Table 1. Surface compositions and oxidation states of K, Mn, O and Si species calculated from XPS analyses.
| Catalysts | Mn 2p R% |
R% |
R% |
||||
|---|---|---|---|---|---|---|---|
| Mn3+ | Mn4+ | O-I | O-II | O-III | Si4+ | Si-OH | |
| K-OMS-2/SiO2-20 | 63.1 | 36.9 | 7.3 | 90.5 | 2.2 | 96.9 | 3.1 |
| K-OMS-2/SiO2-50 | 65.9 | 34.1 | 14.9 | 82.7 | 2.4 | 97.9 | 2.1 |
| K-OMS-2/SiO2-70 | 68.1 | 31.9 | 17.3 | 80.2 | 2.5 | 98.1 | 1.9 |
| K-OMS-2/silica gel-50 | 66.3 | 33.7 | 11.5 | 85.8 | 2.7 | 95.7 | 4.3 |
| MnOx/SiO2-50 | 62.3 | 37.7 | 10.1 | 87.7 | 2.2 | 97.1 | 2.9 |
| KNO3/SiO2-50 | — | — | 3.7 | 92.8 | 3.5 | 98.4 | 1.6 |
R%: the ratio of single component to total component.