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

Abstract

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.

Deciphering the Nature of Ru Sites in Reductively Exsolved Oxides with Electronic and Geometric Metal–Support Interactions

“…Core-level Ru 3d spectra feature a doublet corresponding to the Ru 3d 5/2 and Ru 3d 3/2 states due to spin–orbit splitting. Calcined Sm 2 Ru 0.2 Ce 1.8 O 7 exhibits two deconvolved Ru 3d 5/2 core peaks at binding energies (BE) of 282.5 and 281.4 eV, corresponding to the Ru 4+ state and Ru in a lower oxidation state, denoted as a Ru δ+ state. − We note that a Ru δ+ state with a BE of 281.4 eV has been ascribed previously to Ru 2+ cationic species. ,, Notably, in comparison to Ru K-edge XANES (i.e., a bulk probe used at 1 bar), a higher fraction of surface Ru δ+ species was detected by XPS analysis. This difference can be explained by the surface sensitivity (sampling depth, ca.…”