Study on the deactivation of the deoxygen catalyst during the landfill gas upgrading process

• Catalysts of Pt/γ-Al2O3 show excellent deoxygen performance for LFG upgrading.
• Carbon deposit is the main cause of the catalyst deactivation.
• Activity of the spent catalysts could be partially regained by heat treatment.
• Silicate and sulfate deposits would cause permanent catalyst deactivation.

Landfill gas (LFG) could be upgraded to bio-methane when CO2 and other harmful minor components are removed. Catalytic oxidation of CH4 is an effective deoxygen method for upgrading LFG as an alternative for natural gas or a vehicle fuel to meet the requirement of O2 content limitation. The durability of the deoxygen catalyst is an important factor that needs to be studied before it is put into practical application. To investigate the catalyst durability and the causes that lead to the deactivation of the catalysts, two catalysts of Pt/γ-Al2O3 coated on the metallic substrate were prepared and used for LFG deoxygen process under the conditions of the gas hourly space velocity of 20,000 h−1 and inlet temperature around 300 °C until deactivation. The deoxygen conversions of the catalysts were measured at different stages of use, and the fresh and spent catalysts were characterized and compared by various techniques. The results demonstrated that the catalysts prepared in this study showed excellent deoxygen performances while deactivation of them took place gradually. The lifetimes of the two catalysts were 724 and 508 h respectively under the experimental condition in this study. The carbon, silicate, sulfate and elementary sulfur deposited on the active sites of the catalysts could be the causes of the deactivation. The catalytic performances of the spent catalysts could be regenerated through the removal of carbon deposit by heat treatment under air atmosphere. The accumulation of silicate and sulfate deposits, which are generated from the oxidation of siloxanes and hydrogen sulfide in LFG, could lead to permanent catalyst deactivation.