2023, Articolo in rivista, ENG
Pardanaud C.; Martin C.; Roubin P.; Roussin G.; Dellasega D.; Passoni M.; Lungu C.; Porosnicu C.; Dinca P.; Bogdanovic Radovic I.; Siketic Z.; Pegourie B.; Bernard E.; Diez M.; Hakola A.
Plasma-wall interaction in magnetic fusion devices is responsible for wall changes and plasma pollution with major safety issues. It is investigated both in situ and ex situ, especially by realizing large scale dedicated post-mortem campaigns. Selected parts of the walls are extracted and characterized by several techniques. It is important to extract hydrogen isotopes, oxygen or other element content. This is classically done by ion beam analysis and thermal desorption spectroscopy. Raman microscopy is an alternative and complementary technique. The aim of this work is to demonstrate that Raman microscopy is a very sensitive tool. Moreover, if coupled to other techniques and tested on wellcontrolled reference samples, Raman microscopy can be used efficiently for characterization of wall samples. Present work reviews long experience gained on carbon-based materials demonstrating how Raman microscopy can be related to structural disorder and hydrogen retention, as it is a direct probe of chemical bonds and atomic structure. In particular, we highlight the fact that Raman microscopy can be used to estimate the hydrogen content and bonds to other elements as well as how it evolves under heating. We also present state-of-the-art Raman analyses of beryllium- and tungsten-based materials, and finally, we draw some perspectives regarding boron-based deposits.
2022, Abstract in atti di convegno, ENG
Anastasia Anceschi, Alessia Patrucco e Raffaella Mossotti
In the past few decades, global fiber consumption has been progressively increasing, leading to a higher amount of post-industrial and post-consumer fiber waste. Thus, an enormous amount of synthetic waste is generated, most of which is disposed of in landfills. Post-industrial waste is generated in the manufacturing process and, depending on the stage of manufacturing activities, it can be a single polymer or a complex multi-material system. Since a single polymer is easier to be recycled, a blend recycling process should be designed and projected. For companies, industrial blended scraps management is a very high challenge. The most used textile fiber is polyester (PET), with an estimated production of 26 million tons per year. The PET is often blended with other polymers, mainly with polyurethane (PU), to improve the elastic characteristics of the final products. The PET-PU separation is not an easily manageable process, especially for industrial scraps. For this reason, in this work, the obtainment of a high-value carbon material from PET-PU industrial waste was investigated. The PET-PU scraps were subjected to a pyrolysis treatment at 800°C leading to an 18% of carbon yield. The carbon was thoroughly characterized with several techniques (FTIR spectroscopy, surface area analysis, SEM) and a comparison with PET and PU carbons was also performed. Moreover, the adsorbing properties were evaluated in simulated-wastewater treatment by measuring their adsorption performances in removing two dyes: Orange II and Methylene Blue. These tests showed that the PET-PU-derived carbon is able to remove more than 60% of the two selected dyes. Thus, these preliminary results underline that the PET-PU blend can be easily recycled in an open-loop system in which the synthetic scraps are efficiently transformed into a new high- added value product.
2022, Abstract in rivista, ENG
Michele Freppaz, Emanuele Pintaldi, Nicola Colombo, Michele D'Amico, Maria Martin, Giampiero Lombardi, Michele Lonati, Marco Giardino, Luigi Perotti, Raffaella Balestrini, and Franco Salerno
The vast majority of studies in the ecological literature last less than three years, and only a small number of research works capture unusual events. To detect changes in high-mountain ecosystems, long-term research is mandatory, as these areas are important bellwethers of climate change. The LTER macrosite "Northwestern Italian Alps" includes the research site "Istituto Scientifico Angelo Mosso", located in the alpine tundra close to the Monte Rosa Massif (NW Italy). The core of the LTER site is the Research Institute Angelo Mosso (2901 m a.s.l.), founded in 1907 by Angelo Mosso, professor of human physiology at the University of Turin. Over the years, the Institute has given support to scientists and scholars from all over the world, who could stay there even for long periods, while conducting their research activities in different research fields. At present times, it includes permanent plots, where different variables are constantly monitored, such as snow cover duration, vegetation composition and phenology, soil temperature, soil water content, and C and N forms. Moreover, the chemical characteristics of rainwater and snowfall are measured, as well as the water chemistry in ponds, focusing for example on how the soil properties control several hydrochemical properties such as the C and N content in water, following the critical zone paradigm. Research is also being carried out in order to investigate the hydrochemical characteristics of ponds and streams fed by different cryospheric features such as rock glaciers, glaciers, and permafrost, with a focus on the main associated weathering processes. Other permanent plots have been established in order to carry out investigations on paleoclimate through the information that could be derived from soils, integrating the information obtained in the same study area by ice core drilling. There is evidence that the paleoclimate influenced the cycling of soil carbon through shifting biomes and by altering soil physicochemical properties. The current distribution of soil carbon stocks thus contains footprints of the paleoclimate at timescales ranging from centuries to millennia. New research lines, aimed at investigating the most recent environmental challenges, have been added to the previous ones. Investigations on sources and routes of atmospheric nitrogen species, on the scarcely known biodiversity hosted in the glacial meltwater, and on the microplastic content in snow are ongoing, thus further extending the range of environmental processes investigated at this high-elevation site.
