Simultaneous Reduction of Particulate Matter and NO^sub x^ Emissions Using 4-Way Catalyzed Filtration Systems

The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NO... and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NO... and DPM control performance of miniature 4WCFS made from a...

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Bibliographic Details
Published in:Environmental science & technology 2013-05, Vol.47 (9), p.4521
Main Authors: Swanson, Jacob J, Watts, Winthrop F, Newman, Robert A, Ziebarth, Robin R, Kittelson, David B
Format: Article
Language:English
Subjects:
Airborne particulates
Chemical filters
Diesel fuels
Emissions
Nitrogen
Porosity
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Summary:The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NO... and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NO... and DPM control performance of miniature 4WCFS made from acicular mullite, an advanced ceramic material (ACM), that were challenged with diesel exhaust. The impact of catalyst loading and substrate porosity on catalytic performance of the NO... trap was evaluated. Simultaneously with NO... measurements, the real-time solid particle filtration performance of catalyst-coated standard and high porosity filters was determined for steady-state and regenerative conditions. The use of high porosity ACM 4-way catalyzed filtration systems reduced NO... by 99% and solid and total particulate matter by 95% when averaged over 10 regeneration cycles. A "regeneration cycle" refers to an oxidizing ("lean") exhaust condition followed by a reducing ("rich") exhaust condition resulting in NO... storage and NO... reduction (i.e., trap "regeneration"), respectively. Standard porosity ACM 4-way catalyzed filtration systems reduced NO... by 60-75% and exhibited 99.9% filtration efficiency. The rich/lean cycling used to regenerate the filter had almost no impact on solid particle filtration efficiency but impacted NO... control. Cycling resulted in the formation of very low concentrations of semivolatile nucleation mode particles for some 4WCFS formulations. Overall, 4WCFS show promise for significantly reducing diesel emissions into the atmosphere in a single control device. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0013-936X