Pd/Al_2O_3 monolithic catalysts were prepared using Al_2O_3 porous material with both mesopores and three-dimensional interconnected macropores as the support and Ce,Zr as additives. Ultra-low concentration ventilation air methane combustion activity on the as-synthesized catalysts was investigated and the reaction path was predicted. Results show that the reaction performance of catalysts with the additives is excellent owing to the maintained special microstructure of the original support and large BET su...