2022, Articolo in rivista, ENG
Alidoost M.; Mangini A.; Caldera F.; Anceschi A.; Amici J.; Versaci D.; Fagiolari L.; Trotta F.; Francia C.; Bella F.; Bodoardo S.
Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si-S cell.
2022, Articolo in rivista, ENG
Francesco Miccio
The paper reports on research focused on the use of largely available carbonaceous materials, such as graphite, carbon black and chars, as thermoelectric materials for micro-generation at high temperature. The key feature is the possibility to ignite the thermoelectric device to self-sustain electric generation. The results of the tests performed with such materials, under both cold and hot conditions, showed that a significant change of the electromotive force, with absolute increase up to three orders of magnitude, occurred under hot conditions with flame irradiation, achieving measured values of electromotive force up to 55 mV, in the best case. Monoliths based on biomass chars and covered with a layer of gunpowder gave rise to similar variation of the Seebeck coefficient, as the case of the flame exposed samples. This result confirms the basic idea of the investigation and the possibility of generating an electrical peak in a self-sufficient combustion thermoelectric device with power up to 1.0 W. A theoretical assessment has been proposed to provide an interpretation of the observed phenomenology, which is related to the non-linear dependence of the material properties on temperature, in particular the Seebeck coefficient and thermal conductivity.
DOI: 10.3390/en15218105
2022, Articolo in rivista, ENG
Alfonso Policicchio, Giuseppe Conte, Raffaele Giuseppe Agostino, Giovanni Desiderio, Georgia Papanikolaou, Paola Lanzafame, Daniela Cozza, Girolamo Giordano, Massimo Migliori
Zeolite-Template-Carbon is a new class of porous ordered carbon-based materials synthetized using 3-D zeolites as a template, then for these features have been investigated CO2 capture. This work presents the synthesis and characterization of ZTC on beta-type zeolite with a tuning-surface properties procedure resulting from different post-synthesis strategies aimed to tune the surface Ocontaining functional groups. It shows how a suitable micropore size distribution, a high specific surface area and a pore wall functionalization could maximize the reversible CO2 adsorption. Structural, chemical and morphological characterization has been obtained by X-ray diffraction, Thermo-gravimetric analysis, Raman/FT-IR spectroscopy, Branauer-Emmett-Teller analysis and scanning electron microscopy, while adsorption properties were investigated with Sievert's-type apparatus. XRD patters showed good replica of 3-D zeolite frameworks without presence of graphene and FT-IR spectroscopy indicated the presence of different carbon-oxygen functional groups. Adsorption measurements, at room temperature and pressure range 0-15 bar, showed a reversible CO2 uptake of 76.5 wt%. Furthermore, using deconvolution approach, a deep Raman spectroscopy analysis allowed us to assess the change in the structural order and in oxygen atomic coordination induced by post-synthesis treatment in correlation with the adsorption capacity. Post-synthesis treatments induced structure modification elucidated by evidence of an increased order of the porous structure and variation of the amorphous carbon fraction.
2021, Articolo in rivista, ENG
Yates R.J.; Harrison R.J.; Loi A.; Steel E.J.; Edwards T.J.; Nutt B.J.; Porqueddu C.; Gresta F.; Howieson J.G.
