Soot represents one of the most important pollutants in the exhaust gases emitted from combustion processes. The combustion conditions determine to a large extent soot micro- and nanostructure (i.e. primary particle dimension, length and arrangement of the graphene layers) and soot surface chemistry (i.e. number and typology of functional groups). Soot chemicophysical features have a direct influence on its reactivity towards the combustion gases [1]. One of the most meaningful parameters that have a direct influence on the soot reactivity is the oxygenation degree. In this work soot surrogates of uniform size bearing different kind of oxygenated functionalities have been produced through wet oxidations of a commercial carbon black (CB). The selected CB presents morphological and chemico-physical characteristics close to soot generated in combustion environments (flames [2], engines). CB microstructure consists of chain-like aggregates of spherical primary particles with an average diameter in the range of 15-20 nm. The CB organization at a nanoscale level is typical of a disordered carbon exhibiting a concentric organization of the stacked graphitic layers throughout each primary particle, in the better organized areas. Two different oxidation strategies were performed in order to vary the typologies of oxygenated functionalities introduced. Nitric acid [3] (67 wt.%, at 100 °C) and a mixture of concentrated sulphuric acid/hydrogen peroxide in ratio 70:30 v/v (piranha mixture) in accordance with the procedure reported for carbon nanotubes (CNT) [4] were used. The reaction time ranged from 4 to 24 hours with the aim to modulate the number of oxygenated functionalities. The CB-derived soot were gathered in two groups according with the oxidation procedure adopted (nitric acid: SN, piranha mixture: SP) and with the reaction time (SN4, SN15, SN24, SP4, SP15, SP24). Following purification, the soot surrogates were fully characterized by applying a large array of analytical techniques (TEM microscopy, infrared and UV-Visible spectroscopy, thermogravimetry, BET specific surface area, elemental analysis, dynamic light scattering). The evaluation of surface acid site content has been performed by a fluorimetric test with thionine acetate.
Production and characterization of oxygenated soot surrogates from carbon black and comparison with real diesel soot
Alfè M;Gargiulo V;
2013
Abstract
Soot represents one of the most important pollutants in the exhaust gases emitted from combustion processes. The combustion conditions determine to a large extent soot micro- and nanostructure (i.e. primary particle dimension, length and arrangement of the graphene layers) and soot surface chemistry (i.e. number and typology of functional groups). Soot chemicophysical features have a direct influence on its reactivity towards the combustion gases [1]. One of the most meaningful parameters that have a direct influence on the soot reactivity is the oxygenation degree. In this work soot surrogates of uniform size bearing different kind of oxygenated functionalities have been produced through wet oxidations of a commercial carbon black (CB). The selected CB presents morphological and chemico-physical characteristics close to soot generated in combustion environments (flames [2], engines). CB microstructure consists of chain-like aggregates of spherical primary particles with an average diameter in the range of 15-20 nm. The CB organization at a nanoscale level is typical of a disordered carbon exhibiting a concentric organization of the stacked graphitic layers throughout each primary particle, in the better organized areas. Two different oxidation strategies were performed in order to vary the typologies of oxygenated functionalities introduced. Nitric acid [3] (67 wt.%, at 100 °C) and a mixture of concentrated sulphuric acid/hydrogen peroxide in ratio 70:30 v/v (piranha mixture) in accordance with the procedure reported for carbon nanotubes (CNT) [4] were used. The reaction time ranged from 4 to 24 hours with the aim to modulate the number of oxygenated functionalities. The CB-derived soot were gathered in two groups according with the oxidation procedure adopted (nitric acid: SN, piranha mixture: SP) and with the reaction time (SN4, SN15, SN24, SP4, SP15, SP24). Following purification, the soot surrogates were fully characterized by applying a large array of analytical techniques (TEM microscopy, infrared and UV-Visible spectroscopy, thermogravimetry, BET specific surface area, elemental analysis, dynamic light scattering). The evaluation of surface acid site content has been performed by a fluorimetric test with thionine acetate.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
