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“Ni-, Co- and Cu-TiO2 catalysts for the steam reforming of ethanol: how the preparation method affects catalytic performance”
Get PDFConcept
A set of Ni-, Co-, Cu-based catalysts supported over TiO2 for the steam reforming of ethanol were prepared by different procedures. For most of them the support was prepared by precipitation and calcined at 500°C or 800°C. Other samples were prepared by flame pyrolysis (FP), aiming at high metal dispersion coupled with synthesis at high temperature, to impart a strong metal-support interaction, besides high thermal resistance. The samples were characterised by AAS, XRD, N2 adsorption-desorption, TPR, SEM, TEM and FT-IR. Activity testing for the steam reforming of ethanol was performed after activation at 500°C or 800°C in H2 flow on a continuous micropilot plant, by feeding a 3:1 (mol/mol) mixture of water/ethanol at 500°C for 8 h-on-stream.
Motivations and Objectives
Ni-based catalysts raised much interest for the present application [1-3]. Very high activity has been observed at high reaction temperature (>600°C), but it would be interesting to operate under milder conditions, in order to lower the energy input to the process and to improve H2 productivity by favoring the water gas shift reaction. The major inconvenient for Ni-based samples is usually ascribed to coking, often due to the formation of carbon filaments over the active phase. This phenomenon is correlated to catalyst deactivation and appearance of by-products. Indeed, if at high reaction temperature with excess steam carbon may be gasified, at operation at 500°C the C balance, often much lower than 100% evidences coke accumulation.
Results and Discussion
H2 productivity at 500°C seemed firmly dependent on the calcination and on activation temperature of the catalyst when Ni was supported over TiO2 prepared by impregnation. When the sample was calcined and activated at 500°C, no H2 production was observed due to poor ethanol conversion, with selectivity mostly to acetaldehyde and poor carbon balance. By contrast, calcination of the sample at 800°C induced very high H2 productivity, higher C balance and negligible byproducts formation except some CH4 These results were attributed to the formation of a mixed oxide between Ni and the support during synthesis at high temperature (both for Impregnation and FP), which keeps the metal well dispersed in spite of the high activation temperature. This leads to very small Ni particles after activation, which demonstrated to be more active and, most of all, more stable towards coking. C balance was in general much higher for the Co- and Cu-containing samples than for the Ni-based ones. One may conclude that for most of these samples there is no additional coking on the catalyst due to the active phase. However, they proved in general less active than Ni-based ones when tested at 500°C.
References
[1] I. Rossetti, A. Gallo, V. Dal Santo, C.L. Bianchi, V. Nichele, M. Signoretto, E. Finocchio, G. Ramis, G. Garbarino, A. Di Michele, ChemCatChem, 5 (2013) 294.
[2] I. Rossetti, C. Biffi, C. Bianchi, V. Nichele, M. Signoretto, F. Menegazzo, E. Finocchio, G. Ramis, A. Di Michele, Appl. Catal. B, 117-118 (2012) 384.
[3] E. Finocchio, I. Rossetti, G. Ramis, Int. J. Hydrogen Energy, 38 (2013) 3213
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
“La donna e l’espressione indeuropea della proprietà”
No full textRassegna etimologica delle radici indoeuropee designanti la proprietà, con riferimento agli spunti ideologici relativi all'universo femminil
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Ecoactive porcelain gres tiles: a new challenge for environmental sustainability
No full textAt the beginning of the industrial productions, porcelain gres tiles were considered as just a technical material characterized by strong resistance to both abrasion and acid attack, almost lack of porosity, but aesthetically not very beautiful. Today thanks to new industrial production methods, both properties and beauty of these materials completely fit the market requests. In particular, the possibility to prepare slabs of large sizes [1] is the new frontier of building materials.
Slabs are generally manufactured under high pressure by dry-pressing fine processed ceramic raw materials with large proportions of quartz, feldspar, and other fluxes. Afterwards, the body of these materials is fired at very high temperatures (1200–1300°C) in kilns. The final material is thus characterized by lack of porosity, complete water-proofing, durability, hardness, wear resistance properties, and a complete frost resistance. Beside these noteworthy features, new surface properties have been introduced in the last generation of these materials.
The present work deals with the characterization and photocatalytic activity of commercially available tiles, named ActiveTM, prepared with a surface application of a commercial photoactive micro-sized TiO2 [2] stabilized by a sort of inorganic glue (Si-based) heated at 680°C [3].
Industrially prepared tiles were fully characterized (HR-SEM in Fig.1) and the photocatalytic properties of these materials have been verified through depollution and discoloration tests. In details, the pollution degradation of both NOx [4] and VOCs (acetone and acetaldehyde) in the gas phase and two different organic dyes directly put at the tiles surfaces (Rhodamine B and Metanil yellow) have been investigated. Dyes degradation was monitored by Vis-spectrometer equipped with an integrated sphere (OceanOptics, USB4000-VIS-NIR-ES). The color analysis was performed using the CIEXYZ (Fig.2) and CIELAB models.
Moreover ISO 27448-1 self-cleaning test performed by means of contact angle measurement were also shown [5]
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
Ultrasonidos y microondas en la preparacion de catalizadores soportados a base de hierro para la sintesis de Fischer-Tropsch
No full textCatalizadores con un contenido de hierro del 30% en peso, promovidos con K (2,0% en peso) y Cu (3,75% en peso), fueron sintetizados utilizando tres métodos: 1) el método de impregnación tradicional (TR); 2) El método de impregnación tradicional asistido por ultrasonido (US) y 3) El método de impregnación tradicional asistido por microondas (MW). Todas las muestras fueron caracterizadas por BET, XRPD, TG-DTA, FT-IR, TPR, SEM y TEM y evaluadas en una planta de laboratorio para la síntesis de Fischer-Tropsch bajo condiciones de operación de 220oC y 20 bar. Los resultados de la caracterización de los catalizadores indicaron que la morfología de las muestras depende en gran medida del método de preparación. Los mejores resultados en términos de rendimiento (41%) y selectividad hacia los hidrocarburos pesados, fueron obtenidos utilizando las microondas; mientras que en términos de conversión de CO los mejores resultados fueron obtenidos utilizando ultrasonidos (58%). Las muestras preparadas con métodos no tradicionales arrojaron mejores resultados, probablemente debido a una distribución más amplia y uniforme del Fe en el medio durante la fase de síntesis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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