Over the last three decades, farming systems in Europe and Australia have seen a decline in legume plantings, leading to reduced soil carbon and fertility, and an increase in plant disease, reliance on industrial nitrogen fertilizer and herbicides. In Australia, one reason for this decline has been the movement towards sowing crops and forages into dry soil, before the opening rains, as a consequence of climate variability. This practice predicates against the survival of rhizobial inoculants, and hence generates uncertainty about legume performance. The research reported here was initiated to improve the robustness of a specific forage legume/rhizobia symbiosis to increase nitrogen fixation in low pH, infertile soils. Rhizobial strains (Rhizobium leguminosarum biovar viciae) from Pisum sativum L. were sourced from acid soils in southern Italy and southern Australia. Strains were evaluated for N fixation on the forage legumes P. sativum, Vicia sativa and Vicia villosa, then for survival and persistence in acid soils (pHC? 4.6). Fourteen of the strains produced a higher percentage of nitrogen derived from the atmosphere (%Ndfa) compared to commercial comparator strain SU303 (<78%). Twenty-two strains survived sufficiently into the second season to form more nodules than SU303, which only achieved 3% of plants nodulated. Elite strains WSM4643 and WSM4645 produced six times more nodulated plants than SU303 and had significantly higher saprophytic competence in acid soil. These strains have the ability to optimize symbiotic associations with field peas and vetch in soils with low fertility, carbon and pH that are restrictive to the current commercial strain SU303.
DOI: 10.1111/gfs.12524
2021, Articolo in rivista, ENG
Werner Oberhauser, Claudio Evangelisti, Laura Capozzoli, Gabriele Manca, Maria Pia Casaletto, Francesco Vizza
Palladium nanoparticles stabilized by a sterically demanding secondary diamine ligand have been synthesized by hydrogen reduction of a palladium acetate complex bearing the corresponding diimine ligand. The obtained nanoparticles were used to catalyze the aerobic oxidation of 1,2-propandiol in n -hexane, and after their heterogenization onto a high surface area carbon, in water. In n -hexane 2,4-dimethyl-1,3-dioxolan-2-yl ( i.e ketal formed between hydroxyacetone and 1,2-propandiol) has been obtained as major product with a selectivity of > 80%, whereas in water acetic acid with a selectivity of > 85% has been achieved. The selectivity switch observed was a clear induced by water. The robustness of diamine-stabilized palladium nanoparticles under real aerobic oxidation conditions has been proved by recycling experiments, TEM measurements of the recovered catalysts and by comparison of its performance with that of palladium nanoparticles generated by the metal vapor synthesis technique and supported onto the same carbon in the absence of the stabilizing diamine ligand.
2021, Articolo in rivista, ENG
Jakubowska, K.; Mancelli, D.; Benocci, R.; Trela, J.; Errea, I.; Martynenko, A. S.; Neumayer, P.; Rosmej, O.; Borm, B.; Molineri, A.; Verona, C.; Cannata, D.; Aliverdiev, A.; Roman, H. E.; Batani, D.
In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into solid multi-layered diamond samples. The target design allows shock velocity in diamond and in two metal layers to be measured as well as the free surface velocity after shock breakout. As diagnostics, we used two velocity interferometry systems for any reflector (VISARs). Our measurements show that for the pressures obtained in diamond (between 3 and 9 Mbar), the propagation of the shock induces a reflecting state of the material. Finally, the experimental results are compared with hydrodynamical simulations in which we used different equations of state, showing compatibility with dedicated SESAME tables for diamond.
