Changes in Structure and Reactivity of Soot during Oxidation and Gasification by Oxygen, Studied by Micro-Raman Spectroscopy and Temperature Programmed Oxidation

Micro-Raman spectroscopy (micro-RS) and Temperature Programmed Oxidation (TPO) combined with FTIR gas analysis have been used to determine structural changes and oxidation behavior in samples of spark discharge (GfG) and heavy duty engine (EURO IV) soot upon oxidation by oxygen in a temperature range between 293 K and 873 K. Raman spectra of soot and FTIR spectra of oxidation products have been recorded before and during the oxidation process. For micro-RS analysis spectral parameters have been determined by a five band curve fitting procedure (G, D1–D4). For GfG soot the relative intensity of D3 band is decreasing and the two observed Raman peaks are getting more separated during the TPO. This suggests a rapid preferential oxidation of highly reactive amorphous carbon. The decrease of the D1 band width indicates a decrease of chemical heterogeneity and an increase of structural order upon oxidation. Changes in Raman spectroscopic parameters are in good agreement with the behavior of soot during oxidation determined by CO2 emission with FTIR. In contrast to GfG soot the spectral parameters of EURO IV soot remained mostly unchanged during the oxidation process, so that EURO IV soot shows just minor changes in structure upon oxidation. Overall Raman spectroscopic parameters provide information about changes in structural order of graphitic and amorphous carbon fractions during oxidation and can be used to analyze oxidation readiness of soot. Thus micro-Raman spectroscopy may become a rapid analytical tool for the determination of soot reactivity by analysis of the structure.

[1]  J. Casado,et al.  Raman spectroscopic characterization of some commercially available carbon black materials , 1995 .

[2]  R. Niessner,et al.  Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an ELPI: Soot, Humic-Like Substances, and Inorganic Compounds , 2007 .

[3]  R. McCreery,et al.  Raman Spectroscopy for Chemical Analysis: McCreery/Raman Spectroscopy , 2005 .

[4]  M. Lance,et al.  Influence of soot surface changes on DPF regeneration , 2004 .

[5]  G. Zerbi,et al.  A Computational Study of the Raman Spectra of Large Polycyclic Aromatic Hydrocarbons: Toward Molecularly Defined Subunits of Graphite† , 2002 .

[6]  J. Robertson,et al.  Interpretation of Raman spectra of disordered and amorphous carbon , 2000 .

[7]  Jean-Noël Rouzaud,et al.  On the characterization of disordered and heterogeneous carbonaceous materials by Raman spectroscopy. , 2003, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[8]  D. Su,et al.  Morphology-controlled reactivity of carbonaceous materials towards oxidation , 2005 .

[9]  D. Su,et al.  Diesel engine exhaust emission: oxidative behavior and microstructure of black smoke soot particulate. , 2006, Environmental science & technology.

[10]  N. Siddique,et al.  Raman spectroscopic characterization of carbonaceous aerosols , 2001 .

[11]  R. V. Vander Wal,et al.  Carbon Nanostructure Examined by Lattice Fringe Analysis of High-Resolution Transmission Electron Microscopy Images , 2004, Applied spectroscopy.

[12]  Reinhard Niessner,et al.  Comprehensive kinetic characterization of the oxidation and gasification of model and real diesel soot by nitrogen oxides and oxygen under engine exhaust conditions: Measurement, Langmuir–Hinshelwood, and Arrhenius parameters , 2006 .

[13]  Andre Nel,et al.  Health effects of air pollution. , 2004, The Journal of allergy and clinical immunology.

[14]  R. Niessner,et al.  Characterization and discrimination of pollen by Raman microscopy , 2005, Analytical and bioanalytical chemistry.

[15]  J. Moulijn,et al.  Correlation between Raman spectroscopic data and the temperature-programmed oxidation reactivity of coals and carbons , 1990 .

[16]  David B. Kittelson,et al.  Size-Selected Nanoparticle Chemistry: Kinetics of Soot Oxidation , 2002 .

[17]  Reinhard Niessner,et al.  Raman microspectroscopy of soot and related carbonaceous materials: Spectral analysis and structural information , 2005 .

[18]  R. Niessner,et al.  Raman microspectroscopic analysis of changes in the chemical structure and reactivity of soot in a diesel exhaust aftertreatment model system. , 2007, Environmental science & technology.

[19]  D. Su,et al.  Fullerene-like soot from EuroIV diesel engine: consequences for catalytic automotive pollution control , 2004 .

[20]  S. Dahlén,et al.  Health effects of diesel exhaust emissions. , 2001, The European respiratory journal.

[21]  G. Saracco,et al.  Catalytic traps for diesel particulate control , 1999 .

[22]  J. Heintzenberg,et al.  NIR FT Raman spectroscopic study of flame soot , 1999 .

[23]  Richard L. McCreery,et al.  Raman Spectroscopy for Chemical Analysis , 2000 .

[24]  Christopher D. Simpson,et al.  Microstructure and oxidation behaviour of Euro IV diesel engine soot: a comparative study with synthetic model soot substances , 2004 .

[25]  R. Niessner,et al.  Advances in the development of filterless soot deposition systems for the continuous removal of diesel particulate matter , 2004 .

[26]  T. Novakov,et al.  Raman scattering and the characterisation of atmospheric aerosol particles , 1977, Nature.