Recent Research Developments

Index of Recent Research News
Mar 5, 2003
    Oxidation of Size-Selected Diesel Nano-Aerosol Particles

    Pollution and public health concerns make particulate emission from diesel engines a topic of great concern. The Environmental Protection Agency is set to introduce strict new regulations on diesel particle emissions, and a number of other countries are also considering regulatory action. A great deal of research effort is therefore being devoted to reducing the amount of particulate matter produced by diesel engines.

    A team of researchers from the University of Minnesota, led by Chemistry professor Jeff Roberts and Mechanical Engineering professors Michael Zachariah and David Kittelson, has developed a new method to study surface oxidation rates of size-selected diesel soot nano-aerosol particles. Working with post-doctoral associate Kelly Higgins and graduate student Heejung Jung, Profs. Roberts, Zachariah, and Kittelson have built an apparatus capable of creating monodisperse streams of diesel particles suspended in air. The particle streams are sent through a high temperature furnace, and the size changes that result from oxidation are measured with a device called a differential mobility analyzer. Between 500 and 1000 °C, the oxidation kinetics are well modeled by a single Arrhenius expression, with an activation energy of ca. 110 kJ⋅mol-1. The activation energy is nearly 55 kJ⋅mol-1 lower than for flame soot (Higgins et al J. Phys. Chem. A 2002, 106, 96.), but the preexponential factors are also lower, by three orders of magnitude. The Minnesota team speculates that the origin of this behavior is in a surface catalytic effect, possibily derived from a small amounts of alkali or alkali earth metals known to be entrained in diesel soot particles.

    A description of some of this work has been accepted for publication in Environmental Science and Technology

    Figure 1 Representative data for the oxidation of 130 nm diesel soot particles. Each scan shows the size distributions of a particle stream after it leaves the furnace as a function of the furnace temperature. The most probably particle diameter (measured as Dp, the mobility diameter) decreases with increasing furnace temperature because the oxidation rate increases.

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Next scheduled update: Mar. 19, 2003.

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