Ilenia Rossetti

University of Milan, Milano, Lombardy, Italy

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Publications (70)269.54 Total impact

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    ABSTRACT: Experiments were conducted on the liquid-phase oxidation of benzyl alcohol over Pd nanoparticles, with the aim of determining the operative chemical reaction. Experiments were conducted in a batch reactor with para-xylene as the solvent and continuous gas purging of the headspace. The following experimental parameters were varied: the initial benzyl alcohol concentration, the oxygen partial pressure in the headspace, and the reactor temperature. From trends in the concentration profiles and integrated production of each product, it was determined that there are two primary reaction paths: A) an alkoxy pathway leading to toluene, benzaldehyde, and benzyl ether, and B) a carbonyloxyl pathway (“neutral carboxylate”) leading to benzoic acid, benzene, and benzyl benzoate. From the mechanism elucidated, it is clear that the coverages of atomic hydrogen, atomic oxygen, and surface hydroxyls must be accounted for to achieve a complete description of the quantitative kinetics.
    ChemCatChem 09/2014; 6(12). DOI:10.1002/cctc.201402552 · 5.04 Impact Factor
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    ABSTRACT: In this work the performance of CaO-doped Ni/ZrO2 catalysts in ethanol steam reforming was studied. The addition of CaO did not affect the morphology or the crystalline structure of the support. On the contrary, Ni reducibility markedly increased. Moreover, the Lewis acidity of zirconia gradually decreased as the CaO content increased, thus inhibiting coke deposition and improving the carbon balance. The addition of a basic oxide helps to prevent some of the side reactions responsible for coke formation and deposition, that can gradually deactivate the catalyst.
    Applied Catalysis B Environmental 05/2014; s 150–151:12–20. DOI:10.1016/j.apcatb.2013.11.037 · 6.01 Impact Factor
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    ABSTRACT: TiO2 was used as support for Ni, Co and Cu to prepare catalysts for the steam reforming of ethanol, due to its known tendency to form strong metal-support interaction (SMSI) with some metals. The samples were prepared following different procedures, tuning the reducibility of the active phase and its interaction with the support. The latter parameter showed pivotal to impart suitable catalytic activity and most of all stability towards coking. Indeed, the insurgence of SMSI may allow to keep the active phase dispersed, improving activity and inhibiting the formation of carbon filaments over the active phase. The comparison between different active phases (Ni, Co, Cu, 10 wt%) confirmed Ni as very active, although it has a higher tendency to form carbon filaments. This drawback may be at least partially controlled by favouring high Ni dispersion through the formation of a mixed oxide with the support. The calcination temperature, and in general the preparation procedure for the catalyst, showed of pivotal importance to establish SMSI. In particular, calcination at relatively low temperature (i.e. 500 degrees C) induced initially a higher dispersion of the active phase (mean Ni crystal size 7 nm), however not accompanied by sufficient stabilisation during activity testing (mean Ni crystal size increased to 44 nm). By contrast, calcination at higher temperature (i.e. 800 degrees C) favoured the instauration of a SMSI and the formation of a mixed oxide (NiTiO3), which, after activation, allowed the coexistence of smaller particles, more active and resistant to deactivation and sintering, together with the more sintered ones (mean Ni crystal size 27 nm before and after activity testing). Different characterisation data (XRD, FT-IR, TPR, TEM) allowed to conclude the need of calcination at high temperature to achieve sufficient activity and resistance of the catalyst for this application. Co and Cu proved more promising as for C balance, although their activity at low temperature was unsatisfactory, mainly due to poor activity for C C bond cleavage. The characterisation of the spent catalysts by XRD, TEM and Raman allowed to evidence the different types of C deposed and to check for active phase stability against sintering.
