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Flame Spray Pyrolysis: catalysts for the Steam Reforming of bio-ethanol
No full textFlame Spray Pyrolysis (FSP) is a one step high temperature synthesis able to impart strong metal-support interaction [1], besides high thermal resistance. A set of Ni catalysts supported over ZrO2 doped with different basic oxide (CaO, MgO) were prepared by this innovative technique. Steam Reforming catalytic test were carried out for the production of hydrogen using bio-ethanol. The catalytic activity was compared with catalysts of the same composition, but prepared with a traditional precipitation/impregnation method (multistep synthesis). Very high activity has been observed at high reaction temperature (>600°C), but further kinetic studies were done under milder conditions (500-300°C), in order to lower the energy input to the process and to improve H2 productivity favoring the water gas shift reaction [2]. Two different bioethanol samples, 50 and 90 vol%, produced and supplied by Mossi&Ghisolfi, have been used for 8 h-on-stream at each temperature. Attention was paid to the catalyst resistance towards deactivation by coking, besides its activity and selectivity. The acidity of the support was tuned by doping ZrO2 with basic oxides, helping to prevent ethanol dehydration and coking by ethylene polymerization. Fresh and spent samples were characterized by XRD, TPR, TPO, TEM, FE-SEM and Raman analysis.
Figure: scheme and image of Flame Spray Pyrolysis
[1] G. Ramis, I. Rossetti, E. Finocchio, M. Compagnoni, M. Signoretto, A. Di Michele, Progress in Clean Energy, I. Dincer, Ed. Springer, in press.
[2] I. Rossetti, J. Lasso, E. Finocchio, G. Ramis, V. Nichele, M. Signoretto, A. Di Michele, Appl. Catal. B: Environmental, 150-151 (2014) 257-267
HYDROGEN PRODUCTION FROM RENEWABLE PRIMARY SOURCES
Full text linkABSTRACT
One of the most attracting renewable sources for energy production is bioethanol, which can be obtained from biomass. Special attention is here focused on the steam reforming reaction of ethanol (SRE) in which the principal product, hydrogen, is an interesting energy vector to produce power, electricity and heat. However, the process has not yet come to maturity and it should be optimized in order to made it industrially available.
To this aim, we focused our work on catalysts synthesis for SRE, trying to couple high activity and durability. Different catalyst formulations based on Ni as active phase, supported over zeolite-BEA, zirconia, titania and lanthana were synthesized and characterized by N2 adsorption/desorption, temperature programmed reduction (TPR), X-rays diffraction, transmission electron microscopy and infra-red Fourier transform spectroscopy. The performance of the catalysts was evaluated for SRE by using absolute ethanol and bioethanol 50 and 90 vol%, obtained from second generation biomass and kindly supplied by Mossi&Ghisolfi. An important aim of the work was the intensification of the process from the energetic point of view, decreasing the energy input to the reformer (endothermal reaction) to better integrate this high temperature stage with the hydrogen purification section and the possible use of Proton Exchange Membrane Fuel Cells (PEM-FC)
M. J. Lasso de la Vega, Sintaxis griega I (Enciclopedia clásica, n° 6), 1968
No full textBurguière Paul. M. J. Lasso de la Vega, Sintaxis griega I (Enciclopedia clásica, n° 6), 1968. In: Revue des Études Anciennes. Tome 71, 1969, n°3-4. pp. 510-511
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Flame pyrolysis prepared catalysts for the steam reforming of ethanol
No full textIntroduction
Among the methods to produce H2, Steam Reforming (SR) is one of the most common and feasible to use [1-7]. One challenge for SR at high temperature is catalyst deactivation by sintering, so that high thermal resistance is a pressing need. By contrast, it is envisaged to operate at lower temperature, to lower the heat input to the reactor. Nevertheless, catalyst deactivation may be impressive by coking, due to the formation of carbon filaments and occurs mainly over big nickel particles [8]. Additional coking may occur over acidic sites of the support. Therefore, an appropriate catalyst formulation should be found, which allows to reach the highest catalytic performance at low operating temperature (i.e. ca. 500°C) together with proper resistance.
The aim of this work is the synthesis of catalysts for the SR of ethanol. A set of catalysts was synthesized by Flame Spray Pyrolysis (FP) and another set was prepared by impregnation of the active phase on the FP-prepared support. This high temperature synthesis was here adopted to impart suitable thermal resistance to the samples and to provide a high metal support interaction, which showed a pivotal importance to improve resistance towards coking.
2 Experimental/methodology
A first set of samples was directly prepared by FP, inserting in one-step the Ni-based active phase into the selected support, TiO2 and La2O3 with different metal loading of 5, 10 and 15 wt%. For comparison, the same formulations have been prepared by impregnation of Ni on the FP prepared supports. The catalysts were reduced for 1h at 800°C in a 20 vol% H2 / N2 gas mixture.
