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Your search keyword '"Ghiotti, Giovanna"' showing total 74 results
Start Over Author "Ghiotti, Giovanna" Publication Type Academic Journals
74 results on '"Ghiotti, Giovanna"'

19. Investigation of acid-base properties of catalysts obtained from layered double hydroxides

Author

Prietto, Federica, Ghiotti, Giovanna, Durand, Robert, Tichit, Didier, and Wignall, G.D.

Subjects
Hydroxides -- Chemical properties, Catalysts -- Research, Acid-base chemistry -- Research, Chemicals, plastics and rubber industries
Abstract

Layered double hydroxides (LDH) materials in the lamellar or mixed-oxide form, which can be obtained by controlled calcination, have shown very attractive properties as catalysts in a wide variety of base-catalyzed reactions. They have also been largely used as supports or precursors of supported metal catalysts exhibiting a basic character and a particular metal-support interaction.

Published
2000

20. Characterization of oxidized surface phases on Vox/ZrO2 catalysts

Author

Prinetto, Federica, Ghiotti, Giovanna, Occhiuzzi, Manlio, and Indovina, Valerio

Subjects
Catalysts -- Research, Surfaces (Technology) -- Research, Zirconium oxide -- Research, Vanadium -- Research, Chemicals, plastics and rubber industries
Abstract

A study was conducted to characterize oxidized surface phases on Vox/ZrO2 catalysts. The zirconia support was made by hydrolysis of zirconium oxychloride with ammonia. The Philips PW 1710 diffractometer was utilized to perform X-ray diffraction analysis. In addition, the XPS spectra was determined with a Leybold-Hereaus LHS 10 spectrometer. Results indicated that increases in the selective catalytic reduction activity of Vox/ZrO2 with the vanadium content correlated with increases in the concentration of polynuclear vanadium species.

Published
1998

21. Effect of water and ammonia on surface species formed during NOx storage–reduction cycles over Pt–K/Al2O3 and Pt–Ba/Al2O3 catalysts.

Author

Morandi, Sara, Prinetto, Federica, Castoldi, Lidia, Lietti, Luca, Forzatti, Pio, and Ghiotti, Giovanna

Abstract

The effect of water, in the temperature range 25–350 °C, and ammonia at RT on two different surface species formed on Pt–K/Al2O3 and Pt–Ba/Al2O3 NSR catalysts during NOx storage–reduction cycles was investigated. The surface species involved are nitrates, formed during the NOx storage step, and isocyanates, which are found to be intermediates in N2 production during reduction by CO. FT-IR experiments demonstrate that the dissociative chemisorption of water and ammonia causes the transformation of the bidentate nitrates and linearly bonded NCO− species into more symmetric species that we call ionic species. In the case of water, the effect on nitrates is observable at all the temperatures studied; however, the extent of the transformation decreases upon increasing temperature, consistent with the decreased extent of dissociatively adsorbed water. It was possible to hypothesize that the dissociative chemisorption of water and ammonia takes place in a competitive way on surface sites able to give bidentate nitrates and linearly bonded NCO− that are dislocated, remaining on the surface as ionic species. [ABSTRACT FROM AUTHOR]

Published
2013
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22. Reduction by CO of NO x species stored onto Pt–K/Al2O3 and Pt–Ba/Al2O3 lean NO x traps

Author

Morandi, Sara, Ghiotti, Giovanna, Castoldi, Lidia, Lietti, Luca, Nova, Isabella, and Forzatti, Pio

Subjects
*CHEMICAL reduction, *CARBON monoxide, *NITROGEN oxides, *PLATINUM catalysts, *ALUMINUM oxide, *FOURIER transform infrared spectroscopy, *TEMPERATURE effect, *CHEMICAL reactions
Abstract

Abstract: In this paper the results obtained in our previous studies on the reduction of nitrates by CO over Pt–K/Al2O3 and Pt–Ba/Al2O3 catalysts are compared and discussed in order to define the chemistry that leads to nitrogen evolution during the regeneration of the different lean NO x traps. The reaction mechanisms and pathways leading to N2 formation under dry conditions are investigated by complementary transient dynamic experiments and FT-IR analyses. In both cases, the reduction of stored NO x by CO occurs according to a Pt catalyzed surface pathway that does not involve the release of NO x in the gas phase as a first step, is effective already at low temperature and leads to nitrogen. The proposed reaction scheme implies the formation of surface isocyanate species followed by their reaction with residual stored NO x to give nitrogen. This is the exclusive route for nitrogen formation. [Copyright &y& Elsevier]

Published
2011
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23. Reaction Pathways in the Reduction of NO x Species by CO over Pt–Ba/Al2O3: Lean NO x Trap Catalytic Systems.

Author

Nova, Isabella, Lietti, Luca, Forzatti, Pio, Frola, Francesca, Prinetto, Federica, and Ghiotti, Giovanna

Subjects
SURFACE chemistry, SURFACE tension, REACTION mechanisms (Chemistry), FOURIER transform infrared spectroscopy, EVAPORATION (Chemistry)
Abstract

The reduction by CO of NO x species stored over Pt–Ba/Al2O3 Lean NO x Trap systems is analysed in this work. The reaction mechanisms and pathways leading to N2 formation both under dry and wet conditions are investigated by complementary transient dynamic experiments and FTIR analyses. [ABSTRACT FROM AUTHOR]

Published
2009
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