Support-Induced Effects of LaFeO₃ Perovskite on the Catalytic Performances of Supported Pt Catalysts in DeNO_<i>x</i> Applications

Abstract

A comparative investigation of the catalytic performance in the simultaneous conversion of NO x and N 2 O has been achieved on supported nanosized Pt particles interacting with conventional alumina and perovskite based materials. Particular attention has been paid to successive thermal treatments under reductive and oxidative atmospheres which induce bulk and surface reconstructions. Those modifications considerably alter the catalytic behavior of Pt in interaction with LaFeO 3 or γ-Al 2 O 3 in terms of activity and selectivity toward the selective transformation of NO x to nitrogen at low temperature. Changes in physicochemical properties have been examined using appropriate techniques, such as H 2 -temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) of CO adsorption. It has been found that oxidic Pt 4+ species initially stabilized on LaFeO 3 lead after subsequent H 2 reduction to the formation of metallic nano-Pt particles in stronger interaction than on γ-Al 2 O 3 support and then become more resistant to sintering during thermal aging in 1000 ppm NO, 1000 ppm N 2 O, 3 vol % O 2, 0.5 vol % H 2 O, and 0.5 vol % H 2 at 500 °C. Correlatively, significant improvements have been observed in the selective reduction of NO x to nitrogen. This study opens new prospects in the development of supported catalysts containing low Pt loadings because of the existence of stronger interactions with perovskite supports.