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.
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