We have studied the condensation of ethylene glycol 1 and a series of methylketones 2a-e in the presence of the acid activated clay HA without solvent and under autogeneous pressure. The structures of 2-methyl-2-(R)-dioxolanes 3a-e were characterized by 1H and 13C NMR spectroscopy. These compounds were fully optimized at DFT level of theory with the functional B3LYP and 6-31G (d,p) basis set as minimum on the potential surfaces at the same level of theory. The more stable geometries of these compounds have been determined and characterised. A good agreement was then obtained between the experimental and theoretical results. Moreover, we have proposed the mechanism of the formation of dioxolanes 3 by acetalization of methylketones 2 catalysed by Bronsted and Lewis acid sites localized on the active surface of the acid activated clay HA.
W. Hagui, A. Mostefai, A. Rahmouni, M.L. Efrit, E. Srasra, N. Besbes
Tunisian acid activated clay, dioxolane, atomic charge, Mulliken charge, DFT calculation
Degradation of methyl orange (MO), also called the Heliantine , organic azo dye belongs to a class of highly toxic dyes ( indigo ) was studied by thin layers of birnessite electrodeposited onto a transparent semiconductor substrate (SnO2) at room temperature. The experimental results showed that 68% of the MO solution was completely discolored by thin layers of birnessite, and the decay kinetic always follows a pseudo-first-order reaction. An electrochemical activation of samples of birnessite and a non-spontaneous discoloration of MO have been successfully tested and a great improvement was reported in the treatment. These results suggest that birnessite thin layers may be envisaged as a new non-toxic material for treatment of colored wastewater.
W. Chouchene, C. Annabi, M. Zaied, S. Peulon, A. Chausse, N. Bellakhal
Thin layers manganese oxide, Birnessite, Dyes, Discoloration
Modelization of local atmospheric quality beeing difficult, it is important to monitor the major air pollutants in order to know, understand and eventually remedy the pollutions. The monitoring of the air quality in urban area is done in Tunis, capital of Tunisia, from 2003 to 2014, for the major gazeous pollutants: tropospheric ozone O3, nitrogene oxydes NOx and sulphur dioxyde SO2. The resulting diel patterns highlight the local atmospheric phenomena as well as the relationship between the studied parameters.
H. Kchih, S. Cherif
urbain pollution, O3, NOx, SO2, Great Tunis
The present study reports on the formation of nanocrystalline Fe-Ni-Zr-B alloy using the mechanical alloying technique. Morphological, microstructural, structural and thermal characterizations of the powders milled several times were investigated by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The patterns obtained were analyzed using the Rietveld refinement. The final products of the mechanically alloying process were a duplex nanostructure of Fe(Ni,Zr,B) and Fe2B type boride nanocrystals. The increase of mechanical milling induced a continuous decrease in the crystallite sizes and an increase in the lattice strains. Recovery, recrystallization and ferro-paramagnetic transition at Curie temperature are revealed in the thermal analysis in the temperature range 35-700°C.
A. Sekri, M. Mhadhbi, L. Escoda, J. J. Suñol, M. Khitouni, T. Makhlouf
Fe-Ni-Zr-B alloy, X-ray methods, Nanostructures, High energy ball milling
The electrochemical behaviour of bronze alloy (Cu10Sn) corrosion in aqueous chloride solution was studied by electrochemical polarization methods. Results showed that the surface’s compounds were mainly (hydroxide) oxides of tin and copper, incorporating very low amounts of chlorides. The variation of three experimental factors such as the sweep rate, the chloride concentration and the temperature allow us to deduce the activation thermodynamic parameters of this process.
R. Ben Channouf, N. Souissi, N. Bellakhal
Synthetic bronze, Copper-tin allow, Analytical and electrochemical characterizations, Corrosion
The present study aims to evaluate the catalytic performance of synthetic minerals containing manganese, for methane combustion. Al-Mn-silicate nanobubbles and Mn-zeolite (analcime) were first hydrothermally synthesized using the one-pot method. The thermal stability of an Al-Mn-silicate nanobubbles sample was studied. Elaborated solids were characterized by powder X-ray diffraction, N2-physisorption, Fourier transformed infrared spectroscopy, 27Al and 29Si magic angle spinning nuclear magnetic resonance and transmission electron microscopy and tested in methane combustion. Catalytic tests have shown that the conversion strongly depends on the nature of used mineral. Catalytic performances are controlled by both acidic and redox properties of the catalyst. Interesting activity, selectivity and stability were recorded for Al-Mn-silicate nanobubbles. These results may encourage the development of Mn-porous minerals as promising catalysts for methane combustion. They may be the best alternative to replace noble metals based catalysts which are characterized by their poor resistance to deactivation and their high cost.
A. Bejar, S. Ben Chaabene, L. Bergaoui
Mn-analcime, Al-Mn-silicate nanobubbles, hydrothermal synthesis, methane combustion
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