible light photoreactivity. Generally, the existence of defects leads to imperfections in the crystal lattice, which in turn affect the dynamics of the evolution of defects and the corresponding physical properties of TiO2. Until now, how lattice distortion affects the formation of Ti3+ defects as well as the corresponding visible light photoreactivity in TiO2 has remained elusive. Herein, we have successfully introduced Ti3+ defects based on lattice distortion in TiO2 microspheres and found the photocurrent of anatase TiO2 has been significantly enhanced from 1.78 to 80 μA cm−2 with an increase in photocatalytic activity of almost three times under visible light irradiation. Furthermore, we show that lattice distortions have minimal contribution to enhancing the visible light photocatalytic activity because the band gap cannot be narrowed due to the absence of Ti3+ defects, yet the existence of lattice distortions could suppress the recombination of electron–hole pairs. Moreover, the formation of Ti3+ defects is energetically favored in lattice-distorted TiO2 compared to that of pristine TiO2. This work highlights the design and development of highly efficient TiO2 photocatalysts that operate under visible light irradiation.

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Introducing Ti3+ defects based on lattice distortion for enhanced visible light photoreactivity in TiO2 microspheres

Nitrogen, iron-single modified (N-TiO2, Fe-TiO2) and co-modified (Fe,N-TiO2) rutile titanium dioxide as visible-light active photocatalysts

Dehydrogenation of ethylbenzene to styrene under excess carbon dioxide flow was carried out over activated carbon-supported metal oxide catalysts (Cr, Mn, Co, Ni, Mo, Ru, La, and Ce) at 823 K and W/F = 35 g of catalyst·h/mol. The highest yield of styrene (about 40%) with selectivity of above 80% was obtained using activated carbon-supported chromium oxide (Cr/AC) and cerium oxide (Ce/AC) catalysts. The initial activities of the Cr/AC and Ce/AC catalysts were comparable to that of an iron-loaded activated carbon catalyst reported previously. Only chromium(III) oxide and cerium(IV) oxide were detected by X-ray diffraction before and after reactions at higher loading levels, and these species might have been active forms. However, a reduced chromium oxide species was detected by X-ray photoelectron spectroscopy after reaction under argon. In addition to the produced styrene, equivalent amounts of carbon monoxide and water were formed. These results suggest that the dehydrogenation of ethylbenzene to styrene ...

Dehydrogenation of Ethylbenzene with Carbon Dioxide Using Activated Carbon-Supported Catalysts

Dehydrogenation of ethylbenzene and propane over Ga2O3–ZrO2 catalysts in the presence of CO2

Fe 2 O 3 -TiO 2 solid acid catalysts have been prepared by a sol–gel route, characterized and tested in the isomerization of α-pinene oxide. The textural, morphological and microstructural characterization of the catalysts was carried out by BET surface area measurements, X-ray diffraction (XRD) and scanning electron microscopy with elemental X-ray analysis (SEM-EDX). Characterization data have shown that, on the pure TiO 2 catalyst , titania is mainly in the anatase phase. On the contrary the rutile phase and/or Fe 2 TiO 5 , amorphous iron–titanium mixed oxides and hematite were found on the Fe-promoted TiO 2 catalysts, depending on the Fe content. Temperature programmed desorption (TPD), microcalorimetry and FT-IR spectroscopy of adsorbed probe basic molecules (ammonia or pyridine) have shown that addition of iron to titania favours formation of new acid sites having a stronger Lewis character. Fe 2 O 3 -TiO 2 catalysts show a higher activity compared to pure titania in the isomerization of α-pinene oxide to campholenic aldehyde. The products distribution was also influenced by the composition of the catalysts. A correlation between the selectivity to campholenic aldehyde and the amount of Lewis acid sites on the catalysts was found. Based on the characterization and catalytic results, Fe–Ti–O mixed structures were proposed to be the active sites for the selective isomerization of α-pinene oxide to campholenic aldehyde.

Sol–gel synthesis, characterization and catalytic properties of Fe–Ti mixed oxides

The mixed metal oxides TiO2-Fe2O3 and ZrO2-Fe2O3 were examined as potential catalysts for the dehydrogenation reaction of ethylbenzene. The acidic and basic properties and surface area, pore volume and pore size distribution of these catalysts were measured. The catalytic activities can be correlated very well with the surface area and the acidity and basicity of ZrO2-Fe2O3 catalysts. However, for TiO2-Fe2O3 catalysts, the surface area, the amount of acidic and basic sites and TiFe2O5 crystallinity are all important factors affecting the catalytic activities for ethylbenzene dehydrogenation. A synergistic effect was found for the TiO2-Fe2O3 and ZrO2-Fe2O3 catalyst system and also for the TiO2-Fe2O3-ZrO2 system, i.e. the activities of these catalysts can be ranked in the following order: TiO2-Fe2O3-ZrO2>TiO2-Fe2O3 >ZrO2>Fe2O3>TiO2. Meanwhile, all of these catalysts showed higher activities than the conventional potassium-promoted iron catalysts.

Der-Sun Liu

Papers

Dehydrogenation of ethylbenzene over TiO2-Fe2O3 and ZrO2-Fe2O3 mixed oxide catalysts