Norma Amadeo - Academia.edu (original) (raw)

Papers by Norma Amadeo

AIChE Journal, 2011

... The beginning of the practical use of homotopy methods in solving system of equations is attr... more ... The beginning of the practical use of homotopy methods in solving system of equations is attributed to Davidenko,21 and this topic has received contributions by several researchers.22 26 Allgower and Georg26 played an essential role in popularizing the method. ...

Topics in Catalysis, 2008

... A Kinetic Study of Ethanol Steam Reforming Using a Nickel Based Catalyst ... Abstract A kinet... more ... A Kinetic Study of Ethanol Steam Reforming Using a Nickel Based Catalyst ... Abstract A kinetic study of ethanol steam reforming to produce hydrogen within the region of kinetic rate control was carried out. A Ni(II)Al(III) lamellar double hydroxide as catalyst precursor was used. ...

Chemical Engineering Journal, 2015

h i g h l i g h t s Glycerol reforming on catalysts obtained from MgAl layered double hydroxides.... more h i g h l i g h t s Glycerol reforming on catalysts obtained from MgAl layered double hydroxides. Weak to moderate basic sites render catalysts more selective to hydrogen. More stable carbon deposits play major role in catalyst deactivation. Highly dispersed metal sites are important for in situ catalyst surface cleanness.

Catalysis Today, 2015

H 2 rich gas produced from Scenedesmus almeriensis biomass residue after lipidic extraction by lo... more H 2 rich gas produced from Scenedesmus almeriensis biomass residue after lipidic extraction by low temperature catalytic gasification is addressed. The pyrolysis-gasification behavior under different atmospheres (CO 2 /He, H 2 O/He and CO 2 + H 2 O/He) were investigated using thermal gravimetric analysis. The conversion of the biomass takes place into three stages, according to its composition and corresponding to: loose of water bonded (30-200 • C), major pyrolysis involving devolatilization (200-500 • C) and decomposition of bio-char produced (500-800 • C). The calculated apparent activation energy for the main pyrolysis stage was 97 kJ mol −1. Ni-based supported alumina catalysts (Ni, Ni-Pt and Ni-Rh) were prepared by impregnation. The catalyst influence on the final gas composition as well as in its HHV determined in mixed CO 2 + H 2 O/He gasification carried out in a double fixed bed reactor configuration with the catalyst located in the second bed upstream. Parallel and secondary reactions as reforming of tar and char together with WGS and Boudouard also take place favoring gas fraction yield with a value close to 0.3 Nm 3 of gas per kg of biomass. The catalytic role of Ni-Pt/Al 2 O 3 catalyst in further reforming of the gas resulting from the gasification improves H 2 content even at low temperature interval (600-700 • C).

Chemical Engineering Science, 1992

An algorithm for simulation and optimization of adiabatic fixed-bed reactors subject to catalyst ... more An algorithm for simulation and optimization of adiabatic fixed-bed reactors subject to catalyst deactivation is developed. It is applied to the low-temperature CO converter, the kinetic model for which is deduced from some industrial data and considering chlorine as the main cause of catalyst poisoning. Sintering is not considered due to the short range of variation of temperature in the catalyst bed. Optimal inlet temperature trajectories are determined to maximize the obtained total amount of reaction over a fixed operation time. Approximate optimal trajectories in discrete steps of temperature are proposed to be followed in industrial practice.

Chemistry Letters, 1992

The cathode of carbon whisker was active for the oxidation of toluene into benzaldehyde and benzy... more The cathode of carbon whisker was active for the oxidation of toluene into benzaldehyde and benzyl alcohol during the H2-O2 fuel cell reaction under short circuit conditions. Synergism of carbon whisker and active carbon was observed. The increase in the concentration of H3PO4 used as an electrolyte improved the selectivity and the oxidation efficiency remarkably.

Latin American Applied Research, 1995

Los catalizadores de antimonato de vanadio sustituidos con titanio fueron probados en la reaccion... more Los catalizadores de antimonato de vanadio sustituidos con titanio fueron probados en la reaccion de oxidacion parcial de tolueno en fase vapor, encontrandose que la actividad catalitica esta vinculada con la relacion V4+/Sb5+ y su desempeno como catalizador de oxidacion parcial con la separacion de los potenciales de reduccion del vanadio y del antimonio. A su vez la formacion de CO y CO2 esta favorecida por la presencia de cadenas V-O-V en el solido. Surge como desafio encontrar un dopante que reemplace el vanadio en la celda para desfavorecer la formacion de CO y CO2, pero que a la vez proporcione un buen comportamiento redox del solido. El Fe3+ se presenta como una alternativa interesante por lo que el objetivo de este trabajo es preparar oxidos de Fe/V/Sb y determinar las caracteristicas estructurales y redox, y analizar su posible aplicacion como catalizador de oxidacion parcial de hidrocarburos.

Chemical Engineering & Technology, 2010

ABSTRACT A thermodynamic analysis of steam reforming of glycerol using the stoichiometric method ... more ABSTRACT A thermodynamic analysis of steam reforming of glycerol using the stoichiometric method has been performed. Since the aim of this work is to study product distribution and coke formation in equilibrium, two different models have been proposed: (a) CO as primary product and (b) CO2 as primary product. Moreover, substantial information regarding the behavior of the different reactions could be acquired. Product distribution at equilibrium has been investigated in a broad range of conditions: temperature (600–1200 K), water-to-glycerol feed molar ratio (0:1–10:1), and pressure (1–9 atm). Glycerol conversion results completely over the whole range of the mentioned conditions. Consequently, product distribution at equilibrium is determined by water gas shift (WGS) and methanation or methane steam reforming reactions. Finally, high temperatures and a high water-to-glycerol feed molar ratio favor hydrogen production and decrease both methane and coke.

