Search results for "O2"
showing 10 items of 1115 documents
Enhancing Selectivity In Photocatalytic Formation Of P-Anisaldehyde In Aqueous Suspension Under Solar Light Irradiation Via Tio2 N-Doping
2012
The photocatalytic partial oxidation of 4-methoxybenzyl alcohol to the corresponding aldehyde (p-anisaldehyde) was performed under simulated solar irradiation by using home prepared N-doped TiO2 catalysts. The photocatalysts were prepared by a sol–gel method, using TiCl4 as TiO2 precursor and NH4Cl, urea or NH4OH as N-doping sources. A commercial TiO2 (Degussa P25) was also used for comparison aims. The prepared catalysts were characterized by BET specific surface area, XRD, ESEM and UV-vis spectroscopy. The reactivity results show that (i) the doped catalysts are predominantly amorphous, and they show selectivity values far higher than those of the corresponding undoped ones and of well cr…
New Porphyrin/Fe-Loaded TiO2 Composites as Heterogeneous Photo-Fenton Catalysts for the Efficient Degradation of 4-Nitrophenol
2013
A new class of porphyrin(Pp)/Fe co-loaded TiO2 composites opportunely prepared by impregnation of [5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (H2Pp) or Cu(II)[5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (CuPp) onto Fe-loaded TiO2 particles showed high activities by carrying out the degradation of 4-nitrophenol (4-NP) as probe reaction in aqueous suspension under heterogeneous photo-Fenton-like reactions by using UV-visible light. The combination of porphyrin-Fe-TiO2 in the presence of H2O2 showed to be more efficient than the simple bare TiO2 or Fe-TiO2.
ChemInform Abstract: Elemental Bromine Production by TiO2Photocatalysis and/or Ozonation.
2016
Significant production of elemental bromine (Br2 ) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO2 photocatalyst, ozone, or a combination thereof. Br2 selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.
TiO2-Based Photocatalysis for Organic Synthesis
2010
A major aim of the contemporary chemistry is to replace old environmentally hazardous processes with new, energy efficient routes allowing to reduce or totally avoid the use and production of harmful chemicals and to maximise the quantity of raw material that ends up in the final product. This chapter gives an account of TiO2-based selective photocatalysis as a green synthetic tool for the production of organics. Some case studies of the most common transformations carried out by means of photocatalytic reactions are illustrated in a midway perspective between photochemistry and organic chemistry.
Le cycle biogéochimique du carbone.
2013
5 pages; National audience; Bien qu’il ne soit pas l’élément chimique le plus présent sur Terre, le carbone est l’un des composés les plus marquants dans le fonctionnement et l’évolution du système Terre. Un ensemble de processus biogéochimiques nombreux et complexes permet son transfert d’un réservoir à un autre conduisant à un cycle planétaire. Ce dernier est partagé entre un cycle rapide, impliquant les réservoirs atmosphère, océan et biosphère, et un cycle lent, impliquant la croûte terrestre, les sols et l’océan.Le dioxyde de carbone étant un gaz à effet de serre, le cycle du carbone interagit très étroitement avec la machine climatique, aboutissant à la mise en place de boucles de rét…
Effects of initial performance, gross efficiency and VO_2peak characteristics on subsequent adaptations to endurance training in competitive cyclists
2018
The present study investigated the effects of initial levels of cycling performance, peak oxygen uptake (www.frontiersin.orgO2peak) and gross efficiency (GE) on the subsequent adaptations of these variables and their relationship following high-intensity training (HIT) designed to increase www.frontiersin.orgO2peak in competitive cyclists. Sixty cyclists (www.frontiersin.orgO2peak = 61 ± 6 mL kg-1 min-1) were assigned a 12-week training program consisting of twenty-four supervised high-intensity interval training sessions and ad libitum low intensity training. GE was calculated at 125, 175, and 225 W and performance was determined by mean power during a 40-min time-trial (Power40 min). In a…
Dynamic Role of Gold d-Orbitals during CO Oxidation under Aerobic Conditions
2022
High-energy-resolution fluorescence detection-X-ray absorption near-edge structure (HERFD-XANES) at the Au L3 edge was used to study gold catalysts supported on ceria in order to unravel the role of gold 5d orbital modifications during the activation of molecular oxygen. The variations in the HERFD-XANES resonance peak, which are directly correlated with the d-band occupancy, were monitored in situ during the redox process of the CO oxidation at room temperature under both aerobic and anaerobic conditions. Interestingly, upon the oxidation treatment and also during the aerobic CO oxidation treatment, the gold d-band fluctuates around an average value, proving that the gold clusters are part…
Wpływ handlu zagranicznego Unii Europejskiej na rzeczywistą emisję CO2
2016
Emisja CO2 jest problemem globalnym. Oznacza to, że walka tylko części krajów w tym obszarze niewiele zmienia. Celem niniejszego artykułu jest próba ukazania rzeczywistego poziomu emisji CO2 w UE, jak również wpływ wymiany handlowej Unii na emisję CO2 u jej głównych partnerów handlowych. Badanie zostało przeprowadzone na grupie 20 głównych partnerów handlowych UE i samej Unii. Rzeczywisty poziom emisji CO2 uzyskano przez zastosowanie wskaźnika emisji rzeczywistej. Jego wielkość uwzględnia transfer CO2 w produktach i usługach eksportowych, a także importowanych przez poszczególne kraje. W wyniku jego zastosowania okazało się, że rzeczywisty poziom emisji CO2 w badanych krajach jest znacznie …