Parametric Analysis of Catalytic Converter Plugging Caused by Manganese-Based Gasoline Additives 2007-01-1070
A parametric analysis, based on engine dynamometer tests, was performed to evaluate the influence of exhaust gas temperature, catalyst cell density, exhaust system configuration and the presence of the manganese fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT) in motor fuel on catalytic converter deposits and plugging. Analysis of catalytic converter deposits revealed they consisted mainly of trimanganese tetroxide (Mn3O4), with traces of Ca, P, and Zn. Deposits on catalysts from customer vehicles from Canada, where MMT was known to be in the majority of gasoline in the 1999-2005 timeframe, and from road test vehicles were virtually identical to the catalyst deposits from the engine dynamometer tests.
The engine dynamometer tests were conducted at three different exhaust gas temperatures (600° C, 715° C and 805°C), using two different catalyst cell densities (400 and 600 cells per square inch), and five different angles of incidence of the exhaust gas to the converter inlet surface (30°, 45°, 60°, 75° and 90°). These studies demonstrated that each of those three parameters has a significant influence on catalyst plugging by MMT. Higher cell density and close-coupled catalyst placement are two of the key technologies utilized to meet more stringent exhaust emissions standards that have been, or are being, enacted in many countries. The results demonstrate that these key emission control technologies are more susceptible to plugging from MMT.