A Novel One-Step Hydrothermal Preparation of Ru/SnxTi1−xO2 Diesel Oxidation Catalysts and its Low-Temperature Performance

Abstract

The rutile SnxTi1−xO2 (x = 0, 0.33, 0.5, 0.67, 1) solid solution was synthesized by a one-step hydrothermal method, in which tetrabutyl titanate and Tin (IV) chloride pentahydrate were used as raw materials. A series of Ru/SnxTi1−xO2 were then prepared by the impregnation process in RuCl3 to investigate the performance and stability of CO and C3H8 oxidation. These catalysts were characterized through XRD, N2 adsorption-desorption, FT-IR, TEM, XPS, H2-TPR, and O2-TPD techniques. The effect of Sn/Ti molar ratio and hydrothermal condition on the low-temperature catalytic oxidized performance and stability of Ru/SnxTi1−xO2 were investigated. The results indicated that Ru/Sn0.67Ti0.33O2 catalyst showed an excellent activity and stability at low temperatures. The CO conversion reached 50% at 180 °C and 90% at 240 °C. Besides, the C3H8 conversion reached 50% at 320 °C, the complete conversion of C3H8 realized at 500 °C, and no deactivation occurs after 12 h of catalytic reaction. The excellent low-temperature activity and stability of the Ru/Sn0.67Ti0.33O2 were attributed to the following factors. Firstly, XRD results showed that Sn4+ was successfully introduced into the lattice of TiO2 to replace Ti4+ forming a homogeneous solid solution (containing –Sn4+–O–Ti4+– species), which was consistent with TEM and N2 adsorption-desorption results. The introduction of Sn could suppress the growth of anatase crystal and promote the formation of rutile phase, and this phase transition was helpful to improve the low-temperature activity of the catalysts. Secondly, TEM images showed that ultrafine Ru nanoparticles (~ 5 nm) were dispersed on Sn0.67Ti0.33O2 support, suggesting that the formation of SnxTi1−xO2 solid solution was beneficial to the dispersion of Ru particles.