Air Injection to an Electrically-Heated Catalyst for Reducing Cold-Start Benzene Emissions from Gasoline Vehicles 902115
This paper describes the laboratory effort to determine the emissions benefit of cold-start air injection to a preheated automotive catalyst. Previous experimentation with an electrically-heated catalyst on a gasoline-fueled vehicle with no supplemental air showed little improvement in hydrocarbon emission control.
In this study, air was injected ahead of an electrically-heated catalyst during cold-start operation. Analysis of continuously recorded raw exhaust emissions were used to determine air injection calibrations and oxidation-reduction trade-offs. Improved control of non-methane hydrocarbons (NMHC), benzene, and carbon monoxide (CO) emissions was observed. Nitrogen oxides (NOx) emission control was maintained by the use of a carefully controlled air injection flow-rate and schedule.
This study determined that heating an auto-motive exhaust emission catalyst prior to cold-start operation may not be sufficient in itself. Supplemental oxygen may be required for improved emissions control. Finally, it was demonstrated that the gasoline vehicle used in this study, equipped with an electrically-heated catalyst and air injection, provided FTP emission rates of non-methane organic gases (NMOG), CO, and NOx near or at the California standards for the ultra-low emission vehicle (ULEV).