Laboratorio Of Fisicoquimica Of Superficies

Montevideo, Uruguay

Laboratorio Of Fisicoquimica Of Superficies

Montevideo, Uruguay

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Bussi J.,Laboratorio Of Fisicoquimica Of Superficies | Musso M.,Laboratorio Of Fisicoquimica Of Superficies | Veiga S.,Laboratorio Of Fisicoquimica Of Superficies | Bespalko N.,Laboratorio Of Fisicoquimica Of Superficies | And 2 more authors.
Catalysis Today | Year: 2013

NiLaZr and NiCuLaZr mixed metal oxide catalysts were prepared by co-precipitation with oxalic acid in alcoholic medium, followed by calcination. XRD analysis of the unreduced catalysts showed the formation of crystalline phases corresponding to the pyrochlore structure La2Zr 2O7 and NiO following calcination at 850 C, 900 C and 950 C. TEM microscopy of the amorphous solids obtained by calcination at 700 C showed the formation of nanoparticles 20-30 nm in size. TPR analysis showed a shift in the Ni and Cu reduction temperature towards lower values with increasing calcination temperature. All catalysts were active in runs of ethanol steam reforming, leading to the formation of gaseous mixtures containing hydrogen, carbon monoxide, carbon dioxide and methane. Deactivation due to carbon formation was observed at the lowest reaction temperature tested (500 C). XRD, FTIR and thermogravimetric analysis revealed differences in the textural properties of catalysts before and after reforming, which varied in degree according to the catalyst calcination temperature. The NiCuLaZr catalysts showed a lower activity than their NiLaZr analogues, a fact that was ascribed to the formation of a nickel-copper solution, with a lower catalytic activity in the cleavage of C-C bonds. © 2013 Elsevier B.V. All rights reserved.

Bussi J.,University of the Republic of Uruguay | Bussi J.,Laboratorio Of Fisicoquimica Of Superficies | Cabrera M.N.,University of the Republic of Uruguay | Chiazzaro J.,University of the Republic of Uruguay | And 5 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2010

BACKGROUND: Release of mercury from fluorescent lamps must be minimized to avoid its hazardous effects on human beings and other living organisms. Because of this, increasing attention is given to the improvement of existing techniques for its recovery as well as the development of new ones. This paper describes the application of heterogeneous photocatalysis for the selective reduction of mercury from fluorescent lamps. The whole process involves mercury chemical extraction using aqueous solutions of sodium hypochlorite. After pH adjustment of the resulting aqueous solution, the photocatalytic reduction of mercury is performed in the presence of titanium dioxide and citric acid as an auxiliary organic agent. RESULTS: Mercury removal from the aqueous solution is higher than 99% and the final residual concentration is 4 ppb. A mixture of different mercury compounds is obtained in solid form deposited on the titanium oxide photocatalyst which can easily be redissolved into a small volume of sodium hypochlorite. Metallic mercury could be obtained from the residual Hg(II) solution by conventional cementation techniques with iron as reducing agent. CONCLUSION: Results show high efficiencies of the photocatalytic technique for recovery and recycling of mercury from fluorescent lamps. © 2009 Society of Chemical Industry.

Bespalko N.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Bespalko N.,Laboratorio Of Fisicoquimica Of Superficies | Roger A.-C.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | Bussi J.,Laboratorio Of Fisicoquimica Of Superficies
Applied Catalysis A: General | Year: 2011

The catalytic performance of trimetallic oxides MeLaZr (Me: Ni, Co) was evaluated in the steam reforming of ethanol for hydrogen production. Rh doped and non doped catalysts were prepared by the pseudo sol-gel like method, characterized by X-ray diffraction (XRD), thermo-programmed reduction (TPR), micro-homogeneity analysis (TEM-EDXS), specific surface areas (BET). A phase-segregation process takes place during the calcination for both trimetallic systems leading to the formation of La2Zr 2O7 pyrochlore-type compound in coexistence with the Me-oxide. NiLaZr and CoLaZr catalysts show high activity and high selectivity for hydrogen production. Addition of Rh promotes reducibility at lower temperatures for both trimetallic catalysts and remarkably improves the activity and selectivity for H2. The H2 selectivity is lowered by CO2 injection because of the increase of the rate of the reverse WGSR and/or methanation reaction. The CH4 selectivity is lowered by the dry reforming reaction. The key-role played by oxycarbonate species formed during the reforming tests leads to a highly efficient gasification of carbon deposits by the Boudouard reaction. © 2011 Elsevier B.V. All rights reserved.

