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.