    Applied Catalysis A General 05/2014; 477:42–53. DOI:10.1016/j.apcata.2014.03.004 · 3.67 Impact Factor
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    ABSTRACT: Ethanol steam reforming is an attracting process to produce hydrogen in a sustainable way. In this work the performance of Ni/TiO2 catalysts in ethanol steam reforming was studied. In particular, the effect of the synthesis procedure on the properties of the catalysts and on their activity was deeply investigated. On the basis of the experimental results, it was evidenced that TiO2-supported Ni systems are very sensitive to the synthesis parameters. We found that a proper thermal activation by calcination at 800 degrees C allows to obtain stable catalysts by means of strong interactions between the active phase and the support, preserving the catalyst from sintering phenomena. Nevertheless, the synthesis conditions must be properly tuned in order to prevent Ni incorporation in scarcely reducible structures which would depress catalytic activity. Copyright
    International Journal of Hydrogen Energy 03/2014; 39(9):4252–4258. DOI:10.1016/j.ijhydene.2013.12.178 · 2.93 Impact Factor
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    ABSTRACT: Abstract The activity of bimetallic Ni-Cu catalysts in ethanol steam reforming was evaluated and compared to the activity of the corresponding monometallic Ni catalyst. Copper addition positively affected the catalytic activity only if the proper metal-support interactions, as well as the proper ratio between the different reducible species, were maintained. This target can be pursued by tuning the synthesis conditions. Graphical Abstract .
    Catalysis Letters 02/2014; 145(2):549-558. DOI:10.1007/s10562-014-1414-2 · 2.29 Impact Factor
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    ABSTRACT: One of the limitations for CO2 photoreduction in the liquid phase is due to its low solubility in water. This point has been here addressed by designing a fully innovative concept of pressurised photoreactor, allowing operation up to 20 bar and applied for the first time to improve the productivity of this very challenging process.
    RSC Advances 01/2014; 4(55):28883. DOI:10.1039/C4RA03751K · 3.71 Impact Factor
  • Ilenia Rossetti, Gianguido Ramis
    International Journal of Hydrogen Energy 10/2013; 38(30):13309-13317. DOI:10.1016/j.ijhydene.2013.07.080 · 2.93 Impact Factor
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    ABSTRACT: Methods and models describing oxygen diffusion and desorption in oxides have been developed for slightly defective and well crystallised bulky materials. Does nanostructuring change the mechanism of oxygen mobility? In such a case, models should be properly checked and adapted to take into account new material properties. In order to do so, temperature programmed oxygen desorption and thermogravimetric analysis, either in isothermal or ramp mode, have been used to investigate some nanostructured La1-xAxMnO3±δ samples (A = Sr and Ce, 20-60 nm particle size) with perovskite-like structure. The experimental data have been elaborated by means of different models to define a set of kinetic parameters able to describe oxygen release properties and oxygen diffusion through the bulk. Different rate-determining steps have been identified, depending on the temperature range and oxygen depletion of the material. In particular, oxygen diffusion was shown to be rate-limiting at low temperature and at low defect concentration, whereas oxygen recombination at the surface seems to be the rate-controlling step at high temperature. However, the oxygen recombination step is characterised by an activation energy much lower than that for diffusion. In the present paper oxygen transport in nanosized materials is quantified by making use of widely diffused experimental techniques and by critically adapting to nanoparticles suitably chosen models developed for bulk materials.
    Physical Chemistry Chemical Physics 09/2013; 15(39). DOI:10.1039/c3cp52928b · 4.20 Impact Factor
  • Ilenia Rossetti
    ChemInform 06/2013; 44(24). DOI:10.1002/chin.201324199
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    ABSTRACT: Co- and Cu-based catalysts prepared by means of a flame pyrolysis (FP) technique are proposed as possible substitutes for Ni-based catalysts, very active for the Ethanol Steam Reforming reaction, but showing poor stability towards coke formation when operating at relatively low temperature.The FP method allowed to achieve a partial incorporation of the active phase into the support, leading to high dispersion and lower reducibility, at least in the case of Co. Cu was much more reducible than both Co and Ni, but it was almost completely inactive for the reforming reaction, mainly leading to ethanol dehydrogenation to acetaldehyde. The two different supports chosen, characterized by semiconducting behaviour and different reducibility (SiO2 and TiO2), were able to differently interact with the active phase. The best results, especially at 625 and 750 °C, were achieved with 10 wt% Co/SiO2, which led to higher activity, good C balance and low CO/CO2 ratio. This was ascribed to the high initial dispersion of Co into the silica matrix, which led to available Co particles well dispersed and stable on the catalyst surface.
