Technical Submission: Automotive Sulfate Emissions

This document presents data generated by Exxon Research and Engineering Company on factors affecting the emission of sulfates from vehicles equipped with oxidation catalysts. The major findings are: (1) Under federal test procedure (FTP) conditions monolithic catalysts emit about 10-15% of the sulfur in gasoline as sulfate. This is lower than the 25-35% emission rate previously reported by Exxon Research based on preliminary measurements on prototype catalysts. (2) Under FTP conditions pelleted catalysts emit about 5-10% of the sulfur in gasoline as sulfate. This value is in agreement with earlier findings. (3) Under high speed (60-70 mph) cruise conditions both types of catalyst emit about 25-35% of the sulfur in gasoline as sulfate, again in agreement with earlier findings. (4) Storage of SO₂, SO₄, or both on catalyst surfaces occurs with both types of catalyst and accounts for many of the differences in SO₄ emission rates observed. (5) Significant differences exist between the amount of SO₄ emitted from nominally similar monolithic catalysts. Catalysts from one manufacturer emitted less SO₄ under certain conditions and also stored less sulfur oxide than did nominally similar catalysts manufactured by another. The reasons for these differences are unknown. (6) Reducing the amount of excess air used over a catalyst significantly lowers SO₄ emissions. Removing air pumps could lower SO₄ emissions by 50-75% in pelleted catalyst systems. (7) CaO was demonstrated to be effective in removing SO₄ from exhaust, but trapping SO₂ and SO₄ causes the sorbent to swell and unacceptable back pressure buildup occurs.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 64p

Subject/Index Terms

Filing Info

  • Accession Number: 01539415
  • Record Type: Publication
  • Report/Paper Numbers: EPA420-R-75-001
  • Contract Numbers: 68-03-0497; 68-02-1279
  • Files: TRIS
  • Created Date: Jul 28 2014 9:53AM