Study on ceria-modified SnO2 for CO and CH4 oxidation

Tetragonal Rutile SnO2 Solid Solutions for NOx-SCR by NH3: Tailoring the Surface Mobile Oxygen and Acidic Sites by Lattice Doping

“…Figure 6 depicts that individual SnO 2 displays a big reduction peak at 667 °C ascribed to the reduction of Sn 4+ to Sn 0 . 18,20 After forming a solid solution structure with the other metal cations, this peak of all the samples shifts evidently to lower temperatures, proving that the lattice oxygen becomes more reducible. It is mentioned here that SnCu9-1 shows two low temperature peaks positioned at 142 and 219 °C, which correspond to the stepwise reduction of Cu 2+ cations in the lattice into metallic Cu; 17 SnW9-1 shows also an extra peak at 860 °C, which belongs to the reduction of W 6+ cations in the solid solution lattice into metallic W. 35 For all the catalysts, except for the major reduction peak, a shoulder peak below 400 °C is detected also, which pertains to the reduction of the surface facile oxygen species over the catalysts.…”

“…Its lattice oxygen can also be reduced easily and involved in redox reactions. Furthermore, SnO 2 has both excellent thermal and physical chemical stability because of it high melting point at 1630 °C. − Our previous studies have demonstrated that a bunch of metal cations − can enter into the crystal structure of rutile SnO 2 to generate noncontinuous solid solutions, which can stabilize the specific surface areas and the metastable surface deficient oxygen sites at higher temperature, hence achieving catalysts with evidently enhanced reaction performance. To understand deeper the relationship between reactivity and structure of solid solution catalysts, a simple and feasible XRD extrapolation method has been developed by our group for the first time to quantify the lattice capacity of different cations in SnO 2 matrix recently. , …”

Enhancement of resistance to chlorine poisoning of Sn-modified MnCeLa catalysts for chlorobenzene oxidation at low temperature

“…Compared to fresh MnCeLa, the diffraction peak of fresh Sn-MnCeLa become less intense and shi to higher Bragg angles, from 32.9 to 33.3 , indicating that part of Sn species can enter the uorite lattice to form SnCeO x solid solutions. 28 This result is because the ionic radius of Sn 4+ (0.071 nm) is smaller than that of Ce 4+ (0.094 nm), and the incorporation of Sn 4+ into the uorite lattice will result in the decrease in lattice parameters. These very low intensity reections of Sn-MnCeLa catalysts conrm that the crystallinity of the samples can signicantly decrease due to Sn doping, 29 which is better illustrated by the XRD patterns of different Sn amounts of Sn-MnCeLa catalysts in Fig.…”

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

“…Our group has been performing systematic research on SnO 2 catalysis over the past nine years for different reactions. − It is discovered that the abundance and mobility of the surface deficient oxygen anions are very important for the catalytic activity, whereas for pure SnO 2 , the surface deficient oxygen sites can be depleted almost completely due to the improved crystallinity after calcination above 300 °C . However, it is observed that by doping a secondary metal cation, such as Nb 5+ , Cu 2+ , Ce 4+ , Cr 3+ , and Mn 3+ , into the SnO 2 matrix to form a noncontinuous solid solution structure, the quantity of the surface deficient oxygen species can be enhanced and its thermal stability can be improved. − Even if the prepared SnO 2 -based solid solution catalysts were calcined above 450 °C, a certain quantity of surface deficient oxygen anions can still be detected, which contribute significantly to their activity for CO oxidation; methane, VOC, and soot combustion; , and NOx selective reduction by NH 3 . Moreover, we found that by doping the SnO 2 surface with alkali metal oxides, the quantity of its surface mobile oxygen sites could be significantly improved, which subsequently influences the activity of the catalyst. , In addition, the construction of 3DOM solid solution structure can also produce a large number of surface active oxygen sites, which are critical to improve the catalytic activity …”