November 1997
WHAT IS THE EFFECT ON AUTOMOBILE EXHAUST EMISSIONS OF CHANGING FUEL SULFUR CONTENT?
Background
Over the past several years, interest in evaluating the effect of fuel sulfur content on motor vehicle emissions prompted the initiation of a number of test programs that focused on advanced technology vehicles. For example, the Coordinating Research Council and the Petroleum Environmental Research Forum conducted programs to test the effect of fuel sulfur content on exhaust emissions control catalysts. These studies generated the question as to how well the results represented "real world" conditions. The present test program provided an opportunity to address this question and related issues.
Scope
Exhaust emissions and catalyst oxygen storage measurements were obtained on four catalysts designed for a 1993 Honda Civic VX Transitional Low Emission Vehicle (TLEV). The measurements were made using two test fuels: (a) a base fuel (a California emissions certification test fuel with a sulfur content of 35 ppm), and (b) the base fuel with the sulfur content spiked to 600 ppm. The four catalysts included: (a) the original catalyst on the vehicle when purchased new; (b) two stock replacement catalysts that had been artificially aged to 100,000 miles on gasolines with 40 ppm and 1000 ppm sulfur, respectively; and (c) a field-aged catalyst obtained from an in-use 1993 Honda Civic VX TLEV with approximately 100,000 odometer miles.
Results
The results showed that: (a) on average, lowering fuel sulfur content from 600 to 35 ppm reduced exhaust emissions measured over the Federal Test Procedure (FTP) by 21 to 27% depending on the pollutant; (b) fuel sulfur content did not have an effect on the long-term emissions performance of catalysts that have been artificially aged; (c) rapid catalyst aging did not have a large effect on sulfur response compared to in-use aging; and (d) gasoline sulfur content did not have a significant effect on catalyst oxygen storage capacity for this catalyst type. The 21 - 27% emissions reduction obtained in this study due to lowering fuel sulfur was about one-half that observed in a previous study using an identical Honda catalyst but in a laboratory setting.
Ordering
Copies of "Vehicle Emissions Testing of Rapidly Aged Catalysts" (Order No.: I46670 Price: $36.00) are available from API's Publications Department (202) 682-8375. Please refer to source code IS3104 when ordering. For information about the research, please contact the HESD Information Specialist at (202) 682-8319.
