Effect of Ceramic Monolith Particulate Filters on Diesel Exhaust Odorant and Irritant Species

Ceramic monolith particulate filters were evaluated for reduction of odor and irritant species in diesel exhaust. Three types of diesel particulate filters (DPF's) were tested: high efficiency catalyzed and uncatalyzed, and mid efficiency uncatalyzed. Testing was done with a single cylinder CFR diesel test engine run under steady-state conditions at low, mid and high equivalence ratios. Exhaust was sampled immediately upstream and downstream of the DPF's and analyzed on liquid chromatographs. The odorant species analyzed were oxygenated hydrocarbons (oxygenates), measured using the DOAS methodology. The irritant species analyzed were Cl to C5 aldehydes, measured using a DNPH reagent method. The high efficiency catalyzed DPF reduced exhaust oxygenate concentrations about 30% at low and mid equivalence ratios, which was the only substantial oxygenate reduction seen. However, this corresponds to only a slight reduction in perceived diesel odor intensity, due to the logarithmic dependence of TIA (total intensity of aroma) on oxygenate concentration. None of the measured exhaust aldehydes were affected by the DPF's.