CARBON IN DIESEL PARTICULATE MATTER - STRUCTURE, MICROWAVE-ABSORPTION, AND OXIDATION

The structural, microwave absorption, and oxidation characteristics of diesel particulate matter (DPM) collected from a CAT 3304 diesel engi ne are reported. The x-ray diffraction of DPM yields the characteristi c peaks of pregraphitic carbons (cokes and pitches), and its modeling yields d((002)) approximate to 3.429 Angstrom and a crystallite size o f about 20 Angstrom. The real and imaginary parts of the dielectric co nstant epsilon = epsilon' + i epsilon '' are measured at 8.7 GHz using the cavity perturbation technique. The measured values for the DPM ar e epsilon' = 8.6 +/- 1.7 and epsilon '' = 7.4 +/- 1.5, compared to eps ilon' approximate to 1.0 and epsilon '' approximate to 6 x 10(-5) for the ceramic trap material used for collecting DPM. The oxidation produ cts of the DPM, analyzed by FTIR spectroscopy, are found to contain CO 2 and CO with a peak yield occurring around 500 degrees C. Since micro wave power absorption is proportional to epsilon '', these results sho w that selective microwave heating of the DPM in the ceramic traps sho uld be a very efficient process with CO2 and CO as the main oxidation products.