An investigation of the role of Zr and La dopants into Ce 1− x− yZr xLa yO δ enriched γ-Al 2O 3 TWC washcoats

Abstract

This work involves the synthesis of composite three-way catalytic (TWC) washcoats consisting of 80 wt% of γ-alumina as the main supporting material, promoted with 20 wt% of ceria based solid solution. Pt in low loading (0.5 wt%) was employed as the only active phase. Washcoats varying in the solid solution composition (Ce x Zr y La z O δ ), prepared by coprecipitation, are comparatively investigated in an attempt to elucidate the effect of Ce, Zr and La oxide promoters on the catalytic activity and thermal durability. For this purpose, catalytic activity measurements as well as detailed structural and morphological evaluations (differential thermal analysis (DTA), X-ray diffraction (XRD), N 2 adsorption, oxygen storage capacity and DRIFTS analyses) were carried out before and after thermal aging in oxidative atmosphere. The catalytic performance was studied in loaded cordierite monoliths (TWCs form) under simulated exhaust conditions at the stoichiometric point. Doping ceria with Zr and La cation proved beneficial for both catalytic performance and thermal durability of the washcoat, with Ce 0.4Zr 0.5La 0.1O 1.9/γ-Al 2O 3/Pt sample presenting the optimum properties. The catalytic behavior is discussed based on oxygen storage capacity, noble metal dispersion and textural characteristics of the examined samples.