DOI: 10.1017/hpl.2020.38
2020, Tesi, ENG
Tesista: Corrado Biondo; Tutors: Dario PAPALE, Alessio COLLALTI
The soil stores more carbon than the whole atmosphere and vegetation together, about 1950 Pg, as well as an amount of nitrogen 20 times higher than the quantity stored in the standing vegetation of either forests or cultivations. Furthermore, soil exchanges several greenhouse gases which entrap the longwavelength radiation, causing an increase of the global mean air temperature. Hence, soil plays a key role in the mitigation of climate change by terrestrial ecosystems, especially forests, which cover about 4 million hectares on the planet, equal to 30.6% of the lands. The carbon and nitrogen compounds stored into the soil and exchanged with the atmosphere are regulated by the soil biogeochemical processes. Some of them are expected to be more affected by climate change - in particular the processes under the temperature control - such as the soil organic matter decomposition and heterotrophic respiration. However, studying the temperature effect on these key processes is complex, both under present-day and even more on the long-term (up to 100 years), because of many other physical, chemical and biological factors involved. To manage this complexity, models are fundamental, even if they are based on different approaches, reflecting different assumptions. For example, most models simulate an exponential decomposition rate-soil temperature relationship that never reaches an optimum, even if the laboratory and field experiments show an acclimation of the process, that is, a decrease of the decay rate after an optimum temperature, always explained as the enzyme denaturation. A recently developed theory - the Macromolecular Rate Theory (MMRT) - explains through a thermodynamic point of view the reason why the acclimation occurs at definitely lower temperatures than those of enzyme denaturation, which can be registered under the expected climate change, but also under current climate. In the present work, two different approaches to simulate the temperature effect on the heterotrophic respiration (Rhet) have been compared: the classical empirical Exponential Function (EF) and the MMRT. Both approaches have been implemented in the conventional scheme introduced by the CENTURY model. The work aimed to understand if, and to what extent, simulating the acclimation of the process at high, or increasing, temperatures implies some relevant differences in the Rhet estimates, especially on the long-term projections. The model has been ran on two contrasting forest ecosystems and with different climate conditions, a temperate European beech forest located in Germany (Hainich) and a tropical forest located in Central Africa (Ankasa, Ghana), at different modeling time scales (from daily to monthly), both under current and climate change scenarios (2006-2099). Moreover, sensitivity and uncertainty analyses have been 6 carried out to detect the parameters to which the model is more sensitive and to quantify the uncertainty in the Rhet estimates. Thus, the work aimed also to understand if the implementation of the MMRT can reduce the uncertainty, compared to the EF, in the model estimates. The results show that the incorporation of the acclimation in a conventional scheme of the soil biogeochemical cycles - despite the application of a more complex mechanistic approach than the classical empirical EF - conversely to the initial hypothesis, does not imply relevant differences in the Rhet simulation by the two approaches. Indeed, the MMRT does not improve the simulation of the monthly Rhet fluxes under current climate scenario, with a difference of the correlation coefficient (rPea) between EF and MMRT equal to just 0.004 at Hainich and 0.0013 at Ankasa. Under climate change scenario, the relevant differences are detected only for the warmest Representative Concentration Pathway (RCP8.5) and only if the result is scaled on the entire surface of the analyzed forests, with a difference in the Rhet simulated by the two approaches on the whole period 2006-2099 equal to 95?103 tons C at Hainich and 307?103 tons C at Ankasa. Furthermore, the MMRT is more uncertain than EF both under present-day and climate change scenarios. The results achieved in the present work put in doubt the possibility to simulate the Rhet acclimation at increasing soil temperature by a mechanistic approach - the MMRT - using the ,,conventional" scheme of soil C and N cycles. This point is crucial to have reliable model predictions of the CO2 fluxes from the soil under changing climate a
2020, Articolo in rivista, ENG
Armano, Angelo; Buscarino, Gianpiero; Messina, Fabrizio; Sciortino, Alice; Cannas, Marco; Gelardi, Franco Mario; Giannazzo, Filippo; Schiliro, Emanuela; Agnello, Simonpietro
Graphene (Gr)-a single layer of two-dimensional sp(2) carbon atoms-and Carbon Dots (CDs)-a novel class of carbon nanoparticles-are two outstanding nanomaterials, renowned for their peculiar properties: Gr for its excellent charge-transport, and CDs for their impressive emission properties. Such features, coupled with a strong sensitivity to the environment, originate the interest in bringing together these two nanomaterials in order to combine their complementary properties. In this work, the investigation of a solid-phase composite of CDs deposited on Gr is reported. The CD emission efficiency is reduced by the contact of Gr. At the same time, the Raman analysis of Gr demonstrates the increase of Fermi energy when it is in contact with CDs under certain conditions. The interaction between CDs and Gr is modeled in terms of an electron-transfer from photoexcited CDs to Gr, wherein an electron is first transferred from the carbon core to the surface states of CDs, and from there to Gr. There, the accumulated electrons determine a dynamical n-doping effect modulated by photoexcitation. The CD-graphene interaction unveiled herein is a step forward in the understanding of the mutual influence between carbon-based nanomaterials, with potential prospects in light conversion applications.
