163,193 research outputs found
Videoclub iPhone iStreamrTV
No full textRamis Munilla, J. (2010). Videoclub iPhone iStreamrTV. https://riunet.upv.es/handle/10251/10239.Archivo delegad
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Kinetic modelling of the biodegradation of polymeric materials
No full textKinetic modelling of the biodegradation of polymeric materials
Francesco Contea, Ilenia Rossettia, Gianguido Ramis b
a Dipartimento di Chimica, Università degli Studi di Milano, via C. Golgi 19, 20133, Milano, Italy
b DICCA, Università degli Studi di Genova, via all’Opera Pia 15A, 16149 Genova, Italy
[email protected]
Abstract
Methods to treat kinetic data for the biodegradation of different plastic materials are comparatively discussed [1-4]. Different commercial plastic samples were tested for biodegradation under standard testing methods in different environments. The following standard procedures have been used for kinetic data collection: i) ISO14855 for aerobic biodegradation in compost; ii) ASTM D6691 for aerobic biodegradation in marine environment; iii) ISO 15985 for anaerobic digestion with high solids content and biogas production and iv) ISO 14853 for anaerobic biodegradability in aqueous medium and production of biogas.
Starting from the raw data, the conversion vs. time entries were elaborated using relatively simple kinetic models [5], such as integrated kinetic equations of zero, first and second order, through the Wilkinson model, or using a Michaelis Menten approach, which was previously reported in the literature. The results were validated against the experimental data and allowed to correctly compute the time for half degradation of the substrate and, by extrapolation, to estimate the final biodegradation time for all the materials tested. At the same time, a comparison between the rates of CO2 emission rate during aerobic degradation vs. biogas formation rate could be established.
The reprocessing of the kinetic data by means of a model of the first order was satisfactory in most cases of aerobic biodegradation. By contrast, The reprocessing of the data for test ISO 15985 by means of a model of the first order was unsuitable. Significantly better results were obtained with a Stover-Kincannon model, which, however, has highlighted for all substrates, including cellulose used as reference, the persistence of a fraction of the material not converted. The reliability of the model is confirmed by the data collected for cellulose, for which is estimated reliably the maximum biodegradable fraction. Also in the case of the tests carried out according to ISO 14853 the most appropriate model was found to be the Stover-Kincannon one, which also in this case has highlighted the lack of complete biodegradability of all the three substrates.
Conversion (%) of the three commercial samples and reference cellulose as a function of time.
Linear regression of the conversion data for the A formulate according to a first-order model. Blue diamonds were not included in the regression pertaining to the plateau region.
References
1. S. Ghatge, Y. Yang, J.H. Ahn, H.G. Hur, Appl. Biol. Chem. 2020, 63, 1.
2. S. Fontanella, S. Bonhomme, M. Koutny, L. Husarova, J.M. Brusson, J.P. Courdavault, S. Pitteri, G. Samuel, G. Pichon, J. Lemaire, Polym. Degrad. Stab. 2010, 95, 1011.
3. E. Castro-Aguirre, R. Auras, S. Selke, M. Rubino, T. Marsh, Polym. Degrad. Stab. 2017, 137, 251.
4. F. Kawai, M. Watanabe, M. Shibata, S Yokoyama, Y. Sudate, Polym. Degrad. Stab. 2002, 76, 129.
5. I. Rossetti, F. Conte, G. Ramis, Engineering, 2021, 2, 54
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
Doubinger J. et Alvarez-Ramis. (1969). — Sphenopteris asturica nueva especie. Acta Geologica Hispanica, IV, 3, p. 60-63
No full textDoubinger J. et Alvarez-Ramis. (1969). — Sphenopteris asturica nueva especie. Acta Geologica Hispanica, IV, 3, p. 60-63. In: Bulletin du Service de la carte géologique d'Alsace et de Lorraine, tome 22, n°4, 1969. Sédimentologie et géochimie de la surface. p. 359
J. Doubinger et С. Alvarez-Ramis (1965). — Pseudomariopteris villablinensis n.sp. du Stéphanien de Villablino (Léon, Espagne), p. 235-237
No full textJ. Doubinger et С. Alvarez-Ramis (1965). — Pseudomariopteris villablinensis n.sp. du Stéphanien de Villablino (Léon, Espagne), p. 235-237. In: Bulletin du Service de la carte géologique d'Alsace et de Lorraine, tome 19, n°3-4, 1966. Sédimentologie et géochimie de la surface. p. 325
Doubinger J. et Alvarez-Ramis. (1969). — Sphenopteris asturica nueva especie. Acta Geologica Hispanica, IV, 3, p. 60-63
No full textDoubinger J. et Alvarez-Ramis. (1969). — Sphenopteris asturica nueva especie. Acta Geologica Hispanica, IV, 3, p. 60-63. In: Bulletin du Service de la carte géologique d'Alsace et de Lorraine, tome 22, n°4, 1969. Sédimentologie et géochimie de la surface. p. 359
Multisummability of formal power series solutions of linear ordinary differential equations
No full textBalser, W.; Braaksma,B.L.J.; Ramis, J.-P.; Sibuya, Y.. (1990). Multisummability of formal power series solutions of linear ordinary differential equations. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/1454
J. Doubinger et С. Alvarez-Ramis (1965). — Pseudomariopteris villablinensis n.sp. du Stéphanien de Villablino (Léon, Espagne), p. 235-237
No full textJ. Doubinger et С. Alvarez-Ramis (1965). — Pseudomariopteris villablinensis n.sp. du Stéphanien de Villablino (Léon, Espagne), p. 235-237. In: Bulletin du Service de la carte géologique d'Alsace et de Lorraine, tome 19, n°3-4, 1966. Sédimentologie et géochimie de la surface. p. 325
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