This collaborative research project focuses on investigating the long-term hydrothermal stability of SCR catalysts for the efficient reduction of nitrogen oxides (NOx) in mobile and stationary, greenhouse gas-neutral hydrogen (H2) and ammonia (NH3) lean-burn engines. It is being carried out in close collaboration between the TU Bergakademie Freiberg (TUBAF) and the TU Braunschweig (TU BS). The findings obtained within the scope of the project are expected to make a significant contribution to advancing the development, design, and application of long-lasting exhaust aftertreatment systems for future CO2-neutral powertrains and combined heat and power plants.
To meet legal targets for reducing greenhouse gas emissions, research is increasingly focusing on CO2-free fuels such as H₂ and NH₃ in lean-burn engines. Since their combustion produces nitrogen oxides (NOx), exhaust aftertreatment using selective catalytic reduction (SCR) is absolutely essential. The main problem, however, lies in the exhaust gas composition: due to the hydrogen-rich fuels, the exhaust gas has extremely high water content of over 20 vol.%. It is currently unclear how well established SCR catalysts (VWT, Cu, and Fe zeolites), which were primarily developed for diesel exhaust, can withstand this severe hydrothermal stress, as high temperatures and water content can lead to structural degradation and a significant loss of catalyst performance.
To address this problem, the project combines systematic aging tests in the laboratory with investigations on an actual engine. TUBAF conducts laboratory experiments using synthetic exhaust gases to fundamentally evaluate the aging behavior of various catalyst technologies, while TU BS validates these results through stress tests on an H2 research engine. The main objective is to elucidate the exact aging mechanisms (e.g., structural changes or the leaching of catalyst components). Based on these findings, countermeasures will then be developed, SCR catalysts will be specifically optimized, and stability criteria will be defined to reliably meet current and future ultra-low NOx limits (e.g., (Post-)EU-7) during continuous operation.