Catalytic partial oxidation of methane (CPOM) to synthesis gas over a Ni/alpha-Al2O3 catalyst in fixed-bed and fluidized-bed reactors with and without membranes was investigated by means of mathematical modeling and simulations. The reactors were simulated by applying conditions which are of relevance for industrial applications (p=5 and 30 bar, T=750-800 degrees C). Since, at high pressures, the performance of a fixed-bed reactor for the CPOM reaction was strongly influenced by the intraparticle mass-transport limitation, the yield of syngas in fluidized-bed reactor was higher compared to the fixed-bed reactor. In both reactor types, the conversion of methane and yield of syngas could be significantly improved by means of integrated product separation on applying porous membranes. Due to the higher selectivity of separation the membrane fluidized bed was superior to the fixed bed. In turn, the higher selectivity of separation in fluidized-bed membrane reactors was attributed to the mass-transfer limitation between the bubble and emulsion phases that acted as a prefiltering membrane. However, the improvement of the selectivity of separation due to the interphase gas exchange decreased with increasing pressure.