A study on the feasibility of the catalytic methane oxidation for landfill gas deoxygen treatment

When landfill gas (LFG) is upgraded as an alternative natural gas or vehicle fuel, in addition to the separation of carbon dioxide, several components such as water vapor, hydrogen sulfide (H2S), oxygen (O2) and siloxanes are also need to be eliminated to meet the demands of the corresponding standards. Among these minor components higher content of O2 would cause some operation problems of the engine combustion equipment that are designed to use natural gas as the fuel. Therefore the oxygen content in upgraded LFG should be strictly controlled to meet the limitation of the corresponding standards. It is difficult to separate O2 from LFG through conventional technologies. In order to find an effective method to accomplish this work, a deoxygen treatment by which O2 was removed through the catalytic oxidation of methane was experimentally studied in this paper. In the test, bimetallic Pt–Rh/γ-Al2O3 coated on the metallic honeycomb monolith was employed as the catalyst and the compressed raw LFG or the decarbonized LFG at 5.0 bar were used as the feed gas. Results showed that after the catalytic deoxygen reaction was started-up, 100% of deoxygen conversion could be obtained in short time and keep on stably without extra heat supplied. The deoxygen process could be carried out under wide range of operating conditions (gas hourly space velocity up to 1.0 × 105 h−1, O2 content attaining 2.6 vol.%), and the reaction was easier to be started-up for the decarbonized LFG than the raw LFG. Besides, a small amount of gaseous methanol or ethanol mixed into LFG was found to promote the deoxygen reaction remarkably, which might be useful in some special conditions such as cold start. In conclusion, this technique was proved to be promising for the removal of O2 in the LFG upgrading treatment.