Comparative Study on Physicochemical Properties and Combustion Behaviors of Diesel Particulates and Model Soot

The physicochemical properties and combustion characteristics of model soot (i.e., Printex U) and diesel particulates with different origins were compared. Their elemental composition and structures were determined using several kinds of techniques including element analysis, infrared spectroscopy (I R), X-ray fluorescence spectroscopy (XRF), and X-ray photoelectron spectroscopy (XPS), and their different reactivities were measured by a number of temperature-programmed oxidation (TPO) experiments. It was found that the Brunauer-Emmett-Teller (BET) surface area of the particulates increased with the increase of the amount of adsorbed hydrocarbons. The main element components of model carbon were basically consistent with those of the practical diesel particulates, including C, H, O. etc. However, their element contents and surface properties were very different. The major ingredient of Printex U was carbon, and its content reached 92%; however, the carbon content of diesel particulates was about 65-74%, and the contents of O, H, and N in the diesel particulates were about 3-10 times as much as those of Printex U. TPO results showed that the diesel particulates could be more easily removed than Printex U by the combustion method, and the combustion temperatures for both Printex U and diesel particulates could be lowered when catalysts were present. Printex U is very well-suited as a kind of model soot for the study on the combustion performances of the soot fraction of diesel particulates.