Thermal deactivation mechanism and the effect of Nd addition on the deactivation of the Pt/SiO2 catalyst for NO oxidation reaction

Abstract

Pt-based catalysts cannot be used permanently for the diesel after-treatment system because the catalytic activity is decreased due to coarsening of Pt particles at high temperature of the exhaust gas. In this study, to prevent Pt-based catalyst from deactivation, Nd was added to the Pt/SiO2 catalyst, and the effect of the Nd addition on the catalytic activity was investigated. The Pt/SiO2 catalyst showed a high catalytic activity for the oxidation of NO but was severely deactivated after the fast thermal aging process. Pt crystallite size was increased and some Pt particles were buried in the SiO2 pore during the fast thermal aging process, which led to the decrease of catalytic activity. Nd-added Pt/SiO2 catalyst showed lower activity than Pt/SiO2 catalyst, but Pt–Nd/SiO2 catalyst maintained its catalytic activity after fast thermal aging process. It can be postulated that a stable Nd silicate, on which Pt particle is placed, protects SiO2 pores from destruction and so the number of the catalytically active sites remains nearly unchanged. As a result the Pt–Nd/SiO2 catalyst maintained its catalytic activity after fast thermal aging process.