SO deactivation mechanism of NO oxidation and regeneration of the LaCoO perovskite

• Published in: Catalysis science & technology 2020-04, Vol.1 (7), p.2193-222
• Main Authors: Martinovic, Ferenc, Tran, Quang Nguyen, Deorsola, Fabio Alessandro, Bensaid, Samir, Palkovits, Regina, Paulus, Werner, Bonelli, Barbara, Di Renzo, Francesco, Pirone, Raffaele
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/c9cy02478f

The deactivation mechanism and methods to cope with the poisoning by SO 2 of LaCoO 3 perovskite-based NO oxidation catalysts were investigated. The LaCoO 3 perovskite was synthesized by a sol-gel method and the fresh, sulphate-deactivated and regenerated catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H 2 -and soot-temperature programmed reduction, temperature programmed desorption and diffuse reflectance infrared Fourier transform spectroscopy. The SO 2 poisoning strongly affected the NO oxidation activity. It was demonstrated that the deactivation mechanism proceeds in two stages: initially the active sites with a basic character are blocked by SO 3 and subsequently the lanthanum sulphate salts grow progressively on the surface and cobalt is unaffected. Above 500 °C, the surface bound sulphates become mobile and migrate into the bulk of the catalyst. Several prevention and regeneration methods were proposed and tested. By mixing the catalyst with Ca(OH) 2 as an adsorbent nearly 50% of the original activity was retained. Regeneration by diesel soot was presented here for the first time, where the blocking oxygen can spill over to the soot oxidizing it and releasing the bound sulphur as SO 2 and CO 2 . Furthermore, a facile regeneration method was explored by washing the deactivated catalyst to dissolve the small amounts of sulphates on the surface. The deactivation mechanism and methods to cope with the poisoning by SO 2 of a LaCoO 3 perovskite-based NO oxidation catalyst were investigated.