Sulfur poisoning and regeneration of NO_x storage-reduction Cu/K₂Ti₂O₅ Catalyst

A new Cu/K₂Ti₂O₅ catalyst has been developed recently to remove NO_x through the NO_x storage-reduction (NSR) process. However, its NSR performance in the presence of sulfur has not been investigated. In this article, the sulfur poisoning of the NO_x storage-reduction catalyst Cu/K₂Ti₂O ₅ and the corresponding deactivation mechanisms are reported for the first time. The effect of the sulfur concentration, adsorption/regeneration cycling tests, and temperature-programmed regeneration are studied. At low temperatures, the poisoning effect is negligible when the SO₂ concentration is lower than 20 ppm, and the sulfated samples can be easily regenerated by 3.5% H₂ at 550 °C. However, at high temperatures, the sulfur species are adsorbed on K⁺ sites to form K ₂SO₄ and, consequently, induce a structure transformation from K₂Ti₂O₅ to K₂Ti ₆O₁₃ nanoparticles. The structural change is reversible, and the sulfated catalyst can be regenerated by hydrogen at 650-700 °C.