Characterization of Field Deterioration in V-Based SCR Catalysts Retrieved from an Operating Marine Vessel

Marine selective catalytic reduction (SCR) systems are widely used to comply with stringent NOx emission limits, yet the long-term deterioration of catalysts under traceable real-world ship operation remains insufficiently documented. In this study, V-based SCR catalysts were recovered from the generator-engine SCR system of the training ship T/S SEGERO after approximately 1000 and 3600 h of actual vessel operation and compared with a fresh reference. The field-aged catalysts were evaluated by visual inspection, pressure-drop measurements, SEM–EDS, ICP-OES, N2 physisorption, and laboratory NH3-SCR activity testing. After 3600 h, localized carbonaceous and inorganic deposits were observed together with an approximately 9–18% increase in pressure drop relative to the fresh catalyst. Ca, P, and Zn accumulation increased with field exposure, while Ca and S showed spatial co-localization at the catalyst surface. The BET surface area decreased by approximately 10% after 1000 h and 35% after 3600 h. Relative DeNOx activity remained close to that of the corresponding fresh reference after 1000 h but was lower after 3600 h, with mean reductions of 8.3–13.3% in the first layer and 2.0–5.9% in the second layer across 300–400 °C. These results demonstrate the value of a training vessel as a traceable longitudinal platform for linking marine operating history with catalyst deterioration.