Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) applied to the chemical characterization of diesel soot

Abstract

In this work, diesel soot has been characterized chemically using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique. Diesel soot samples were generated under combustion conditions reproducing the typical urban operating mode of a diesel engine. Initial experiments performed to ensure the repeatability of the DRIFTS analysis and the sample preparation method showed that the standard deviations were always lower than 20% for the DRIFTS analysis itself, and lower than 25% when sample preparation was included. This is of special interest as regards application of the DRIFTS technique for quantitative analysis. The functional groups on the soot surface were identified on the basis of the infrared bands observed in the spectra at room temperature, indicating that the diesel soot analyzed comprises a mixture of aromatic hydrocarbons, carboxylic compounds, hydroxyl species, ether groups, and methylene and methyl groups. Analyses were also carried out at different temperatures in the interval of 298-858 K in order to analyze the thermal stability of the functional groups, with carbonyl groups, lactones and ethers appearing to be the most thermally stable compounds.