Revealing of alternative pathway for C3H8-SCR over specific Cu species on the MFI topology via experimental and computational studies

Selective catalytic reduction of NOx with propane (C3H8-SCR) on Cu-zeolite aims to advance the development of more sustainable deNOx technologies. Cu-ZSM-5 catalysts with specific Cu species exhibited remarkable deNOx efficiency with over 95 % at 350 °C. Interestingly, the TPSR and in situ FTIR studies indicated an alternative pathway for C3H8-SCR without -NCO or R-CN species. Characterizations (H2-TPR, EPR, NO-TPD, and C3H8-TPD etc.) and DFT calculations imply those Z[CuOH]-10R-12T were identified as the active sites for the reaction. Further DFT studies investigating the new pathway involving the Cu motif reveal that the activation and dehydrogenation of C3H8 occur on Cu2+-NO3, leading to the production of allyl species. It proved that CH2CHCH2NO, CH2CHCONH2, and CH2CHCOOH were the key intermediates during the reaction. This process circumvents NCO or NH3 species while demonstrating a reduced activation barrier. Based on these findings, C3H8-SCR process over the specific Cu2+ ions was established and the rate determining step of the mechanism was clarified. This investigation elucidates the structure-activity relationship between specific Cu species and reaction mechanisms while revealing novel reaction pathways for C3H8-SCR through in situ characterization and DFT calculations. This study paves the way for Cu-zeolites for HC-SCR applications.