To counter the adverse impact on the formation of harmful unregulated emissions such as nitro-polycyclic aromatic hydrocarbons (NPAH), catalyst companies and researchers have been developing catalytic coatings that have the capability of suppressing the formation of NO2. NO2 is formed at low exhaust temperatures with potentially greater concentrations at part load engine operation. Haldor Topsoe, a catalyst company from Denmark, developed such a catalytic coating for DPFs. A sample was provided to Southwest Research Institute (SwRI) to conduct this research with a view of potentially improving NO2-suppressing formulations in the future.
The Haldor Topsoe diesel particulate filter (DPF) with its novel coating was tested together with three other DPFs and the results confirmed the capability of this DPF to suppress the formation of NO2. This characteristic was apparent in all five engine test modes selected to cover the full engine operating range. On average, the NO2 reduction when the exhaust flowed through the DPF was 55 percent from the engine-out levels for all five engine operating modes. This result contrasts with 39, 15, & - 66 percent for the bare DPF, 0.88g/l, and 1.77g/l Pt coated DPFs, respectively.
