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

Abstract

The rutile Sn_xTi_1−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/Sn_xTi_1−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/Sn_xTi_1−xO₂ were investigated. The results indicated that Ru/Sn_0.67Ti_0.33O₂ 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/Sn_0.67Ti_0.33O₂ 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 Sn_0.67Ti_0.33O₂ support, suggesting that the formation of Sn_xTi_1−xO₂ solid solution was beneficial to the dispersion of Ru particles.