Cold-start and low-temperature emissions challenges

Robert  McCabe, Ford Motor Company

Cold-start emissions and fast catalyst light-off remain the greatest challenge to compliance with emission phase-in plans.  The potential introduction of lower temperature combustion systems can be expected to further aggravate the cold-start challenge in the future.  For diesel engines, even warmed-up exhaust temperatures are marginal for achieving the most stringent emission standards.  Moreover, the recent increase in use of technologies such as direct injection and turbochargers can increase cold-start emissions of species such as hydrocarbons and particulate emissions, while adding turbo thermal lag to catalyst warm-up.  I will review the current status of cold-start and low-temperature emission challenges for both gasoline and diesel engines, summarize our understanding of factors that limit low-temperature catalyst performance, and discuss technologies under consideration for enhancing low-temperature catalyst performance.  While hardware-intensive solutions such as electrically heated catalysts and bypass hydrocarbon traps always remain an option, a stand-alone low-temperature light-off catalyst remains elusive.  40 years of exhaust catalyst research and development still results in three-way catalysts that light off above 200 °C.

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