    International Journal of Hydrogen Energy 03/2013; 38(8):3213–3225. DOI:10.1016/j.ijhydene.2012.12.137 · 2.93 Impact Factor
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    ABSTRACT: Ni-based catalysts supported on TiO2, ZrO2 and SiO2 (in the form of mesoporous Santa Barbara Amorphous 15 (SBA-15) and amorphous dense nanoparticles), were employed in the steam reforming of glycerol. Each sample was prepared by liquid phase synthesis of the support followed by impregnation with the active phase and calcination at 800 °C or by direct synthesis through flame pyrolysis. Many techniques have been used to assess the physical chemical properties of both the fresh and spent catalysts, such as atomic absorption, N2 adsorption/desorption, XRD, SEM, TEM, temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), Micro-Raman and FTIR spectroscopy. The samples showed different textural, structural and morphological properties, as well as different reducibility and thermal resistance depending on the preparation method and support. Some of these properties were tightly bound to catalyst performance, in terms of H2 productivity and stability towards coking and sintering. A key parameter was the metal–support interaction, which strongly depended on the preparation procedure. In particular, the stronger the interaction, the more stable the metallic Ni clusters, which in turn lead to a higher catalytic activity and stability. Surface acidity was also taken into account, in which the nature of the acid sites was differentiated (silanols, titanols or Lewis acid sites). The characterisation of the spent catalysts also allowed us to interpret the deactivation process. The formation of multi-walled nanotubes was observed for every sample, though it was only in some cases that this led to severe deactivation.
    ChemCatChem 01/2013; 5(1). DOI:10.1002/cctc.201200481 · 5.04 Impact Factor
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    ABSTRACT: Site isolation of V active sites has been often correlated to catalytic performance for the oxidative dehydrogenation (ODH) of propane to propylene. In particular, catalyst selectivity seems favored by high V dispersion. The latter property is hardly attainable by traditional preparation methods, especially by impregnation except at very low V loading, which however may lead to a too high surface exposure of the acidic sites of the support. In this paper, the effect of the preparation procedure on catalyst properties has been investigated, particularly considering catalysts prepared by flame pyrolysis, a synthesis method which induced a very high V dispersion also at relatively high vanadium loading. Transmission electron microscopy also allowed us to assess V oxide dispersion depending on both the support type and the preparation method. Furthermore, the local structure of the V active sites has been deeply investigated by X-ray absorption spectroscopy, allowing us to propose a possible structure of the active sites. The average oxidation state of surface V species was then studied by X-ray photoelectron spectroscopy (XPS), showing a role of V oxidation state on catalyst selectivity. The catalytic performance has been interpreted on the basis of V species and catalyst acidity (as measured by IR spectroscopy), another fundamental parameter that in turn results to be correlated with V dispersion on different supports. More selective catalysts were indeed characterized by the presence of weaker Brønsted acidic sites.
    The Journal of Physical Chemistry C 10/2012; 116(42):22386. DOI:10.1021/jp307031b · 4.84 Impact Factor
  • Olga Buchneva, Alessandro Gallo, Ilenia Rossetti
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    ABSTRACT: LaMnO(3), either pure or doped with 10 mol % Sr, has been prepared by flame pyrolysis in nanostructured form. Such catalysts have been tested for the catalytic flameless combustion of methane, achieving very high catalytic activity. The resistance toward poisoning by some model N-containing impurities has been checked in order to assess the possibility of operating the flameless catalytic combustion with biogas, possibly contaminated by S- or N-based compounds. This would be a significant improvement from the environmental point of view because the application of catalytic combustion to gas turbines would couple improved energy conversion efficiency and negligible noxious emissions, while the use of biogas would open the way to energy production from a renewable source by means of very efficient technologies. A different behavior has been observed for the two catalysts; namely, the undoped sample was more or less heavily poisoned, whereas the Sr-doped sample showed slightly increasing activity upon dosage of N-containing compounds. A possible reaction mechanism has been suggested, based on the initial oxidation of the organic backbone, with the formation of NO. The latter may adsorb more or less strongly depending on the availability of surface oxygen vacancies (i.e., depending on doping). Decomposition of NO may leave additional activated oxygen species on the surface, available for low-temperature methane oxidation and so improving the catalytic performance.