International Journal of Hydrogen Energy, 2006

An analysis of the chemical equilibrium of ethanol/water system, using the stoichiometric method,... more An analysis of the chemical equilibrium of ethanol/water system, using the stoichiometric method, has been performed. Intermediate compounds and coke formation are analyzed. Ethanol is completely converted to ethylene and/or acetaldehyde. Taking into account the equilibrium constant values of formation and transformation reactions of ethylene and acetaldehyde, both compounds are intermediates in this system. Due to the relevance of carbon monoxide if hydrogen is used as feed of a PEM-type fuel cell, CO concentration in the equilibrium mixture was studied assuming two different scenarios: (a) CO as primary product and (b) CO 2 as primary product. These two scenarios lead to suggest different routes for reaching the equilibrium. Thus, the results obtained in this work might help to interpret the experimental results far away from the equilibrium with the aim of elucidating the reaction mechanism. The knowledge of this mechanism is essential in order to minimize the CO formation. The thermodynamic feasibility of coke formation shown in a temperature vs. water/ethanol molar ratio has also been analyzed. The results indicate that if moderate temperatures are used, a molar ratio higher than 3 is required to avoid coke formation.

Chemical Engineering …, 2004

In this work, the ethanol steam reforming on Ni/␥Al 2 O 3 catalyst at temperatures between 573 an... more In this work, the ethanol steam reforming on Ni/␥Al 2 O 3 catalyst at temperatures between 573 and 773 K was studied and an overall reaction scheme as a function of temperature was proposed. It can be concluded that higher water/ethanol ratio (6:1) and higher temperature (773 K) promote hydrogen production (91% selectivity). Over Ni-based catalyst there would not be evidences that water gas shift reaction occurs. The presence of oxygen in the feed produces a favorable effect on carbon deposition; nevertheless the carbon monoxide production is not reduced.

Applied Surface Science, 2008

We have theoretically studied the influence of antimony and vanadium cation vacancies in the elec... more We have theoretically studied the influence of antimony and vanadium cation vacancies in the electronic structure and reactivity of vanadium antimonate, using molecular orbital methods. From the analysis of the electronic properties of the VSbO4 crystal structure, we can infer that both antimony and vanadium vacancies increase the oxidation state of closer V cations. This would indicate that, in the

Applied Catalysis A: General, 2000

Catalysts of nominal compositions VSb 1−x Ti x O 4 , with x = 0, 0.1, 0.2 and 0.4, were prepared ... more Catalysts of nominal compositions VSb 1−x Ti x O 4 , with x = 0, 0.1, 0.2 and 0.4, were prepared by solid state reaction of vanadium(V) oxide, antimony(III) oxide and titanium(IV) oxide mixtures. Their structural and catalytic properties were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and catalytic heterogeneous oxidation of toluene to benzaldehyde. The samples with 10% (x = 0.1) and 20% (x = 0.2) of titanium present the highest activity and selectivity to benzaldehyde under the operating conditions used in this work. When the titanium content is 40% (x = 0.4), the activity level drops strongly below the level found for the undoped vanadium antimonate. X-ray patterns show the presence of vanadium(V) oxide as a separate phase in this sample, and this is probably the cause of the low catalytic performance. TPR results show that the replacement of antimony by titanium changes the oxidation-reduction properties of the vanadium antimonate phase. In the samples with titanium content up to 20%, there seems to be a direct relationship between the selectivity and the separation of the reduction temperatures of both reduction peaks of the TPR profile: the larger the separation, the higher is the selectivity to benzaldehyde. All the samples with x = 0, 0.1 and 0.2 show surface antimony excess despite being prepared from stoichiometric mixtures of nominal V/Sb ratios larger than or equal to 1.

Applied Catalysis A: General, 2003

The catalytic selective oxidation on vanadium antimonate oxides partially doped with titanium was... more The catalytic selective oxidation on vanadium antimonate oxides partially doped with titanium was studied. Solids with nominal composition VSbO 4 , V 0.8 SbTi 0.2 O 4 and VSb 0.8 Ti 0.2 O 4 were prepared by solid-state reaction. The solids were characterised by sorptometry, X-ray diffraction (XRD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). Catalytic tests were carried out in a fixed-bed reactor using toluene and air as reactants. It was found that partial substitution of V or Sb by Ti produces changes in the unit-cell composition and the redox properties of the solids. A possible role for V and Sb in the reaction mechanism of partial oxidation was established. Vanadium sites (V 4+) are involved in the incorporation of gaseous oxygen as lattice oxygen and hold the Sb sites in an oxidation state (Sb 5+) high enough to insert the lattice oxygen in the hydrocarbon molecule. A relationship between activity and V 4+ /Sb 5+ ratio of the unit-cell was found. The selectivity to benzaldehyde is correlated with the redox properties of the solids while the selectivity to total oxidation products could be interpreted by the site isolation theory.

Applied Catalysis A: General, 2006

The accessibility in aluminas considered to be representative of matrices used in FCC resid catal... more The accessibility in aluminas considered to be representative of matrices used in FCC resid catalysts, with mean pore sizes between 64 and 201Å, was characterized through a kinetic approach by means of the conversion of 1,3,5-tri-isopropylbenzene (TIPB) at 500°C in a CREC Riser Simulator fluidized bed laboratory reactor. The product distribution was essentially the same as that observed on an

Applied Catalysis A: General, 2014

Proceedings of the 7th …, 2004

... sensitive to its value. Our simulation results showed a satisfactory agreement with those of ... more ... sensitive to its value. Our simulation results showed a satisfactory agreement with those of the test case and best fitting was obtained with the correlation of U reported by Rajesh et al. [23] and was thus adopted. Feed per tube ...