Nonstoichiometric Oxygen in Mn–Ga–O Spinels: Reduction Features of the Oxides and Their Catalytic Activity
Full article
| Общее |
Language:
Английский,
Genre:
Full article,
Status:
Published,
Source type:
Original
|
| Journal |
RSC Advances
ISSN: 2046-2069
|
| Output data |
Year: 2018,
Volume: 8,
Number: 21,
Pages: 11598-11607
Pages count
: 10
DOI:
10.1039/c7ra11557a
|
| Tags |
THIN-FILMS; MANGANESE OXIDES; CO OXIDATION; NANOPARTICLES; TEMPERATURE; PERFORMANCE; COMBUSTION; MN2O3 |
| Authors |
Bulavchenko O. A.
1,2
,
Venediktova O. S.
1,2
,
Afonasenko T. N.
3
,
Tsyrul'nikov P. G.
3
,
Saraev A. A.
1,2
,
Kaichev V. V.
1,2
,
Tsybulya S. V.
1,2
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis SB RAS, Lavrentieva Ave. 5, Novosibirsk, 630090, Russia
|
| 2 |
Novosibirsk State University, Pirogova Str. 2, Novosibirsk, 630090, Russia
|
| 3 |
Institute of Hydrocarbons Processing SB RAS, Neftezavodskaya Str. 54, Omsk, 644040, Russia
|
|
Funding (1)
|
1
|
Federal Agency for Scientific Organizations
|
0303-2016-0002
|
The subject of this study was the content of oxygen in mixed oxides with the spinel structure Mn1.7Ga1.3O4 that were synthesized by coprecipitation and thermal treatment in argon at 600–1200 °C. The study revealed the presence of excess oxygen in “low-temperature” oxides synthesized at 600–800 °C. The occurrence of superstoichiometric oxygen in the structure of Mn1.7Ga1.3O4+δ oxide indicates the formation of cationic vacancies, which shows up as a decreased lattice parameter in comparison with “high-temperature” oxides synthesized at 1000–1200 °C; the additional negative charge is compensated by an increased content of Mn3+ cations according to XPS. The low-temperature oxides containing excess oxygen show a higher catalytic activity in CO oxidation as compared to the high-temperature oxides, the reaction temperature was 275 °C. For oxides prepared at 600 and 800 °C, catalytic activity was 0.0278 and 0.0048 cm3 (CO) per g per s, and further increase in synthesis temperature leads to a drop in activity to zero. The process of oxygen loss by Mn1.7Ga1.3O4+δ was studied in detail by TPR, in situ XRD and XPS. It was found that the hydrogen reduction of Mn1.7Ga1.3O4+δ proceeds in two steps. In the first step, excess oxygen is removed, Mn1.7Ga1.3O4+δ → Mn1.7Ga1.3O4. In the second step, Mn3+ cations are reduced to Mn2+ in the spinel structure with a release of manganese oxide as a single crystal phase, Mn1.7Ga1.3O4 → Mn2Ga1O4 + MnO.