    Inorganic Chemistry 10/2012; 51(21). DOI:10.1021/ic3015892 · 4.79 Impact Factor
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    ABSTRACT: The physical-chemical properties of some nanostructured perovskite-like catalysts of general formula La(1-x)M(x)MnO(3+δ) (M = Ce, Sr) have been investigated, in particular by using the electron paramagnetic resonance (EPR) technique. We show that the interplay between the -O-Mn(3+)-O-Mn(4+)-O- electron double-exchange and the electron mobility is strictly dependent on the dopant nature and the annealing conditions in air. A relationship between the observed properties of these samples and their activity in the methane flameless catalytic combustion is proposed.
    Inorganic Chemistry 07/2012; 51(15):8433-40. DOI:10.1021/ic300977e · 4.79 Impact Factor
  • Chimica oggi 05/2012; 30(3):29-32. · 0.45 Impact Factor
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    ABSTRACT: A power unit constituted by a reformer section, a H2 purification section and a fuel cell stack is being tested c/o the Dept. of Physical Chemistry and Electrochemistry of Università degli Studi di Milano, on the basis of a collaboration with HELBIO S.A. Hydrogen and Energy Production Systems, Patras (Greece), supplier of the unit, and some sponsors (Linea Energia S.p.A., Parco Tecnologico Padano and Provincia di Lodi, Italy). The system size allows to co-generate 5 kWe (220 V, 50 Hz a.c.) + 5 kWt (hot water at 65 °C) as peak output. Bioethanol, obtainable by different non-food-competitive biomass, is transformed into syngas by a pre-reforming and reforming reactors couple and the reformate is purified from CO to a concentration below 20 ppmv, suitable to feed a proton exchange membrane fuel cell (PEMFC) stack that will be integrated in the fuel processor in a second step of the experimentation. This result is achieved by feeding the reformate to two water gas shift reactors, connected in series and operating at high and low temperature, respectively. CO concentration in the outcoming gas is ca. 0.4 vol% and the final CO removal to meet the specifications is accomplished by two methanation reactors in series. The second methanation step acts merely as a guard, since ca. 15 ppmv of CO are obtained already after the first reactor.The goals of the present project are to test the integrated fuel processor, to check the effectiveness of the proposed technology and to suggest possible adequate improvements.
    International Journal of Hydrogen Energy 05/2012; 37(10):8499–8504. DOI:10.1016/j.ijhydene.2012.02.095 · 2.93 Impact Factor
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    ABSTRACT: SiO2 and ZrO2 supported Ni catalysts were prepared for use in the steam reforming of ethanol. The catalytic performances, in terms of both H2 productivity and stability towards coking and sintering, were related to the physico-chemical properties of the catalysts.The samples were prepared either by synthesis of the support by precipitation and subsequent impregnation with the active phase, or by direct synthesis through flame pyrolysis. The latter has been chosen because it leads to nanostructured oxides, often quenched in very disperse or metastable form, characterised by high thermal resistance, important for this high temperature application.Many techniques have been used to assess the physico-chemical properties of the catalysts. The samples showed different textural, structural and morphological properties, as well as different reducibility and thermal resistance, depending on the preparation method and support. Therefore, besides evaluating the effect of catalyst formulation and preparation method on the catalytic performance, the influence of all such properties has been considered. The fundamental parameter governing the final catalyst properties was metal–support interaction. In particular, the stronger the latter parameter, the higher was metal dispersion, leading to small and stable Ni clusters. This influenced both activity and the resistance towards coking. Surface acidity was also taken into account considering the effect of the different nature of acid sites (silanols or Lewis a.s.) of both support and metal phase on catalyst deactivation. The best results were obtained with a 10 wt% Ni/SiO2 sample, prepared by FP, when tested at 625 °C. H2 productivity of 1.44 mol H2/min kgcat was reached, corresponding to ca. 80% of the maximum value achievable under the selected conditions. This result was accompanied by the lowest CO/CO2 ratio and 100% carbon balance without by-products in the outflowing gas.
