Analysis of Changes in Structure and Reactivity of Soot Undergoing Oxidation by Raman Microscopy
Objectives
- Characterization of soot structure upon oxidation and gasification
- Information about structure-reactivity relationship for different soot samples
Methods of Approach
- Diesel Exhaust Aftertreatment Model System
- Raman Microscopy
Description
Soot particles emitted by diesel engines (“diesel exhaust particles”, DEP) are hazardous environmental pollutants and account for a major fraction of fine air particulate matter in urban areas. The environmental and health effects as well as the oxidation and gasification of soot in DEP trapping and filter systems are strongly influenced by the chemical composition, structure and size of the particles.
The goals of this project are the investigation of changes in the structure and reactivity of soot undergoing oxidation by Raman Microscopy. For quantitative analysis of spectra we use the fitting procedures with five bands (G, D1-D4). Our findings suggest that Raman spectroscopic parameters – in particular the D1 band width and the D3 band intensity – provide information about the relative abundance and structural order of graphite-like and amorphous carbon, respectively, and can be used as proxies for the chemical reactivity of soot undergoing oxidation and gasification. Thus Raman spectroscopy promises to become an efficient tool for further investigation and optimization of diesel exhaust aftertreatment. This may become increasingly important if soot particles formed in modern diesel engines become more reactive but also more susceptible to structural rearrangement and passivation.
Pubilcations
M. Knauer, M. E. Schuster, D. Su, R. Schlögl, R. Niessner & N. P. Ivleva, Soot Structure and Reactivity Analysis by Raman Microspectroscopy, Temperature Programmed Oxidation and High Resolution Transmission Electron Microscopy, The Journal of Physical Chemistry A, 113, 13871, (2009)
M. Knauer, M. Carrara, D. Rothe, R. Niessner & N. P. Ivleva, Changes in Structure and Reactivity of Soot during Oxidation and Gasification by Oxygen, Studied by Raman Microscopy and Temperature Programmed Oxidation, Aerosol Science and Technology, 43, 1 (2009)
N. P. Ivleva, M. Knauer, U. Pöschl, R. Niessner & C. Haisch, Raman microspectroscopic Analysis of Soot Structure and Reactivity, Preprints of Extended Abstracts presented at the ACS National Meeting, American Chemical Society, Division of Environmental Chemistry, 48, 880 (2008)
N. P. Ivleva, U. McKeon, R. Niessner & U. Pöschl, Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an Electrical Low Pressure Impactor: Soot, Humic-Like Substances and Inorganic Compounds, Aerosol Science and Technology, 41, 655 (2007)
N. P. Ivleva, A. Messerer, X. Yang, R. Niessner & U. Pöschl, Raman Microspectroscopic Analysis of Changes in the Chemical Structure and Reactivity of Soot in a Diesel Exhaust Aftertreatment Model System, Environmental Science and Technology, 41, 3702 (2007)