The samples characterization was carried out by conventional methods of XRD, BET, SEM, EDX, TEM and TPR.
Finally the activity test of the samples were performed by means of a micro pilot plant constituted by an Incoloy 800 continuous down flow reactor heated by an electric oven. Catalyst activation was accomplished by feeding 50 cm3/min of a 20 vol% H2/N2 gas mixture, while heating by 10 °C/min up to 800 °C, then kept for 1 hour. For activity testing 0.017 cm3/min of a 3:1 (mol/mol) H2O:CH3CH2OH liquid mixture were feed to the reactor by means of a HPLC pump (Waters, mod. 501). The activity tests were carried out at atmospheric pressure, GHSV=2.500 h-1 (referred to the ethanol + water gaseous mixture) at 500, 625 and 750 °C. The analysis of the out-flowing gas was carried out by a gas chromatograph (Agilent, mod. 7980) ca. 8h.
3 Results and discussion
Nickel-based catalysts at three different loadings (5, 10 and 15wt%), supported over lanthana and titania were synthesized and tested for ethanol steam reforming at 500 and 750 °C. All of them were more active and stable at the latter temperature while at the former the impregnated catalysts with low Ni loading exhibited low H2 productivity, mainly due to unreformed CH4. By contrast, the FP ones demonstrated superior catalytic activity and satisfactory stability, especially with lanthana support, which effectively reduced deactivation by coking at the lowest operating temperature.
The catalytic activity has been correlated to metal dispersion and to the metal-support interaction strength. Both parameters affected also catalyst resistance to coking at 500°C. Overall, lanthana demonstrated and interesting support due to its basic character, which prevented significant coke formation related to the acidic properties of the support. Furthermore, high metal dispersion and proper stabilization on the support allowed to limit the formation of carbon nanofilaments as deactivation mode.
References
[1] Ni, M., Leung, D.Y.C., Leung, M.K.H., Int. J. Hydrogen Energy, 2007, 32, 3238.
[2] Muroyama, H., Nakase, R., Matsui, T., Eguchi, Eguchi, K., Int. J. Hydrogen Energy 2010, 35, 1575.
[3] Llorca, J., Homs, N., Sales, J., De la Piscina, P.R., J. Catal. 2002, 209, 306.
[4] Fatsikostas, A.N., Verykios, X.E., J. Catal. 2004, 225, 439.
[5] Cheekatamarla, P.K., Finnerty, C.M., J. Power Sources 2006, 160, 490.
[6] Frusteri, F., Freni, S., Spadaro, L., Chiodo, V., Bonura, Donato, S., Catal. Commun. 2004, 5, 611.
[7] Wang, C.B., Lee, C.C., Bi, J.L., Siang, Liu, J.Y., Yeh, C.T., Catal. Today 2009, 146, 76.
[8] Yoshida, H. Yamaoka, R., Arci, M., J. Mol. Science, 2015, 16, 350-362
Steam reforming of crude bio-ethanol for hydrogen production over FP catalysts
No full textThe production of “bio-hydrogen” is an interesting alternative with respect the traditional production from hydrocarbons. In particular, the production from the bioethanol steam reforming process represent a promising route to improve its sustainability for energy-related purposes. The so-called 2nd generation bio-ethanol, derived from lignocellulosic biomass, such as sorghum, mischantus or poplars possibly growing in marginal lands, appears interesting. Unfortunately, the environmental and energetic impact of next generation biofuels depends on concentration, impurities and operative conditions.
In this work two different bioethanol feeds, 50 and 90 vol%, supplied by Mossi&Ghisolfi Group (Proesa process), have been tested for low and high temperature steam reforming. Home-made prepared catalysts were employed in the catalytic tests. Ni was chosen as active phase and several supports were investigate (ZrO2, MxO-ZrO2, La2O3). The Flame Spray Pyrolysis technique was employed for their synthesis.
The steam reforming reaction was carried out at several temperature (300°C - 750°C) on a continuous micropilot plant. The effect of impurities was evaluated in term of catalyst performance because deactivation due to long chain alcohols (coke precursors) and sulfur represent key issues. At low temperature the use of bioethanol 90% showed almost the equal H2 productivity (1-1.2 mol min-1 kgcat-1) and ethanol conversion (100%) with respect pure ethanol[1]. By contrast, bioethanol with lower concentration (50%) induced different performance with an increase of coke deposition rate. The acidity of the support was tuned by using several oxidic supports, in order to prevent ethanol dehydration and coking through ethylene polymerization. Fresh and spent samples were characterized by XRD, TPR, TPO, TEM, FE-SEM and Raman analysis.
Figure: scheme and image of Flame Spray Pyrolysis
References
[1] Rossetti, I.; Lasso, J.; Compagnoni, M.; De Guido, G.; Pellegrini, L.; Tian, W.; Wang, Y.; Zhang, H. Chem. Eng. Trans. 2015, 43, 229-234
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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