Experimental Study On Influence Of MMT On Three-way Catalyst

The octane enhancing fuel additive Methylcyclopentadienyl ManganeseTricarbonyl (MMT) is widely used in China to meet market demand for octane in theunleaded gasoline pool, as the use of gasoline of the appropriate octane level iscritical to obtaining optimal vehicle fuel economy. The impact of combustionproducts resulting from the use of MMT-containing gasoline on vehicle emissionscontrol components, including high cell density three-way catalysts, has long beendebated. In order to better understand this issue, a fundamental research program wasundertaken to investigate the interactions of combustion products fromMMT-containing gasoline with high cell density catalysts during severe catalystoperating conditions typical of those used to accelerate catalyst aging for the vehicledurability demonstration process.The paper reports tests conducted to evaluate the influence of engine runningcondition, the absence or presence of MMT (at18mg Mn/L), and the impact ofcatalyst inlet temperatures on deposition phenomena occurring at the catalyst facethat can lead to plugging. Additionally, a1000hour test based upon the type Vdurability procedure was conducted using MMT-containing gasoline (also at18mgMn/L) to evaluate the impact of the additive under longer term exposure conditionsmore representative of those encountered during typical real-world vehicle operation.Results were consistent with the conclusion that plugging was influenced primarilyby the test cycle condition, as plugging was only observed during continuous longterm exposure of catalysts to MMT-containing fuel at the most severe catalyst inlettemperatures (>820C) under steady-state operating conditions. Plugging was notobviously observed under dynamic operating conditions regardless of the MMTconcentration or temperature.