title: Simultaneous reduction of particulate matter and NO(x) emissions using 4-way catalyzed filtration systems.
abstract: The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NOx and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NOx 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 NOx trap was evaluated. Simultaneously with NOx 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 NOx 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 NOx storage and NOx reduction (i.e., trap "regeneration"), respectively. Standard porosity ACM 4-way catalyzed filtration systems reduced NOx 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 NOx 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.
authors.affiliation: University of Minnesota, Department of Mechanical Engineering, 111 Church Street SE, Minneapolis, Minnesota 55455, USA. js2011@cam.ac.uk
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Swanson
authors.forename: Winthrop F
authors.initials: WF
authors.lastname: Watts
authors.forename: Robert A
authors.initials: RA
authors.lastname: Newman
authors.forename: Robin R
authors.initials: RR
authors.lastname: Ziebarth
authors.forename: David B
authors.initials: DB
authors.lastname: Kittelson
mesh_terms: D000336:Aerosols; D002384:Catalysis; D005374:Filtration / Q000379:methods*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000336:Aerosols; D009589:Nitrogen Oxides