Cu- and Pd-substituted nanoscale Fe-based perovskites for selective catalytic reduction of NO by propene

A series of Fe-based perovskites with high specific surface area was prepared by a new method, reactive grinding, and characterized by N2 adsorption, XRD, SEM, H2-TPR, TPD of O2, TPD of NO + O2, TPD of C3H6, and TPSR of NO + O2 under C3H6/He flow. These materials were then subjected to activity tests in the selective catalytic reduction of NO by propene. The catalytic performance over LaFeO3 is poor but can be improved significantly by incorporating Cu into its lattice, resulting in N2 yields over LaFe0.8Cu0.2O3 of 81% at 450 °C and 97% at 700 °C with a reactant mixture containing 3000 ppm NO, 3000 ppm C3H6, and 1% O2 in helium at a space velocity of 50,000 h−1. The enhanced NO reduction after Cu substitution is attributed to the easy formation of nitrate species, which have high reactivity toward C3H6. A mechanism was proposed with the formation of nitrate species as the first step and organo nitrogen compounds as important intermediates. Great catalytic performance at low temperature was also achieved over LaFe0.97Pd0.03O3 with a N2 yield of 67% and C3H6 conversion of 68% at 350 °C corresponding to the outstanding redox properties of this catalyst. O2 can act as a promoter to oxidize NO into strongly adsorbed nitrate species, and also can accelerate the transformation of organo nitrogen compounds and isocyanate to get the desired products. In contrast, at higher concentrations O2 has a detrimental effect, leading to consumption of the reducing agent by the complete oxidation of C3H6.