Harb M.,Catalysis Research Center |
Harb M.,French Institute of Petroleum |
Sautet P.,Ecole Normale Superieure de Lyon |
Raybaud P.,French Institute of Petroleum
Journal of Physical Chemistry C | Year: 2013
Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.
Haslinger S.,TU Munich |
Raba A.,TUM |
Pothig A.,Catalysis Research Center |
Kuhn F.E.,TU Munich
Journal of Catalysis | Year: 2015
Three different bio-inspired Fe(II) complexes are applied as powerful catalysts for the oxidation of unreactive C-H bonds under ambient conditions. Cyclohexane as the main model substrate is oxidized to cyclohexanol, cyclohexyl hydroperoxide, and cyclohexanone. Alcohol + cyclohexyl hydroperoxide to ketone ratios ((A + H)/K) of up to 26 are obtained with comparatively high turnovers of up to 43. Bio-inspired modification of the Fe(II) complexes in the axial positions is used to increase catalyst stability toward hydrogen peroxide, leading to an increase in turnovers of up to 34%. Several parameters for the catalytic oxidation are investigated, e.g., the amount and type of oxidant, reaction temperature, and the relative catalyst concentration. Among others, 9,10-dihydroantracene and 2,3-dimethylbutane are used as substrates for the catalytic C-H bond oxidation. © 2015 Elsevier Inc. All rights reserved.
Zhang S.,Catalysis Research Center |
Wang Y.,Catalysis Research Center |
Song Z.,Catalysis Research Center |
Nakajima K.,Aichi University of Education |
Takahashi T.,Catalysis Research Center
Chemistry Letters | Year: 2013
Dimerization of 2-hydroxyanthracene was investigated with 5mol% of various catalysts that are efficient catalysts for the dimerization of 2-naphthol. Catalysts such as Cu(OH)Cl TMEDA, [Mn(acac) 3], and [Mn(acac) 2] did not give satisfactory results. However, MnI2, which gave only trace amounts of dimerization product of 2-naphthol under the same conditions,afforded 2,2-dihydroxy-1,1-bianthracene in 74% yield. © 2013 The Chemical Society of Japan.