Sulfur poisoning and hydrothermal aging effects on a Cu-SSZ-13 selective catalytic reduction (SCR) catalyst

Yu-Ren  Chen, University of Virginia

Cu-SSZ-13 catalysts are widely used for selective catalyst reduction (SCR) to reduce NOx. However, they still suffer from sulfur poisoning and hydrothermal aging. Literature shows that mild hydrothermal aging does not affect the zeolite structure, but changes the Cu distribution from ZCuOH to Z2Cu. Literature also shows that ZCuOH sites have better oxidation activity than Z2Cu sites. This caused the catalyst’s oxidation activity to decrease after mild hydrothermal aging. Our experimental data show that such mild hydrothermal aging can protect the catalysts from SO₂ poisoning, but not from SO₃ poisoning. Analyzing results from experiments with different SO₂ exposure temperatures and O₂ concentrations during the SO₂ those exposure suggests that the sulfur poisoning effect follows the trend in the catalyst’s oxidation activity. This indicates that the catalyst oxidation activity is related to the severity of sulfur poisoning, likely through SO₂ oxidation to SO₃ and SO₃ being the primary poison.

Download Presentation: