Activity of monolithic Pd/Al₂O₃ catalysts in the combustion of mine ventilation air methane

The activity of Pd/Al₂O₃ catalysts increases when Pd content is increased from 1% to 2%. Among these catalysts, 2%Pd/Al₂O₃ shows the highest methane combustion activity. In a reduced form, the catalyst displays a higher activity than in the oxidized form. 24-hour ageing at 600°C to 800°C lowers the catalytic activity of 2%Pd/Al₂O₃ due to Pd crystallite sintering. After 110-hour oxidation of 1% methane in air over 2%Pd/Al₂O₃, conversion decreases from 100% to 88%. Upon reduction with hydrogen (performed after 24-hour ageing at 700°C and 110-hour methane oxidation), the 2%Pd/Al₂O₃ catalyst regains its initial activity. The high activity of Pd catalysts renders them suitable for methane removal from coal mine ventilation air at high gas flow velocities and temperatures lower than 600°C.