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 engine are reported. The x-ray diffraction of DPM yields the characteristic peaks of pregraphitic carbons (cokes and pitches), and its modeling yields d((002)) approximate to 3.429 Angstrom and a crystallite size of about 20 Angstrom. The real and imaginary parts of the dielectric constant epsilon = epsilon' + i epsilon '' are measured at 8.7 GHz using the cavity perturbation technique. The measured values for the DPM are epsilon' = 8.6 +/- 1.7 and epsilon '' = 7.4 +/- 1.5, compared to epsilon' approximate to 1.0 and epsilon '' approximate to 6 x 10(-5) for the ceramic trap material used for collecting DPM. The oxidation products of the DPM, analyzed by FTIR spectroscopy, are found to contain CO2 and CO with a peak yield occurring around 500 degrees C. Since microwave power absorption is proportional to epsilon '', these results show that selective microwave heating of the DPM in the ceramic traps should be a very efficient process with CO2 and CO as the main oxidation products.