A Novel One-Step Hydrothermal Preparation of Ru/Sn(x)Ti(1−x)O(2) Diesel Oxidation Catalysts and its Low-Temperature Performance

The rutile Sn(x)Ti(1−x)O(2) (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(x)Ti(1−x)O(2) were then prepared by the impregnation process in RuCl(3) to investigate the performance and stability of CO and C(3)H(8) oxidation. These catalysts were characterized through XRD, N(2) adsorption-desorption, FT-IR, TEM, XPS, H(2)-TPR, and O(2)-TPD techniques. The effect of Sn/Ti molar ratio and hydrothermal condition on the low-temperature catalytic oxidized performance and stability of Ru/Sn(x)Ti(1−x)O(2) were investigated. The results indicated that Ru/Sn(0.67)Ti(0.33)O(2) 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 C(3)H(8) conversion reached 50% at 320 °C, the complete conversion of C(3)H(8) 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(0.67)Ti(0.33)O(2) were attributed to the following factors. Firstly, XRD results showed that Sn(4+) was successfully introduced into the lattice of TiO(2) to replace Ti(4+) forming a homogeneous solid solution (containing –Sn(4+)–O–Ti(4+)– species), which was consistent with TEM and N(2) 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(0.67)Ti(0.33)O(2) support, suggesting that the formation of Sn(x)Ti(1−x)O(2) solid solution was beneficial to the dispersion of Ru particles.