PCDD/F formation in an iron/potassium-catalyzed diesel particle filter

Area of Science:

• Environmental Science
• Catalysis
• Chemical Engineering

Background:

• Diesel particle filters (DPFs) are crucial environmental technology for reducing particulate matter emissions.
• Fuel-borne catalysts (FBCs) are used to enhance soot combustion and DPF regeneration.
• Iron- and cerium-based FBCs are commercially prevalent, but new formulations are explored.

Purpose of the Study:

• To investigate the effects of a novel iron/potassium (Fe/K)-based FBC on polychlorinated dibenzodioxins/furans (PCDD/F) emissions.
• To assess PCDD/F formation potential under worst-case conditions for DPF approval (VERT protocol).
• To understand the influence of the Fe/K catalyst on the chemical pathways of PCDD/F generation.

Main Methods:

• Evaluation of an uncoated silicon carbide filter with an Fe/K FBC.
• Assessment of PCDD/F emissions under standard and chlorine-spiked fuel conditions.
• Analysis of PCDD/F congeners and TEQ-weighted emissions using VERT protocol standards.

Main Results:

• Low TEQ-weighted PCDD/F emissions were observed with Fe/K FBC and low-sulfur fuel.
• Chlorine addition (10 μg/g) drastically increased TEQ-based PCDD/F emissions 51-fold.
• Emissions of highly toxic congeners 2,3,7,8-TCDD and 2,3,7,8-TCDF increased significantly (320- and 540-fold, respectively), with a preference for tetrachlorinated dibenzofurans.

Conclusions:

• The investigated Fe/K-catalyzed DPF system exhibits a high potential for PCDD/F formation, particularly in the presence of chlorine.
• Potassium's role as a structural promoter, potentially forming magnetite (Fe3O4), may influence iron's catalytic activity and PCDD/F pathways.
• This Fe/K DPF's high PCDD/F formation potential is comparable to prohibited copper-catalyzed filters, raising regulatory concerns.