The role that Methylcyclopentadienyl Manganese Tricarbonyl (MMT) can play in improving low-temperature performance of diesel particulate filters

摘要

Control and elimination of mobil-source particulate matter (PM) emissions is of increasing interest to engineers and scientists as regulators in industrialized countries promulgate lower emission levels in diesel engines. Relative to their gasoline engine counterparts, today's diesel engines, in general, still emit a higher mass of PM. While strictly speaking, this PM is an agglomeration of organic and inorganic particles, the predominant component is carbon and is commonly referred to as "soot." For mobil-source PM control, one of the current preferred technologies is the ceramic closed-cell monolith Diesel Particulate Filter (DPF). Ideally, DPFs accumulate and store PM during low-speed/temperature engine operation and burn the accumulated PM during high-speed/temperature operation. The transition between accumulation and burning is a complex relationship between the amount of stored soot, soot accumulation rate, soot oxidation temperature, exhaust flow rate, exhaust backpressure, and exhaust gas temperature and composition. Lowering the temperature at which the predominantly organic soot oxidizes can have a positive impact on overall engine operation, leading to higher available power and fuel economy, and reduced engine stress. There are several methods for lowering soot oxidation temperature. One method is to employ a separate catalyst prior to the DPF that oxidizes the NO in the exhaust gas to NO{sub}2 promoting soot oxidation at lower temperatures within the DPF. Some manufacturers have chosen to incorporate catalytic metals directly into the DPF substrate. Another method for lowering the soot oxidation temperature in the DPF is the inclusion of metallic catalysts in the fuel. This study evaluates the impact of the manganese- containing fuel additive MMT (Methylcyclopentadienyl Manganese Tricarbonyl) on the performance of a DPF, and a DPF preceded by a catalyst (Continuously Regenerating Technology, or CRT system). MMT, a multifunctional fuel additive used in gasoline and diesel fuel for over 20 years, is demonstrated to have a significant beneficial impact on the rate of soot accumulation within the DPF, and the DPF balance point temperature. These benefits are demonstrated to reduce exhaust backpressure during low-temperature and high-temperature regimes, in both steady state and transient operation.