Vetenskaplig slutrapport
Abstract
Emissions of particulate matter (PM) from diesel automotives are commonly reduced by including a particulate filter in the exhaust aftertreatment system. PM is trapped in the filter and depending on the application requirements, various strategies for regeneration of the filter may be used. In common for these strategies is the conversion of carbonaceous matter via oxidation by oxygen (O2) and/or nitrogen dioxide (NO2) into mainly carbon dioxide and water, with or without the influence of a catalyst. Thus, to increase the efficiency of the regeneration process by improved catalytic filter design, it is essential to understand the mechanisms behind non-catalytic as well as catalytic oxidation of carbonaceous matter by O2 and NO2. Regarding catalytic oxidation, it is of specific importance to understand how the interaction between the catalyst and the carbonaceous matter affect the reaction mechanisms. The present objectives are to investigate the non-catalytic as well as catalytic oxidation kinetics of particulate matter and to contribute to an understanding of the reaction mechanisms.
Firstly a method for determining intrinsic global kinetic parameters for non-catalytic oxidation of particulate matter was developed and validated by comparing the obtained kinetic parameters with previously reported literature values for a commercial carbon black. This method offers the specific advantages of minimized thermal gradients due to the uniform sample distribution and 500 times higher cordierite weight and negligible mass transfer due to the open structure of the monolith enabling a high flow rate. Although the kinetic studies were performed on commercial carbon black samples, the reactivity of PM samples collected from vehicles with various combustion concepts and fuels were also studied and compared with the commercial carbon black. Finally a the influence of carbon-catalyst interactions on the low temperature oxidation of carbon black by either O2 or NO2 was studied by temperature programmed oxidation experiments with varying carbon-catalyst contact and catalyst loading. When platinum is present an increase in oxidation rate was observed, depending on both the size of the Pt-carbon interface area and the quality of the contact. These results show that the obtaining a close contact between the catalyst and carbonaceous matter is important for an overall efficient regeneration process.
Kontaktperson: Per Ericsson
Utgivare: Department of Chemical and Biological Engineering, Competence Centre for Catalysis, Chalmers University of Technology, 412 96 Göteborg
Författare: Carolin Ohlson
Språk: Engelska
Sidor: 20