Vazquez S.,Laboratorio Of Cristalografia | Davyt S.,Laboratorio Of Cristalografia | Basbus J.F.,Grupo Caracterizacion de Materiales | Soldati A.L.,Grupo Caracterizacion de Materiales | And 4 more authors.
Journal of Solid State Chemistry | Year: 2015

Nanocrystalline La0.6Sr0.4Fe0.8Cu0.2O3-δ (LSFCu) material was synthetized by combustion method using EDTA as fuel/chelating agent and NH4NO3 as combustion promoter. Structural characterization using thermodiffraction data allowed to determine a reversible phase transition at 425 °C from a low temperature R-3c phase to a high temperature Pm-3m phase and to calculate the thermal expansion coefficient (TEC) of both phases. Important characteristics for cathode application as electronic conductivity and chemical compatibility with Ce0.9Gd0.1O2-δ (CGO) electrolyte were evaluated. LSFCu presented a p-type conductor behavior with maximum conductivity of 135 S cm-1 at 275 °C and showed a good stability with CGO electrolyte at high temperatures. This work confirmed that as prepared LSFCu has excellent microstructural characteristics and an electrical conductivity between 100 and 60 S cm-1 in the 500-700 °C range which is sufficiently high to work as intermediate temperature Solid Oxide Fuel Cells (IT-SOFCs) cathode. However a change in the thermal expansion coefficient consistent with a small oxygen loss process may affect the electrode-electrolyte interface during fabrication and operation of a SOFC. © 2015 Elsevier Inc. All rights reserved.

Veiga S.,Laboratorio Of Fisicoquimica Of Superficies | Bussi J.,Laboratorio Of Fisicoquimica Of Superficies
Topics in Catalysis | Year: 2016

Glycerol is a side product of biodiesel production which is available in the world market at relatively low cost and could be used to obtain other valuable products. H2 and H2-CO mixtures can be obtained from glycerol by steam reforming using Ni based catalysts. NiLaZr catalysts prepared by a coprecipitation technique were tested in the steam reforming of pure glycerol. The tests were performed at 500 and 650 °C and at glycerol:water molar ratios 1:6 and 1:12. Glycerol conversion to gas phase products and H2 yields were greatly improved with the increase of Ni loading from 5 to 15 %. The addition of 0.5 % of Rh is also very effective at low temperature to attain almost total glycerol conversions and high H2 yields. The catalyst containing 15 % of Ni and the NiO and La2Zr2O7 phases showed the best catalytic performance with glycerol conversion above 99 % and a H2 yield close to the thermodynamic value at 650 °CThis catalyst also showed the best results in term of stability and low carbon formation. Fast deactivation of the Rh impregnated catalyst is ascribed to its ability to yield carbon by dissociation of C-C and C-H bonds in glycerol and other C1-C3 intermediates. Carbon morphology is greatly influenced by Ni interactions with the rest of the catalyst structure. © 2015 Springer Science+Business Media New York.

De Leon M.A.,Laboratorio Of Fisicoquimica Of Superficies | Sergio M.,Laboratorio Of Fisicoquimica Of Superficies | Bussi J.,Laboratorio Of Fisicoquimica Of Superficies
Reaction Kinetics, Mechanisms and Catalysis | Year: 2013

The catalytic activity of iron pillared montmorillonitic clays in the discoloration of methylene blue aqueous solutions by the heterogeneous photo- Fenton process was studied. Catalysts were prepared using two different-sized aggregate fractions of the clay, ranging below 250 μm and within the range of 250-450 μm. Two calcination temperatures, 400 and 600 °C, were used. The solids were characterized by thermo-gravimetric analysis, nitrogen adsorption isotherms, elemental analysis, X-ray diffraction and iron content. A higher specific surface area and specific pore volume were found for the solid obtained from the finer aggregates of the clay and the lowest calcination temperature. Under photo-Fenton like conditions, this catalyst also displayed the highest catalytic activity which remained practically the same at pHs 3.0 and 5.6 and for H2O2 concentrations in the range from 5 to 20 mM. The observed differences in catalytic performance can be explained on the basis of the catalysts' iron content and textural properties. Leaching of iron ions from the catalysts could not be detected. Long term stability for dye waste water treatment could thus be expected for these catalysts. © Akadémiai Kiadó, Budapest, Hungary 2013.

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