title: Effects of a combined Diesel particle filter-DeNOx system (DPN) on reactive nitrogen compounds emissions: a parameter study.
abstract: The impact of a combined diesel particle filter-deNO(x) system (DPN) on emissions of reactive nitrogen compounds (RNCs) was studied varying the urea feed factor (α), temperature, and residence time, which are key parameters of the deNO(x) process. The DPN consisted of a platinum-coated cordierite filter and a vanadia-based deNO(x) catalyst supporting selective catalytic reduction (SCR) chemistry. Ammonia (NH₃) is produced in situ from thermolysis of urea and hydrolysis of isocyanic acid (HNCO). HNCO and NH₃ are both toxic and highly reactive intermediates. The deNO(x) system was only part-time active in the ISO8178/4 C1cycle. Urea injection was stopped and restarted twice. Mean NO and NO₂ conversion efficiencies were 80%, 95%, 97% and 43%, 87%, 99%, respectively, for α = 0.8, 1.0, and 1.2. HNCO emissions increased from 0.028 g/h engine-out to 0.18, 0.25, and 0.26 g/h at α = 0.8, 1.0, and 1.2, whereas NH₃ emissions increased from <0.045 to 0.12, 1.82, and 12.8 g/h with maxima at highest temperatures and shortest residence times. Most HNCO is released at intermediate residence times (0.2-0.3 s) and temperatures (300-400 °C). Total RNC efficiencies are highest at α = 1.0, when comparable amounts of reduced and oxidized compounds are released. The DPN represents the most advanced system studied so far under the VERT protocol achieving high conversion efficiencies for particles, NO, NO₂, CO, and hydrocarbons. However, we observed a trade-off between deNO(x) efficiency and secondary emissions. Therefore, it is important to adopt such DPN technology to specific application conditions to take advantage of reduced NO(x) and particle emissions while avoiding NH₃ and HNCO slip.
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Testing and Research, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland. norbert.heeb@empa.ch
authors.forename: Norbert V
authors.initials: NV
authors.lastname: Heeb
authors.forename: Regula
authors.initials: R
authors.lastname: Haag
authors.forename: Cornelia
authors.initials: C
authors.lastname: Seiler
authors.forename: Peter
authors.initials: P
authors.lastname: Schmid
authors.forename: Markus
authors.initials: M
authors.lastname: Zennegg
authors.forename: Adrian
authors.initials: A
authors.lastname: Wichser
authors.forename: Andrea
authors.initials: A
authors.lastname: Ulrich
authors.forename: Peter
authors.initials: P
authors.lastname: Honegger
authors.forename: Kerstin
authors.initials: K
authors.lastname: Zeyer
authors.forename: Lukas
authors.initials: L
authors.lastname: Emmenegger
authors.forename: Yan
authors.initials: Y
authors.lastname: Zimmerli
authors.forename: Jan
authors.initials: J
authors.lastname: Czerwinski
authors.forename: Markus
authors.initials: M
authors.lastname: Kasper
authors.forename: Andreas
authors.initials: A
authors.lastname: Mayer
mesh_terms: D002384:Catalysis; D004777:Environment; D005374:Filtration / Q000295:instrumentation*; D005742:Gasoline / Q000032:analysis*; D009566:Nitrates / Q000032:analysis*; D009569:Nitric Oxide / Q000032:analysis; D009573:Nitrites / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry*; D026361:Reactive Nitrogen Species / Q000032:analysis*; D013696:Temperature; D013997:Time Factors; D019415:Torque; D014508:Urea / Q000737:chemistry; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D005742:Gasoline; D009566:Nitrates; D009573:Nitrites; D052638:Particulate Matter; D026361:Reactive Nitrogen Species; D001335:Vehicle Emissions; D009569:Nitric Oxide; D014508:Urea