The Influence of RuO₂Distribution and Dispersion on the Reactivity of RuO₂−SnO₂Composite Oxide Catalysts Probed by CO Oxidation

Abstract

To elucidate the distribution and dispersion of RuO2 species on the reactivity, RuO2−SnO2 catalysts with 2 % and 5 % Ru contents have been prepared with impregnation (IMP), deposition‐precipitation (DP) and co‐precipitation (CP) methods, and probed by CO oxidation. With IMP and DP methods, RuO2 crystallites are predominantly formed on the catalyst surface, which is favorable for CO oxidation. Moreover, the IMP catalyst possesses surface RuO2 having smaller mean crystallite size and better dispersion than the DP catalyst, thus SnRuO‐IMP displays higher activity than SnRuO‐DP at the same Ru loadings. However, with CP method, RuO2 species is mainly present as Ru4+ cations in the lattice of rutile SnO2 to form a solid solution structure below the lattice capacity, which is less reactive than the surface RuO2 due to the restriction by the SnO2 lattice. In conclusion, surface RuO2 is revealed to be the active species, whose amount and dispersion determine the activity of the catalysts. By changing preparation methods, the distribution of RuO2 species in the catalysts is varied and impacts the reactivity of the catalysts evidently. The traditional impregnation is found to be the best method to prepare RuO2−SnO2, which shows the highest activity among all the catalysts.

Identifying Surface Active Sites of SnO2: Roles of Surface O2–, O22– Anions and Acidic Species Played for Toluene Deep Oxidation

“…The α peak is related to the reduction of facially bonded active deficient oxygen on tin oxide surface, and the higher-temperature β peak is related to the reduction of SnO 2 lattice oxygen, which results finally into metallic Sn. 56 Indeed, the fully reduction of SnO 2 into Sn 0 can also be supported by the quantified H 2 consumption quantity of the β peak in Table S2, which is in line with the theoretical H 2 uptake value of 13.2 mmol g −1 for SnO 2 fully reduction within °C lower-temperature region, proving that the lattice oxygen of these two samples becomes more facile and reducible, possibly due to their higher surface area and more abundant porous structure.…”

Preparation, Characterization and CO Oxidation Performance of Ag2O/γ-Al2O3 and (Ag2O+RuO2)/γ-Al2O3 Catalysts

“…Three peak regions were observed for SLOAL such as 100-220 • C, around 300 • C, and T max at around 380 • C. Those peaks corresponded to the reduction of small-sized silver oxides and well-dispersed oxide phases [39] and the T max represents the reduction of the bulk oxide phase (from Ag 2 O to metallic Ag) of the sample, which is size dependent (bigger particle size for SLOAL). For RUOAL, the low-temperature peak at 150 • C and high-temperature peaks at 200 and 370 • C represent the reduction of surface RuO 2 crystallite [40], small-sized particles, and bulk reductions of rod structures [7], respectively. The mixed catalyst exhibited a shift in the peak towards lower temperature and a slight shift to high temperature as compared to RUOAL.…”

Elucidating Ru Distribution State of Ru‐Promoted Pr2Sn2O7 Pyrochlore and its Effect on the Catalytic Performance for Toluene Deep Oxidation

“…Therefore, this could be another strong evidence to validate that Ru 4+ cations have been doped into the Pr 2 Sn 2 O 7 lattice and partially substituted the Sn 4+ cations at B‐site. Notably, an additional shoulder peak around 475 cm −1 is also observed for these two samples, which belongs to the E g mode of the residue SnO 2 phase, [13] as detected by XRD.…”