A Preliminary Evaluation of Unregulated Emissions During Low Temperature Operation of a Small Diesel Engine with a Multi-Function SCR Catalyst

Ammonia (NH₃) slip from the selective catalytic reduction (SCR) of NO_x process using urea or NH₃ is a rather unavoidable phenomenon especially when the operation temperature is relatively low, or a sudden change in load is observed. As a possible solution to this issue, a unique vanadium-free titania-based SCR catalyst, which can treat excess NH₃ within itself, was examined its capability to destroy NH₃ slip from SCR catalysts using small diesel engine test equipment. With this unique SCR catalyst, a relatively to considerably high conversion rate of NH₃ was achieved even at 175-200°C. Compared with this, a conventional oxidation catalyst as an NH₃ slip control device showed poor performance in NH₃ conversion at the same temperature range. Further, at higher temperatures, the conventional oxidation catalyst produced a considerable amount of nitrous oxide (N₂O), while the multi-function SCR catalyst could prevent N₂O formation almost completely or suppress to a significantly low level.