DOI: 10.3390/nano10030528
2019, Articolo in rivista, ENG
Tonezzer, Matteo; Izidoro, Sandro C.; Moraes, Joao P. A.; Le Thi Thanh Dang
The analysis of ambient (home, office, outdoor) atmosphere in order to check the presence of dangerous gases is getting more and more important. Therefore, tiny sensors capable to distinguish the presence of specific pollutants is crucial. Herein, a resistive sensor based on a carbon modified tin oxide nanowires, able to classify different gases and estimate their concentration, is presented. The C-SnO2 nanostructures are grown by chemical vapor deposition and then used as a conductometric sensor under a temperature gradient. The device works at lower temperatures than pure SnO2, with a better response. Five outputs are collected and combined to form multidimensional data that are specific of each gas. Machine learning algorithms are applied to these multidimensional data in order to teach the system how to recognize different gases. The six tested gases (acetone, ammonia, CO, ethanol, hydrogen, and toluene) are perfectly classified by three models, demonstrating the goodness of the raw sensor response. The gas concentration can also be estimated, with an average error of 36% on the low concentration range 1-50 ppm, making the sensor suitable for detecting the exceedance of the danger thresholds.
2019, Rapporto di progetto (Project report), ENG
Elena Gregoris, Elisa Morabito, Elena Barbaro, Matteo Feltracco, Giuseppa Toscano, Andrea Gambaro, Eva Merico, Fabio M. Grasso, Daniela Cesari, Marianna Conte, Daniele Contini
LIST OF CONTENTS. 1.Sampling; 2. Particulate matter concentration; 2.1.Material and methods; 2.2.Results and discussion; 3.Analysis of ions; 3.1.Material and methods; 3.2.Results and discussion; Distribution of ions in particulate matter; Size distribution of ions; 4.Analysis of metals; 4.1.Material and methods; 4.2.Results and discussion; Distribution of metals in particulate matter; Size distribution of metals; 5.Analysis of carbon; 5.1.Material and methods; 5.2.Results and discussion; Distribution of carbon in particulate matter; Size distribution of carbon; 6.Analysis of polycyclic aromatic hydrocarbons; 6.1.Material and methods 6.2.Results and discussion; Distribution of PAHs in particulate matter; Size distribution of PAHs; 7.Measurement campaign; 7.1.Material and methods; 7.2.Results and discussion; Meteorology during the campaign; Particle number concentrations and size distributions.
2019, Articolo in rivista, ENG
Jouve, Andrea; Cattaneo, Stefano; Capelli, Sofia; Stucchi, Marta; Evangelisti, Claudio; Villa, Alberto; Prati, Laura
Carbon nanofibers (CNFs) have been functionalized by introducing O, N, and P containing groups in order to investigate the effect of support functionalization in Ru catalysed hydroxymethyl furfural (HMF) and levulinic acid (LA) hydrogenation. In the case of HMF, despite the fact that no effect on selectivity was observed (all the catalysts produced selectively gamma-valerolactone (GVL)), the functionalization strongly affected the activity of the reaction. O-containing and N-containing supports presented a higher activity compared to the bare support. On the contrary, in HMF hydrogenation, functionalization of the support did not have a beneficial effect on the activity of a Ru-catalysed reaction with respect to bare support and only CNFs-O behaved similarly to bare CNFs. In fact, when CNFs-N or CNFs-P were used as the supports, a lower activity was observed, as well as a change in selectivity in which the production of ethers (from the reaction with the solvent) greatly increased.
2018, Articolo in rivista, ENG
Cattaneo, Stefano; Naslhajian, Hadi; Somodi, Ferenc; Evangelisti, Claudio; Villa, Alberto; Prati, Laura
We report the use of Ru catalysts supported in the activated carbon (AC) and carbon nanofibers (CNFs) for the selective production of liquid fuel dimethylfuran (DMF) and fuel additives alkoxymethyl furfurals (AMF). Parameters such as the reaction temperature and hydrogen pressure were firstly investigated in order to optimise the synthesis of the desired products. Simply by using a different support, the selectivity of the reaction drastically changed. DMF was produced with AC as support, while a high amount of AMF was produced when CNFs were employed. Moreover, the reusability of the catalysts was tested and deactivation phenomena were identified and properly addressed. Further studies need to be performed in order to optimise the stability of the catalysts.
