This report includes a literature search to determine possible reactions involving sulfur in automotive exhaust systems, an assessment of the effect of various operating parameters (i.e. exhaust oxygen level) on the level of sulfate emissions, and a feasibility study on the use of sorbents as traps to eliminate sulfate from the exhaust gas before release to the atmosphere. It was discovered in the study that exhaust oxygen level and catalyst age were major variables affecting level of sulfate emissions. Other variables, such as noble metal composition, noble metal loading, catalyst temperature and residence time of the exhaust gas over the catalyst had little or no significant effect on sulfate emissions. It was also discovered that only calcium based materials (such as calcium oxide) removed sulfate efficiently enough with little physical degradation during laboratory testing of potential sorbents. Vehicle tests using the most promising sorbents as traps showed high sulfate removal but with unacceptably high exhaust back pressures.

Contract 68-03-0497. "May 1976." "EPA/460-3-76-017." Includes bibliographical references.