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Biofuel-Promoted Polychlorinated Dibenzodioxin/furan Formation in an Iron-Catalyzed Diesel Particle Filter

Author:
Heeb, Norbert V., Rey, Maria Dolores, Zennegg, Markus, Haag, Regula, Wichser, Adrian, Schmid, Peter, Seiler, Cornelia, Honegger, Peter, Zeyer, Kerstin, Mohn, Joachim, Bürki, Samuel, Zimmerli, Yan, Czerwinski, Jan, Mayer, Andreas
Source:
Environmental Science & Technology 2015 v.49 no.15 pp. 9273-9279
ISSN:
1520-5851
Subject:
European Union, biofuels, catalysts, diesel fuel, emissions, fatty acid methyl esters, filters, furans, iron, iron oxides, laws and regulations, oxidation, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, potassium, risk, soot, toxicity
Abstract:
Iron-catalyzed diesel particle filters (DPFs) are widely used for particle abatement. Active catalyst particles, so-called fuel-borne catalysts (FBCs), are formed in situ, in the engine, when combusting precursors, which were premixed with the fuel. The obtained iron oxide particles catalyze soot oxidation in filters. Iron-catalyzed DPFs are considered as safe with respect to their potential to form polychlorinated dibenzodioxins/furans (PCDD/Fs). We reported that a bimetallic potassium/iron FBC supported an intense PCDD/F formation in a DPF. Here, we discuss the impact of fatty acid methyl ester (FAME) biofuel on PCDD/F emissions. The iron-catalyzed DPF indeed supported a PCDD/F formation with biofuel but remained inactive with petroleum-derived diesel fuel. PCDD/F emissions (I-TEQ) increased 23-fold when comparing biofuel and diesel data. Emissions of 2,3,7,8-TCDD, the most toxic congener [toxicity equivalence factor (TEF) = 1.0], increased 90-fold, and those of 2,3,7,8-TCDF (TEF = 0.1) increased 170-fold. Congener patterns also changed, indicating a preferential formation of tetra- and penta-chlorodibenzofurans. Thus, an inactive iron-catalyzed DPF becomes active, supporting a PCDD/F formation, when operated with biofuel containing impurities of potassium. Alkali metals are inherent constituents of biofuels. According to the current European Union (EU) legislation, levels of 5 μg/g are accepted. We conclude that risks for a secondary PCDD/F formation in iron-catalyzed DPFs increase when combusting potassium-containing biofuels.
Agid:
5358471