The heterogeneous reaction between soot and NO_2 at elevated temperature

摘要

Two commercial soot samples are analysed by temperature programmed desorption mass spectroscopy (TPD-MS) in order to determine the functional groups at their surface. A systematic approach has been developed, which assures that all functional groups decomposing between 100 deg C and 900 deg C can be distinguished and assigned. For the understanding of the mechanism of the reaction between soot and NO_2 diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and TPD-MS are applied. Both spectroscopic techniques monitor the formation of new species. The reaction with NO_2 results in the formation of an acidic functional group, which decomposes into CO_2 and NO at 140 deg C. It is proven that N_2 reacts directly with the carbon surface. Pre-existing functional groups do not interfere. From these results the reaction sequence has been concluded.