A Comparative Study of Platinum- Versus Palladium-Based Catalysts on FeCrAl-Sintered Metal Fiber Filter Substrate for Reducing Gaseous Diesel Engine Emissions

This study aims to evaluate and compare the performance of platinum- versus palladium-based catalysts on a sintered metal fiber substrate made of FeCrAl alloy. The target application of these catalysts is an active diesel particulate filter (ADPF) using electrically heated filter cartridges that contain pleated sintered metal fiber filter elements. The coating of the platinum- and palladium-based catalysts on the sintered metal fibers starts with applying an aluminum and yttrium oxide nano-washcoat as a base, followed by tungsten and platinum or palladium topcoats. Elemental EDS layer mapping shows uniform distributions of aluminum, tungsten, platinum, and palladium on the fibers’ surface. Experimental investigations were performed to measure the diesel emissions of two identical ADPFs coated with these two catalysts. The objective is to compare the emission reductions using the off-road steady-state (8-mode C1) and the heavy-duty federal transient (US HD FTP) test cycles. The emission measurements show that platinum-based catalysts efficiently reduce carbon monoxide and hydrocarbons and keep the engine back pressure low compared to palladium-based catalysts. However, the platinum-based catalysts increased the NO₂ of the composite emissions for the 8-mode C1 and US HD FTP test cycles by 163% and 93%, respectively. On the other hand, the palladium-based catalysts are very efficient in reducing NO₂ to near-zero emissions.