[Zurück]

J. Ofner, H. Muckenhuber, H. Grothe:
"Mechanisms Of Heterogeneous Reactions On Soot Surfaces";
Vortrag: 12.Österreichische Chemietage, Alpen-Adria-Universität Klagenfurt; 10.09.2007 - 13.09.2007; in: "All About Water", (2007), Paper-Nr. MS-25, 1 S.

Soot emissions of diesel engines are suspected of causing negative health effects.
Possible ways to reduce these emissions are particle filters, from which the particles are
removed by strong oxidants such as NO2 or O2. The interactions of these oxidizers with
the carbonaceous surface and a possible promoting effect of H2O have been studied in
recent publications focussing mainly on kinetics. However, mechanistic details of these
reactions are rarely reported.
Diffuse-Reflectance-Infrared-Fourier-Transform-Spectroscopy (DRIFTS) provides
detailed information about functional groups on the soot surface and have been recorded
before and after the respective reaction treatment with the above-mentioned oxidizing
gases. DRIFTS-Spectra have been recorded at high vacuum and at temperatures up to
723 K. Temperature-Programmed-Desorption-Mass-Spectroscopy (TPD-MS) pyrolyses
the functional surface groups and allows a subsequent detection of the fragments by a
quadrupole mass spectrometer (QMS) as a function of the decomposition temperature
(up to 1173 K). Temperature-Programmed-Oxidation-Mass-Spectroscopy (TPO-MS)
indicates the same changes but measures continuously during the oxidation process.
Combination of DRIFTS, TPD, and TPO supplies the understanding of the interaction
of NO2 with the soot surface [1,2,3] on a molecular level and consequently resolves the
mechanisms of soot surface oxidation by NO2 and its site-effects with oxygen and
water, i.e. the cooperation effect [4]. Additionally, pre-existing functional groups on the
soot surface and their changes as a function of temperature und oxidation could be
assigned.
[1] Muckenhuber H., Grothe H., The heterogenous reaction between soot and NO2 at elevated
temperature, Carbon, 2006, 44, 546
[2] Muckenhuber H., Grothe H., The reaction between soot and NO2 investigation of functional
groups using TPD-MS, Topics in Catalysis, 2004, 30/31, 287
[3] Muckenhuber H., Grothe H., A DRIFTS study of the heterogenous reaction of NO2 with
carbonaceous materials at elevated temperature, Carbon, 2007, 45, 321
[4] Ofner J., Grothe H., A mechanistic study of the cooperative effect of NO2 and O2 on the soot
surfaces, Asian Chemistry Letters, 2007, 11, 1&2, 57-61