Emissions of PCDD/Fs, PCBs, and PAHs from a Modern Diesel Engine Equipped with Selective Catalytic Reduction Filters

Exhaust emissions of seventeen 2,3,7,8-substituted chlorinated dibenzo-p-dioxin/furan (CDD/F) congeners, tetra-octa CDD/F homologues, twelve WHO 2005 chlorinated biphenyls (CB) congeners, mono-nona CB homologues, and nineteen polycyclic aromatic hydrocarbons (PAHs) from a model year 2008 Cummins ISB engine equipped with aftertreatment including a diesel oxidation catalyst (DOC) and wall flow copper or iron urea selective catalytic reduction filter (SCRF) were investigated. These systems differ from a traditional flow through urea selective catalytic reduction (SCR) catalyst because they place copper or iron catalyst sites in close proximity to filter-trapped particulate matter. These conditions could favor de novo synthesis of dioxins and furans. The results were compared to previously published results of modern diesel engines equipped with a DOC, catalyzed diesel particulate filter (CDPF) and flow through urea SCR catalyst. Testing included the use of fuel that contained the maximum expected chlorine concentration of United States' (U.S.) highway diesel fuel. Results indicate there is no risk for an increase in polychlorinated dibenzo-p-dioxin/furan and polychlorinated biphenyl emissions from modern diesel engines with wall flow urea SCRF catalysts when compared to flow through urea SCR catalysts for the configurations tested in this program. These results, along with PAH results, compare well with results from other modern diesel engines in the literature.