2018, Abstract in atti di convegno, ENG
B. Apicella 1, P. Prè 2 , J.N. Rouzaud 3 , J. Abrahamson 4, R.L. Vander Wal 4 , A. Ciajolo 1, A. Tregrossi 1, C. Russo 1
The present work reports about the laser-induced modifications undergone by a typical turbostratic carbon material as soot, formed at the first inception stage (nascent) and final maturation degree (mature) in different premixed flames. The structural modifications induced by laser heating were studied by advanced HRTEM imaging, provided the detailed characterization of the carbon network of pristine soot carried out by HRTEM, Raman, UV-Vis absorption and electron energy loss spectroscopy (EELS) [1,2]. The laser induced modifications resulted to be nanostructure-sensitive producing structures in form of "rosette" and void shells in the case of mature and coalesced amorphous material, respectively. These structures are observable in Fig. 1, where HRTEM images of nascent and mature ethylene soot before and after laser heating treatment are reported. The sensitivity to nanostructure is promising for developing laser heating as a structural diagnostic tool for carbon materials, but just such sensitivity has to be carefully considered when the laser is employed for diagnostic purposes.
2018, Articolo in rivista, CPE
Theofanidis, Stavros Alexandros; Galvita, Vladimir V.; Poelman, Hilde; Dharanipragada, N. V. R. Aditya; Longo, Alessandro; Meledina, Maria; Van Tendeloo, Gustaaf; Detavernier, Christophe; Marin, Guy B.
We report a MgFexAl2-xO4 synthetic spinel, where x varies from 0 to 0.26, as support for Ni-based catalysts, offering stability and carbon control under various conditions of methane reforming. By incorporation of Fe into a magnesium aluminate spine!, a support is created with redox functionality and high thermal stability, as concluded from temporal analysis of products (TAP) experiments and redox cycling, respectively. A diffusion coefficient of 3 x 10(-17) m(2) s(-1) was estimated for lattice oxygen at 993 K from TAP experiments. X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) modeling identified that the incorporation of iron occurs as Fe3+ in the octahedral sites of the spinel lattice, replacing aluminum. Simulation of the X-ray absorption near edge structure (XANES) spectrum of the reduced support showed that 60 +/- 10% of iron was reduced from 3+ to 2+ at 1073 K, while there was no formation of metallic iron. A series of Ni/MgFexAl2-xO4 catalysts, where x varies from 0 to 0.26, was synthesized and reduced, yielding a supported Ni-Fe alloy. The evolution of the catalyst structure during H-2 temperature-programmed reduction (TPR) and CO2 temperature-programmed oxidation (TPO) was examined using time-resolved in situ XRD and XANES. During reforming, iron in both the support and alloy keeps control of carbon accumulation, as confirmed by O-2-TPO on the spent catalysts. By fine tuning the amount of Fe in MgFexAl2-xO4, a supported alloy was obtained with a Ni/Fe molar ratio of similar to 10, which was active for reforming and stable. By comparison of the performance of Ni-based catalysts with Fe either incorporated into or deposited onto the support, the location of Fe within the support proved crucial for the stability and carbon mitigation under reforming conditions.
2017, Articolo in rivista, ENG
Senneca O.
Solid carbons include a very wide range of materials, form biomass and wood, with their disordered structure, high content of oxygen and hydrogen, to progressively more ordered and pure materials, passing through the large family of coals of different geological age and degree of graphitization, through soot, ending up with nearly perfectly organized materials such as graphene, graphite, nanotubes, fullerene (Fig.1). The large variety of carbonaceous solid materials corresponds also to a large variety of applications. Beyond the numerous and strategic industrial applications, from the field of energy production to that of innovative materials, we can recall also the role played in natural and biological processes: atmospheric dust, for example, is responsible of several meteorological phenomena, carbonaceous nanoparticles are related to lung deseases, solid active carbon is employed in drug delivery etc. We can probably say that oxidation of solid carbon is the reaction that mankind exploited earliest, since men learned to light up a fire. Over the ages combustion of wood first and of fossil fuels later, has continued to sustain the energy demand and the progress of human society and, despite the efforts of the scientific community to find alternative routes for energy production, a significant fraction of the global energy demand is likely to remain dependent on combustion of solid carbon also in the near future. In the second half of the last century the need to reduce pollution from coal fired power plants, in particular soot, NOx and SOx emissions, motivated significant research on the chemistry as well as on the physical phenomena involved in coal combustion. The basis of our current knowledge in carbon oxidation was formed at that time, allowing some important scientific and technological advances in the field of coal to energy. Over the last decade the environmental challenge and the rising concerns about climate change have become prime drivers of scientific and technological development in the field of solid fuel