Acceleration of Fast-SCR Reactions by Eliminating “The Ammonia Blocking Effect” 2024-37-0001

The recent and future trends of energy for heavy-duty vehicles are considered e-fuel, H2, and electricity, and the Selective Catalytic Reduction (SCR) system is necessary for achieving the goals of zero-emission internal combustion engines that use e-fuel and H2 as a fuel. The Japanese automotive industry uses a Cu-zeolite based SCR catalyst since Vanadium is designated as a specific chemical substance, which the Ministry of Environment prohibits its release into the atmosphere. This study attempted purification rate improvement by controlling the NH3 supply with a mini-reactor and by simulated exhaust gas. Specifically, the experiment was done by examining the effect of the pulse amplitude, frequency, and duty ratio on the purification rate by supplying the NH3 pulse injection to the test piece Cu-chabazite catalyst. Additionally, the results of the reactor experiment were validated by numerical simulation considering the detailed surface reaction processes on the catalyst. The results have shown that the purification of the NOx at lower temperature conditions (200℃) improves from 45% to 62% by doing a pulse supply of reducing agent (NH3) compared to a constant supply. The result of improvement of the purification rate in pulse injection means that during the off time of the pulse supply of the reducing agent, it has promoted the reaction of the decomposition of ammonium nitrate (NH4NO3), which leads to the improvement of the purification rate of NOx. Moreover, the simulation model introduced in this research has indicated that the gas concentration and purification rate in the catalyst and the unique phenomena in the lower temperature range, such as the formation and decomposition of ammonium nitrate and the ammonia-blocking effect, can also be reproduced and simulated.