Synergistic Mechanism for Simultaneous Abatement of Nitrous Oxide and Multi-Pollutants over Fe-Beta Catalysts in P-Phenylenediamine Production Tail Gas

Abstract

The production of p-phenylenediamine caused abundant emission of the greenhouse gas N2O, which has not yet received much attention. This study tackles the significant yet overlooked N2O emissions by developing a synergistic catalytic system for simultaneous purification of N2O and co-pollutants (NO, CH3OH, H2) in tail gases. Among transition metal (Fe, Cu, Co)-modified zeolites, 1%Fe-Beta demonstrated superior activity for integrated pollutant removal, achieving complete N2O conversion at 400°C under an NH3 + CH3OH + O2 reaction system. Mechanistic investigations (TPSR, in situ FTIR, TPD, and DFT analyses) revealed that N2O was activated as NN-O-Z over the Fe-Beta under the reaction atmosphere of NH3 + N2O + O2; however, the introduction of CH3OH switches the predominant cleavage pathway from the N-O bond to the N-N bond, leading to the formation of a Z-ONN species. The nitrogen atom from the -NNO moiety then combines with CH3OH to form a formamide intermediate (HCONH2), which plays a vital role in enhancing the deN2O performance. Furthermore, the presence of NH3 opens a lower-energy route for the formation of the key formamide intermediate by facilitating N-O bond cleavage in N2O. This synergistic mechanism enhances the low-temperature conversion efficiency of N2O. DFT calculations further confirm the presence of NH3 reduces the energy barrier during the reaction process, with the Z2[Fe-O-Fe] binuclear site serving as the primary center for N2O adsorption and activation. This study elucidates the dual activation pathways and synergistic mechanism of N2O under complex reaction conditions, providing new strategies and a theoretical basis for the synergistic control of multiple pollutants in industrial waste gases. The demonstrated effectiveness of 1%Fe-Beta highlights its potential for practical greenhouse gas mitigation, bridging fundamental catalytic insights with environmental engineering applications. KEYWORDS: N2O; Simultaneous purification; P-phenylenediamine; Methanol; Synergistic effect; DFT calculations