combustion and gasification. Studies in this field are targeted to the development of novel combustion concepts that make CO2 capture and sequestration inherently more economical and feasible. This goal is pursued by re-thinking combustion technologies in such a way that carbon dioxide is highly concentrated at the exhaust, possibly free of any contaminants, so that it can be more easily compressed and disposed of through the sequestration path. Chemical looping combustion and Oxy-combustion are two examples of these new generation "capture ready" combustion technologies. In such innovative technologies carbon oxidation is carried out under more severe conditions than ever, for instance at very high temperature and pressure, in CO2 rich environments, or experiencing continuous temperature and oxygen swings. The knowledge so far available on coal combustion has proved unable to explain the behavior of coal oxidation under such conditions. On a different, but parallel route, the current rush towards the development of innovative carbon based materials, for a multitude of industrial applications, has also entailed investigations on the affinity of solid carbons towards oxygen. The attention has been put, in this case, on ordered carbon materials such as graphene and graphite, carbon composites, carbon nanotubes etc. and on how their properties are altered by oxidation under mild oxidizing or even ambient conditions. It is astonishing that despite the very long time research on coal, on the one side, and the more recent but massive research carried out on graphene on the other, there are still many unresolved (or poorly understood) aspects in the heterogeneous oxidation of carbons:: what are the bonding modes of oxygen on different solid carbons? What is the range of atomic equilibrium distance? What are the spin state of the absorbing site and of the absorption complexes? What is the energetic range of C-O bond? Is it a strong physisorption or a weak chemisorption? What are the kinetics of the absorption and desorption on the molecular scale?.
2017, Articolo in rivista, ENG
Sabine Reinsch 1, Eva Koller 2, Alwyn Sowerby 1, Giovanbattista de Dato 3,4, Marc Estiarte 5,6, Gabriele Guidolotti 7, Edit Kovács-Láng 8, György Kröel-Dulay 8, Eszter Lellei-Kovács 8, Klaus S. Larsen 9, Dario Liberati 4, Josep Peñuelas 5,6, Johannes Ransijn 9, David A. Robinson 1, Inger K. Schmidt 9, Andrew R. Smith 1,2, Albert Tietema 10, Jeffrey S. Dukes 11,12, Claus Beier 9, Bridget A. Emmett 1
Above- and belowground carbon (C) stores of terrestrial ecosystems are vulnerable to environmental change. Ecosystem C balances in response to environmental changes have been quantified at individual sites, but the magnitudes and directions of these responses along environmental gradients remain uncertain. Here we show the responses of ecosystem C to 8-12 years of experimental drought and night-time warming across an aridity gradient spanning seven European shrublands using indices of C assimilation (aboveground net primary production: aNPP) and soil C efflux (soil respiration: Rs). The changes of aNPP and Rs in response to drought indicated that wet systems had an overall risk of increased loss of C but drier systems did not. Warming had no consistent effect on aNPP across the climate gradient, but suppressed Rs more at the drier sites. Our findings suggest that above- and belowground C fluxes can decouple, and provide no evidence of acclimation to environmental change at a decadal timescale. aNPP and Rs especially differed in their sensitivity to drought and warming, with belowground processes being more sensitive to environmental change.
DOI: 10.1038/srep43952
2017, Articolo in rivista, ENG
Ackerman P., Williams C., Ackerman S., Nati C.
Recent and increasing use of mechanized cut-to-length (CTL) operations in South Africa has been associated with greater diesel and lubricant requirements than was previously the case with motor-manual or semi-mechanized activities, placing a strain on the environmental and economic sustainability of operations. This case study explores diesel and lubricant consump- tion of a typical CTL pine saw timber operation, taking into account the stand and terrain factors, with the aim of setting baselines for these consumption rates as well as carbon emis- sions. Data analyzed was provided by Bosbok Ontginning, a contractor based in Mpumu- langa, throughout their clear-fell operations over the 49 compartments from May 2014 to June 2015. The mean diesel consumption rate was found to be 0.64 l m-3 and 0.38 l m-3, while the lubricant consumption was 0.08 l m-3 and 0.03 l m-3 for the harvester and the forwarder, re- spectively. Carbon emissions from diesel were found to account for less than 1% of the carbon stored in the harvested timber. Statistical analysis showed that tree size, stand density and ground condition were not significant predictors of either diesel or lubricant consumption. Prior research suggests that other factors not included in this study (i.e. machine character- istics, operator habits and productivity) may have a more pronounced effect on diesel consump- tion. Future studies should therefore be conducted to analyze these factors within South Afri- can conditions as well as explore stand and terrain conditions more specifically and over more diverse stand and terrain conditions as well as machine types.