    Applied Catalysis B Environmental 05/2012; 117-118:384-396. DOI:10.1016/j.apcatb.2012.02.006 · 6.01 Impact Factor
  • O. Buchneva, I. Rossetti, A. Kryukov
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    ABSTRACT: Modified LaCoO3 and LaMnO3 were investigated as catalysts for low tvemperature flameless combustion of methane. Modifications were carried out by the substitution part of La for Sr2+ and Ce4+, by the addition of 0.5% of Pt or Pd and by the substitution with Ag, which have limited solubility in the perovskite structure and may exist as intraframework Ag+ and extraframework metallic silver. Catalysts were synthesized by flame pyrolysis, which lead to a significant increase of both surface area and thermal resistance in comparison with the catalysts prepared by traditional sol-gel method. Samples were mainly characterized by XRD, BET and TPR techniques. Catalytic activity for the flameless combustion of methane was investigated by means of bench scale continuous apparatus, equipped with a quadrupolar mass spectrometer. In addition the resistance of every catalysts against sulphur poisoning was tested by using tetrahydrothiophene (THT) as poisoning agent. In most cases modification of perovskites led to an activity improvement, which was much more evident in the case of silver substitution. All the FP-prepared catalysts showed full methane conversion below 600°C, with CO2 and H2O as the sole detected products. Sr-substitution and addition of noble metals increased resistance to sulphur poisoning, while silver was not effective from this point of view, its main advantage being a substantial increase of the initial activity, which lead to satisfactory performance even after poisoning.
    Catalysis in Industry 04/2012; 4(2). DOI:10.1134/S2070050412020043
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    ABSTRACT: Two V-SBA-15 and V-MCF materials (containing about 2.5wt.% vanadium) were prepared by direct synthesis and tested as catalysts in the decomposition of the most stable chlorinated-alkane, dichloromethane (a total oxidation reaction) and in the oxidative dehydrogenation (ODH) of propane (a partial oxidation reaction). Comparison was made with: (i) two V-SBA-15 and V-MCF materials prepared by “traditional” impregnation method and (ii) a non-porous V-SiO2 catalyst prepared by flame pyrolysis. All catalysts tested had a vanadium content of about 2.5wt.%. Samples properties were investigated by means of complementary techniques (TEM, IR and DR UV–vis spectroscopies, N2 sorption at −196°C) in order to find possible correlations between catalytic properties of the studied materials and their different physico-chemical features. It is shown that direct synthesis allows a better vanadium dispersion to be achieved, a feature that positively affects catalytic performances in both total and partial oxidations. The different porous networks of the SBA-15 and MCF supports also play an important role on catalytic activity: both V-SBA-15 samples gave better results in dichloromethane decomposition, whereas both V-MCF samples were more selective in propane ODH. The latter findings are ascribed to different molecules diffusion and residence time inside the channels of either SBA-15 or MCF networks.
    Catalysis Today 01/2012; 179(1). DOI:10.1016/j.cattod.2011.06.028 · 3.31 Impact Factor
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    ABSTRACT: Two V-SBA-15 and V-MCF materials (V content ca. 2.5wt.%) were prepared by direct synthesis and tested in the catalytic decomposition of dichloromethane. Their catalytic properties were compared to those of other materials with the same vanadium content, namely two mesoporous materials prepared by impregnation (V-SBA-15-i and V-MCF-i) and a non-porous one prepared by flame pyrolysis (V-SiO2). Both direct synthesis and flame pyrolysis methods allowed a better vanadium dispersion that lead to better catalytic properties above 350°C, due to the presence of well dispersed V species partially incorporated into silica. The higher dichloromethane conversion achieved with both V-SBA-15 and V-SBA-15-i samples, as compared to MCF samples, are ascribed to longer residence times of both reactants and products within SBA-15 mesoporous channels, in contrast to three-dimensional MCF ultra large pores facilitating diffusion. Below 350°C, both V-SBA-15-i and V-MCF-i samples showed higher dichloromethane conversion, basically due to the presence of micro-crystalline V2O5 formed at the external surface of both materials.
    Catalysis Today 11/2011; 176(1):458-464. DOI:10.1016/j.cattod.2010.10.066 · 3.31 Impact Factor