Synergy of CuNiFe-LDH based catalysts for enhancing low-temperature SCR-C3H6 performance: Surface properties and reaction mechanism

Abstract

A series of SCR-C3H6 catalysts derived from CuxNiyFez-LDHs were synthesized via a modified co-precipitation method. The strong synergy between Ni and Cu promotes the SCR-C3H6 performance at low temperatures. The most active Cu0.18Ni0.49Fe0.33-C catalyst, achieved 61% NO conversion and 86% N2 selectivity at 250 °C under 5% H2O. Several technologies were employed to probe the relationship between performance and structure. XPS and H2-TPR certify the existence of strong synergy between Ni and Cu. XRD, FTIR, and HRTEM, reveal that this strong synergy leads to the presence of CuxNiyFe2O4. As reflected by O2-TPD, the incorporation of Ni increases the ability to activate oxygen, and the strong synergy between Ni and Cu motivates the formation of active oxygen species (O-, Olatt2-). H2-TPR further reveals that this strong synergy enhances the redox properties of catalysts. BET and Py-FTIR respectively demonstrate the enhancement in specific surface area and acidity due to this strong synergy. As confirmed by In situ DRIFTS, monodentate, bidentate, and bridging nitrates, as well as acetates, are active species. Wherein, monodentate nitrates, acetates, together R-NCO are facilitated in the formation, resulting from the synergy between Ni and Cu. Moreover, R-NO2 species appear after incorporating Ni. A possible mechanism of SCR-C3H6 over CuxNiyFez-C catalysts was proposed by the TPSR experiment.