Table 1. Catalytic CH4 Oxidation Rates for Various Zeolite Topologiesa.
| material | framework | cage shape | cage size (Å)26 | channel size (Å)27 | Si/Alnomb | Si/Altotc | Cu/Altotd | specific activitye | STY (h–1 × 10–3)f |
|---|---|---|---|---|---|---|---|---|---|
| H-ZSM-5 | MFI | 5.3 × 5.6 | 11.5 | 13.2 | 0.31 | 1.79 ± 0.02 | 5.2 ± 0.05 | ||
| 5.1 × 5.5 | |||||||||
| H-Beta | BEA | 6.6 × 6.7 | 12.5 | 13.3 | 0.30 | 0.80 ± 0.01 | 2.4 ± 0.04 | ||
| 5.6 × 5.6 | |||||||||
| MCM-41 | MCM-41 | 30 | 12 | 16.1 | 0.74 | 0.36 ± 0.02 | 0.6 ± 0.03 | ||
| H-ZSM-5 | MFI | 5.3 × 5.6 | 11.5 | 13.9 | 0.13 | 0.84 ± 0.02 | 6.0 ± 0.17 | ||
| 5.1 × 5.5 | |||||||||
| H-mordenite | MOR | 6.5 × 7 | 10 | 11.1 | 0.14 | 0.84 ± 0.01 | 4.6 ± 0.08 | ||
| 2.6 × 5.7 | |||||||||
| H-ferrierite | FER | 4.2 × 5.4 | 10 | 10.6 | 0.12 | 0.44 ± 0.01 | 2.7 ± 0.04 | ||
| 3.5 × 4.8 | |||||||||
| Na-ZSM-5 | MFI | 5.3 × 5.6 | 11.5 | 13.6 | 0.37 | 0.88 ± 0.02 | 2.2 ± 0.04 | ||
| 5.1 × 5.5 | |||||||||
| Na-Y | FAU | spherical | 9.6 × 9.6 | 7.4 × 7.4 | 5.1 | 4.6 | 0.45 | 0.30 ± 0.01 | 0.3 ± 0.01 |
| Na-SAPO-34 | CHA | ellipsoidal | 9.4 × 9.4 × 12.7 | 3.8 × 3.8 | 0.3 | 0.6 | 0.02 | 0.84 ± 0.03 | 7.9 ± 0.29 |
| Na-SSZ-13 | CHA | ellipsoidal | 9.4 × 9.4 × 12.7 | 3.8 × 3.8 | 15 | 13.8 | 0.50 | 3.12 ± 0.01 | 6.1 ± 0.03 |
| CuOx-MFIg | MFI | 5.3 × 5.6 | ∞ | ∞ | ∞ | 0 | 0 | ||
| 5.1 × 5.5 | |||||||||
| CuOx-BEAg | BEA | 6.6 × 6.7 | ∞ | ∞ | ∞ | 0 | 0 | ||
| 5.6 × 5.6 | |||||||||
| H-ZSM-5g | MFI | 5.3 × 5.6 | 11.5 | 12.9 | 0 | 0 | 0 | ||
| 5.1 × 5.5 |
Catalyst pretreatment: 5 h at 823 K under flowing O2, cooled to 483 K under O2 flow and then purged under He for 0.5 h. Initial CH4 oxidation: 0.5 h under 2400 mL h–1 gcat–1 CH4 at 483 K. Reaction conditions: T = 483 K, WHSV = 2400 mL h–1 gcat–1, PCH4 = 98.1 kPa, PH2O = 3.2 kPa, PO2 = 0.0025 kPa (25 ppm).
Si/Alnom denotes the nominal silicon to aluminum ratio in the zeolite based on commercial figures or ratios of SiO2 to Al2O3 in synthesis procedures.
Si/Altot denotes the ratio of silicon to aluminum atoms ratio within the zeolite calculated using data from inductively coupled plasma mass spectrometry (ICP-MS) measurements.
Cu/Altot denotes the ratio of copper to aluminum atoms within the zeolite calculated using ICP-MS.
Specific activity = μmolCH3OH h–1 gcat–1.
Site time yield (STY) defined as mol CH3OH (mol Cu)−1 h–1.
T = 483 K, WHSV = 2400 mL h–1 gcat–1, PCH4 = 93.1 kPa, PH2O = 3.2 kPa, PO2 = 0.051 kPa. The ± symbol denotes 95% confidence intervals.