Study on Catalytic Incineration of Methane Using Cr₂O₃/γ-Al₂O₃ as the Catalyst

Abstract

A fixed bed reactor was employed to investigate the catalytic incineration of CH₄ by various supported transition metal oxide catalysts, with a view of finding the optimal one. Results indicated that the active species, the support, the metal content, the weight hourly space velocity (WHSV), and the inlet CH₄ concentration were all important factors affecting CH₄ oxidation. Cr₂O₃/γ-Al₂O₃ was found to be the most active catalyst among the seven γ-Al₂O₃-supported metal oxide catalysts tested. With Cr₂O₃ as the active species, γ-Al₂O₃ was the most suitable of six supports tested. Furthermore, the optimal Cr content of Cr₂O₃/γ-Al₂O₃ was 9 wt.%. X-ray diffraction (XRD) patterns showed that it was formation of Cr₂O₃ crystals that caused a decline in catalyst activity at Cr content above 9 wt.%. Using the optimal Cr₂O₃/γ-Al₂O₃ catalyst, CH₄ was completely oxidized at about 390°C, much lower than the temperature required by noble metal catalysts for the same outcome. The stability of Cr₂O₃/γ-Al₂O₃ was good and was not affected by the reaction temperature, demonstrated by a nearly constant conversion rate of CH₄ of 57% at 350°C and 97% at 380°C during a 20 h on-stream test. However, WHSV and inlet concentration of CH₄ did affect CH₄ conversion noticeably. For complete oxidation of CH₄, the reaction temperature required increased with WHSV and inlet CH₄ concentration.

Keywords:

• Catalytic incineration
• CH₄
• Cr₂O₃/γ-Al₂O₃
• Weight hourly space velocity
• CH₄ concentration

Acknowledgment

The authors are grateful to Professor Hung-Shan Weng for his thorough instruction.