Title: The benzene problem: impact of three-way catalyst technology: potential for further improvement

Authors: Norbert V. Heeb, Anna-Maria Forss, Christian J. Saxer, Patrick Wilhelm, Stefan Bruhlmann, Claudio Rudy, Martin F. Weilenmann

Addresses: Laboratory of Organic Chemistry, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, CH-8600 Dubendorf, Switzerland. ' Laboratory of Internal Combustion Engines, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, 8600 Dubendorf, Switzerland. ' Laboratory of Organic Chemistry, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, 8600 Dubendorf, Switzerland. ' Blaser Swisslube, Research and Development Metalworking Fluids, 3415 Hasle-Rugsau, Switzerland. ' Laboratory of Organic Chemistry, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, 8600 Dubendorf, Switzerland. ' Laboratory of Internal Combustion Engines, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, 8600 Dubendorf, Switzerland. ' Laboratory of Internal Combustion Engines, Swiss Federal Laboratories for Materials Testing and Research (EMPA), Uberlandstrasse 129, 8600 Dubendorf, Switzerland

Abstract: Chemical ionisation mass spectrometry (CI-MS) was applied to study the benzene emission characteristics of a TWC-vehicle at a time resolution of one Hertz. Three important operating conditions with increased emissions were identified: at vehicle start; at extended stop-and-go situations; and whenever a catalyst-induced benzene formation occurs. The cold start influence was detectable for about 200 seconds of driving corresponding to a distance of 1.2 km. At hot engine/catalyst mean pre- and post-catalyst emission rates of 25–150 mg km^-1 and 0.1–135 mg km^-1 were determined. Catalyst conversion varied from 0.07 to >0.99. Even negative conversion efficiencies were observed at several occasions, indicating that benzene can be formed de novo in a TWC. It is of importance to lower benzene emissions at these critical operating conditions to further reduce ambient air levels in cities and with it the cancer risk for large proportions of our population.

Keywords: benzene emissions; conversion efficiency; time resolved exhaust gas analysis; chemical ionisation mass spectrometry; cold start; vehicle emissions; pollution emissions; three-way catalyst vehicles; cancer risk.

DOI: 10.1504/IJEP.2004.005545

International Journal of Environment and Pollution, 2004 Vol.22 No.3, pp.287 - 300

Published online: 19 Oct 2004 *

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