Mesoporous NiO-Al2O3 catalysts were applied to catalytic partial oxidation of methane at 650 degrees C, 1 MPa with a feed composition of CH4/O-2/N-2/Ar = 5.2 vol.%/2.6 vol.%/4.9 vol.%/balance. In order to investigate the effect of mesopore of the catalyst on the catalytic activity, we used various types of organic reagents, such as P123, F127, PEG6000, and some carboxylic acids, to prepare bulk NiO-Al2O3 catalysts. Among the organic reagents P123. F127, and PEG6000 were effective for the formation of mesopores. As a result of activity tests, the catalyst prepared by using P123 showed the highest oxidative activity and selectivity; the values were higher than those of NiO catalyst supported on alpha-Al2O3 or gamma-Al2O3. Results of pulse reaction indicated that the oxidation tolerance of NiO-Al2O3 prepared with P123 was high under reaction conditions. The effect of pore size of the catalyst was predominant because in the mesopores the diffusion values of the reactant gases are different and the CH4/O-2 ratio in the pores was kept high. These factors contributed to the high selectivity of the mesoporous NiO-Al2O3 catalysts. (C) 2010 Elsevier B.V. All rights reserved.