The Interaction of MMT® Combustion Products with the Exhaust Catalyst Face

Since the introduction of the catalytic converter, some automobile manufacturers have questioned whether the converter is compatible with the use of the gasoline fuel additive MMT®. Concerns have generally revolved around possible interactions between combustion products of MMT® (i.e., manganese containing compounds) and catalytic converters. In particular, concern has been raised over the possibility that MMT® combustion products physically “plug” the catalyst and cause catalyst failure, where plugging refers to blockage of contiguous pores at the catalyst inlet face or within the body of the converter. In modern vehicles this could result in the illumination of the malfunction indicator light (MIL) due to storing of an on-board diagnostic (OBD) failure code pertaining to catalyst operation or failure of a vehicle inspection and maintenance (I/M) test. In this paper, work that advances the fundamental understanding of the interactions between MMT® combustion products and monolithic automotive catalysts is presented. Specific emphasis is placed on evaluating the physical interaction between the combustion products of MMT® and catalysts of the type used on vehicles with the most advanced emission control systems (i.e., Tier II or Euro IV vehicles).